(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Illinois agronomy handbook, 1991-1992"

NOT/CE: Return or renew all Library Materia.sl The M/n.mum Fee for 
each Lost Book is $50.00. 

The oerson charging this material is responsible for 
Us remrTto the l^ra'ry from which .t was w.thdrawn 
on or before the Latest Date stamped below. 

To renew call Telephone Center, 333-8400 

UNIVERSITY OFJLUNOISUBRA^^URBA^^ 



L161— O-1096 



ACES LIBRARY | 

It 


SEP 9 5 2001 


UNIVERSITY OF ILLINOIS | 



Digitized by the Internet Archive 

in 2011 with funding from 

University of Illinois Urbana-Champaign 



http://www.archive.org/details/illinoisagronomy1311univ 




ILLINOIS AGRONOMY HANDBOOK 



1991-1992 



University of Illinois at Urbana-Champaign • College of Agriculture 



/ Cooperative Extension Service • Circular 1311 



Agricultural Research and 
Demonstration Centers 




Northern Illinois 
Agronomy Research 
Center, DeKalb 

Northwestern IlHnois 
Agricultural Research 
and Demonstration 
Center, Monmouth 

Illinois River Valley 
Sand Farm, Kilbourne 

University of Illinois 
South Farms 

Orr Agricultural 
Research and 
Demonstration Center, 
Perry 

Brownstown 
Agronomy Research 
Center 

Dixon Springs 
Agricultural Center/ 
Ilhnois Forest 
Resource Center 



D Centers for research in the areas of agron- 
omy, agricultural engineering, agricultural 
entomology, animal sciences, forestry, 
horticulture, and plant pathology. 



Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may be similar. Persons using such 
products assume responsibility for their use in accordance with the current label directions of the manufacturer. 



Urbana, Illinois December 1990 

This publication replaces Circular 1290. Cover photo by David 
Riecifs. Designer: Joan R. Zagorski. Editor: Alison Fong 
Weingartner. Editorial and production assistance: Anita Povich, 
Bernard Cesarone, and Cloydia Larimore. 

7M— 1 2-90— Phillips— AFW 



Issued in futherance of Cooperative Extension Work, Acts of May 
8 and June 30, 1914, in cooperation with the U.S. Department of 
Agriculture. Donald L. Uchtmann, Director, Cooperative Exten- 
sion Service, University of Illinois at Urbana-Champaign. The 
Illinois Cooperative Extension Service provides equal opportu- 
nities in programs and employment. 



A LIBRARY 



ILLINOIS AGRONOMY HANDBOOK 
1991-1992 

University of Illinois at Urbana-Champaign • College of Agriculture 
Cooperative Extension Service • Circular 1311 



AGRiCULTURE LIBRARY 

JAI\5 ^0 1991 
"JWiVFPSITY OF ILLINOIS 



Contents 



1. CORN 1 

Yield goals ' 1 

Hybrid selection 1 

Planting date 3 

Planting depth 4 

Plant population 4 

Row spacing 5 

Replanting 5 

Weather stress in corn 6 

Estimating yields 6 

Specialty types of corn 7 

2. SOYBEANS 9 

Planting date 9 

Planting rate 9 

Planting depth 10 

Crop rotation 10 

Row width 11 

When to replant 11 

Double-cropping 12 

Seed source 12 

Seed size 13 

Varieties 13 

3. SMALL GRAINS 17 

Winter wheat 17 

Spring wheat 19 

Rye 19 

Triticale 20 

Spring oats 20 

Winter oats 20 

Spring barley 20 

Winter barley 21 

4. GRAIN SORGHUM 22 



5. COVER CROPS AND CROPPING 
SYSTEMS 24 

Cover crops 24 

Cropping systems 25 

6. MISCELLANEOUS CROPS 27 

Sunflowers 27 

Oilseed rape (canola) 27 

Buckwheat 28 

Crambe 28 

Jerusalem artichoke 28 

Grain amaranth 28 

Other crops 28 

7. HAY, PASTURE, AND SILAGE 29 

High yields 29 

Establishment 29 

Fertilizing and liming before or at 

seeding 30 

Fertilization 30 

Management 30 

Pasture establishment 31 

Pasture renovation 31 

Selection of pasture seeding mixture 32 

Pasture fertilization 32 

Pasture management 32 

Species and varieties 33 

Inoculation 35 

Grasses 35 

Forage mixtures 38 

8. SEED PRODUCTION 42 

Seed production of forage legumes 42 

Plant Variety Protection Act 42 



9. WATER QUALITY 44 

Drinking water contaminants 44 

Point source prevention 44 

Groundwater vulnerability 45 

Surface water contamination 45 

Management practices 45 

Chemical properties and selection 46 

Precautions for irrigators 46 

Well water testing 47 

10. SOIL TESTING AND FERTILITY 48 

Soil testing 48 

Plant analysis 49 

Lime 50 

Calcium-magnesium balance in Illinois 

soils 53 

Nitrogen 54 

Phosphorus and potassium 64 

Phosphorus 66 

Potassium 67 

Secondary nutrients 70 

Micronutrients 71 

Method of fertilizer application 72 

Nontraditional products 74 

11. SOIL MANAGEMENT AND TILLAGE 
SYSTEMS 75 

Moldboard plow system (conventional clean 

tillage) 75 

Chisel plow system 75 

Disk system 76 

Ridge-tillage system (till-plant) 76 

No-tillage system (zero-tillage) 76 

Soil erosion and residue management 76 

Water runoff 17 

Crop production with conservation 

tillage n 

Weed control 79 



Insect control 80 

No-till pest problems 80 

Crop yields 80 

Production costs 82 

12. WATER MANAGEMENT 83 

The benefits of drainage 83 

Drainage methods 84 

The benefits of irrigation 87 

The decision to irrigate 88 

Subsurface irrigation 89 

Irrigation for double-cropping 89 

Fertigation 89 

Cost and return 90 

Irrigation scheduling 90 

Management requirements 91 

13. 1991 WEED CONTROL FOR CORN, 
SOYBEANS, AND SORGHUM 93 

Precautions 93 

Cultural and mechanical control 95 

Herbicide incorporation 95 

Chemical weed control 96 

Herbicide combinations 96 

Herbicide rates 97 

Postemergence herbicide principles 97 

Conservation tillage and weed control 97 

Herbicides for corn 98 

Herbicides for sorghum 103 

Herbicides for soybeans 103 

Problem perennial weeds Ill 

14. 1991 WEED CONTROL FOR SMALL GRAINS, 
PASTURES, AND FORAGES 115 

Small grains 115 

Grass pastures 116 

Forage legumes 118 

Acreage conservation reserve program 120 



Contributing Authors 



CD. ANDERSON, Extension Assistant, Weed Science 
Extension, Department of Agronomy (1991 Weed 
Control for Corn, Soybeans, and Sorghum; 1991 
Weed Control for Small Grains, Pastures, and 
Forages) 

T.J. BICKI, Assistant Professor, Pedology Extension, 
Department of Agronomy (Soil Management and 
Tillage Systems) 

L.V. BOONE, Agronomist, Soil Fertility, Department 
of Agronomy (Soil Testing and Fertility) 

W.S. CURRAN, Associate Agronomist, Department of 
Agronomy (1991 Weed Control for Small Grains, 
Pastures, and Forages) 

D.W. GRAFFIS, Professor, Forage Crops Extension, 
Department of Agronomy (Cover Crops and Crop- 
ping Systems; Hay, Pasture, and Silage; Seed 
Production) 

R.G. HOEFT, Professor, Soil Fertility Extension, De- 
partment of Agronomy (Soil Testing and Fertility) 

C.J. KAISER, Associate Professor, Forage Crops, De- 
partment of Agronomy (Hay, Pasture, and Silage; 
Seed Production) 

E.L. KNAKE, Professor, Weed Science Extension, De- 
partment of Agronomy (1991 Weed Control for 
Corn, Soybeans, and Sorghum; 1991 Weed Con- 
trol for Small Grains, Pastures, and Forages) 



D.E. KUHLMAN, Professor, Program Leader for En- 
vironmental Issues, College of Agriculture (Soil 
Management and Tillage Systems) 

M.D. McGLAMERY, Professor, Weed Science Exten- 
sion, Department of Agronomy (1991 Weed Con- 
trol for Corn, Soybeans, and Sorghum; 1991 Weed 
Control for Small Grains, Pastures, and Forages) 

E.D. NAFZIGER, Associate Professor, Crop Production 
Extension, Department of Agronomy (Com; Small 
Grains; Grain Sorghum; Cover Crops and Crop- 
ping Systems; Miscellaneous Crops) 

T.R. PECK, Professor, Soil Chemistry Extension, De- 
partment of Agronomy (Soil Testing and Fertility) 

G.E. PEPPER, Associate Professor, Soybean Extension, 
Department of Agronomy (Soybeans) 

D.R. PIKE, Agronomist, Weed Science Extension, De- 
partment of Agronomy (1991 Weed Control for 
Com, Soybeans, and Sorghum) 

J.C. SIEMENS, Professor, Power and Machinery Ex- 
tension, Department of Agricultural Engineering 
(Soil Management and Tillage Systems) 

F.W. SIMMONS, Assistant Professor, Soil and Water 
Management, Department of Agronomy (Water 
Quality; Water Management) 



I 



Chapter 1. 
Corn 



Yield goals 

Management decisions are made more easily if the 
corn producer has set reahstic yield goals based on 
the soil, climate, and available equipment. Usually it 
is not realistic, for example, to set yield goals of 180 
bushels per acre for a soil rated to produce only 100 
bushels per acre and from which the highest yield 
ever produced was 130 bushels per acre. Instead, 
managing to achieve a realistic yield goal should result 
in yields greater than the goal in years when conditions 
are better than average and reduced losses when the 
weather is unfavorable. The yield goal should be 
considered an average; it will not guarantee high yields 
when the weather is poor. 

The first step in establishing a yield goal is a thorough 
examination of the soil type. Information for each soil 
type, such as the productivity ratings given in Soils of 
Illinois (Bulletin 778), can be a useful guideline. This 
information, however, should be supplemented by 3- 
to 5 -year yield records, county average yields, and the 
yields on neighboring farms. An attempt should be 
made to ignore short-term weather and to set a goal 
based on long-term temperature and rainfall patterns. 



Hybrid selection 

When tested under uniform conditions, the range 
in yields among available hybrids is often 30 to 50 
bushels per acre. Thus it pays to spend time choosing 
the best hybrids. Maturity, yield for that maturity, 
standability, and disease resistance are the most im- 
portant factors to consider when making this choice. 

Concern exists with what many consider to be a 
lack of genetic diversity among commercially available 
hybrids. Although it is true that a limited number of 
genetic pools, or populations, were used to produce 
today's hybrids, it is important to realize that these 
pools contain a tremendous amount of genetic diver- 
sity. Even after many years of breeding, there is no 
evidence that this diversity has been fully exploited. 
In fact, a number of studies have shown that breeding 
progress is not slowed even after a large number of 



cycles of selection. Continued improvements in most 
desirable traits are evidence that this is true. Many of 
today's hybrids are substantially better than those that 
are only a few years old. For this reason, some pro- 
ducers feel that a hybrid "plays out" within a few 
years. Actually, the performance of a given hybrid 
remains constant over the years; but comparison with 
newer and better hybrids may make it appear to have 
declined in yielding ability. 

Despite considerable genetic diversity, it is still pos- 
sible to buy the same hybrid from several different 
companies. This happens when different companies 
buy inbreds from a foundation seed company that has 
a successful breeding program, or when hybrid seed 
is purchased on the wholesale market, then resold 
under a company label. In either case, hybrids are 
being sold on a nonexclusive basis, and companies 
simply put their own name and number on the bags. 

Many producers, however, would like to avoid 
planting all of their acres to the same hybrid. One 
way is to buy from only one company, though this 
may not be the best strategy if it discourages looking 
at the whole range of available hybrids. Another way 
of assuring genetic diversity is to use hybrids with 
several different maturities. Finally, many dealers have 
at least some idea of what hybrids are very similar or 
identical and can provide such information if asked. 

It is also important to remember that genetics are 
only part of the performance potential of any hybrid. 
The care with which hybrid seed is produced — de- 
tasseling, harvesting, drying, grading, testing, and han- 
dling — can and does have a substantial effect on its 
performance. Be certain that the seed you are buying 
was produced in a professional manner. 

Maturity is one of the important characteristics used 
in choosing a hybrid. Hybrids that use most of the 
growing season to mature generally produce higher 
yields than those that mature more quickly. The latest- 
maturing hybrid should reach maturity at least 2 weeks 
before the average date of the first killing freeze (32°F), 
which occurs about October 8 in northern Illinois, 
October 18 in central Illinois, and October 25 in 
southern lUinois. Physiological maturity is reached 
when kernel moisture is 30 to 35 percent and is easily 



identified by the appearance of a black layer on the 
base of the kernel where it attaches to the cob. The 
approach to maturity also can be monitored by check- 
ing the "milk line," which moves from the crown to 
the base of the kernel as starch is deposited. The kernel 
is mature about the time this milk line disappears at 
the base of the kernel. 

Although full-season hybrids generally produce the 
highest yields, most producers choose hybrids of sev- 
eral different maturities. This practice allows harvest 
to start earlier and also reduces the risk of stress 
damage by lengthening the pollination period. 

Comparing hybrid maturities may be difficult be- 
cause there is no uniform way of describing this 
characteristic. Some companies use days to maturity, 
while others use growing degree days (GDD). Growing 
degree days is becoming more widely used, and it is 
usually possible to obtain this measure for any hybrid, 
either directly or by comparing maturity with a hybrid 
for which GDD is known. 

The following formula can be used to calculate 
GDD accumulated on any given day: 

H + L 
GDD = — 50°F 



These GDD numbers will vary with hybrid maturity. 
The relative proportion of full-season GDD required 
to reach each growth stage will, however, remain 
relatively constant. For example, GDD to silking will 
generally be about one-half of the GDD to physiolog- 
ical maturity. 

A full-season hybrid for a particular area will gen- 
erally mature in several hundred fewer GDD than the 
number given in Figure 1.1. Thus, a full-season hybrid 
for northern Illinois would be one that matures in 
about 2,500 GDD, while for southern Illinois a hybrid 
that mahires in 2,900 to 3,000 GDD would be con- 
sidered full season. This GDD "cushion" reduces the 
risk of frost damage and also allows some flexibility 
in planting time; it may not be necessary to replace a 
full-season hybrid with one maturing in fewer GDD 
unless planting is delayed until late May. 

After yield and maturity, resistance to lodging is 
probably the next most important factor in choosing 
a hybrid. Because large ears tend to draw nutrients 
from the stalk, some of the highest-yielding hybrids 
also have a tendency to lodge. Such hybrids may be 
profitable because of their high yields, but they should 



where H is the high temperature for the day (but no 
higher than 86°F) and L is the low temperature (but 
no lower than 50°F). For example (see the following 
table), if the daily high temperature were 95°F, cal- 
culate at 86°F, the cutoff point for high temperatures. 
If the daily low temperature were 40°F, calculate at 
50°F, the cutoff point for low temperatures. These 
high and low cutoff temperatures are used because 
growth rates do not increase above 86°F and they do 
not decrease below 50°F. 

The following figures are examples of daily high 
and low temperatures and the resulting GDD, calcu- 
lated using the GDD formula: 



Daily temperature 






High 


Low 


GDD 


80 


60 


20 


60 


40 


5 


95 


70 


28 


50 


35 






It is useful to keep a running total of daily GDD 
because GDD has been found useful in predicting the 
rate of development of the corn plant. For a full- 
season hybrid grown in central Illinois, the following 
table gives the approximate GDD required to reach 
certain growth stages: 



Stage 



GDD 



Emergence 
Two-leaf 


120 


200 


Six-leaf (tassel initiation) 


475 


Ten-leaf 


740 


Fourteen-leaf 


1,000 


Tassel emergence 


1,150 


Silking 


1,400 


Dough stage 


1,925 


Dented 


2,450 


Physiological maturity (black layer) 


2,700 





2,800 2,700 










< 


^ ^ 




( 


2,900 
3,000 sg^ 


^ 


V 


^5= 


^ 


:i 


2,700 
L 2,800 


fr^ 




— 


— 9 onn 


\; 


_j 


£,9UU 


3,100 jJ^ 


^ 


I 


" 3,000 


3,200 -i^ 


\,_^ 


L^ ^. 


- 




"* 


■^ /n 






3,300 n|^ 


§^ 


x~- 


/ 


- 3,100 


Vs 


rrs T- 


z^ 


^: 


r 


^ 3,200 


sK 


K -y 


"^ i 


t 3,300 
3,400 

500 


\2r 

3,400 

< 


rv 









V. 


!>- ^^ 


^ ^1 










— 


nT 




- ^ 


;/ 


3,50( 




-" 


i' 


r — r 




=H 


p 



Figure 1.1. Average number of growing degree days. May 
1 through September 30, based on temperature data 
provided by the U.S. Department of Commerce, National 
Weather Service, 1951-1980. 



♦ 



be closely watched as they reach maturity. If lodging 
begins, or if stalks become soft and weak (as deter- 
mined by pinching or pushing on stalks), then har- 
vesting these fields should begin early. 

Resistance to diseases and insects are important 
characteristics in a corn hybrid. Leaf diseases are easiest 
to spot, but stalks also should be checked for diseases. 
Resistance to insects such as the European corn borer 
also is being incorporated into modern hybrids. An- 
other useful trait is the ability of the hybrid to emerge 
under cool soil conditions, a trait that is especially 
important in reduced or zero-till planting. 

With the large number of hybrids being sold, it is 
difficult to choose the best one. An important source 
of information on hybrid performance is the annual 
report Performance of Commercial Corn Hybrids in Illi- 
nois, which is available in Extension offices each year 
following harvest. This summary reports hybrid tests 
run each year in ten locations and includes information 
from the previous 2 years. The report gives data on 
yields, kernel moisture, and lodging of hybrids. Other 
sources of information include your own tests and 
tests conducted by seed companies, neighbors, and 
county Extension personnel. 

You should see the results of as many tests as 
possible before choosing a hybrid. Good performance 
for more than one year is one important criterion. You 
should not base your decision on the results of only 
one "strip test." These tests use only one strip of each 
hybrid; the difference between two hybrids may there- 
fore be due to location in the field rather than to an 
actual superiority of one over the other. 



Planting date 

Long-term studies show that the best time to plant 
corn in Illinois is around May 1, with little or no yield 
loss when planting is within a week on either side of 
this date. Weather and soil conditions permitting, you 
should begin planting sometime before this date to 
allow for bad working days (Table 1.1). Corn that is 
planted 10 days or 2 weeks before the optimum date 
may not yield quite as much as that planted on or 
near the optimum date, but it will usually yield con- 
siderably more than that planted 2 weeks or more 
after the optimum date (Table 1.2). 

In general, yields will decline slowly as planting is 
delayed up to May 10. From May 10 to May 20, the 
yield will decline about one-half bushel for each day 
that planting is delayed. This loss will increase to 1 to 
Vh bushels per day from May 20 to June 1, with 
greater reductions in northern Illinois than in the 
southern part of the state. After June 1, yields decline 
very sharply with delays in planting. The latest prac- 
tical date to plant corn ranges from about June 15 in 
northern to July 1 in southern Illinois. If you plant 
this late, expect only 50 percent of the normal yield. 

Early planting results in drier corn in the fall, allows 
for more control over the planting date, and allows 



Table 1.1. Days Available and Percent of Calendar 
Days Available for Field Operations in 
Illinois^ 

Northern Central Southern 

Period Ilhnois Illinois Illinois 

Days % Days % Days % 

April 1-20'' 5.8 (29) 4.2 (21) 2.6 (13) 

April 21-30^ 3.5 (35) 3.1 (31) 2.6 (26) 

May 1-10^ 5.8 (58) 4.3 (43) 3.5 (35) 

May 11-20" 5.5 (55) 5.0 (50) 4.4 (44) 

May 21-30"^ 7.4 (74) 5.8 (58) 5.4 (54) 

May 31-]une 9^ . . 6.0 (60) 5.4 (54) 5.6 (56) 

June 10-19' 6.0 (60) 5.4 (54) 5.8 (58) 

^ Summary prepared by R.A. Hinton, Department of Agricultural Economics 
of the University of Illinois Cooperative Crop Reporting Service, unpublished 
official estimates of Favorable Work Days, 1955-1975. The summary is the 
mean of favorable days omitting Sundays, less one standard error, representing 
the days available 5 years out of 6. 
*> 20 days 
" 10 days 



Table 1.2. Effect of Planting Date on Yield" 



Northern 
Illinois 



Central 
Illinois 



Southern 
Illinois 



- bushels per acre 

Late April 156 

Early May 151 162 

Mid-May 150 

Early June 100 133 

■" 3-year average at each location 



102 

105 

82 

58 



for a greater choice of maturity in hybrids. In addition, 
if the first crop is damaged, the decision to replant 
can often be made early enough to allow you to use 
your first-choice hybrid. Of course, early planting has 
some disadvantages: (1) cold, wet soil may produce a 
poor stand; (2) weed control may be more difficult; 
and (3) plants may suffer from frost. Improved seed 
vigor, seed treatments, and herbicides have greatly 
reduced the first two hazards; and the fact that the 
growing point of the corn plant remains below the 
soil surface for 2 to 3 weeks after emergence minimizes 
the third hazard. Because it is below the surface, this 
part of the plant is seldom damaged by cold weather 
unless the soil freezes. Even when corn is frosted, 
therefore, the probability of regrowth is excellent. For 
these reasons, the advantages of early planting out- 
weigh the disadvantages. 

The lowest temperature at which corn will germinate 
is about 50°F. You should know what the soil tem- 
perature is, either from your own measurement or 
from reported measurements that are taken beneath 
bare soil. Soil temperature, however, is not the only 
consideration in deciding when to start planting. A 
more important consideration may be the condition of 
the soil: it generally is a mistake to till and plant when 
soils are wet, and the advantages of early planting 
may well be lost to soil compaction and other problems 
associated with "mudding in" corn, whether using 
conventional tillage or no-till techniques. If the weather 
conditions have been warm and dry enough to result 
in workable soils by early April, then planting can 



probably begin by April 10 or 15 with little danger of 
loss. The weather may change after planting, however, 
and a return to average temperatures will mean slow 
growth for corn planted this early. You may also want 
to increase seeding rates by 1,000 to 2,000 seeds per 
acre if planting in April, both to allow for greater 
losses and to take advantage of the more favorable 
growing conditions that the crop is likely to encounter. 

With typical spring weather, soils can be tilled in 
preparation for corn planting to begin sometime in the 
last ten days of April. Delays due to low soil temper- 
ature (below 50°F) should be considered only if the 
weather outlook is for continued cold air temperatures. 
After April 30, soil temperature should probably be 
ignored as a factor, and corn should be planted as 
soon as soil conditions allow. You may wish to plant 
low-lying areas (such as river bottoms) last, because 
they warm up more slowly and are more prone to late 
freezes. 

When planting begins in April, it is generally best 
to plant very full-season hybrids first, but planting the 
midseason and early hybrids in sequence tends to 
"stack" the times of pollination and harvest of the 
different maturities. It is probably better to alternate 
between early and midseason hybrids during later 
planting to help spread both pollination risks and the 
time of harvest. 



Planting depth 

Ideal planting depth varies with soil and weather 
conditions. Emergence will be more rapid from rela- 
tively shallow-planted corn; therefore, early planting 
should not be as deep as later planting. For normal 
conditions, an ideal depth is IV2 to 2 inches. Early- 
planted corn should be in the shallower end of this 
range. Later in the season, when temperatures are 
higher and evaporation is greater, planting as much 
as 2V2 to 3 inches deep to reach moist soil may be 
advantageous. 

Depth-of-planting studies show that not only do 
fewer plants emerge when planted deep but also that 
those emerging often take longer to reach the polli- 
nating stage and may have higher moisture in the fall. 



Plant population 

Your goal at planting time is the highest population 
per acre that can be supported with normal rainfall 
without excessive lodging, barren plants, or pollination 
problems. But how do you know when you have 
found the ideal or optimum population for a particular 
field? Check the field for average ear weight. You can 
check at maturity or estimate by counting kernels 
(number of rows multiplied by number of kernels per 
row) once the kernel number is set. Most studies in 
Illinois suggest that the optimum plant population will 
produce ears weighing about one-half pound and 



having about 640 kernels. A half-pound ear should 
shell out about 0.4 pound of grain at 15 percent 
moisture. 

In the study reported in Table 1.3, ear size reached 
one-half pound when the plant population was slightly 
less than 25,000 per acre. At higher populations, the 
increase in the number of plants was nearly matched 
by the reduction in ear size. 

The optimum population for a particular field is 
influenced by several factors, some of which you can 
control and some over which you have little or no 
control. Concentrate on those factors that you can 
control. For instance, you can do little to affect the 
amount of water available to the crop during the 
growing season. This variable is determined by the 
soil type and the total amount and distribution of the 
rainfall between the time the crop is planted and when 
it is mature. You can, however, influence how efficiently 
this water is used. The more efficient its use, the higher 
the population that can be supported with the water 
that is available. Remember that ear number is gen- 
erally more important than ear size. 

Two very important controllable factors influencing 
the efficiency of water use are soil fertility and weeds. 
Keep the fertility level of your soil high and the weed 
population low. 

Other factors that are important include: 

1. Hybrid selection. Hybrids differ in their tolerance 
to the stress of high populations. Most modern 
hybrids can, however, tolerate populations of 20,000 
to 24,000 per acre on most Illinois soils. Some need 
even higher populations — 25,000 to 30,000 per 
acre — to produce the best yields, especially on 
more productive soils. 

2. Planting date. Early planting enables the plant to 
produce more of its vegetative growth during the 
long days of summer and to finish pollinating before 
the hot, dry weather that is normal for late July 
and early August. Early planting usually produces 
larger root systems as well. 

3. Row spacing. The more uniform distribution of 
plants grown in narrow rows improves the effi- 
ciency of water use. 

4. Insect and disease control. 

The harvest population is always less than the 
number of seeds planted. Insects, diseases, adverse 
soil conditions, and other hazards take their toll. You 



Table 1.3. Effect of Plant Population on Corn Yield 



Plants per acre 


Yield^ 


15,000 
20,000 
25,000 
30,000 
35,000 


bushels per acre 
140 
163 
175 
179 
179 



^ Average of 8 trials (with 2-4 hybrids each) conducted at Urbana, Monmouth, 
and DeKalb over a 3-year period 



can expect from 10 to 20 percent fewer plants at 
harvest than seeds planted (Table 1.4). 



Row spacing 

Because of the clear yield advantage from using a 
row spacing of less than 40 inches (Table 1.5), many 
producers have reduced row spacing; some 40 percent 
of the com acres in Illinois are planted in 30 -inch 
rows, and the average row spacing in the state is about 
35 inches. A few producers in the Com Belt use rows 
less than 30 inches apart. Most studies have shown 
yield increases of about 5 to 8 percent when rows are 
narrowed from 30 to 20 inches (Table 1.6). Equipment 
for harvesting 20-inch rows is not readily available at 
present, but some harvesting equipment can be mod- 
ified for this purpose. 



Replanting 

Although it is normal that 10 to 15 percent of 
planted seeds fail to establish healthy plants, additional 
stand losses due to insects, frost, hail, flooding, or poor 
seedbed conditions may call for a decision on whether 
or not to replant a field. The first rule in such a case 
is not to make a hasty decision. Com plants can and 
often will outgrow leaf damage, especially when the 
growing point, or tip of the stem, is protected beneath 
the soil surface or up until about the six-leaf stage. If 
new leaf growth appears within a few days after the 
injury, then the plant is likely to survive and produce 
normal yields. 

When deciding whether to replant a field, you will 
need the following information: (1) original planting 
date and plant stand, (2) possible replanting date and 
plant stand, and (3) cost of seed and pest control for 
replanting. 

If you did not count the plant stand before damage 
occurred, population can be estimated by reducing the 
dropped seed rate by 10 percent, providing that con- 
ditions for emergence were normal. To estimate stand 
after injury, count the number of Uving plants in yi,o.oo 
of an acre (Table 1.7). Take counts as needed to get a 
good average, one count for every 2 to 3 acres. 

When the necessary information on stands and 
planting and replanting dates has been assembled, use 
Table 1.8 to determine both the loss in yield to be 
expected from the stand reduction and the yield you 
can expect if you replant the field. 

To use Table 1.8, locate the expected yield of the 
reduced plant stand by reading across from the original 
planting date to the plant stand after injury. Then 
locate the expected replant yield by reading across 
from the expected replanting date to the stand you 
would replant to. The difference between these num- 
bers is the percentage yield increase (or decrease) to 
be expected from replanting. For example, corn that 
was planted on April 25, but with a plant stand reduced 



Table 1.4. Planting Rate That Allows for a 15 Percent 
Loss from Planting to Harvest 



Plants per acre 


Seeds per acre 


at harvest 


at planting time 


16,000 


18,800 


18,000 


21,200 


20,000 


23,500 


22,000 


25,900 


24,000 


28,200 


26,000 


30,600 


28,000 


33,000 


30,000 


35,300 



Table 1.5. Effect of Row Width on Corn Yield, 
Urbana 



Plants per acre 



Row width 



40 inches 



30 inches 



bushels per acre 

16,000 127 132 

24,000 133 144 

32,000 126 138 



Table 1.6. Corn Yields in 20- and 30-Inch Rows at 
Urbana 



Plants per acre 



Row width 



30 inches 



20 inches 



bushels per acre 

20,000 165 174 

25,000 172 188 

30,000 174 187 



Table 1.7. Row Length Required to Equal 1/1,000 
Acre 



Row width 






Row length 






20' 






26'1' 






28' 






18'8' 






30' 






17'5' 






32' 






16'4' 






36' 






14'6' 






38' 






13'9' 






40' 






13'1' 




Table 1.8. 


Yield of Uniformly Spaced Corn Plants 




with Different 


Planting Dates and Plant 




Populations 








Planting 




Plants 


> per acre at harvest 




date 


14,000 


16,000 18,000 


20,000 22,500 


25,000 






percent of maximum yield 




April 25 ... . 


.. 81 


86 


90 


93 96 


98 


May 6 


.. 83 


88 


92 


95 98 


100 


May 16 


.. 81 


86 


90 


93 96 


98 


May 26 


.. 75 


80 


84 


87 90 


92 


June 10 


.. 58 


63 


67 


70 73 


75 



to 18,000 by cutworm injury, would be expected to 
yield 90 percent of a normal stand. If such a field 
were replanted on May 16 to establish 25,000 plants 
per acre, the expected yield would be 98 percent of 
normal. Whether or not it will pay to replant such a 
field will depend on whether the yield increase of 
eight percentage points would repay the replanting 
costs. In this example, if replanting is delayed until 
near the end of May, the yield increase to be gained 
from replanting disappears. 

Although uniformity of stand cannot be measured 
easily, studies have indicated that reduced plant stands 
will yield better if plants are spaced uniformly than if 
there are large gaps in the row. As a general guideline, 
yields will be reduced an additional 5 percent if there 
are many gaps of 4 to 6 feet in the row and an 
additional 2 percent for gaps of 1 to 3 feet. 



Weather stress in corn 

Corn frequently encounters some weather-related 
problems during the growing season. The effect of 
such problems differs with the severity and duration 
of the stress and the stage of crop development at the 
time of the stress. Some of the possible stress conditions 
and their effects on corn growth and yield are: 

1. Flooding. The major stress caused by flooding is 
simply a lack of oxygen needed for the proper 
function of the root system. When plants are very 
small, they will generally be killed after about five 
or six days of being submerged. Death will occur 
more quickly if the weather is hot, because high 
temperatures speed up the biochemical processes 
that use oxygen and warm water has less dissolved 
oxygen. Cool weather, on the other hand, may 
allow plants to live for more than a week under 
flooded conditions. When plants reach the 6- to 8- 
leaf stage, they can tolerate a week or more of 
standing water, though total submergence may in- 
crease disease incidence, and plants will suffer from 
reduced root growth and function for some days 
after the water recedes. Tolerance to flooding gen- 
erally increases with age, but reduced root function 
due to lack of oxygen is probably more detrimental 
to yield before and during pollination than during 
rapid vegetative growth or during grainfill. 

2. Hail. The most common damage from hail is loss 
of leaf area, though stalk breakage and bruising of 
the stalk and ear can be severe. Loss charts based 
on leaf removal studies generally confirm that de- 
foliation at the time of tasseling causes the greatest 
yield loss, while loss of leaf area during the first 
month after planting or when the crop is near 
maturity generally causes little yield loss. Loss of 
leaf area in small plants usually delays their de- 
velopment, however, and plants that experience 
hail may not always grow normally afterward. 

3. Cold injury. Corn is of tropical origin and is not 



especially tolerant of cold weather. While the death 
of leaves from frost is the most obvious type of 
cold injury, leaves are damaged by temperatures 
below the low 40s, and photosynthesis can be 
reduced even if the only symptom is a slight loss 
of leaf color. The loss of leaves from frost is 
generally not serious when it happens to small 
plants, though such loss will delay plant develop- 
ment and could delay pollination to a less favorable 
(or, rarely, a more favorable) time. Frost injury 
symptoms may appear on leaves even when night 
temperatures do not fall below the mid-30s; radia- 
tive heat loss can lower leaf temperatures to several 
degrees below air temperatures on a clear, calm 
night. If frost kills leaves before physiological ma- 
turity (black layer) in the fall, sugars can usually 
continue to move from the stalk into the ear for 
some time, although yields will generally be lowered 
and harvest moisture may be high due to high 
grain moisture at the time of frost and slow drying 
rates that usually follow premature death. 

4. Drought. Through the late vegetative stage (i.e., 
the end of June in normal years), corn is fairly 
tolerant of dry soils, and mild drought during June 
may even be beneficial, because roots generally 
grow downward more strongly as surface soils dry, 
and the crop benefits from the greater amount of 
sunlight that accompanies dry weather. During the 
two weeks before and two weeks following polli- 
nation, corn is very sensitive to drought, however, 
and dry soils during this period can cause serious 
yield losses. Most of these losses are due to failure 
of pollination, and the most common cause of such 
failure is the failure of silks to emerge from the 
end of the ear. When this happens, the silks do not 
receive pollen; thus the kernels are not fertilized 
and will not develop. Drought later in grainfill has 
a less serious effect on yield, though root function 
may decrease and kernels may not fill completely. 

5. Heat. Because drought and heat usually occur to- 
gether, many people assume that high temperatures 
are a serious problem for corn. In fact, corn is a 
crop of warm regions, and temperatures less than 
100°F usually do not cause much injury // soil 
moisture is adequate. Extended periods of hot, dry 
winds can cause some tassel "blasting" and loss of 
pollen, but pollen shed usually takes place in the 
cooler hours of the morning, and conditions severe 
enough to cause this problem are unusual in Illinois. 
There is evidence that hybrids vary in their sensi- 
tivity to both heat and drought, though very tolerant 
hybrids usually give up some yield potential. As a 
result, they may not be good choices for average 
conditions. 



Estimating yields 

Making plans for storage and marketing of the corn 
crop often calls for estimating yields before the crop 



6 



is harvested. Such estimations are easier to make for 
corn than for most other crops because we can count 
fairly accurately the number of plants or ears per acre. 

Estimating corn yields is done by counting the 
number of ears per acre and the number of kernels 
per ear, then multiplying these two numbers to get an 
estimate of the number of kernels per acre. Next, 
simply divide by an average number of kernels in a 
normal bushel to get the yield in bushels per acre. 

Corn yields can be estimated after the kernel number 
is fixed — about 2 weeks after the end of pollination. 
The following steps are suggested: 

1. Walk out in the field a predetermined number of 
rows and paces: For example, go 25 rows from the 
edge of the field and 85 paces from the end of the 
field. If this pattern is not determined beforehand, 
there will be a tendency to stop where the crop 
looks better than average. Stop exactly where 
planned. 

2. Measure Vioooof an acre (Table 1.7), and count the 
number of ears (not stalks) in that distance. Do not 
count ears with only a few scattered kernels. 

3. Take three ears from the row that was counted. To 
avoid taking only good ears, take the third, sixth, 
and tenth ears in the length of row. Do not take 
ears with so few kernels that they were not included 
in the ear count. 

4. Count the number of rows of kernels and the 
number of kernels per row on each ear. Multiply 
these two numbers together for each ear, then 
average this kernel count for the three ears. 

5. Calculate yield using the following formula: 

number of ears per Vi ooo acre x 
bu/acre = average number of kernels per ear 

90 

6. To get a reliable average, repeat this process at least 
once for every 5 acres in a field. 

In the formula given, the number 90 is used based on 
the assumption that a bushel of normal-sized seed 
contains about 90,000 kernels. The zeros are dropped 
because the plant population is given in thousands 
per acre. 



Specialty types of corn 

Erratic and generally low world corn prices have 
resulted in considerable interest among producers in 
growing various specialty types of corn, either for 
export or for domestic use. This may mean higher 
profits if the supply of such types is quite small. 
Because the total demand might also be quite limited, 
however, the price advantage may disappear as more 
producers start growing a particular specialty type. It 
is therefore important to have other uses for the crop 
(for example, as livestock feed) and to grow types that 
do not yield substantially less than normal corn, in 



the event that the corn cannot be sold for its intended 
special use. 

Many specialty types are grown under contract. The 
contract buyers often specify what hybrids may or 
may not be used, and they may specify other pro- 
duction practices to be used. Some contracts also may 
include pricing information and quality specifications. 

Risks associated with growing specialty types of 
corn vary considerably. Milling companies may buy 
corn with "food-grade endosperm," requiring only that 
the grower choose hybrids from a relatively long list 
of popularly grown hybrids; the risk in this case is 
small. On the other hand, inbreds used to produce 
some hybrids are not very vigorous, and seed corn 
production with such inbreds might be very risky. 
Production contracts in such cases may shift some of 
the risk to the buyer. In any case, every grower of 
specialty types of corn should be aware of risks as- 
sociated with each type. 

White corn. Most of the white corn grown in the 
United States is used to make cornflakes, cornmeal, 
and grits. It often sells at a higher price than yellow 
com, sometimes as much as double that of yellow com. 

The cultural practices for producing white corn are 
the same as those for yellow corn except that many 
of the white hybrids are quite late in maturity when 
grown in Illinois. Choice of hybrid is therefore im- 
portant. In addition, kernels fertilized by pollen from 
yellow hybrids will be light yellow. These yellowish 
kernels are undesirable. The official standards for corn 
specify that white corn cannot contain more than 2 
percent of corn of other colors; therefore, white corn 
probably should not be planted on land that produced 
yellow com the year before. It may also be desirable to 
harvest the outside ten or twelve rows separately from 
the rest of the field. Most of the pollen from adjacent 
yellow com will be trapped in those outer rows. 

High-Iysine corn. Lysine is one of the amino acids 
essential to animal life. Livestock producers need not 
be concerned whether or not the protein that ruminant 
animals eat contains this amino acid because the 
microflora in rumen can synthesize lysine from lysine- 
deficient protein. Nonruminants cannot do this, how- 
ever, so swine, poultry, and humans must have a 
source of protein that contains sufficient lysine to meet 
their needs. 

Normal dent corn is deficient in lysine. The discov- 
ery in 1964 that the level of this essential amino acid 
is controlled genetically and can be increased by in- 
corporating a gene called opaque-2 was exciting news 
to both the corn geneticist and the animal nutritionist. 
The potential value of this discovery to the swine 
farmer was obvious when feeding trials demonstrated 
that substantially less soybean meal was required when 
high-lysine corn was fed to swine. 

Agronomic research with high-lysine corn indicates 
that it is slightly lower in yield and higher in moisture 
than its normal counterpart. Furthermore, the kernel 
is softer and more susceptible to damage. Current 



research with more sophisticated hybrids, however, 
has successfully reduced some of these differences. 

The opaque-2 gene is recessive: high-lysine com 
pollinated by normal pollen produces normal low- 
lysine grain. Although isolation from normal corn is 
not essential, regular hybrids should not be strip- 
planted in high-lysine corn nor should high-lysine 
corn be planted where the number of volunteer corn 
plants will be high. 

Popcorn. As with several of the other specialty 
types of corn, most of the popcorn produced in Illinois 
is under contract to processors. While there are several 
dozen hybrids from which to choose, the processor 
may require that a hybrid be grown for its particular 
kernel characteristics rather than for yield alone. Thus, 
income per acre should be considered because low- 
yielding hybrids may often bring a higher price. 

Cultural practices for popcorn are much like those 
for field corn. Popcorn often is attacked by stalk rot; 
therefore, excessively high plant populations should 
be avoided, and harvest should begin as soon as the 
grain is dry enough. Weed control also may be more 
difficult because of slower emergence and early growth. 
Rotary hoeing and cultivation may be useful supple- 
ments to chemical weed control. Because popcorn 
yields 30 to 40 percent less than field corn, fertilizer 
needs should generally be somewhat lower. 

Many newer popcorn hybrids are "dent sterile," 
meaning that field-corn pollen cannot fertilize popcorn 
kernels. This trait should reduce the need for isolation, 
but be sure to check with the contractor to verify this. 
Generally, it is best to avoid planting popcorn in a 
field where field com grew the previous season. 

High-oil corn. In the summer of 1896, C.G. Hopkins 
of the University of Illinois started breeding corn for 
high oil content. With the exception of 3 years during 
World War II, this research has continued. The oil 
content of the material that has been under continuous 
selection has been increased to 17.5 percent from the 
4 to 5 percent that is normal for dent com. 

Until recently, yields were disappointing for varieties 
with higher oil content than normal dent corn. Recent 
research involving new gene pools of high-oil material 
unrelated to the original Illinois High Oil indicates that 



varieties containing 7 to 8 percent oil may be produced 
with little or no sacrifice in yield. Higher-oil hybrids 
are now being marketed on a limited scale. 

Because oil is higher in energy per pound than 
starch is, a livestock ration containing high-oil com 
should have some advantage over one containing 
normal corn. Feeding trials involving high-oil com 
have generally confirmed this assumption. Interest by 
the corn-milling industry in high-oil com as a source 
of edible oil is increasing. Com oil has a high ratio of 
polyunsaturated fatty acids to saturated fatty acids. It 
is used in salad oils, margarine, and cooking oils. 

Waxy maize. Waxy maize is a type of com that 
contains 100 percent amylopectin starch instead of the 
75 percent typical for ordinary dent hybrids. Amylo- 
pectin starch is used in many food and industrial 
products. Several corn-milling companies annually 
contract for its production in the central Com Belt. 

The waxy characteristic is controlled by a recessive 
gene, which means that waxy com pollinated by pollen 
from normal com will develop into normal dent com. 
Waxy corn, like high-lysine corn, should not be planted 
in fields where dent com is likely to volunteer. The 
outside six to ten rows may also need to be segregated 
from the rest of the field to keep the amount of 
contamination from normal com at an acceptable level. 

Normal dent corn hybrids can be converted to waxy 
hybrids by the relatively straightforward method of 
backcrossing, which introduces the waxy characteristic 
but leaves most of the agronomic traits intact. There 
are, therefore, a number of good waxy hybrids on the 
market, and their yields are often comparable to those 
of normal hybrids. The time required to complete the 
backcross process, however, will usually mean that the 
introduction of a waxy type lags a few years behind 
that of its normal parent hybrid. 

High-amylose corn. In high-amylose com, the amy- 
lose starch content has been increased to more than 
50 percent. Normal com contains 25 percent amylose 
starch and 75 percent amylopectin starch. 

The amylose starch content also is controlled by a 
recessive gene; therefore, isolation of production fields 
is important, as is selecting production fields that were 
not planted in normal com the previous year. 






8 



Chapter 2. 
Soybeans 



Planting date 

Soybeans generally yield best when planted in May, 
with full-season varieties tending to yield best when 
planted in early May. Earlier varieties, however, often 
yield more when planted in late May than in early 
May. When the planting of full-season varieties is 
delayed until late May, the loss in yield is minor 
compared with the penalty for planting corn late. 
Therefore, the practice of planting soybeans after corn 
has been planted is accepted and wise. 

The loss in yield of soybeans becomes more severe 
when planting is delayed past early June. The penalty, 
however, for late-planted corn is proportionally greater, 
and the danger of wet or soft corn becomes such a 
threat that soybeans are, under most conditions, a 
better crop for late planting than corn. Table 2.1 
illustrates yield losses resulting from delayed planting 
of soybeans. 

Planting date has an effect upon the length of time 
it takes soybeans to mature. The vegetative stage 
(planting to the beginning of flowering) is 45 to 60 
days for full-season varieties planted at the normal 
time. This period is shortened as planting is delayed 
and may be only about 25 days when these varieties 
are planted in late June or early July. 

Soybeans are photoperiod responsive and the length 
of the night or dark period is the main factor that 
determines when flowering begins. Also, the vegetative 
period is influenced by temperatures — with high tem- 
peratures shortening and low temperatures lengthen- 
ing it. But the main effect remains that of the length 
of the dark period. 

As planting is delayed, the length of the flowering 
period and that of pod filling also are shortened; but 
the effect of planting time on these periods is minor 
compared with that on the vegetative period. 

As the length of the vegetative period grows shorter, 
because of delayed planting, soybean plants mature 
in fewer days (Table 2.2). 

Planting rate 

Maximum yields for May and very early June plant- 
ings of soybeans generally are provided by planting 



Table 2.1. Effect of Planting Date on Soybean Yields 



Variety 




Date of 


planting 




May 7 


May 21 


June 8 


June 19 


Urbana location 

Corsoy 

Beeson 

Calland 


.. 56 
.. 57 
.. 56 


bushels 

62 
55 
51 


per acre 

49 
52 
47 


42 
47 
40 




May 3 


May 17 


June 7 


July 1 


Carbondale location 

Corsoy 

Cutler 

Dare 


.. 27 
62 
72 


38 
46 
45 


43 
54 
37 


28 
27 
32 



Table 2.2. Effect of Planting Date on Days to Ma- 
turity, Soybeans 

Date of planting 

Variety 

May 1 June 1 June 12 

days to maturity 
Columbia, Missouri 
(6-year average) 

Hawkeye 122 104 98 

Clark 149 115 105 

May 3 May 17 June 7 July 1 

Carbondale location 

Corsoy 118 103 107 101 

Wayne 131 117 117 105 

Cutler 145 133 117 108 

Dare 159 153 138 122 



rates that result in 8 to 10 plants per foot of row at 
harvest in 40-inch rows, 6 to 8 plants in 30-inch rows, 
4 to 6 plants in 20-inch rows, or 3 to 4 plants in 10- 
inch rows. Higher populations will usually result in 
excessive lodging in all varieties except those that are 
extremely lodging resistant. With populations that are 
sufficiently low, yield may be lower because the plants 
fail to form a complete canopy, which fully utilizes 
available sunlight. Lower population densities also 
tend to branch more and pod lower, two factors that 
can lead to increased harvest losses and lower yields. 



9 



As row spacing narrows, fewer seeds per foot of 
row are needed to achieve a given rate of seeds per 
acre (Table 2.3). Remember that the plant population 
achieved is always less than the seeding rate used. 
Some seeds simply are not viable, while others fail to 
establish a plant because of disease, excessive planting 
depth, or other problems. 

Seeding-rate studies have demonstrated the pro- 
ductive capacity of soybeans at rather low plant dens- 
ities. At extremely low plant densities, a considerable 
amount of the production may not be harvestable with 
a conventional combine because of low podding and 
excessive branching on the plant. Precipitation during 
vegetative development will help determine what the 
"ideal" plant density is for a given year. In a dry year, 
when vegetative development of plants is restricted, 
thicker stands of soybeans are desirable so that the 
smaller plants can develop a full crop canopy. In a 
year with considerable rain during May and June, 
which causes plants to grow taller and can lead to 
lodging by the crop, somewhat lower plant densities 
are better to avoid excessive lodging. At the time of 
planting, however, you cannot predict precipitation 
during vegetative growth, so a compromise in seeding 
rate offers the most potential. 

Seeding-rate trials conducted on numerous varieties 
across several years suggest that a wide range of 
seeding rates will produce good yields. Seeding rates 
of 110,000 to 150,000 seeds per acre tend to produce 
the best yields (Figure 2.1). For seed of average size, 
these rates correspond to roughly 40 to 60 pounds per 
acre. Planting at rates toward the high end of this 
range helps ensure a full stand, while planting toward 
the low end of the range helps conserve seed. Virtually 
all soybean varieties respond to changes in seeding 
rate in a similar manner. Possible exceptions are va- 
rieties with weak stems (which lodge easily) and those 
with a determinate growth habit (which have reduced 
capacity to produce vegetative growth after the onset 
of flowering). 

If seeding of soybeans is delayed until late June or 
early July, vegetative development of the plant will be 
greatly reduced. The smaller plants that develop will 
be resistant to lodging. The small stature of the plants 
limits the amount of sunlight each can intercept; to 
compensate for this effect, the seeding rate is increased. 
Increases of 50 to 100 percent over that suggested for 
May plantings are advisable. 



Table 2.3. Number of Seeds Required to Achieve 
Given Seeding Rates in Various Row 
Widths 



Desired seed rate per acre 



Row width, inches 



36 



30 



20 



15 



10 



seeds required per row-foot 



100,000 6.9 

125,000 8.6 

150,000 10.3 

175,000 12.1 

200,000 13.8 



5.7 

7.1 

8.6 

10.0 

11.4 



3.8 
4.7 
5.7 
6.7 
7.6 



2.9 
3.6 
4.3 
5.0 
5.8 



1.9 
2.4 
2.9 
3.3 
3.8 



1.3 
1.6 
2.0 
2.3 
2.6 



60 t- 



0) 

o 

(0 

Q. 
W 

(/) 

3 

o 
>■ 



30 



15 



50 80 100 110 140 150 170 200 
Seeds per acre in 1000's 

Figure 2.1. Effect of seeding rate on soybean yields. 



sufficiently when planting is deeper than recom- 
mended. Scores for emergence are usually given on a 
l-to-5 scale, with a score of 1 indicating that the 
likelihood of emergence is very good and a score of 
5 indicating that such probability is very weak. Special 
attention should be given to the planting depth of 
varieties that are known to have weaker emergence 
potentials. Because a variety has a tendency to emerge 
slowly or weakly from excessively deep planting does 
not mean it lacks the ability to produce a good crop 
when planted at a reasonable depth. It simply means 
that extra attention to depth of planting is needed to 
ensure a good stand. 



Planting depth 

Emergence will be more rapid and stands will be 
more uniform if soybeans are planted only IV2 to 2 
inches deep. Deeper planting often results in lower 
emergence and poor stands. 

Varieties differ in their ability to emerge when 
planted more than 2 inches deep. The description of 
a variety may mention an "emergence score," which 
reflects the ability of the seedhng hypocotyl to elongate 



Crop rotation 

The crop preceding soybeans has an influence on 
yield potential. If soybeans are planted after soybeans, 
diseases and other pest problems may be intensified 
in the second and later years of production. Difficult- 
to-control weed problems will become worse. In ad- 
dition, research evidence suggests that growth-inhib- 
iting substances (allelopathic chemicals) are released 



10 



from soybean residue as it decomposes in the soil. 
These substances have a negative effect on growth 
and production of soybeans. To avoid this problem, 
sufficient time must elapse between one soybean crop 
and the next to allow decomposition of the soybean 
crop residue. Planting soybeans after soybeans will 
not provide a sufficient interval. 

Several studies on the rotation benefits for soybean 
yield have been done. Table 2.4 summarizes these 
results, which indicate that higher yields tend to result 
from soybeans grown in rotation, compared to those 
from soybeans after soybeans. 



Row width 

If weeds are controlled, soybeans often will yield 
more in narrow rows than in traditional row spacings 
of at least 30 inches. The yield advantage for narrow 
rows is usually greatest for earlier-maturing varieties, 
with full-season varieties showing smaller gains in 
yield as row spacing is reduced to less than 30 inches. 
A multiyear study illustrates that average gains for 
narrow versus wider row spacings will vary from year 
to year (Table 2.5). 

The following rule of thumb predicts situations in 
which narrower row spacings will likely be advantageous 
to yield: If a full canopy of leaves is not developed over 
the ground by the time that pod development begins, 
narrower spacings for soybeans can be advantageous to 
yield. 

In addition to row spacing, factors that influence 
canopy development by the time podding begins are 
(1) relative maturity of the variety grown, (2) growing 
conditions during the vegetative period of plant de- 
velopment, and (3) planting date. Varieties that mature 
relatively early generally have the smallest canopies 
when podding begins and, consequently, can benefit 
most from narrow-row spacings. Dry or otherwise 
undesirable weather early in the season will reduce 
the amount of canopy developed before the onset of 
flowering by the soybean. When such weather patterns 
occur, rows that are more narrow help develop a full 
canopy by the time podding begins. Delays in planting 
reduce the amount of canopy that develops before 
seed formation activity of the plant begins; thus when 
planting is delayed considerably, soybeans respond to 
narrower rows with yield increases. Double-crop soy- 
beans planted after the small-grain harvest should be 
planted in rows no wider than 20 inches (Table 2.6). 

For many years, some Illinois farmers have planted 
their soybeans with a grain drill. Interest in this 
planting method has increased to the point that about 
20 percent of the soybean acres of Illinois are planted 
this way. The availability of improved herbicides has 
helped producers to expand the use of this planting 
method. If the weeds can be kept under control, the 
small-grain drill is a practical narrow-row planting 
device for soybeans. Research does not always show 
an advantage for the 7- or 8 -inch rows over 15- or 



Table 2.4. Effect of Crop Rotation on Soybean Yields 



Location 



Soybeans after 
Soybeans Com 



bushels per acre 

DeKalb 39 44 

Dixon 30 35 

Urbana 44 50 

Brownstown 30 35 



Table 2.5. 



Average Yield of 30 Soybean Lines in 
Wide- and Narrow-Row Spacings, 
1980-83 



Year 


Row 


spacings. 


inches 


Narrow-row 


30 


15 


10 


yield advantage 


1980.... 
1981.... 
1982.... 
1983.... 


. . 39.8 
.. 55.8 
.. 56.1 

. . 53.5 


41.4 


61.6 
57.9 
54.4 


4% 

10% 

3% 

2% 



Table 2.6. Yield of Double-Crop Soybeans When 
Planted in 20- and 30-Inch Rows, 1972 



Site 


Row spacings, inches 


20 30 


Dixon Springs 

Brownstown 

Urbana 


53 43 

37 32 

33 24 



20-inch spacings, but the drilled beans usually yield 
better than those planted in rows spaced at least 30 
inches apart. A key factor to successful planting with 
a grain drill is good weed control. Also, with a grain 
drill, planting depth is more difficult to control. Because 
of these possible problems, farmers trying this planting 
method are wise to do so on a small acreage first. 

For additional information about planting soybeans 
with a grain drill, see Illinois Cooperative Extension 
Service Circular 1161, Narrow-Row Soybeans: What to 
Consider 



When to replant 

Uniform full stands have been compared to those 
with irregular deficiencies of varying magnitudes to 
evaluate yield potentials of stands that are less than 
perfect (Tables 2.7 and 2.8). Studies strongly suggest 
that the soybean plant has a tremendous ability to 
compensate for missing plants. By developing more 
branches and podding more heavily, the effect of 
missing plants in the stand is often not detected in 
yields. Yield reduction that is suffered with very poor 
stands may still be more profitable to the grower than 
a replanted field, which has additional costs associated 
with replanting and a reduced yield potential because 
of a delayed seeding date. 

Data in Table 2.7 illustrate the soybean's ability to 



11 



compensate for missing plants when randomly placed 
gaps occur in the stand. The influence of plant density 
in the remaining row sections is also apparent from 
the table. For soybeans to exhibit their full capacity to 
compensate for missing plants, it is necessary to control 
weed growth in the areas without soybean plants. In 
a field situation where poor stands are realized, man- 
agement to control weeds is essential to prevent further 
yield losses due to the poor stand. The cost of main- 
taining the necessary weed control must be considered 
a cost of keeping a less-than-perfect stand. 

Growers who replant do so at a later planting date 
than is the optimum. A penalty to yield due to delayed 
planting of 2 to 3 weeks is reflected in values presented 
in Table 2.8. The plant density per foot of row achieved 
with replanting, along with possible gaps in that stand, 
will also influence yield potential. It is wise to remem- 
ber that replanted soybeans are not guaranteed to 
grow: A perfect stand is not always achieved when a 
poor stand is destroyed and the field replanted. 

At a given level of stand reduction, the impact on 
yield is minimized if the gaps are small rather than 
large in size. A gap size of 16 inches has been found 
to have no influence on yield of soybeans grown in 
30-inch row spacing, provided adjacent rows have a 
full stand. Compensation for gaps in the row has been 
found to occur not only in the row where the gap is 
located but also in the rows bordering the gap. The 
degree of compensation exhibited by soybeans should 
be enhanced as rows are spaced closer together, for 
under such planting arrangements the plants are initially 
more uniformly spaced in the field, making it more 
likely they can fully compensate for a stand deficiency 
of a given level. Extension Circular 1265, Soybean 
Replanting Considerations for Maximizing Returns, can be 
useful to growers making a replanting decision. 



Double-cropping 

See Illinois Cooperative Extension Circular 1106, 
Double-Cropping in Illinois. 



Table 2.7. Percent of Full-Yield Potential for Timely 
Planted Soybeans, as Influenced by Plants 
per Foot of Row and Percent Stand Re- 
duction 

Plants per foot of row^ 

Stand reduction 

8 6 4 

percent of full-yield potential 

(full stand) 100 97 95 

10 percent 98 96 93 

20 percent 96 93 91 

30 percent 93 90 88 

40 percent 89 86 83 

50 percent 84 81 78 

60 percent 78 75 73 

^ Plants per foot of row in row sections with no gaps or skips. 



Table 2.8. Percent of Full Yield Expected from Re- 
planting Soybeans, as Influenced by 
Plants per Foot of Row and Stand Defi- 
ciency 

Plants per foot of row^ 

Stand-deficiency level 

8 6 4 

percent of full-yield potential 

(full stand) 89 86 83 

10 percent 88 85 83 

20 percent 86 84 81 

30 percent 84 81 79 

40 percent 81 78 75 

50 percent 76 74 71 

60 percent 71 69 66 

^ Plants per foot of row in row sections with no gaps or skips. 



Table 2.9. Quality Differences in Soybeans from 
Different Sources 



Source 


Germi- 
nation, 
% 


Pure 
seed, 

% 


Inert 

matter, 

% 


Seed 

cleaned, 

% 


Seed germina- 
tion tested, 
% 


1985 survey 
Certified seed 
Bin-run seed . 

1986 survey 
Certified seed 
Bin-run seed . 


88.2 
85.9 

89.0 
87.7 


99.5 
98.1 

99.4 
98.6 


0.42 
1.19 

0.29 
1.59 


100 
51 

100 
90 




100 
14 

100 
10 



Seed source 

To ensure a good crop, you must do a good job of 
selecting seed. When evaluating seed quality, consider 
the percent germination, percent pure seed, percent 
inert matter, percent weed seed, and the presence of 
diseased and damaged seed. 

Samples of soybean seed taken from the planter 
box as farmers were planting showed that homegrown 
seed was inferior to seed from other sources (Table 
2.9). The number of seeds that germinate and the pure 
seed content of homegrown seeds were lower. Weed 
seed content, percent inert material (hulls, straw, dirt, 
and stones), and presence of other crop seeds (partic- 
ularly corn) in homegrown seed were higher. 

This evidence indicates that the Illinois farmer can 



improve soybean production potential by using higher- 
quality seed. Homegrown seed is the basic problem. 
Few producers are equipped to carefully harvest, dry, 
store, and clean seeds, and to perform laboratory tests 
that adequately assure high-quality seed. A grower 
who is not a professional seed producer and processor 
may be well advised to market the homegrown soy- 
beans and obtain high-quality seed from a reputable 
professional dealer. 

A state seed tag is attached to each legal sale from 
a seed dealer. Read the analysis and evaluate if the 
seed being purchased has the desired germination, 
purity of seed, and freedom from weeds, inert material, 
and other crop seeds. The certification tag verifies that 
an unbiased nonprofit organization (in our state, the 



12 



Illinois Crop Improvement Association) has inspected 
the production field and the processing plant. These 
inspections make certain that the seeds are of a par- 
ticular variety as named and have met certain mini- 
mum quality standards. Because some seed dealers 
may have higher quality seed than others, it always 
pays to read the tag. 



Seed size 

The issue of how the size of seed planted affects 
soybean growth and the final yield often arises fol- 
lowing a year with stress during the seed-fill period, 
which reduces final seed size. Research suggests little 
detrimental effect from planting seed that is smaller 
than normal. 

Across a broad range of seed sizes, insignificant 
effects on emergence have been reported. Seed of 
extremely small size, which normally do not make 
their way into the seed market, may be reduced in 
emergence when planted at a normal seeding depth 
of 1 to 2 inches. Interestingly, though, at excessive 
seeding depths (3 inches) the smaller seeds have been 
reported to enjoy an advantage over large ones. This 
advantage may be caused by the smaller cross-sectional 
dimension of their cotyledons, which must be dragged 
up through the soil. 

Final differences in plant size, which might result 
from planting seed of different sizes, do not suggest 
any problems with using small seed. Any differences 
reported on final plant size are so small (less than 4 
inches) that they would likely not have a significant 
effect on yield. 

The size of seed produced by soybeans is determined 
by a combination of genetic factors for the variety and 
the environment in which the seed develop. Whether 
soybeans are large or small, seed for a given variety 
has the same genetic potential. Therefore, the size of 
the seed produced on a plant established by planting 
a small seed will be expected to be the same as those 
from a plant grown from large seed. 

Effects of the seed size on final yield, which is the 
ultimate concern of growers, appears to be minimal. 
When shopping for soybean seed, seed quality should 
be a more important consideration than actual seed 
size. If smaller-than-normal seed will be used to es- 
tablish soybeans, check your planter calibration to 
meter the seed at the proper rate. Excessive seeding 
rates, resulting from misadjusted planting equipment 
metering small seed, can result in excessively thick 
stands that will be more prone to lodging. 



Varieties 

Soybean varieties are divided into maturity groups 
according to their relative time of maturity (see Tables 
2.10, 2.11, and 2.12). Varieties of Maturity Group I 
are nearly full season in northernmost Illinois but are 



too early for good growth and yield farther south. In 
extreme southern Illinois, varieties in Maturity Groups 
IV and V are best adapted. 

Traditionally, soybeans grown in the Midwest had 
indeterminate growth habits; that is, vegetative growth 
continues beyond the time when flowering begins, 
continuing generally until seed filling begins. In recent 
years, a few varieties with determinate growth habits 
have been developed and released in the Midwest. 
The main reason for their introduction was to provide 
varieties that are highly resistant to lodging, which 
would be most useful in environments where lodging 
is a yield-limiting factor. The determinate growth habit, 
which is a genetically controlled trait, stops vegetative 
growth on the main stem when flowering begins; this 
produces a relatively short plant that is quite resistant 
to lodging. With this growth pattern, determinate 
soybeans must develop adequate leaf material before 
flowering. 

While determinate varieties can be very productive 
in a favorable environment, they can also disappoint 
growers when production is attempted in a low-yield 
environment. Determinate varieties will be most useful 
and profitable to growers in environments where con- 
ditions favor rapid early-season vegetative growth, the 
same conditions that can possibly lead to lodging 
problems with indeterminate varieties. Lacking such 
an environment for soybean production, growers would 
be wise to use only indeterminate varieties. 

The following is a list of public varieties of soybeans 
that are available in Illinois. If a variety is determinate, 
the description so notes — all others are indeterminate. 
Varietal names marked with an asterisk (*) are protected 
varieties. (See the section entitled "Plant Variety Pro- 
tection Act" in Chapter 8.) 

Maturity Group I 

BSR 101 has more genetic resistance to brown stem 
rot than does any other public variety in its maturity 
group. In addition, it has resistance to Phytophthora 
root rot, race 1. BSR 101 has more lodging resistance 
and better yield potential than Hardin, which has 
similar maturity. 

Bell* has a late Group 1 maturity which offers good 
yield potential along with resistance to races 3 and 4 
of the cyst nematode. It does not have resistance to 
Phytophthora. 

Maturity Group II 

BSR 201 has resistance to brown stem rot, which 
makes it particularly useful in fields infested with that 
disease. In the absence of brown stem rot, BSR 201 is 
quite competitive in yield with the Century 84 and 
Corsoy 79 varieties. Resistance to races 1 and 2 of 
Phytophthora root rot and fair resistance to lodging 
are characteristics of BSR 201. 

Burlison* has quite good yield potential for north- 
ern and central Illinois producers. It carries multiple 



13 



Table 2.10. Morphologic Characteristics of Soybean Varieties 

Maturity group Flower Pubescence 

and variety color color 

I 

Bell purple tawny 

BSR 101 purple gray 

II 

BSR 201 white gray 

Burlison white tawny 

Century 84 purple tawny 

Conrad purple tawny 

Corsoy 79 purple gray 

Elgin 87 purple tawny 

Gnome 85 purple tawny 

Hack white gray 

Jack white gray 

Kenwood purple tawny 

Preston purple gray 

III 

Cartter white tawny 

Chamberlain purple tawny 

Fayette white tawny 

Harper 87 purple tawny 

Hobbit 87 white tawny 

Linford white tawny 

Pella 86 purple tawny 

Resnik purple tawny 

Sherman white gray 

Williams 82 white tawny 

IV 

Egyptian white tawny 

Flyer purple tawny 

Hamilton white gray 

Pennyrile white tawny 

Pharaoh purple tawny 

Pyramid purple gray 

Ripley purple gray 

Union white tawny 

V 

Essex purple gray 

^ Imperfect black hilum. 



Pod 
color 



Seed 
luster 



Hilum 
color 



tan 


shiny 


black 


tan 


intermediate 


imblk^ 


brown 


dull 


buff 


tan 


dull 


black 


brown 


shiny 


black 


tan 


dull 


brown 


brown 


dull 


yellow 

black 

black 

buff 

yellow 

black 


brown 
tan 
tan 
brown 


shiny 
shiny 
shiny 
dull 


brown 


dull 


brown 


intermediate 


gray 


tan 

brown 

tan 

brown 

tan 

tan 

tan 


shiny 
shiny 
shiny 
shiny 
shiny 
shiny 
dull 


black 
black 
black 
black 
black 
black 
black 


tan 


dull 


black 


brown 
tan 


shiny 
shiny 


buff 
black 


tawny 
tan 


shiny 
dull 


black 
black 


brown 
tan 


shiny 
dull 


buff 
black 


tan 
tan 


shiny 
shiny 


brown 
imblk^ 


tan 


intermediate 


buff 


tan 


shiny 


black 


tan 


intermediate 


buff 



race resistance to Phytophthora root rot, but is very 
sensitive to metribuzin herbicide. Maturity is toward 
the late side of Group II varieties. 

Century 84* is an improved version of Century. 
Century 84 has multirace resistance to Phytophthora 
(races 1 to 10 and 13 to 15), good lodging resistance, 
and high yield potential. Maturity and plant size are 
like that of Century, which it replaces. 

Conrad* has early Group II maturity which offers 
improved yield potential if Phytophthora and brown 
stem rot are not a problem. Because of susceptibility 
to these disease problems, growers should consider 
likely disease problems. 

Corsoy 79 is an improved version of Corsoy, similar 
to the original, with strong emergence and early Group 
II maturity. Like the original Corsoy, the Corsoy 79 
has poor lodging resistance. Unlike the older Corsoy, 
however, it has resistance to seven races of Phytoph- 
thora root rot. 

Elgin 87, an improved version of the previously 
released Elgin, was developed by backcrossing with 
Williams 82. It has an early Group II maturity and 
resists lodging. It is resistant to the same races of 
Phytophthora root rot as Williams 82. 

Gnome 85* is an improved version of Gnome, a 



previously released short-statured variety of determi- 
nate growth habit. It has the same yield potential and 
lodging resistance as did Gnome. Resistance to Phy- 
tophthora, however, is the same as for Williams 82. 

Hack* has high yield potential and lodging resist- 
ance superior to other varieties of similar maturity. It 
has resistance to Phytophthora root rot, races 1 and 
2, and to bacterial pustule. 

Jack* will provide resistance to races 3 and 4 of 
the cyst nematode with good yield potential in areas 
where a late Group II variety is adapted. It has 
moderate resistance to lodging and is susceptible to 
Phytophthora and brown stem rot disease. 

Kenwood* is an early Group II with good yield 
potential and lodging resistance. It lacks resistance to 
Phytophthora and brown stem rot, however 

Preston has higher yield potential than other public 
varieties of similar maturity. Maturity is very similar 
to Century and Century 84. Preston is susceptible to 
both Phytophthora root rot and brown stem rot. 

Maturity Group III 

Cartter has a relatively early Group III maturity 
that offers growers resistance to cyst nematode races 



14 



Table 2.11. Reactions of Soybean Varieties to 
Phytophthora Root Rot Disease 



Maturity 
group 



Susceptible to 

Phytophthora 

root rot 



Resistant to 
races 1 and 2 



Resistant to 
races 1, 2, 
and others 



I 


Bell 


BSR 101 




II 


Conrad 


BSR 201 


Burlison 




Jack 

Kenwood 

Preston 


Hack 


Century 84 
Corsoy 79 
Elgin 87 
Gnome 85 


Ill 


Cartter 


Chamberlain 


Harper 87 




Fayette 
Lin ford 




Hobbit 87 
Pella 86 




Sherman 




Resnik 
Williams 82 


IV 


Egyptian 

Hamilton 
Pennyrile 

Pyramid 


Ripley 
Union 


Flyer 


V 


Essex 







3 and 4, but it lacks resistance to Phytophthora root 
rot. It was developed from the same breeding program 
that produced Fayette. 

Chamberlain* has a mid-Group III maturity and 
resistance to brown stem rot disease. It also has re- 
sistance to bacterial pustule and races 1 and 2 of 
Phytophthora root rot. It has good resistance to lodg- 
ing and has good yield potential. 

Fayette is most useful to growers needing resistance 
to soybean cyst nematode, races 3 and 4. It matures 
about the same time as Williams 82. Fayette is sus- 
ceptible to Phytophthora root rot and is moderately 
resistant to lodging. In the absence of cyst nematode 
problems, growers should not use Fayette, for other 
varieties of similar maturity yield better. 

Harper 87 was developed by backcrossing Harper 
with Williams 82 to incorporate into the variety the 
resistance to Phytophthora root rot. Harper 87 has a 
maturity and agronomic character essentially the same 
as the earlier released Harper variety. 

Hobbit 87* is an improved version of Hobbit. 
Resistance to Phytophthora equal to that found in 
Williams 82 is the notable improvement in this variety. 
Determinate growth, short stature, lodging resistance, 
and good yield potential of the original Hobbit are 
found in Hobbit 87. 

Linford maturity is toward the late side of Group 
III varieties. It offers resistance to races 3 and 4 of cyst 
nematode, good lodging resistance and good yield 
potential. It lacks resistance to Phytophthora and brown 
stem rot, however. 

Pella 86 is an improved version of Pella. It is a 
relatively early Group III variety with good lodging 
resistance and other characteristics of Pella. The im- 
provement in Pella 86 is in Phytophthora resistance, 
which is equal to that of Williams 82. 

Resnik* is a mid-Group III variety, with good yield 



Table 2.12. Soybean Variety Characteristics, 1990 

„,^,"y\^ J Protected Relative , ^ , . tt„;„ui. Soybean cyst 

fane?y ^^"^'^^ maturity^ ^odgmg Height ^^^^todl' 

days score^ inches race 3 race 4 
I 

Bell Yes -15 2.0 32 R R 

BSR 101 No -12 1.9 35 S S 

II 

BSR 201 No -8 2.5 34 S S 

Burlison Yes -7 1.7 33 S S 

Century 84 Yes -9 1.7 37 S S 

Conrad Yes -12 1.7 34 S S 

Elgin 87 Yes -12 2.3 33 S S 

Hack Yes -9 1.3 32 S S 

Jack Yes -3 2.4 42 R R 

Kenwood Yes -11 2.1 36 S S 

Preston No -8 2.0 36 S S 

III 

Cartter No -4 2.0 33 R R 

Chamberlain.... Yes -1 2.0 35 S S 

Fayette No +3 2.2 33 R R 

Harper 87 Yes 9/26 1.6 32 S S 

Hobbit 87 Yes -1 1.0 20 S S 

Linford No +3 2.1 35 R R 

Pella 86 No -2 1.4 32 S S 

Resnik Yes -2 1.6 31 S S 

Sherman Yes -2 2.2 32 S S 

Williams 82 No +3 1.7 34 S S 

IV 

Flyer Yes +4 1.5 32 S S 

Hamilton Yes +3 1.7 31 S S 

Pennyrile No +13 1.6 33 S S 

Pharaoh Yes +16 1.7 30 R S 

Pyramid No +9 1.9 34 R R 

Ripley Yes +8 1.2 23 S S 

Union No +6 2.0 38 S S 

' U.S. Protected Variety; see the chapter entitled "Seed Production." 

^ Relative to Harper 87. 

■^ R = resistant, S = susceptible. 

'' 1 = all plants standing; 5 = all plants flat. 



potential, lodging resistance, and Phytophthora resist- 
ance equal to that of Williams 82. 

Sherman offers growers an improved yield potential 
in a variety that matures 2 or 3 days later than Pella. 
Although Sherman does not have genetic resistance 
to Phytophthora root rot, it offers yield advantages in 
environments where that disease is not a problem. 

Sprite has determinate growth, making it a short- 
statured and very lodging-resistant variety. It lacks 
resistance to Phytophthora root rot and matures early 
in Group III. 

Williams 82 is an improved version of the Williams 
variety, which was released in the 1970s. It has a late 
Group III maturity. The Williams 82 has a broad base 
of resistance to Phytophthora root rot (races 1 to 10, 
13 to 15, 17, 18, 21, and 22), allowing it to produce 
well across a wide range of root-rot infested fields. 
Plant size and yield potential are the same as in the 
original Williams variety. 

Maturity Group IV 

Egyptian is resistant to races 3 and 4 of soybean 
cyst nematode. It has determinate growth but, because 
of the time it takes to reach maturity, will not be very 



15 



short statured. Maturity is about 2 weeks after the 
Union variety. 

Flyer* offers producers excellent resistance to 
Phytophthora in a relatively early Group IV maturity. 
Resistance to lodging is quite good. Producers using 
Union may find Flyer better yielding. 

Hamilton* is an early Group IV with maturity equal 
to Union. It resists lodging better than Union and has 
higher yield potential, but lacks resistance to Phytoph- 
thora 

Pennyrile has a late Group IV maturity and very 
good resistance to lodging. It does not offer protection 
against cyst nematode or Phytophthora but has im- 
proved yield potential in the Group IV maturity range. 

Pharaoh* is a fairly late Group IV with resistance 
to race 3 of cyst nematode. If race 4 of soybean cyst 
nematode is a production problem, this variety may 
not be a good choice. Yield potential in its maturity 
range appears very good. 

Pyramid matures about 10 days after Union. Al- 
though susceptible to Phytophthora root rot. Pyramid 
is resistant to soybean cyst nematode, races 3 and 4. 

Ripley* has determinate growth and a relative 
maturity similar to that of Union and Pixie (early 
Group IV). Short plant stature makes Ripley very 
resistant to lodging. Although not resistant to Phytoph- 
thora root rot, Ripley is reported to carry a high level 
of field tolerance to the disease. 

Union has resistance to Phytophthora, downy mil- 
dew, and bacterial pustule. Maturity is early in the 
Group IV maturity range. Lodging of Union has been 



a problem in environments that favor abundant veg- 
etative development. 

Maturity Group V 

Essex has relatively early Group V maturity and is 
susceptible to soybean cyst nematode. It is resistant, 
however, to bacterial pustule, downy mildew, and 
frogeye leaf spot and has field tolerance to Phytoph- 
thora root rot. It has very good resistance to lodging. 

Private varieties and blends 

Approximately 750 varieties, blends, and brands of 
soybeans are available to Illinois growers. Each year 
the University of Illinois conducts the Commercial 
Soybean Performance Trials at numerous locations in 
the state. Each year a report on results of the soybean 
trials is published and is available from county Exten- 
sion offices. In addition to yield, maturity, lodging 
resistance, height, and shatter resistance are provided 
in the report. 

Blends (mixtures) of two or more varieties are some- 
times marketed for planting. Usually these are iden- 
tified by a brand name, such as "John Doe 200 Brand." 
Although most blends are composed of the same 
varieties in the same proportions each year, neither 
the Illinois Seed Law nor the Federal Seed Law requires 
this consistency; therefore, performance of blends may 
vary from year to year because of variation in com- 
ponents from which they are made. 



i 



the I 



16 



Chapter 3. 
Small Grains 



Winter wheat 

Although both soft red and hard red winter wheat 
can be grown in Illinois, improved soft wheat varieties 
are widely adapted in the state; nearly all of Illinois 
wheat is the soft type. The primary reasons for this 
are the better yields of soft wheat and the sometimes 
poor quality of hard wheat produced in our w.arm and 
humid climate. It may be difficult to find a market for 
hard wheat in many parts of the state; therefore, it is 
advisable to line up a market before planting the crop. 

Date of seeding 

The Hessian-fly-safe dates for each county in Illinois 
are given in Table 3.1. Wheat planted on or after the 
fly-safe date is much less likely to be damaged by the 
insect than wheat planted earlier. Wheat planted on 
or after the fly-safe date also will be less severely 
damaged in the fall by diseases such as Septoria leaf 
spot, which is favored by the excessive fall growth 
usually associated with early planting. Because the 
aphids that carry the barley yellow dwarf (BYD) virus 
and the mites that carry the wheat streak mosaic virus 
are killed by freezing temperatures, the effects of these 
viruses will be less severe if wheat is planted shortly 
before the first killing freeze. Finally, wheat planted 
on or after the fly-safe date will probably sutfer less 
from soil-borne mosaic; most varieties of soft red 
winter wheat carry good resistance but may show 
symptoms if severely infested. 

Rate of seeding 

While seeding rate recommendations for wheat have 
usually been expressed as pounds of seed per acre, 
differences in seed size can mean that the number of 
seeds per acre or per square foot may not be very 
precisely specified. Recent research in Illinois has meas- 
ured yield in response to varying the number of seeds 
per square foot. Results are given in Table 3.2. 

The results in Table 3.2 indicate that seed rates 
within this range affect yield very little, though in 
northern Illinois, where there was some cold injury in 
the spring, the extra plants gave a slight yield advan- 



tage. On average, though, it appears that about 30 
seeds per square foot is adequate for top yields. 

Seed size in wheat varies by variety and by weather 
during seed production but is usually in the range of 
13,000 to 17,000 seeds per pound. At 15,000 seeds 
per pound, a seeding rate of IV2 bushels per acre 
provides about 31 seeds per square foot. A stand of 
25 to 30 plants per square foot is generally considered 
the optimum, and a minimum of 15 to 20 plants per 
square foot is needed to justify keeping a field in the 
spring. 

Seed treatment 

Treating wheat seeds with the proper fungicide or 
mixture of fungicides is a cheap way to help ensure 
improved stands and better seed quality. Under con- 
ditions that favor the development of seedling diseases, 
the yield from treated seed usually will be 3 to 5 
bushels higher than that from untreated seed. 

The Department of Plant Pathology suggests that 
carboxin (Vitavax) or a combination of carboxin with 
captan, maneb, or thiram be used to treat wheat seed. 
Vitavax controls loose smut in wheat and barley and 
should be used if this disease was present in the field 
where the seed was produced. Because Vitavax is not 
effective on some other seed-borne diseases that cause 
seedling blight (such as Septoria), another fungicide 
should be used along with Vitavax. Should you desire 
additional information about wheat diseases or seed 
treatment methods and materials, contact the Univer- 
sity of Illinois Department of Plant Pathology or your 
county Extension adviser. 

Seedbed preparation 

Wheat requires good seed-soil contact and moderate 
soil moisture for germination and emergence. Gener- 
ally, one or two trips with a disk harrow or field 
cultivator will produce an adequate seedbed if the soil 
is not too wet. It is better to wait until the soil dries 
adequately before preparing it for wheat, even if 
planting is delayed. 

No-till drills may be used for wheat, but the soil 
must be reasonably dry. Do not reduce seeding rates 



17 



Table 3.1. Best Date for Seeding Wheat 



County 



Average date of 
seeding wheat 
for highest yield 



County 



Average date of 
seeding wheat 
for highest yield 



County 



Average date of 
seeding wheat 
for highest yield 



County 



Average date of 
seeding wheat 
for highest yield 



Adams 


Sept. 30-Oct 3 


Ford 


Sept. 23-29 


Livingston 


Sept. 23-25 


Randolph 


Alexander 


Oct. 12 


Franklin 


Oct. 10-12 


Logan 


Sept. 29-Oct. 3 


Richland 


Bond 


Oct. 7-9 


Fulton 


Sept. 27-30 


Macon 


Oct. 1-3 


Rock Island 


Boone 


Sept. 17-19 


Gallatin 


Oct. 11-12 


Macoupin 


Oct. 4-7 


St. Clair 


Brown 


Sept. 30-Oct. 2 


Greene 


Oct. 4-7 


Madison 


Oct. 7-9 


Saline 


Bureau 


Sept. 21-24 


Grundy 


Sept. 22-24 


Marion 


Oct. 8-10 


Sangamon 


Calhoun 


Oct. 4-8 


Hamilton 


Oct. 10-11 


Marshall- 




Schuyler 


Carroll 


Sept. 19-21 


Hancock 


Sept. 27-30 


Putnam 


Sept. 23-26 


Scott 


Cass 


Sept. 30-Oct. 2 


Hardin 


Oct. 11-12 


Mason 


Sept. 29-Oct. 1 


Shelby 


Champaign 


Sept. 29-Oct. 2 


Henderson 


Sept. 23-28 


Massac 


Oct. 11-12 


Stark 


Christian 


Oct. 2-4 


Henry 


Sept. 21-23 


McDonough 


Sept. 29-Oct. 1 


Stephenson 


Clark 


Oct. 4-6 


Iroquois 


Sept. 24-29 


McHenry 


Sept. 17-20 


Tazewell 


Clay 


Oct. 7-10 


Jackson 


Oct. 11-12 


McLean 


Sept. 27-Oct. 1 


Union 


Clinton 


Oct. 8-10 


Jasper 
Jefferson 


Oct. 6-8 


Menard 


Sept. 30-Oct. 2 


Vermilion 


Coles 


Oct. 3-5 


Oct. 9-11 


Mercer 


Sept. 22-25 


Wabash 


Cook 


Sept. 19-22 


Jersey 


Oct. 6-8 


Monroe 


Oct. 9-11 


Warren 


Crawford 


Oct. 6-8 


Jo Daviess 


Sept. 17-20 


Montgomery 


Oct. 4-7 


Washington 


Cumberland 


Oct. 4-5 


Johnson 


Oct. 10-12 


Morgan 
Moultrie 


Oct. 2-4 


Wayne 


DeKalb 


Sept. 19-21 


Kane 


Sept. 19-21 


Oct. 2-4 


White 


DeWitt 


Sept. 29-Oct. 1 


Kankakee 


Sept. 22-25 


Ogle 


Sept. 19-21 


Whiteside 


Douglas 


Oct. 2-3 


Kendall 


Sept. 20-22 


Peoria 


Sept. 23-28 


Will 


DuPage 


Sept. 19-21 


Knox 


Sept. 23-27 


Perry 


Oct. 10-11 


Williamson 


Edgar 


Oct. 2-4 


Lake 


Sept. 17-20 


Piatt 


Sept. 29-Oct. 2 


Winnebago 
Woodford 


Edwards 


Oct. 9-10 


LaSalle 


Sept. 19-24 


Pike 


Oct. 2-4 


Effingham 


Oct. 5-8 


Lawrence 


Oct. 8-10 


Pope 
Pu aski 


Oct. 11-12 




Fayette 


Oct. 4-8 


Lee 


Sept. 19-21 


Oct. 11-12 





Oct. 9-11 
Oct. 8-10 
Sept. 20-22 
Oct. 9-11 
Oct. 11-12 
Oct. 1-5 
Sept. 29-Oct. 1 
Oct. 2-4 
Oct. 3-5 
Sept. 23-25 
Sept. 17-20 
Sept. 27-Oct. 1 
Oct. 11-12 
Sept. 28-Oct. 2 
Oct. 9-11 
Sept. 23-27 
Oct. 9-11 
Oct. 9-11 
Oct. 9-11 
Sept. 20-22 
Sept. 21-24 
Oct. 11-12 
Sept. 17-20 
Sept. 26-28 



Table 3.2. Effect of Seed Rate on Wheat Yield 



Seeds per 
square foot 


Southern Northern 
Illinois^ Illinois^ 






24 

36 

48 


77.2 71.8 

77.6 74.0 

77.8 75.9 



^ Average of 4 trials conducted at Belleville and Brownstown. 
*" Average of 4 trials conducted at Urbana and DeKalb. 



Row spacing 

Research on row spacing generally shows little 
advantage for planting wheat in rows that are more 
narrow than 7 or 8 inches. Yield is usually reduced 
by wider rows, with a reduction of about 1 to 2 bushels 
in 10-inch rows. Wisconsin data show greater yield 
reductions in 10-inch rows, probably due to slower 
early growth than is common in Illinois. 



for no-till. Fertilizer materials may be placed on the 
surface; the drilling action will incorporate them ad- 
equately for wheat. 

Depth of seeding 

Wheat should not be planted more than 1 to 2 
inches deep. Deeper planting may result in poor emer- 
gence, particularly with semidwarf varieties because 
coleoptile length is positively correlated with plant 
height. Drilling is the best way to ensure proper depth 
of placement. 

Though a drill is best for placing seed at the right 
depth, a number of growers use a fertilizer spreader 
to seed wheat. This practice is somewhat risky but 
often works well, especially if rain falls after planting. 
The air-flow fertilizer spreaders will usually give a 
better distribution than the spinner type. If seed is 
broadcast, the seeding rate should be increased to 2 
to 3 bushels per acre to compensate for uneven place- 
ment. After broadcast seeding, the field may be rolled 
with a cultipacker or cultimulcher (with the tines set 
shallow), or it may be tilled very lightly with a disk 
or tine harrow to improve seed-soil contact. 



Varieties 

The genetic improvement of wheat has continued 
with the involvement of both the private sector and 
public institutions. As a result, there are now some 50 
varieties sold in Illinois, with over half of this number 
provided by private companies. 

Both public and private varieties are tested at six 
locations in Illinois each year, and the results are 
assembled in a report titled Wheat Performance in Illinois 
Trials. This report also contains descriptions of vari- 
eties, including both agronomic characteristics and 
resistance to diseases. Copies of this report are available 
in county Extension offices by mid-August, thus al- 
lowing the use of this information before planting. 

Intensive management 

Close examination of the methods used to produce 
very high wheat yields in Europe has increased interest 
in application of similar "intensive" management prac- 
tices in the United States. Such practices generally 
include narrow row spacing (4 to 5 inches); high 
seeding rates (3 to 4 bushels per acre); high nitrogen 
rates, split into three or more applications; and heavy 



18 



use of foliar fungicides for disease control and plant 
growth regulators to reduce height and lodging. 

From research conducted in Illinois, it has become 
apparent that responses to these inputs are much less 
predictable in Illinois than in Europe, primarily because 
of the very different climatic conditions. Following is 
1 a summary of research findings to date: 

1. Research in Indiana and other states shows that 
the response to rows narrower than 7 or 8 inches 
is quite erratic, with little evidence to suggest that 
the narrow rows will pay added equipment costs. 

2. Seeding rates of around IV2 bushels per acre (30 
to 35 seeds per square foot) generally produce 
maximum yields (Table 3.2). 

3. Increasing nitrogen rates beyond the recommended 
rates of 50 to 110 pounds per acre has not increased 
yields. Splitting the spring nitrogen into two or 
more applications has not increased yields. 

4. Although foliar fungicides are useful if diseases are 
found, routine use has resulted in yield increases 
of only 3 to 5 bushels per acre (Table 3.3) and is 
probably not economically justified. 

5. The response to the plant growth regulator Cerone, 
which is labeled for use on wheat, has not been 
consistent. While there has been an occasional yield 
increase from the use of this chemical, especially 
where the yield levels were above 80 bushels per 
acre, the results from a number of Illinois trials 
show no average yield increase (Table 3.3). Where 
yields are poor due to soil and weather problems, 
the use of Cerone can result in further yield de- 
creases and should not be considered. The use of 
this chemical where high yields are expected, and 
where lodging is likely to be a problem, may be 
justified. 
In summary, although more experiments will be 

needed to optimize production practices in winter 
wheat in Illinois, the management recommendations 
in this section appear to be fairly well matched to the 
soils and climate of Illinois. 



Spring wheat 

Spring wheat is not well adapted to Illinois. Because 
it matures more than 2 weeks later than winter wheat, 
it is in the process of filling kernels during the hot 



Table 3.3. Response of Caldwell Wheat to Cerone 
Growth Regulator and Tilt Fungicide 

T-,„, ».„„„» Southern Northern 

^'^^'"'^"* Illinois^ Illinois" 

bushels per acre 

-Cerone 55.6 69.0 

+Cerone 55.1 69.3 

-Tilt 55.2 64.3 

+Tilt 57.7 69.5 

* Average of 7 Cerone trials and 4 Tilt trials at Brownstown and Belleville. 
^ Average of 8 Cerone trials and 4 Tilt trials at Urbana and DeKalb. 



weather typical of late June and the first half of July. 
Consequently, yields average only about 50 to 60 
percent of those of winter wheat. 

With the exception of planting time, production 
practices for spring wheat are similar to those for 
winter wheat. Because of the lower yield potential, 
nitrogen rates should be 20 to 30 pounds less than 
that for winter wheat. Spring wheat should be planted 
in early spring, as soon as a seedbed can be prepared. 
If planting is delayed beyond April 10, yields are likely 
to be very low, and another crop should be considered. 

The acreage of spring wheat in Illinois is extremely 
small, and variety testing has not been extensive. Using 
information from limited testing in Illinois and from 
other states, the following varieties may be considered 
for use in Illinois. Those marked with an asterisk are 
protected varieties. 

Era (Minnesota, 1970) is a bearded, midseason-to- 
late-season semidwarf with good lodging resistance. 
It is resistant to stem and leaf rust and is tolerant to 
Septoria, bunt, loose smut, and ergot. Test weight is 
high. 

Marshall* (Minnesota, 1982) is a bearded, semi- 
dwarf variety with good standability. It is midseason 
in maturity and has good resistance to stem and leaf 
rust and to loose smut. 

Olaf (North Dakota, 1973) is a bearded, midseason 
semidwarf variety with resistance to stem rust, but 
moderate susceptibility to a number of other diseases. 
Standability is fair to good. 

Wheaton* (Minnesota, 1983) is a bearded, midsea- 
son semidwarf with fair standabihty. Resistance to 
stem and leaf rust is good. 



Rye 

Both winter and spring varieties of rye are available, 
but only the winter type is suitable for use in Illinois. 
Winter rye is often used as a cover crop to prevent 
wind erosion of sandy soils. The crop is very winter- 
hardy, grows late into the fall, and is quite tolerant to 
drought. Rye generally matures 1 or 2 weeks before 
wheat. The major drawbacks to raising rye are the 
low yield potential and the very limited market for 
the crop. It is less desirable than other small grains as 
a feed grain. 

The cultural practices for rye are the same as for 
wheat. Planting can be somewhat earlier, and the 
nitrogen rate should be 20 to 30 pounds less than that 
for wheat because of lower yield potential. Watch for 
shattering as grain nears maturity. Watch also for the 
ergot fungus, which replaces grains in the head and 
is poisonous to livestock. 

There has been very little development of varieties 
specifically for the Corn Belt area, and no yield testing 
has been done recently in Illinois. Much of the rye 
seed available in Illinois is simply called common rye; 
some of this probably descended from Balbo, a variety 
released in 1933 and widely grown many years ago 
in Illinois. More recently developed varieties that may 



19 



do reasonably well in Illinois include Hancock, released 
by Wisconsin in 1979, and Rymin, released by Min- 
nesota in 1973. 



Triticale 

Triticale is a crop that resulted from the crossing of 
wheat and rye in the 1800s. The varieties currently 
available are not well adapted to Illinois and are usually 
deficient in some characteristic such as winterhardi- 
ness, seed set, or seed quality. In addition, they are of 
feed quality only. They do not possess the milling and 
baking qualities needed for use in human food. 

The potential exists, however, for plant breeders to 
correct these deficiencies. When this is done, the crop 
may be valuable for its high protein content and quality. 

Cultural practices for triticale are much the same 
as those for wheat and rye. The crop should be planted 
on time to help winter survival. As with rye, the 
nitrogen rate should be reduced to reflect the lower 
yield potential. With essentially no commercial market 
for this crop, growers should make certain they have 
a use for the crop before it is grown. Generally when 
triticale is fed to livestock, it must be blended with 
other feed grains. 

A limited testing program at Urbana indicates that 
the crop is generally lower yielding than winter wheat 
and spring oats. Both spring and winter types of 
triticale are available, but only the winter type is 
suitable for Illinois. Caution must be used in selecting 
a variety because most winter varieties available are 
adapted to the South and may not be winter-hardy 
in Illinois. Yields of breeding lines tested at Urbana 
have generally ranged from 30 to 70 bushels per acre. 



Spring oats 

To obtain high yields of spring oats, plant the crop 
as soon as you can prepare a seedbed. Yield reductions 
become quite severe if planting is delayed beyond 
April 1 in central Illinois and beyond April 15 in 
northern Illinois. After May 1, another crop should be 
considered, unless the oats are being used as a com- 
panion crop for forage crop establishment, and yield 
of the oats is not important. 

If you are planting oats after corn, you will probably 
want to disk the stalks; plowing will produce the 
highest yields but is usually impractical. If you are 
planting oats after soybeans, disking is usually the 
only preparation you will need, and it may be unnec- 
essary if the soybean residue is evenly distributed. 
Make certain that the labels of the herbicides used on 
the previous crop allow oats to be planted; oats are 
quite sensitive to a number of common herbicides. 

Before planting, treat the seed with a fungicide or 
a combination such as captan plus Vitavax. Several 
other fungicides and combinations can be used. For 
more information, see your local Extension adviser or 
contact the Department of Plant Pathology, University 



of Illinois, Urbana, Illinois. Seed treatment protects 
the seed during the germination process from seed- 
and soil-borne fungi. 

Oats may be broadcast and disked in but will yield 
7 to 10 bushels more per acre if drilled. When drilling, 
plant at a rate of 2 to 1% bushels per acre. If the oats 
are broadcast and disked in, increase the rate by one- 
half to one bushel per acre. 

For suggestions on fertilizing oats, see the chapter 
entitled "Soil Testing and Fertility." 

Varieties 

In recent years, Illinois has been a leading state in 
the development of oat varieties. Excellent progress 
has been made in selecting varieties with high yield, 
good standability, and resistance to barley yellow dwarf 
mosaic virus (also called redleaf disease), which is the 
most serious disease of oats in Illinois. 

Table 3.4 lists the characteristics of oat varieties that 
are suitable for production in Illinois. Yields of these 
varieties in Illinois tests are given in Table 3.5. 



Winter oats 

Winter oats are not as winter-hardy as wheat and 
are adapted to only the southern third or quarter of 
the state; U.S. Highway 50 is about the northern limit 
for winter oats. Because winter oats are somewhat 
winter-tender and are not attacked by Hessian fly, 
planting in early September is highly desirable. Ex- 
perience has shown that oats planted before September 
15 are more likely to survive the winter than those 
planted after September 15. 

The same type of seedbed is needed for winter oats 
as for winter wheat. The fertility program should be 
similar to that for spring oats. Seeding rate is 2 to 3 
bushels per acre when drilled. 

Development of winter oat varieties has virtually 
stopped in the Midwest because of the frequent winter 
kill. Of the older varieties, Norline, Compact, and 
Walken are sufficiently winter-hardy to survive some 
winters in the southern third of the state. 

Norline was released by Purdue University in 1960. 
It tends to lodge more than Walken and Compact. 
Compact was released by the University of Kentucky 
in 1968. It is short and more lodging resistant than 
Norline. Walken was released by the University of 
Kentucky in 1970. It is more lodging resistant than 
Norline and Compact but grows a little taller than 
those varieties. 



Spring barley 

Spring barley is damaged by hot, dry weather, and 
therefore is adapted only to the northern part of Illinois. 
Good yields are possible, especially if the crop is 
planted in March or early April, but yields tend to be 



20 



Table 3.4. Characteristics of Spring Oat Varieties Adapted to Illinois Conditions 



Resistance'' 



Name 



State, 
year released 



Kernel 
color 



Maturity" 



Height 



Stand- 
ability 



Barley 
yellow 
dwarf 



Stem 
rust 



Smut 



Don Illinois, 1985 white short 

Hazel Illinois, 1985 grayish 4 medium 

to short 

Larry Illinois, 1981 yellow . . short 

Noble Indiana, 1974 yellow 3 medium 

Ogle Illinois, 1981 yellow 4 medium 

Otee Illinois, 1973 white 1 short 

" Days later than Larry. 

'' R = resistant; MR = moderately resistant; MS = moderately susceptible; S = susceptible; I = 



fair 

very good 

very good 
good 

very good 
good 



I 
R 

MR 
I 

R 
R 



S 
S 

s 

MS 
S 
I 



intermediate. 



Table 3.5. Yield of Spring Oats in Illinois Trials, 
1985-90 



Table 3.6. 



Performance of Spring Barley in Illinois 
Trials 



Variety DeKalb Monmouth Perry 



Urbana 



Yield Test weight 



Don 108 

Hazel 101 

Larry 102 

Noble 94 

Ogle 110 

Otee 90 



bushels per acre - 

110 100 

112 106 

110 101 

111 101 
124 118 
103 97 



108 
119 
114 
108 
123 
98 



Ib/bu 

34 
33 
. 33 
32 
32 
33 



erratic. Markets for malting barley are not established 
in Illinois, and malting quality may be a problem. 
Barley can, however, be fed to livestock. 

Plant spring barley early — about the same time as 
spring oats. Drill IVi to 2 bushels of seed per acre. To 
avoid excessive lodging, harvest the crop as soon as 
it is ripe. Fertility requirements for spring barley are 
essentially the same as for spring oats. 

Varieties 

Because spring barley is not a large crop in Illinois, 
Illinois-grown seed is usually not available. Therefore, 
farmers interested in growing spring barley will need 
to obtain seed from Wisconsin or Minnesota. All of 
the following varieties are grown in those states. Their 
yields in Illinois trials are given in Table 3.6. 

Azure (North Dakota, 1982) is a 6-row variety with 
semismooth awns and blue aleurone. It is of medium 
maturity and has good standability. 

Hazen (North Dakota, 1984) is a 6-row variety with 
medium maturity and good standability. Unlike the 
other three varieties described in this section, Hazen 
is not approved for malting. 

Morex (Minnesota, 1978) has semismooth awns, a 
colorless aleurone, and a 6-row spike. Morex is early- 
maturing and has medium standability. 

Robust (Minnesota, 1983) is a 6-row variety with 
semismooth awns and colorless aleurone. It matures 
several days later than Morex, stands better, and has 
about the same height. 



Variety 


1 


DeKalb 


1 


Urbana 


Yield 


Test wt. 


Yield 


Test wt. 


Azure 


bu/A 
61 


Ib/bu 
42 


bu/A 
62 


Ib/bu 
42 


Hazen 


69 


42 


71 


42 


Morex 


63 


43 


61 


42 


Robust 


64 


44 


61 


45 



Winter barley 

Winter barley is not as winter-hardy as the com- 
monly grown varieties of winter wheat and should be 
planted 1 to 2 weeks earlier than winter wheat. Sow 
with a drill and plant 2 bushels of seed per acre. 

The fertility requirements for winter barley are 
similar to those for winter wheat except that less 
nitrogen is required. Most winter barley varieties are 
less resistant to lodging than are winter wheat varieties. 
Winter barley cannot stand "wet feet"; therefore, it 
should not be planted on land that tends to be low 
and wet. The barley yellow dwarf virus is a serious 
threat to winter barley production. 

Varieties 

The acreage of winter barley is quite small in Illinois, 
and variety testing has not been extensive. Based on 
that limited testing, the following varieties appear to 
have the best chance of producing a good crop under 
Illinois conditions. There has been little or no certified 
seed of these varieties produced in Illinois, but the 
higher yields make it worthwhile to find seed in 
another state. 

Pennco, released in 1985 by Pennsylvania, is a high- 
yielding variety with good disease resistance and stand- 
ability. It is a few days earlier and slightly more winter- 
hardy than Wysor, and even more winter-hardy (though 
later in maturity) than Barsoy, an old variety that was 
once common in Illinois. 

Wysor, released in 1985 by Virginia, is a high- 
yielding variety with good disease resistance and win- 
terhardiness. 



21 



Chapter 4. 
Grain Sorghum 



Although grain sorghum can be grown successfully 
throughout Illinois, its greatest potential, in comparison 
with other crops, is in the southern third of the state. 
It is adapted to almost all soils, from sand to heavy 
clay. Its greatest advantage over corn is tolerance of 
moisture extremes. Grain sorghum usually yields more 
than corn when moisture is in short supply, though it 
seldom yields as much as corn under optimum con- 
ditions. Grain sorghum is also less affected by late 
planting and high temperatures during the growing 
season, but the crop is very sensitive to cool weather 
and will be killed by even light frost. 

Fertilization. The phosphorus and potassium re- 
quirements of grain sorghum are similar to those of 
com. The response to nitrogen is somewhat erratic, 
due largely to the extensive root system's efficiency in 
taking up soil nutrients. For this reason, and because 
of the lower yield potential, the maximum rate of 
nitrogen suggested is about 125 pounds per acre. For 
sorghum following a legume such as soybeans or 
clover, this rate may be reduced by 20 to 40 pounds. 

Hybrids. The criteria for selecting grain sorghum 
hybrids are very similar to those for selecting corn 
hybrids. Yield, maturity, standability, and disease re- 
sistance are all important. Consideration should also 
be given to the market class (endosperm color) and 
bird resistance, which may be associated with palat- 
ability to livestock. Performance tests of commercial 
grain sorghum hybrids are conducted at three locations 
in Southern Illinois, and results are available in county 
Extension offices in December or January. Because of 
the limited acreage of grain sorghum in the eastern 
United States, most hybrids are developed for the 
Great Plains and may not have been extensively tested 
under our conditions. 

Planting. Sorghum should not be planted until soil 
temperature is at least 65 °F. In the southern half of 
the state, mid-May is considered the starting date; late 
May to June 15 is the planting date in the northern 
half of the state. 

Sorghum emerges more slowly than corn and re- 



quires a relatively fine and firm seedbed. Planting 
depth should not exceed IV2 inches, and % to 1 inch 
is considered best. Because sorghum seedlings are slow 
to emerge, growers should use caution when using 
reduced- or no-till planting methods. Surface residue 
usually keeps the soil cooler and may harbor insects 
that can attack the crop, causing serious stand losses, 
especially when the crop is planted early in the season. 

Row spacing. Row-spacing experiments have shown 
that 20- to 30-inch rows produce far better than 40- 
inch rows. Drilling in 7- to 10-inch rows also works 
well if weeds can be controlled without cultivation. 

Plant population. Because grain sorghum seed is 
small and some planters do not handle it well, there 
is a tendency to plant based on pounds of seed per 
acre, rather than by number of seeds. This usually 
results in too-high plant populations that can cause 
lodging and yield loss. Aim for a plant stand of 50,000 
to 100,000 plants per acre, with the lower population 
on droughtier soils. Four to 6 plants per foot of row 
in 30-inch rows at harvest and 2 to 4 plants per foot 
in 20-inch rows are adequate. Plant 30 to 50 percent 
more seeds than the intended stand. Sorghum may 
also be drilled using 6 to 8 pounds of seed per acre. 

Weed control. Because emergence of sorghum is 
slow, controlling weeds presents special problems. 
Suggestions for chemical control of weeds are given 
in the back of this handbook. As with corn, a rotary 
hoe is useful before weeds become permanently es- 
tablished. 

Harvesting and storage. Timely harvest is impor- 
tant. Rainy weather after sorghum grain reaches phys- 
iological maturity may cause sprouting in the head, 
weathering (soft and mealy grain), or both. Harvest 
may begin when grain moisture is 20 percent or greater, 
if drying facilities are available. Sorghum dries very 
slowly in the field. Because sorghum does not die until 
frost, the use of a desiccant (sodium chlorate) can 
reduce the amount of green plant material going 
through the combine, making harvest easier. 



22 



Marketing. Before planting, check on local markets. graze for one week after frost because the danger of 
Because the acreage in Illinois is limited, many ele- prussic acid or hydrocyanic acid (HCN) poisoning is 
vators do not purchase grain sorghum. especially high. Newly frosted plants sometimes de- 
Grazing. After harvest, sorghum stubble may be velop tillers high in prussic acid, 
used for pasture. Livestock should not be allowed to 



23 



Chapter 5. 

Cover Crops and Cropping Systems 



Cover crops 

Rye, wheat, ryegrass, and hairy vetch are sometimes 
used as winter cover crops in the Midwest. The primary 
purpose for using cover crops is to provide plant cover 
for the soil to help reduce soil erosion during the 
winter and spring. Winter cover crops plowed under 
in the spring have been shown to reduce total water 
runoff and soil loss by 50 percent or more, although 
the actual effect on any one field will depend on soil 
type and slope, the amount of cover, the planting and 
tillage methods, and intensity of rainfall. The use of 
winter cover crops in combination with no-till corn 
may reduce soil loss by more than 90 percent. A cover 
crop can only protect the soil while it or its residue is 
present, however, and a field planted after a cover 
crop has been plowed under may lose a great deal of 
soil if there is intense rainfall after planting. Cover 
crops can also help to improve soil tilth and they can 
often contribute nitrogen to the following crop. 

The advantages of grasses such as rye that are used 
as cover crops include rapid establishment of ground 
cover in the fall, vigorous growth, effective recovery 
of residual nitrogen from the soil, and good winter 
survival. Most research has shown, however, that corn 
planted into a grass cover crop often yields less than 
when grown without a cover crop. There are several 
reasons for this. Residue from grass crops, including 
corn, has a high carbon to nitrogen ratio, so nitrogen 
from the soil is often tied up by microbes as they 
break down the residue. Secondly, a vigorously grow- 
ing grass crop such as rye can dry out the surface soil 
rapidly, thereby causing problems with stand estab- 
lishment under dry planting conditions. When the 
weather at planting is wet, heavy surface vegetation 
from a cover crop can also cause soils to stay wet and 
cool, thus reducing emergence. Finally, chemical sub- 
stances released during the breakdown of some grass 
crops have been shown to inhibit the growth of a 
following grass crop or of grass weeds. 

There are several benefits associated with the use 
of legumes as cover crops. Legumes are capable of 
nitrogen fixation; so, providing that they have enough 
time to develop this capability, they may provide some 



"free" nitrogen — fixed from the nitrogen in the air — 
to the follow crop. Most leguminous plants have a 
lower carbon to nitrogen ratio than grasses, and soil 
nitrogen will not be tied up as much when legume 
plant material breaks down. On the negative side, 
early growth by legumes may be somewhat slower 
than that of grass cover crops; many of the legumes 
too are not as winter-hardy as grasses such as rye. 
Legumes seeded after the harvest of a corn or soybean 
crop, therefore, often grow little before winter, resulting 
in low winter survivability, limited nitrogen fixation 
before spring, and ground cover that is inadequate to 
protect the soil. 

Hairy vetch has, at least in the southern Midwest, 
usually worked well as a winter cover crop. It offers 
the advantages of fairly good establishment, good fall 
growth and vigorous spring growth, especially if it is 
planted early — during the late summer. When al- 
lowed to make considerable spring growth, hairy vetch 
has provided as much as 80 to 90 pounds of nitrogen 
per acre to the corn crop that follows. One disadvan- 
tage to hairy vetch is its lack of sufficient winterhar- 
diness; severe cold without snow cover will often kill 
this crop in the northern half of Illinois, especially if 
it has not made at least 4 to 6 inches of growth in 
the fall. The 20 to 40 pound per acre seed rate, with 
seed costs ranging up to $1.00 per pound, can make 
use of this crop quite expensive; some farmers in the 
Midwest are growing their own seed to reduce this 
expense. This crop can also produce a considerable 
amount of hard seed, which may not germinate for 2 
or 3 years, at which time it may be a serious weed, 
especially in a crop such as winter wheat. Other legume 
species that may be used as winter cover crops include 
mammoth and medium red clovers, alfalfa, and ladino 
clover. 

To get the maximum benefit from a legume cover 
crop, such crops must be planted early enough to 
grow considerably before the onset of cold weather in 
the late fall. The last half of August is probably the 
best time for planting these cover crops. They can be 
aerially seeded into a standing crop of corn or soy- 
beans, although dry weather after seeding may result 
in poor stands of the legume. Some attempts have 



24 



been made to seed legumes such as hairy vetch into 
corn at the time of the last cultivation. This may work 
occasionally, but a very good corn crop will shade the 
soil surface enough to prevent growth of a crop 
underneath its canopy, and cover crops seeded in this 
way will often by injured by periods of dry weather 
during the summer. All things considered, the chances 
for successfully establishing legume cover crops are 
best when they are seeded into small grains during 
the spring or after small grain harvest, or when they 
are planted on set-aside or other idle fields. 

There is some debate as to the best management of 
cover crops before planting a field crop in the spring. 
There is usually a trade-off of benefits: planting delays 
will allow the cover crop to make more growth and 
to fix more nitrogen in the case of legume cover crops, 
but this extra growth may be more difficult to kill, and 
it will sometimes result in depletion of soil moisture. 
Most indications are that killing a grass cover crop 
several weeks before planting is preferable to killing 
it with herbicide at the time of planting. Legumes can 
also produce some of the same problems as grass cover 
crops, especially if they are allowed to grow past the 
middle of May. 

Whether or not to incorporate cover crop residue is 
also debatable, with some research showing no ad- 
vantages to incorporation and other results showing 
some benefit. Incorporation may enhance the recovery 
of nutrients such as nitrogen under some weather 
conditions; it may offer more weed control options; 
and it will help in stand establishment, both by re- 
ducing competition from the cover crop and by pro- 
viding a better seedbed. Incorporating cover crop res- 
idue, on the other hand, removes most or all of the 
soil-retaining benefit of the cover crop during the time 
between planting and crop canopy development, which 
is a period of high risk for soil erosion caused by 
rainfall. Tilling to incorporate residue can also stimulate 
the emergence of weed seedlings. One alternative to 
tillage for residue management is to have livestock 
graze off most of the top growth before planting. 



Cropping systems 

The term "cropping system" refers to the crops and 
crop sequences and to management techniques used 
on a particular field over a period of years. This term 
is not a new one, but it has been used more often in 
recent years in discussions about sustainability of our 
agricultural production systems. Several other terms 
have also been used during these discussions, and 
following is a working definition of some of these 
terms: 

• Allelopathy is the release of a chemical substance 
by one plant species that inhibits the growth of 
another crop. 

• Doublecropping is the practice, also known as se- 
quential cropping, of planting a second crop imme- 



diately following the harvest of a first crop, thus 
harvesting two crops from the same field in one year. 
This is a case of multiple cropping. 

• Intercropping is the presence of two or more crops 
in the same field at the same time, planted in an 
arrangement that results in the crops competing with 
one another. 

• Monocropping refers to the presence of a single crop 
in a field. This term is often used incorrectly to refer 
to growing the same crop year after year in the same 
field. 

• Relay intercropping is a form of intercropping in 
which one crop is planted at a different time than 
the other. An example would be dropping cover crop 
seed into a standing soybean crop. 

• Strip cropping is defined as two or more crops 
growing in the same field, but planted in strips such 
that most plant competition is within each crop, rather 
than between the two crops. This practice has ele- 
ments of both intercropping and monocropping, with 
the width of the strips determining the degree of 
each. 

Crop rotations, as a primary aspect of cropping 
systems, have received a great deal of attention in 
recent years, with many people contending that most 
current rotations are unstable and (at least indirectly) 
harmful to the environment, and are therefore not 
sustainable. During the past 50 years, the number and 
complexity of crop rotations used in Illinois have 
decreased as the number of farms producing forages 
and small grains has declined. The corn-soybean ro- 
tation (with only one year of each crop) is now by far 
the most common one in the state. Although some 
consider this crop sequence barely qualifies as a ro- 
tation, it offers several advantages to growing either 
crop continuously. These benefits include more weed 
control options and, often, fewer difficult weed prob- 
lems, less insect and disease buildups, and less nitrogen 
fertilizer use than with continuous corn. Primarily 
because of these (and other, some poorly understood) 
reasons, both corn and soybeans grown in rotation 
yield about 10 percent more than if they were grown 
continuously. Growing these two crops in rotation also 
allows for more flexibility in marketing and it offers 
some protection against weather- or pest-related prob- 
lems in either crop. 

The specific effects of a corn-soybean rotation on 
nitrogen requirements are discussed in the "Soil Testing 
and Fertility" chapter of this handbook. Figure 10.6 
provides data on the effect of the previous crop on 
corn yields and on the nitrogen requirements of the 
corn crop. These data show that, except in the case 
of alfalfa, most of the effect of the previous crop on 
corn yields could be overcome with the use of addi- 
tional nitrogen. Other studies also have shown that 
the yield differential due to crop rotation can be 
overcome partially by additional nitrogen, but the 
differential usually cannot be eliminated. 



25 



One frequent question is whether input costs can 
be reduced by using longer-term, more diverse crop 
rotations. Studies into this question have compared 
continuous corn and soybean and the corn-soybean 
rotation with rotations lasting four or five years that 
contain small grains and legumes, either as cover crops 
or as forage feed sources. Like the corn-soybean ro- 
tation, certain longer rotations can reduce pest control 
costs, while including an established forage legume 



can provide a considerable amount of nitrogen to a 
succeeding corn crop (Figure 10.6). At the same time, 
it should be noted that most of the longer-term rota- 
tions include forage crops or other crops with smaller, 
and perhaps more volatile, markets than com and 
soybeans. Lengthening rotations to include forages will 
be difficult unless the demand for livestock products 
increases. Such considerations will continue to favor 
production of crops such as corn and soybeans. 



26 



Chapter 6. 
Miscellaneous Crops 



A large number of crops that will grow in Illinois have 
not been produced commercially. A few others have 
been produced on a limited scale. This section provides 
a brief introduction to these crops. Production infor- 
mation is given for a few crops that have been tested 
and grown in the state. 



Sunflowers 

Two kinds of sunflowers are produced in Illinois, 
the oilseed sunflower and the nonoil, or confectionary, 
sunflower. The oilseed sunflower bears a relatively 
small seed with an oil content of 38 to 50 percent. 
The hull is thin and dark and adheres closely to the 
kernel. The oil is highly regarded as a salad oil and 
because of its high smoke point is unusually good for 
frying food and popping corn. The meal is used as a 
protein supplement in livestock rations; because sun- 
flower meal is deficient in lysine, however, it cannot 
be used as the only source of protein in rations for 
nonruminant animals. The protein and crude fiber 
content vary with the method of processing. The 
confectionary (nonoil) sunflower bears a larger seed 
with a lower oil content. The hull is also lighter in 
color, is usually striped, and separates easily from the 
kernel. Confectionary sunflowers are used for human 
food and bird feed. 

Planting. Sunflowers should be planted at the same 
time as corn. Because many of the hybrids offered for 
sale in Illinois reach physiological maturity (25 to 30 
percent moisture) in 90 to 100 days, they may also 
follow small grain plantings as second crops. Because 
sunflowers do not host the soybean cyst nematode, 
they are a possible substitute for soybeans as a double 
crop. 

Oilseed sunflowers should be planted at a popu- 
lation rate that will establish 20,000 to 25,000 plants 
per acre on soils with good water-holding capacity 
and 16,000 to 20,000 plants per acre on more coarsely 
textured soils with relatively low water-holding ca- 
pacity. Confectionary sunflowers should be planted at 
a lower population rate to ensure larger seed size. 



The recommended planting depth is 1 Vz to 2 inches, 
or about the same as that recommended for corn. 
Sunflowers perform best when planted in 20- to 30- 
inch rows, but planting in wider rows will also produce 
good yields. 

Harvesting. Agronomists in North Dakota recom- 
mend harvesting after seed moisture has dropped to 
18 or 20 percent. Losses are greatly reduced when 
sunflower attachments are used on the conventional 
combine head. These attachments are long panlike 
guards extending from the cutter bar. 

Problems. Because sunflowers are not commonly 
grown in Illinois, it is important to locate a market 
before planting a crop. 

Feeding by birds can become a serious problem in 
any sunflower field and is most likely to occur near 
farmsteads and wooded areas. Insects and diseases 
can also damage sunflower crops. The severity of the 
damage will increase as the acreage of sunflowers 
increases in a community and will vary from season 
to season. 



Oilseed rape (Canola) 

Rape, a member of the mustard family, is grown as 
a traditional oilseed crop in a number of other countries 
but has not been grown widely in the United States. 
Both spring and winter types exist, but the poor 
performance of this crop in hot weather suggests that 
the winter type will be most likely to succeed in 
Illinois. Most varieties of this type are presently of 
European origin. Their winterhardiness under Illinois 
conditions could be a problem. 

Unimproved varieties and landraces of rapeseed 
contain erucic acid as part of the oil and high levels 
of toxic glucosinolates in the meal. Both of these 
antinutritional factors have been reduced or eliminated 
in some varieties (double-low or double-zero varieties). 
Canadian workers designated this group of improved 
varieties as Canola. Such varieties have better com- 
mercial potential than those containing one or both of 
the antinutritional factors because both the oil and 



27 



meal from double-low varieties can be used. Rapeseed 
oil is of high quality, and the meal can be used as a 
livestock feed supplement. 

Winter rapeseed has been grown only on a limited 
scale in Illinois, and cultural practices are not well 
established. Limited experience with the crop strongly 
suggests that site selection is critical to success. Only 
fields with good drainage should be used because 
excessive moisture (ponding) will kill Canola. The crop 
is generally seeded 3 to 4 weeks before the optimum 
time to sow wheat. The seed is very small, and 5 to 
6 pounds per acre seeded shallowly with a drill or 
forage seeder should be sufficient to establish a stand. 
Fertility requirements are much the same as for winter 
wheat, except that the per-acre nitrogen rate should 
be 20 to 40 pounds higher than for wheat. The crop 
normally will be ready for harvest the same time as 
winter wheat and should be harvested in a timely and 
careful manner to avoid shatter loss. With the limited 
acreage, it is not yet known what insects and diseases 
will attack this crop in Illinois. 

A few elevators in central and southern Illinois have 
accepted Canola in recent years. Compared with corn 
and soybeans, however, there are limited marketing 
opportunities. Limited markets for the crop should be 
considered before planting. 



Buckwheat 

Buckwheat may mature in 75 to 90 days. It can be 
planted as late as July 10 to 15 in the northern part 
of the state and in late July in southern Illinois. The 
crop is sensitive to both cold and hot weather. It will 
be killed by the first frost in the fall. Yields will be 
disappointingly low if it blooms during hot weather. 

The market for buckwheat is limited unless you 
plan to use it for livestock feed. Be sure of a market 
before you plant it. 



Crambe 

Crambe, another member of the mustard family, 
was promoted and grown on a limited acreage a 
number of years ago as a source of erucic acid, which 
has a number of industrial uses. This crop is seeded 
in the early spring and does not thrive in hot weather. 
This trait has led to erratic performance, and crambe 
has failed to become an established crop. Although 
there are some improved varieties and interest in the 
crop has increased in some areas, the susceptibility of 
this crop to warm temperatures is likely to limit its 
production in Illinois. 



Jerusalem artichoke 

This relative of the sunflower has been grown, 
mostly by gardeners, for its edible tubers. In 1983, the 
crop was promoted in Illinois, and a number of pro- 
ducers planted it even though the commercial market 
for the tubers is very small. The crop proved to be 
quite sensitive to drought, and yields were low. Other 
than being grown from tubers rather than from seed, 
cultural practices for the Jerusalem artichoke are similar 
to those for the sunflower. Harvest requires a potato 
harvester, modified for the small tuber size of this 
crop. Tubers that escape harvest can establish as serious 
weeds in succeeding crops. 

Grain amaranth 

This crop, which is a type of pigweed selected for 
seed production, was a traditional crop of Central and 
South America before the Spanish Conquest. The seeds 
are usually ground into flour, which is sold mainly in 
health-food outlets. The nutritional quaUty of the seeds 
is quite good compared to that of cereal grains. While 
efforts are underway to improve this crop genetically, 
limited experience in Illinois has shown most of the 
existing varietal types to be somewhat poorly adapted 
to field-scale production; standability and seed shatter 
can be problems. At the present time, amaranth, which 
is generally produced as a row crop, has a very limited 
market. 



Other crops 

Many other crops can grow in Illinois, but markets 
for them are not established or are very small. Some 
of these crops require a considerable amount of hand 
labor, and competing with areas of the world where 
labor is very cheap will be difficult. 

Crops that remain undeveloped in Illinois include 
industrial crops such as meadowfoam and cuphea 
(specialty oil crops) and kenaf, a possible source of 
paper pulp. There are several medicinal crops such as 
belladonna and evening primrose and spice crops such 
as ginseng and sesame. A number of grain legumes 
such as mungbean, various edible dry beans, and 
lupines could also be produced, though pest problems 
could be serious if any of these were grown on a 
commercial scale. 

While there is plenty of opportunity for individuals 
or small groups of entrepreneurs to explore production 
and marketing of the crops mentioned in this section, 
it is difficult to foresee a substantial move away from 
corn, soybeans, and wheat in favor of any of these 
crops. Nutrients required in very large amounts by 
people and livestock include carbohydrates, protein, 
and oil — a good balance of these is provided by the 
crops now grown in this state. 



28 



' 



Chapter 7. 

Hay, Pasture, and Silage 



High yields 

Thick, vigorous stands of grasses and legumes are 
needed for high yields. A thick stand of grass will 
cover nearly all the ground. A thick stand of alfalfa 
is about 30 plants per square foot at the end of the 
seeding year, 10 to 15 plants per square foot the second 
year, and 5 to 7 plants per square foot for the suc- 
ceeding years. 

Vigorous stands are created and maintained by 
choosing disease- and insect-resistant varieties that 
grow and recover quickly after harvest, by following 
good seeding practices, by fertilizing adequately, by 
harvesting at the optimum time, and by protecting the 
stand from insects. 



Establishment 

Spring seeding date for hay and pasture species 
in Illinois is late March or early April — as soon as a 
seedbed can be prepared. Exceptions are seedings that 
are made in a fall-seeded, winter annual companion 
crop; for such seedings, seed hay and pasture species 
about the time of the last snow. 

Sowing hay and pasture species into spring oats in 
I the spring should be done when the oats are seeded, 
as early as a seedbed can be prepared. 

Spring seedings are more successful in the northern 
half of Illinois than in the southern half. The frequency 
iof success in the southern one-quarter to one-third of 
I the state indicates that late-summer seedings may be 
more desirable than spring seedings. 

Late-summer seeding date is August 10 in the 
inorthem quarter of Illinois, August 30 in central Illi- 
nois, and September 15 in the southern quarter of 
Illinois. Seedings should be made close to these dates, 
and no more than 5 days later, to assure that the 
plants become well established before winter. Late- 
summer seedings that are made extremely early may 
suffer from drought following germination. 

Seeding rates for hay and pasture mixtures are 
shown in Table 7.10. These rates are for seedings made 



under average conditions, either with a companion 
crop in the spring or without a companion crop in 
late summer. Higher rates may be used to obtain high 
yields from alfalfa seeded without a companion crop 
in the spring. Seeding rates higher than described in 
Table 7.10 have proven economical in northern and 
central Illinois when alfalfa was seeded as a pure stand 
in early spring and two or three harvests were taken 
in the seeding year. In northern and central Illinois, 
but not in south-central Illinois, seeding alfalfa at 18 
pounds per acre has produced yields 0.2 to 0.4 ton 
higher than seeding at 12 pounds per acre. 

The two basic methods of seeding are band seeding 
and broadcast seeding. With band seeding, a band of 
phosphate fertilizer (0-45-0) is placed about 2 inches 
deep in the soil with a grain drill; then the forage seed 
is placed on the soil surface directly above the fertilizer 
band (Figure 7.1). Before the forage seeds are dropped, 
the fertilizer should be covered with soil, which occurs 
naturally when soils are in good working condition. 
A presswheel should roll over the forage seed to firm 
the seed into the soil surface. Many seeds will be 
placed one-eighth to one-fourth inch deep with this 
seeding method. 

With broadcast seeding, the seed is spread uniformly 
over a firm, prepared seedbed; then the seed is pressed 
into the seedbed surface with a corrugated roller. The 
fertilizer is applied at the early stages of seedbed 



\ 




V_>^ 


\ \ * .... CnnH 


lube 






\. 


o ^ 


""^ ^tn^ 


^^V-\ 






w 


/ 




xx\» \^\ ^\ 


Packer wheel | 


--/p^ 

^ 


^ 


1 ( 
/ i> / 


rr^ A 


^ )) 

Fertilizer 


Soil 
surface 

_^J; 

IVj"— 2" 


■■18 "^ , \\ 


■•:-:v<ri'-*^'- 


'iV-'Ali-i-.-iK'S'^'.Vii*^''''-''' -* 



Figure 7.1. Placement of seed and high -phosphate fertil- 
izer with grain drilL 



29 



preparation. The seedbed is usually disked and 
smoothed with a harrow. Most soil conditions are too 
loose after these tillage operations and should be firmed 
with a corrugated roller before seeding. The best 
seeding tool for broadcast seeding is the double cor- 
rugated roller seeder. 

Which is the better seeding method? Illinois studies 
have shown that band seeding often results in higher 
alfalfa yields than broadcast seedings for August and 
spring seedings. Seedings on soils that are low in 
phosphorus yield more from band seeding than from 
broadcast seeding. Early seeding on cold, wet soils is 
favored by banded phosphorus fertilization. The greater 
yield from band seeding may be a response to abun- 
dant, readily available phosphorus from the banded 
fertilizer. Broadcast seedings may yield as high as band 
seedings when the soils are medium to high in phos- 
phorus-supplying capacity and are well drained, so 
that they warm up quickly in the spring. 

Forage crop seeds are small and should be seeded 
no deeper than one-eighth to one-fourth inch. The 
seeds should be in close contact with soil particles. 
The double corrugated roller seeder and the band 
seeder with press-wheels roll the seed into contact 
with the soil and are the best known methods of 
seeding forages. 



Fertilizing and liming before or at seeding 

Lime. Apply lime at rates suggested in Figure 10.5. 
If rate requirements are in excess of 5 tons, apply half 
before the primary tillage (in most cases, plowing) and 
half before the secondary tillage (harrowing or disking). 
For rates of less than 5 tons, make a single application, 
preferably after plowing, although applying either 
before or after plowing is acceptable. 

Nitrogen (N). No nitrogen should be applied for 
legume seedings on soils with an organic-matter con- 
tent above 2.5 percent. Applying as much as 20 pounds 
of nitrogen per acre may help assure rapid seedling 
growth of legume-grass mixtures on soils with less 
than 2.5 percent organic matter. When seeding a pure 
grass stand, 50 to 100 pounds of nitrogen per acre in 
the seedbed are suggested. If band seeding, apply 
nitrogen with phosphorus through the grain drill. For 
broadcast seedings, apply broadcast with phosphorus 
and potassium. 

Phosphorus (P). Apply all phosphorus at seeding 
time (Tables 10.17 and 10.18) or broadcast part of it 
with potassium. For band seeding, reserve at least 30 
pounds of phosphate (P2O5) per acre to be applied at 
seeding time. For broadcast seeding, broadcast all the 
phosphorus with the potassium, preferably after pri- 
mary tillage and before final seedbed preparation. 

Potassium (K). Fertilize before or at seeding. Broad- 
cast application of potassium is preferred (Tables 10.18 
and 10.19). For band seeding, you can safely apply a 
maximum of 30 to 40 pounds of potash (K2O) per acre 



in the band with phosphorus. The response to band 
fertilizer will be mainly from phosphorus unless the 
K soil test is very low (perhaps 100 pounds per acre 
or less). For broadcast seeding, apply all the potassium 
after the primary tillage. You can apply up to 600 
pounds of K2O per acre in the seedbed without dam- 
aging seedlings if the fertilizer is incorporated. 



Fertilization 

Nitrogen. See the chapter entitled "Soil Testing and 
Fertility," the subsection about nitrogen. 

Phosphorus. This nutrient may be applied in large 
amounts, adequate for 2 to 4 years. The annual needs 
of a hay or pasture crop are determined from yield 
and nutrient content of the forage harvested (Table 
10.18). Grasses, legumes, and grass-legume mixtures 
contain about 12 pounds of P2O5 (4.8 pounds of P) 
per ton of dry matter. Total annual fertilization needs 
include the maintenance rate (Table 10.18) and any 
needed build-up rate (Table 10.17). 

Potassium. Because potassium helps the plant con- 
vert nitrogen to protein, grasses need large amounts 
of potassium to balance high rates of nitrogen fertil- 
ization. As nitrogen rates are increased, the nitrogen 
percent in the plant tissue also increases. If potassium 
is deficient, however, some nitrogen may remain in 
the plant as nonprotein nitrogen. 

Legumes feed heavily on potassium. Potassium, a 
key element in maintaining legumes in grass-legume 
stands, is credited with improving winter survival. 

Annual potassium needs are determined from yield, 
nutrient content in the forage that is harvested, and 
nutrient build-up requirements of a particular soil 
(Tables 10.18 and 10.19). Grasses, legumes, and grass- 
legume mixtures contain about 50 pounds of K2O (41.5 
pounds of K) per ton of dry matter. 

Boron (B). Symptoms of boron deficiency appear 
on second and third cuttings of alfalfa during droughty 
periods in some areas of Illinois. But yield increases 
from boron fertilization have been infrequent. Appli- 
cation of boron on soils with less than 2 percent 
organic matter is recommended for high-yielding al- 
falfa production in Illinois. If you suspect a boron 
deficiency, topdress a test strip in your alfalfa fields 
with 30 pounds per acre of household borax (3.3 
pounds of boron). For general application, have boron 
added to the phosphorus-potassium fertilizer. 



Management 

Seeding year. Hay and pasture crops seeded into 
a companion crop in the spring will benefit by early 
removal of the companion crop. Oats, wheat, or barley 
should be removed when the grain is in the milk stage. 
If these small grains are harvested for grain, it is 
important to remove the straw and stubble as soon as 



30 



I 



possible. As small-grain yields increase, the under- 
seeded legumes and grasses face greater competition, 
and fewer satisfactory stands are established by the 
companion-crop method. Forage seedings established 
with a companion crop may have one harvest taken 
by late August in northern Illinois and, occasionally, 
two harvests by September 10 in central Illinois and 
by September 25 in southern Ilhnois. 

Spring-seeded hay crops and pastures without a 
companion crop should be ready for harvest 65 to 70 
days after an early April seeding. Weeds very likely 
must be controlled about 30 days after seeding unless 
a preemergence herbicide was used. Postemergence 
herbicides 2,4-DB and Buctril are effective against most 
broadleaf weeds. Grassy weeds are effectively con- 
trolled by Poast. Follow label directions. Leafhoppers 
often become a problem between 30 to 45 days after 
an early April seeding and must be controlled to obtain 
a vigorous, high-yielding stand. 

Second and third harvests may follow the first 
harvest at 35- to 40-day intervals. The last harvest of 
the season should be in late August for the northern 
quarter of Illinois, by September 10 for the central 
section, and by September 20 for the southern quarter. 

Established stands. Maximum dry-matter yield from 
alfalfa and most forages is obtained by harvesting or 
grazing the first cutting at nearly full bloom and 
harvesting every 40 to 42 days thereafter until Sep- 
tember. This management produces a forage that is 
relatively low in digestibility. Such forage is suitable 
for livestock on maintenance, will produce slow weight 
gain, and can be used in low-performance feeding 
programs. In contrast, high-performance feeding pro- 
grams require a highly digestible forage. The optimum 
compromise between high digestibility and dry-matter 
yield of alfalfa is to harvest or graze the first cutting 
at the late-bud to first-flower stage and to make 
subsequent cuttings or grazings at 32- to 35-day in- 
tervals. Rotational grazing is essential to maintaining 
legumes in pastures. A rotational grazing program 
should provide for 5 to 7 days of grazing and 30 to 
35 days of rest. More intensive grazing, using 8 to 11 
pastures, 3 to 4 days of grazing, and 30 to 33 days of 
rest, increases meat or milk production per acre but 
may not increase individual animal performance. In- 
tensive grazing management is being adopted by many 
livestock producers in Illinois. 

Because high levels of root reserves (sugars and 
starches) are needed for winter survival and vigorous 
spring growth, the timing of the fall harvest is critical. 
Following a harvest, root reserves decline as new 
growth begins. About 3 weeks after harvesting, root 
reserves are depleted to a low level, and the top 
growth is adequate for photosynthesis to support the 
plant's needs for sugars. From this point, root reserves 
are replenished gradually until harvest or until the 
plant becomes dormant in early winter. Harvests made 
in September and October affect late-fall root reserves 
of alfalfa more than do summer harvests. After the 
September harvest, alfalfa needs a recovery period 



until late October to restore root reserves. On well- 
drained soils in central and southern Illinois, a "late" 
harvest may be taken after plants have become dor- 
mant in late October or early November. 



Pasture establishment 

Many pastures can be established through a hay 
crop program. Seedings are made on a well-prepared, 
properly fertilized seedbed. If it is intended that the 
hay crop becomes a pasture, the desired legume and 
grass mixture should be seeded. When grasses and 
legumes are seeded together, 2,4-DB or Buctril is a 
herbicide that can be used for broadleaf weed control. 
Apply 2,4-DB or Buctril about 30 days after seeding, 
when the legumes are 2 to 4 inches tall and the weeds 
less than 4 inches tall. 



Pasture renovation 

Pasture renovation usually means changing the plant 
species in a pasture to increase the pasture's quality 
and productivity. Improving the fertility of the soil is 
basic to this effort. A soil test helps identify the need 
for lime, phosphorus, and potassium — the major nu- 
trients important to estabHshing new forage plants. 

Before seeding new legumes or grasses into a pas- 
ture, reduce the competition from existing pasture 
plants. Tilling, overgrazing, and herbicides — used 
singly or in combination — have proven useful in 
subduing existing pasture plants. 

For many years, tilling (plowing or heavy disking) 
has been used to renovate pastures; but success has 
been variable. Major criticisms have been that tilling 
can cause erosion, that the pasture supply for the year 
of seeding is usually limited, and that a seeding failure 
would leave no available permanent vegetation for 
pasturing or soil protection. 

No-till seeding of new pasture plants into existing 
pastures began when herbicides and suitable seeders 
were developed. The practice of using a herbicide to 
subdue existing pasture plants and then seeding with 
a no-till seeder has proven very successful in many 
research trials and farm seedings. Following are eight 
basic steps to no-till pasture renovation. 

1. Graze the pasture intensively for 20 to 30 days 
before the seeding date to reduce the vigor of 
existing pasture plants. 

2. Lime and fertilize, using a soil test as a guide. Soil 
pH should be between 6.5 and 7.0. Desirable test 
levels of phosphorus and potassium vary with soil 
type; phosphorus should be in the range of 40 to 
50 pounds per acre, and potassium in the range of 
260 to 300 pounds per acre. For more information, 
see the chapter entitled "Soil Testing and Fertility." 

3. One or 2 days before seeding, apply a herbicide to 
subdue the vegetation. Gramoxone Super (paraquat) 



31 



and Roundup (glyphosate) are approved for this 
purpose. 

4. Seed the desired species, using high-yielding vari- 
eties. Alfalfa and red clover are the legumes with 
higher yields and are often the only species seeded 
into a pasture that has a desirable grass species and 
in which Gramoxone Super is going to be used in 
preference to Roundup. To seed, use a no-till drill 
that places the seed in contact with the soil. 

5. Seedings may be made in early spring throughout 
the northern two-thirds of Illinois and in late August 
throughout the southern three-fourths of Illinois. 

6. Apply insecticides as needed. Soil insects that eat 
germinating seedhngs are more prevalent in south- 
ern Illinois than in northern Illinois, and a soil 
insecticide may be needed. Furadan has been ap- 
proved for this use. Leafhoppers will be present 
throughout Illinois in early summer and during 
most of the growing season. They must be con- 
trolled where alfalfa is seeded, especially in spring- 
seeded pastures, because they are devastating to 
new alfalfa seedlings. Several insecticides are ap- 
proved; for more information, see the 1991 Illinois 
Pest Control Handbook chapter on Insect Pest Man- 
agement for Field and Forage Crops. Well-established 
alfalfa plants are injured but not killed by leafhop- 
pers; red clover and grass plants are not attacked 
by leafhoppers. 

7. Initiate grazing 60 to 70 days after spring seedings 
and not until the next spring for late-August seed- 
ings. Spring-seeded alfalfa and red clover should 
be at about 50 percent bloom at the first grazing. 
Alfalfa and red clover that are seeded in late August 
should be in the late-bud to first-flower stage of 
growth when grazing begins. Use rotational grazing. 
Graze 5 to 7 days and rest 28 to 30 days; for 
slightly lower-quality and lower-yielding pastures, 
graze 10 days and rest 30 days; for greater animal 
product yield per acre, graze 3 to 4 days and rest 
32 to 33 days. 

8. Fertilize pastures annually on the basis of estimated 
crop removal. Each ton of dry matter from a pasture 
contains about 12 pounds of phosphate (P2O5) and 
50 to 60 pounds of potash (K2O). Do not use 
nitrogen on established pastures in which at least 
30 percent of the vegetation is alfalfa, red clover, 
or both. Because much of the nutrients grazed are 
returned to the pasture in urine and manure, you 
should soil test thoroughly every 4 years and adjust 
your fertilization program according to soil tests. 
Usually less phosphate and potash are needed on 
pastures than hay fields. 



Selection of pasture seeding mixture 

Alfalfa is the single best species for increasing yield 
and improving the quality of pastures in Illinois. Red 
clover produces very well in the first 2 years after 



seeding but contributes very little after that. Birdsfoot 
trefoil establishes slowly and increases to 40 to 50 
percent of the yield potential of alfalfa. Mixtures of 
alfalfa at 8 pounds and red clover at 4 pounds per 
acre or of birdsfoot trefoil at 4 pounds and red clover 
at 4 pounds per acre have demonstrated high yield. 
Red clover diminishes from the stand about the third 
year; and the more persistent species, alfalfa or birds- 
foot trefoil, increases to maintain a high yield level 
for the third and subsequent years. 



Pasture fertilization 

The yield and quahty of many pastures can be 
improved by fertilization. The soil pH is basic to any 
fertilization program. Pasture grasses tolerate a lower 
soil pH than do hay and pasture legumes. For pastures 
that are primarily grass, a minimal pH should be 6.0. 
A pH of 6.2 to 6.5 is more desirable because nutrients 
are more efficiently utilized in this pH range than at 
lower pH values. Lime should be applied to correct 
the soil acidity to one-half plow depth. This liming is 
effective half as long as when a full rate is applied 
and plowed into the plow layer. Consequently, pastures 
will usually require liming more often (but at lower 
rates) than will cultivated fields. 

Phosphorus and potassium needs are assessed by 
a soil test. Without a soil test, the best guess is to 
apply what the crop removes. Pasture crops remove 
about 12 pounds of phosphate (P2O5) and 50 pounds 
of potash (K2O) per ton of dry matter. Very productive 
pastures yield 5 to 6 tons of dry matter per acre; 
moderately productive pastures yield 3 to 5 tons; and 
less productive pastures, 1 to 3 tons. Recycling of 
nutrients from urine and manure reduces the total 
nutrients removed from a pasture. Soil test every 4 
years to monitor changes in fertility status of pastures. 



Pasture management 

Rotational grazing of grass pastures results in greater 
production (animal product yield per acre) than does 
continuous grazing, except for Kentucky bluegrass 
pastures. Pastures that include legumes need rotational 
grazing to maintain the legumes. A rotational grazing 
plan that works well is 5 to 7 days' grazing with 28 
to 30 days' rest, which requires five to six fields. This 
plan provides the high-quality pasture needed by 
growing animals and dairy cows. A more intense 
grazing system for high performance livestock and for 
high animal product per acre is a rotational grazing 
system of 8 to 11 fields, 3 to 4 days' grazing and 32 
to 33 days' rest per pasture field. A less intense grazing 
plan for beef cow herds, dry cows, and stocker animals 
is 10 days' grazing with 30 days' rest, which requires 
four fields. 

Weed control is usually needed in pastures. Clipping 
pastures after each grazing cycle helps in weed control. 



I 



32 



1 



but herbicides may be needed for problem areas. 
Banvel and 2,4-D are effective on most broadleaf 
weeds. Banvel is more effective than 2,4-D for most 
conditions but also has more restrictions. Do not graze 
dairy animals or feed harvested forage from these 
fields until 60 days after treatment with Banvel. Re- 
move meat animals from Banvel-treated pastures 30 
days before slaughter. Restrictions for 2,4-D apply to 
milk cows, which should not be grazed on treated 
pasture for 7 days after treatment. Thistles can usually 
be controlled by 2,4-D or Banvel, although repeated 
applications of the herbicide may be necessary. Mul- 
tiflora rose may be controlled with Banvel applied in 
early spring, when the plant is actively growing, but 
before flower bud formation. 



Species and varieties 

Alfalfa is the highest-yielding perennial forage crop 
suited to Illinois, and its nutritional qualities are nearly 
unsurpassed. Alfalfa is an excellent hay crop species 
and, with proper management, may be used in pas- 
tures, as already mentioned. 

Bloat in ruminant animals often is associated with 
alfalfa pastures. Balancing soil fertility, including grasses 
in mixtures with alfalfa, maintaining animals at good 
nutritional levels, and using bloat-inhibiting feed 
amendments are methods to reduce or essentially 
eliminate the bloat hazard. 

Many varieties of alfalfa are available. Some have 
been privately developed, some developed at public 
institutions. Private varieties usually are marketed 
through a few specific dealers. Not all varieties are 
available in Illinois. 

An extensive testing program has been under way 
at the University of Illinois for many years. The 
performance of alfalfa varieties listed in Table 7.1 is 
based on test data compiled since 1961. Some varieties 
have been tested every year since then; others have 
been tested only 3 or 4 years. Each variety in this list, 
however, has been in tests at least 3 years. 

Bacterial wilt is one of the major diseases of alfalfa 
in Illinois. Stands of susceptible varieties usually de- 
cline severely in the third year of production and may 
die out in the second year under intensive harvesting 
schedules. Moderate resistance to bacterial wilt enables 
alfalfa to persist as long as 4 or 5 years. Varieties listed 
as resistant usually persist beyond 5 years. 

Phytophthora root rot is a major disease of alfalfa 
grown on poorly drained soils, primarily in the north- 
ern half of Illinois. This disease attacks both seedlings 
and mature plants. The root develops a black lesion, 
which progresses and rots the entire root. In mature 
stands, shortened taproots are a symptom of this 
disease. Many alfalfa varieties with high-yield perfor- 
mance have resistance or moderate resistance to phy- 
tophthora root rot. 

Anthracnose is an important disease in the southern 
half of Illinois and may be important in northern 



Table 7.1. Leading Alfalfa Varieties Tested at Least 
3 Years in Illinois 



Brand or variety 



Bacterial 
wilt 
resis- 
tance^ 



Percent of yield 
of check varieties'" 



120 HR 

Acclaim R 

Action R 

AgriBoss HR 

Apollo II R 

Apollo Supreme R 

Armor R 

Arrow R 

A-54 R 

Blazer R 

Centurion HR 

Challenger R 

Cimarron HR 

Clipper HR 

Comet R 

Crown R 

Darxt R 

Decathlon HT 

Endure R 

Epic R 

Excalibur R 

Fortress R 

Garst 630 HR 

Garst 636 R 

GH 747 HR 

G-2852 HR 

G-7730 HR 

Impact HR 

Invincible R 

Jubilee R 

Magnum HR 

Magnum + R 

Mercury R 

Peak R 

Saranac AR MR 

Shenandoah R 

Stetson R 

Surpass R 

Thunder HR 

Trident MR 

Ultra R 

Vector R 

Vernal R 

Verta + HR 

VIP HR 

Voris A-77 HR 

WL 225 Alfalfa HR 

Wrangler R 



Northern 


Central 


Southern 


105.63 


104.52 


105.14 


104.01 


109.87 




108.65 


101.01 




112.88 






109.12 


103.70 




107.47 


100.04' 


95.74' 


107.20 


105.12 


99.68 


108.84 


102.06 


102.57 


105.08 


105.76 


104.50 


111.50 


104.21 


103.28 


102.65 


105.57 


107.56 


104.92 


100.08 


103.11 


103.87 


101.05 


102.05 


105.69 


95.84' 


112.12^ 


103.06 


107.06 




101.86 


105.22 




107.13 


104.36 


98.30 


101.02 




108.67 


106.97 


101.00 


104.81 


107.38 


109.13 


101.10 


100.63 


106.95 


97.48 


106.81 


105.40 




102.27 


104.13 


107.96 


106.03 


105.54 


111.64 


104.33 


108.77 




106.48 


106.17 




105.35 


104.65 


100.30 


107.32 


99.03 


102.14 


107.54^ 


104.43 




105.06 


105.82 


104.22 


101.37 


104.40 


109.55 


116.10 


110.10 




109.06 


108.34 


104.46 


101.14 


104.09 


103.24 


103.60 


100.12 


103.01 


107.58 






103.51 


106.13 
109.60 




105.71 


103.90 


102.73 


107.36 


110.33 




100.50 


100.20 


103.17 


104.09 


111.80 




103.13 


106.98 




106.81 


105.11 


101.45 


102.03 


100.24 


106.45 


105.35 


100.96 


105.04 



^ HR = highly resistant; R = resistant; MR = moderately resistant; HT = 

highly tolerant. 

'' Check varieties are Baker, Riley, Saranac AR, and Vernal. The average yield 

of check varieties equals 100. 

' Only two years of data. 



Illinois during warm, humid weather. The disease 
causes the stem and leaves to brown, with the tip of 
the stem turning over like a hook. The fungus causes 
a stem lesion, usually diamond-shaped in the early 
stages, which enlarges to completely encircle the stem. 
Many alfalfa varieties with high-yield performance 
have resistance or moderate resistance to anthracnose. 
Verticillium wilt is a root-rot disease that is similar 
to bacterial wilt. Verticillium wilt develops slowly, 
requiring about 3 years before plant loss becomes 
noticeable. Associated with cool climates and moist 
soils, this fungus is gradually spreading southward in 
Illinois. Producers in the northern quarter of Illinois 



33 



should seek resistant varieties; and producers in the 
rest of the northern half of the state should observe 
their fields and consider using resistant varieties when 
seeding alfalfa. Many alfalfa varieties with high-yield 
performance have resistance or moderate resistance to 
verticillium wilt. 

Other diseases and insects are problems for alfalfa, 
and some varieties of alfalfa have particular resistance 
to these problems. You should question your seed 
supplier about these attributes of the varieties being 
offered to you. 

Red clover (medium red clover) is the second most 
important hay and pasture legume in Illinois. Although 
it does not have the yield potential of alfalfa under 
good production conditions, red clover can persist in 
more acidic soils and under more shade competition 
than can alfalfa. And, although red clover is a perennial 
physiologically, root and crown diseases limit the life 
of red clover to 2 to 3 years. Many new varieties have 
an increased resistance to root and crown diseases and 
are expected to be productive for at least 3 years. (See 
Table 7.2.) 

Red clover does not have as much seedling vigor 
or as rapid a seedling growth rate as alfalfa. Therefore, 
red clover does not fit into a spring seeding program 
without a companion crop as well as does alfalfa. 

Red clover has more shade tolerance at the seedling 
stage than does alfalfa; therefore, red clover is rec- 
ommended for most pasture renovation mixtures where 
shading by existing grasses occurs. The shade tolerance 
of red clover enables it to establish well in companion 
crops such as spring oats and winter wheat. 

There are fewer varieties of red clover than of 
alfalfa. Private breeders are active in developing more 
varieties of red clover. 

Fewer acres are dedicated to mammoth red clover 
because its yields have been lower than most of the 
improved varieties of medium red clover. 

Ladino clover is an important legume in pastures, 
but it is a short-lived species. The very leafy nature 



of ladino makes it an excellent legume for swine. It is 
also a very high-quality forage for ruminant animals, 
but problems of bloat are frequent. 

Ladino lacks drought tolerance because its root 
system is shallower than that of red clover or alfalfa. 

Birdsfoot trefoil has been popular in permanent 
pastures in northern Illinois. It has a long life but 
becomes established very slowly. Seedling growth rate 
is much slower than that of alfalfa or red clover. 

A root rot has made birdsfoot trefoil a short-hved 
crop throughout southern Illinois. The variety Dawn 
may have adequate resistance to persist throughout 
the state (see Table 7.3 for variety yields). 

Rooting depth of birdsfoot trefoil is shallower than 
that of alfalfa, thus birdsfoot trefoil is not as productive 
during drought. 

Crownvetch is well known for protecting very 
erosive soil areas. As a forage crop, crownvetch is 
much slower than alfalfa or red clover in seedling 
emergence, seedling growth rate, early-season growth, 
and recovery growth. Growth rate is similar to that of 
birdsfoot trefoil. The potential of crownvetch as a hay 
or pasture plant seems restricted to very rough sites 
and soils of low productivity. Crownvetch does not 
tolerate defoliation (grazing or hay harvesting) as well 
as alfalfa, red clover, or birdsfoot trefoil. 

Sainfoin is a legume that was introduced into the 
western United States from Russia. In Illinois tests, 
this species has failed to become established well 
enough to allow valid comparisons with alfalfa, red 
clover, and others. Observations indicate that sainfoin 
has a slow growth and recovery growth rate and is 
not well suited to the humid conditions in Illinois. 

Hairy vetch is a winter annual legume that has 
limited value as a hay or pasture species. Low pro- 
duction and its vinelike nature have discouraged much 
use. Hairy vetch may reseed itself and become a weedy 
species in small grain fields. Hairy vetch seeded with 
winter wheat at 22 to 25 pounds per acre has increased 
the protein yield of wheat-vetch silage. Hairy vetch is 



Table 7.2. Leading Red Clover Varieties Tested at Least 2 Years in Illinois 



Brand or variety Percent of check yield^ 

Northern Central Southern 

Arlington 100 100 100 

Atlas (NK 78045) 101.87 96.74 

E 688 94.759 98.37 

Flare 106.61 107.1 100.28 

Horex 92.55 82.53 

Florie 102.52 102.58 100.6 

Kenland 96.01 95.51 

Kenstar 98.8 

Marathon 100.88 108.66 

Mega 98.58 95.25 

MorRed 102.74 95.77 

Redland 104.91 99.37 101.77 

Redland II 110.11 107.56 104.05 

Redman 1 12.78 97.42 95.91 

Ruby 111.06 105.53 101.65 

^ The check variety is Arlington. The average yield of a check variety equals 100. 
'' R = resistant; T = tolerant; MR = moderately resistant; HR = highly resistant. 
' Data not available. 





Anthracnose 


Powdery 




resistance" 


mildew 


Northern Southern 


resistance 


R 


R 


R 


R 


HR 


R 


T 


R 


R 


MR 


R 


R 


R 


7 


MR 


R 


R 


R 


S 


R 




S 


R 


. . . 


R 


. R 


. . . 


R 


R 


R 


HR 


MR 


HR 


MR 


R 


R 


R 


R 


R 


R 


MR 


R 


R 


R 





34 



a popular cover crop, providing approximately 60 
pounds of available nitrogen to a following crop. Hairy 
vetch should be seeded in September and not killed 
until mid-May to obtain high nitrogen contributions. 
Lespedeza is a popular annual legume in the south- 
em third of Illinois. It flourishes in midsummer when 
most other forage plants are at low levels of produc- 
tivity. It survives on soils of low productivity and is 
low yielding. Even in midsummer, it does not produce 
as well as a good stand of alfalfa, nor will it encroach 
on a good alfalfa stand. As alfalfa or other vigorous 
pasture plants fade out of a pasture, lespedeza may 
enter it. 



Table 7.3. Leading Birdsfoot Trefoil Varieties in 
Illinois 

Percent of check yield' 

Variety Northern Central Southern 

Carroll 114.52 95.27 89.18 

Dawn 113.08 100.63 101.18 

Empire 104.2 97.55 80.51 

KO-4 105.34 95.37 . . ." 

Leo 98.41 92.54 87.52 

Mackinac 101.88 101.63 

Maitland 102.22 103.72 91.5 

Norcen 114.38 105.59 91.88 

Viking 87.04 99.37 99.14 

' Check varieties are Dawn and Viking. The average yield of check varieties 

equals 100. 

'' Data not available. 



Inoculation 

Legumes — such as alfalfa, red clover, crownvetch, 
hairy vetch, ladino, and birdsfoot trefoil — can meet 
their nitrogen needs from the soil atmosphere if the 
roots of the legume have the correct Rhizobium species 
and favorable conditions of soil pH, drainage, and 
temperature. Rhizobium bacteria are numerous in most 
soils; however, the species needed by a particular 
legume species may be lacking. 

There are seven general groups and some other 
specific strains of Rhizobium, with each group specif- 
ically infecting roots of plants within its corresponding 
legume group and some specific strains infecting only 
a single legume species. The legume groups are (1) 
alfalfa and sweet clover; (2) true clovers (such as red, 
ladino, white, and alsike); (3) peas and vetch (such as 
field pea, garden pea, and hairy vetch); (4) beans (such 
as garden and pinto); (5) cowpeas and lespedeza; (6) 
soybeans; and (7) lupines. Some of the individual 
Rhizobium strains are specific to (1) birdsfoot trefoil; 
(2) crownvetch; or (3) sainfoin. 



Grasses 

Cool-season perennials 

Timothy is the most popular hay and pasture grass 
in lUinois, although it is not as high yielding and has 
less midsummer production than smooth bromegrass. 
A cool-season species, it is best suited to the northern 
half of Illinois. There are promising new varieties 
(Table 7.4). 

Smooth bromegrass is probably the most widely 
adapted high-yielding grass species for northern and 
central Illinois. Smooth bromegrass combines well with 
alfalfa or red clover. It is productive but has limited 
summer production when moisture is lacking and 
temperatures are high. It produces well in spring and 
fall and can utilize high-fertility programs. There are 
a few improved varieties, and breeding work continues 
(Table 7.5). 

Orchardgrass is one of the most valuable grasses 
used for hay and pasture in Illinois. It is adapted 



Variety 




Percent of check 


yield^ 




Northern 


Central 




Southern 


Itasca 

Mariposa 

Mohawk 

Richmond 


80.9 

106.2 

95.6 

102.6 


92.0 
104.1 
112.8 

94.6 




88.3 
114.5" 

C 

101.7 



Table 7.4. Leading Timothy Varieties Tested at Least 
2 Years in Illinois 

Perc 
Northern 

809 

106.2 

95.6 

102.6 

^ Check varieties are Potomac orchardgrass and Lincoln smooth bromegrass. 
The average yield for check varieties equals 100. 
^ Only one year of data. 
■^ Data not available. 



Table 7.5. Leading Smooth Bromegrass Varieties 
Tested at Least 2 Years in Illinois 

Percent of check yield^ 

Variety 

Northern Central Southern 

Barton 115.3'' 98.1 114.4 

FS Beacon 111.2 105.6 110.3 

Blair 86.4 105.2 

Bravo 97.0 100.4 103.4" 

Jubilee 91.5 94.7 

Lincoln 93.8" 97.4 99.6 

Rebound 88.5" 109.9 99.1 

Sac 98.1" . . . 107.7 

^ Check varieties are Potomac orchardgrass and Lincoln smooth bromegrass. 
The average yield for check varieties equals 100. 
" Only one year of data. 
^ Data not available. 



throughout the state, being marginally winter-hardy 
for the northern quarter of the state. Orchardgrass 
heads out relatively early in the spring and thus should 
be combined with alfalfa varieties that flower early. 
One of the more productive grasses in midsummer, it 
is a high-yielding species and several varieties are 
available (Table 7.6). 

Reed canarygrass is not widely used, but it has 
growth attributes that deserve consideration. Reed 
canarygrass is the most productive of the tall, cool- 
season perennial grasses that are well suited to Illinois 
hay and pasture lands. Tolerant of wet soils, it also is 
one of the most drought-resistant grasses and can 
utilize high fertility. It is coarser than orchardgrass or 
bromegrass but not as coarse as tall fescue. Grazing 
studies indicate that, under proper management, reed 



35 



canarygrass can produce good weight gains on cattle 
equal to those produced by bromegrass, orchardgrass, 
or tall fescue. Reed canarygrass should be considered 
for grazing during spring, summer, and early fall. Cool 
temperatures and frost retard growth and induce dor- 
mancy earlier than with tall fescue, smooth brome- 
grass, or orchardgrass. New low-alkaloid varieties have 
improved animal performance (Table 1.1). 

Tall fescue is a high-yielding grass (Table 7.8). It is 
outstanding in performance when used properly and 
is a popular grass for beef cattle in southern Illinois. 
Because it grows well in cool weather, tall fescue is 
especially useful for winter pasture; and it is also most 
palatable during the cool seasons of spring and late 
fall. A fungus living within the plant tissue (endophyte) 
has a major influence on the lower palatability and 
digestibility of this grass during the warm summer 
months. Varieties are available that are fungus-free or 
low in fungus. Forager, Johnstone, and Kenhy are 
productive varieties in Illinois that are low in endo- 
phyte fungus. Tall fescue is marginally winter-hardy 
when used in pastures or hay crops in the northern 
quarter of the state. A more extensive list of hay, 
pasture, and silage crop varieties is given in Table 7.9. 

Warm-season annuals 

Sudangrass, sudangrass hybrids, and sorghum- 
sudangrass hybrids are annual grasses that are very 
productive in late summer. These grasses must be 
seeded each year on a prepared seedbed. Although 
the total-season production from these grasses may be 
less than that from perennial grasses with equal fertility 
and management, these annual grasses fill a need for 
quick, supplemental pastures or green feed. These tall, 
juicy grasses are difficult to make into high-quality 
hay. Sudangrass and sudangrass hybrids have finer 
stems than the sorghum-sudan hybrids and thus will 
dry more rapidly; they should be chosen for hay over 
the sorghum-sudan hybrids. Crushing the stems with 
a hay conditioner will help speed drying. 

Sudangrass, sudangrass hybrids, and sorghum- 
sudangrass hybrids produce prussic acid, a compound 
that is toxic to livestock. Prussic acid is the common 
name for hydrogen cyanide (HCN). The compound in 
sorghum plants that produces HCN is dhurrin. Two 
enzymes are required to hydrolyze dhurrin to HCN. 
The microflora in the rumen of ruminant animals are 
capable of enzymatic breakdown of dhurrin. The con- 
centration of dhurrin is highest in young tissue, with 
more found in leaves than in stems. There is more 
dhurrin in grain or forage sorghums than in sorghum- 
sudangrass hybrids, and more in sorghum-sudangrass 
hybrids than in sudangrass hybrids or sudangrass. 

Sudangrass and sudangrass hybrids are considered 
safe for grazing when they are 18 inches tall. The 
sorghum-sudangrass hybrids should be 24 inches tall 
before grazing is permitted. Very hungry cattle or sheep 
should be fed other feeds that are low in prussic-acid 
potential before turning them onto a lush sudangrass 



36 



Table 7.6. Leading Orchardgrass Varieties Tested at 
Least 2 Years in Illinois 

Percent of check yield^ 

Variety ^ 

Northern Central Southern 

Crown 107.9 100.5 101.6 

Dart 104.8 107.9 93.2 

Hallmark 99.6 98.0 99.0 

Hawk 100.2 106.4 . . ." 

Ina 108.0 112.0 

Juno 88.7 98.5 101.8 

Phyllox 102.6 95.4' 

Potomac 91.7 97.3 101.6 

Rancho 97.5 112.9 108.3' 

^ Check varieties are Potomac orchardgrass and Lincoln smooth bromegrass. 
The average yield for check varieties equals 100. 
'' Data not available. 
' Only one year of data. 



Table 7.7. Leading Reed Canarygrass, Bluegrass, and 
Perennial Ryegrass Varieties Tested at 
Least 2 Years in Illinois 

Percent of check yield^ 

Variety 

Northern Central Southern 

Reed canarygrass 

Flare 98.5" 88.8 103.4 

Palaton 115.8 116.5 97.0 

Vantage 90.9'' . . .' 105.0 

Venture 106.4 116.8 103.0 

Bluegrass 

Dormie 71.3 86.4 

Perennial ryegrass 

Bison 105.4 128.0" 

Grimalda 91.9 51.2 

^ Check varieties are Potomac orchardgrass and Lincoln smooth bromegrass. 
The average yield for check varieties equals 100. 
" Only one year of data. 
' Data not available. 



Table 7.8. Leading Tall Fescue Varieties Tested at 
Least 2 Years in Illinois 

Percent of check yield^ 

Variety 

Northern Central Southern 

AU Triumph " 105.6 106.6' 

Forager 118.8 108.0 102.0 

Johnstone 115.1 112.8 97.3 

Kenhy 107.6 1 16.6 104.2 

Ky-31 105.3 109.4 98.4 

Martin 114.5 109.0 109.6 

Mozark 110.2 113.0 102.3 

Mustang 99.8 104.5 

Phyter 105.7 108.7' 

Tandem 114.8 109.7' 

^ Check varieties are Potomac orchardgrass and Lincoln smooth bromegrass. 
The average yield for check varieties equals 100. 
" Data not available. 
' Only one year of data. 



or sorghum-sudangrass pasture. This prefeeding will 
prevent rapid grazing and a sudden influx of forage 
that contains prussic acid. These animals can tolerate 
low levels of prussic acid because they can metabolize 
and excrete the HCN. 

Frost on the crops of the sorghum family causes 
the plant enzymes to come into contact with dhurrin 



\ 



Table 7.9. Hay, Pasture, and Silage Crop Varieties 



Crop 



Variety 



Origin 



Use 



Ladino clover . . 
Birdsfoot trefoil. 



Crownvetch. 



Smooth bromegrass. 



Orchardgrass. 



Tall fescue 



Merit 

. Carroll 
Dawn 
Empire 
Fargo 
Fergus 
Leo 

Mackinaw 
Maitland 
Norcen 
Viking 

. Chemung 
Emerald 
Penngift 

Barton 

Baylor 

Blair 

Bravo 

FS Beacon 

Jubilee 

Lincoln 

Sac 

Benchmark 

Boone 

Crown 

Dart 

Dayton 

Hawk 

Ina 

Juno 

Napier 

Pennlate 

Potomac 

Rancho 

Sterling 

. Alta 
Fawn 
Forager 
Johnstone 
Kenhy 
Kenwell 
Ky-31 
Martin 
Mozark 
Mustang 

. Clair 
Climax 
Itasca 
Mariposa 
Mohawk 
Pronto 
Richmond 
Timfor 
Toro 
Verdant 

Blackwell 

Caddo 

Cave-in-Rock 

Kanlow 

Nebraska 28 

Pathfinder 

Trailblazer 

Eastern gamagrass Pete 

Big bluestem Champ 

Kaw 

Pawnee 

Roundtree 

Caucasian bluestem Caucasian 

Indiangrass Holt 

Osage 

Oto 

Rumsey 



Timothy . 



Switchgrass . 



Iowa 

Iowa 

Missouri 

New York 

North Dakota 

Kentucky 

Canada 

Michigan 

Europe 

Nortn Central States 

New York 

New York 

Iowa 

Pennsylvania 

Land O'Lakes, Inc. 

AgriPro 

AgriPro 

Otto Pick & Sons Seed, Inc. 

Land O'Lakes, Inc. 

Otto Pick & Sons Seed, Inc. 

University of Nebraska 

University of Wisconsin 

Farm Forage Research Cooperative 

Kentucky 

AgriPro 

Land O'Lakes, Inc. 

AgriPro 

AgriPro 

Northrup, King and Co. 

Ottawa Research Station 

AgriPro 

Pennsylvania 

Maryland 

Farm Forage Research Cooperative 

Iowa 

Oregon 

Oregon 

Farm Forage Research Cooperative 

Kentucky 

Kentucky 

Kentucky 

Kentucky 

Missouri 

Missouri 

Rutgers University 

Kentucky 

Indiana 

Minnesota 

Otto Pick & Sons Seed, Inc. 

Farm Forage Research Cooperative 

Pride Company, Inc. 

Otto Pick & Sons Seed, Inc. 

Northrup, King and Company 

AgriPro 

Wisconsin 

Oklahoma 
SCS 

Nebraska 



SCS 

Kansas 

Nebraska 

SCS 



Nebraska 
Kansas 
Nebraska 
SCS 



Pasture 

Hay and 
Pasture 
Pasture 
Hay and 
Hay and 
Hay and 
Hay and 
Hay and 
Hay and 
Hay and 



pasture 



pasture 
pasture 
pasture 
pasture 
pasture 
pasture 
pasture 



Erosion and pasture 
Erosion and pasture 
Erosion and pasture 

Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 

Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 

Pasture 

Pasture 

Pasture (low endophyte fungus) 

Pasture (low endophyte fungus) 

Pasture (more palatable; low endophyte fungus) 

Pasture (more palatable) 

Pasture 

Pasture (higher magnesium; low endophyte fungus) 

Pasture (low endophyte fungus) 

Pasture 

Hay 
Hay 
Hay 
Hay 
Hay 
Hay 
Hay 
Hay 
Hay 
Hay 



Hay and 
Hay and 
Hay and 
Hay and 
Hay and 
Hay and 
Hay and 



pasture 
pasture 
pasture 
pasture 
pasture 
pasture 
pasture 



Hay and pasture 

Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 

Hay and pasture 

Hay and pasture 
Hay and pasture 
Hay and pasture 
Hay and pasture 



37 



and HCN to be released rapidly. For this reason, it is 
advisable to remove grazing ruminant livestock from 
freshly frosted sudangrasses and sorghums. When the 
frosted plant material is thoroughly dry, usually after 
3 to 5 days, grazing can resume. Grazing after this 
time should be observed closely for new tiller growth, 
which will be high in dhurrin; and livestock should 
be removed when there is new tiller growth. 

The sorghums can be ensiled. The fermentation of 
ensiling reduces the prussic acid potential very sub- 
stantially. This method is the safest for using feed that 
has a questionably high prussic acid potential. 

Harvesting these crops as hay is also a safe way of 
using a crop with questionably high levels of prussic 
acid potential. 

Toxic levels of prussic acid (HCN) vary. Some work- 
ers report toxicity at 200 ppm HCN of tissue dry 
weight, while others report moderate toxicity at 500 
to 750 ppm HCN of tissue dry weight. Laboratory 
diagnostic procedures can determine relative HCN 
potential. An alkaline picrate solution is commonly 
used to detect HCN in plant tissue. 

Millets are warm-season annual grasses that are 
drought tolerant. Four commonly known millets are 
pearlmillet {Pennisetum typhoides), browntop millet 
{Panicum ramosum), foxtail or Itahan millet {Setaria 
italica), and Japanese millet {Echinochloa crusgalli). 
Pearlmillet has been evaluated in grazing trials and is 
a suitable alternative for summer annual pastures. 

Pearlmillet requires a warmer soil for rapid estab- 
lishment than does sudangrass. Seedings should be 
delayed until the soil temperature in the seedbed 
averages 70°F. 

Pearlmillet does not have a prussic acid potential 
as does sudangrass, nor is pearlmillet as susceptible 
to leaf diseases. Pearlmillet is more drought tolerant 
than is sudangrass, thus producing more pasture dur- 
ing the hot, dry periods of late summer. 



Forage mixtures 

Mixtures (Table 7.10) of legumes and grasses usually 
are desirable. Yields tend to be greater than with either 
the legume or the grass alone. Grasses are desirable 
additions to legume seedings to fill in where the legume 
ceases to grow, to reduce soil erosion, to increase the 
drying rate, and perhaps to improve animal acceptance. 
Mixtures of two or three well-chosen species are 
usually higher yielding than mixtures that contain five 
or six species, some of which are not particularly well 
suited to the soil, climate, or use. 

Warm-season perennials 

Warm-season perennial grasses also are known as 
native prairie grasses. These prairie grasses normally 
provide ample quantities of good- to high-quality 
pasture during midsummer when cool-season peren- 
nials are low yielding and perhaps of low quality. 



Switchgrasses, big bluestem, and indiangrass have 
been the more popular prairie grasses for use in Illinois. 

Switchgrass (Panicum virgatum L) is a tall, coarse- 
stemmed grass with long, broad leaves that grows 3 
to 5 feet tall, with short rhizomes. It is not as palatable 
as smooth bromegrass. It is native to the Great Plains. 

In Ilhnois, switchgrass starts growing in May but 
makes most of its growth in June to August. Switch- 
grass is one of the earliest maturing prairie grasses. 
Grazing or harvesting should leave a minimum of a 
4- to 6-inch stubble. Close grazing or harvesting quickly 
diminishes the stand. 

Switchgrass needs abundant moisture and fertility 
for maximum growth. Because switchgrass is tolerant 
of moist soils, it is often used in grass waterways. 

Varieties. Blackwell, Caddo, Kanlow, Nebraska 28, 
Pathfinder, and Trailblazer were selected in the south- 
ern and central Great Plains. Trailblazer, released in 
1985, is more digestible than the other varieties. Cave- 
in-Rock was selected from southern IlUnois in 1958 
and released by the Soil Conservation Service, Elsberry, 
Missouri, in 1972. Cave-in-Rock has yielded well in 
Illinois trials. 

Switchgrass should be seeded in mid-April to early 
May. A continuous supply of soil moisture is needed 
for germination and early seedling development. Pre- 
cipitation during the first 10 days following seeding 
has beeen more important for the establishment of 
switchgrass than the seeding date. 

A seeding rate of 6 pounds of pure live seed (PLS) 
per acre of switchgrass is adequate if weeds are con- 
trolled and precipitation is favorable. Increasing the 
seeding rate increases the number of seedlings estab- 
lished but has little effect on forage yield or forage 
quality of established stands. 

Frequent grazing or hay harvesting — more often 
than every 6 weeks — reduces the yield and vigor of 
switchgrass. A harvest may be taken after frost without 
reducing yield and vigor the following year. 

Crude protein and digestible dry matter of switch- 
grass decline with maturity. Animal gains on switch- 
grass may be less than on big bluestem or indiangrass. 

Switchgrass, indiangrass, and big bluestem yield 
well as pasture plants. A major portion of the growth 
occurs after July 1, and nearly all growth from these 
grasses is completed by August 1 in southern Illinois. 
The dry matter yield of switchgrass is greater than 
that of indiangrass and big bluestem. 

The crude protein content of switchgrass is higher 
than indiangrass or big bluestem at the same dates 
during the pasture season. The crude protein values 
range from 3.4 to 6.4 percent for the major yield of 
the season. These values are very low if these forages 
are the only protein source for cattle, sheep, or horses. 
Big bluestem tends to have a higher crude protein 
content than indiangrass. 

The digestible dry matter of warm-season perennial 
grasses tends to be below 50 percent, which is below 
the maintenance level for pregnant beef cows. They 



38 



Table 7.10. Forage Seed Mixture Recommendations, All Entries Given in Pounds per Acre 





For hay crops 




















For rotation and permanent pastures 




Northern, Central Illinois 


Southern Illinois 












Moderately to well-drained soils 




Northern, Central Illinois 


Southern Illinois 




Alfalfa 


12 


Alfalfa 


8 




Moderately to well-drained soils 




Air ^ f 


o 


Orchardgrass 


4 


Alfalfa 


8 


Alfalfa 


8 


Alfalfa 
Bromegrass 


8 
6 


Alfalfa 
Tall fescue 


8 
6 


Bromegrass 
Timothy 


5 
2 


Orchardgrass 
Alfalfa 


4 
8 


Alfalfa 


8 






Alfalfa 


8 


Tall fescue 


6 


Bromegrass 


4 






Orchardgrass^ 


4 






Timothy 


2 








Tall fescue 


8 










Alfalfa 


8 


Ladino clover 


1/2 


Alfalfa 
Timothy 


8 
4 






Orchardgrass^ 
Timothy 


4 
2 


Alfalfa 
Bromegrass 


8 
6 




Poorly drained soils 




Orchardgrass^ 
Ladino clover 


6 


Timothy 


2 


Red clover 


8 


Red clover 


8 


Vz 


Orchardgrass 
Ladino clover 


6 


Timothy 


4 


Bromegrass 


6 


Red clover 


8 


1/2 


Red clover 
Bromegrass 


8 
6 


Reed canarygrass 
Alsike clover 


8 
4 


Ladino clover 
Orchardgrass^ 


1/2 

4 


Tall fescue 


10 


Alsike clover 


5 


Tall fescue 


6 


Red clover 


8 


Orchardgrass 


8 


1 Timothy 


4 


Alsike clover 


4 


Ladino clover 
Tall fescue 


1/2 
6-8 


Red clover 
Ladino clover 


8 

1/2 


Reed canarygrass 
Alsike clover 


8 
3 


Redtop 
Alsike clover 


4 
4 


Birdsfoot trefoil 


5 


Orchardgrass 


4 










Timothy 


2 


Red clover 


8 


Birdsfoot trefoil 
Timothy 


5 
2 


, 




Ladino clover 
Bromegrass 


'/2 

8 


Ladino clover 
Tall fescue 


1/2 
6-8 




Droughty soils 




Tall fescue 


10 






Alfalfa 


8 


Alfalfa 


8 










Bromegrass 


6 


Orchardgrass 


4 


Orchardgrass^ 


8 






Alfalfa 


8 


Alfalfa 


8 




Poorly drained soils 




Tall fescue^ 


6 


Tall fescue 


6 


Alsike clover 


3 


Alsike clover 


2 






Alfalfa 


« 


Ladino clover 


■A 


Ladino clover 


1/2 






j\l 1 CII 1 d 

Bromegrass 


6 


Timothy 
Birdsfoot trefoil 


4 
5 


Tall fescue 
Alsike clover 


8 
3 


















Timothy 


2 


Ladino clover 


1/2 




For horse pastures 








Reed canarygrass 


8 


Northern, Central 








Reed canarygrass 


8 






Illinois 


Southern Illinois 




Alsike clover 


3 






Moderately to well-drained soils 




Ladino clover 


'74 -1/2 






Alfalfa 


8 


Alfalfa 


8 


Alsike clover 


2 






Smooth bromegrass 


6 


Orchardgrass 


3 


Ladino clover 
Tall fescue 


V2 






Kentucky bluegrass 


2 


Kentucky bluegrass 


5 


8 








Poorly drained soils 






Droughty soils 




Ladino clover 


1/2 


Ladino clover 


1/2 


Alfalfa 


8 


Alfalfa 


8 


Smooth bromegrass 


6 


Orchardgrass 


6 


Bromegrass 


5 


Orchardgrass 


4 


Kentucky bluegrass 


2 


Kentucky bluegrass 


5 


Alfalfa 


8 


Alfalfa 


8 


1 Timothy 


2 






Orchardgrass^ 


4 


Tall fescue 


6 


Central Illinois 




Alfalfa 


8 


Red clover 


8 


1 Moderately to well-drained soils 


Poorly drained soils 




Tall fescue 


6 


Ladino clover 
Orchardgrass^ 


1/2 

4 


Alfalfa 


8 


Ladino clover 


Vi 


Red clover 


8 






Orchardgrass 


3 


Orchardgrass 


6 


Ladino clover 


V2 


Red clover 


8 


Kentucky bluegrass 


2 


Kentucky bluegrass 


2 


Orchardgrass 


4 


Ladino clover 


V2 










Red clover 


8 


Tall fescue 


6-8 












For hog pastures 
All soil types, anywhere in Illinois 




Ladino clover 
Tall fescue 


1/2 
6-8 
















Alfalfa 


8 








For pasture 


renovation 




Ladino clover 


2 






















Northern Cfin^ra^ Tllinnic 


QrkiifVi<»rn Tllinnic 




For warm-season 


perennial grasses 




l^VXlAI^£lt, ^« CA .•-«. ■■■■■•■■■-• 


Moderately to well-drained soils 




Moderately 


to well-drai 
anywhere 


ned and droughty soils,^ 
in Illinois 




Alfalfa 
Red clover 


8 
4 


Alfalfa 
Red clover 


8 
4 


Switchgrass 


6 


Big bluestem 


3 




Poorly drained soils 




Eastern gamaerass 


15 


Indiangrass 


4 


Birdsfoot trefoil 


4 


Alsike 


2 


o o 




Switchgrass 
Big bluestem 


2 


Red clover 


4 


Ladino clover 


1/2 


Big bluestem 


7 


3 






Red clover 


4 


Caucasian bluestem 


5 


Indiangrass 


3 










Indiangrass 


7 















* Central Illinois only. 

'' Not recommended for poorly drained soils. 



may need supplemental feed when pasturing on 
switchgrass. Indiangrass and big bluestem tend to be 
a little higher in digestibility than switchgrass, but 
they are marginal for maintenance of pregnant beef 
cows. Dry-matter digestibility may be underestimated 
by in vitro analysis methods. 

Warm-season perennial grasses may yield 5.5 to 7.5 
tons of hay dry matter per acre throughout Illinois. 

Big bluestem {Andropogon gerardii) grows to 4 to 7 
feet tall and is a sod-forming, warm-season perennial 
grass. It was a major contributor to the development 
of the deep, dark, prairie soils of Illinois. This perennial 
has short rhizomes, but it makes a very tough sod. 
Big bluestem thrives on moist, well-drained loam soils 
of relatively high fertility. It is one of the dominant 
grasses of the eastern Great Plains and is found in 
association with little bluestem, switchgrass, and in- 
diangrass. Big bluestem establishes slowly from seed. 

Big bluestem begins growth in May and makes a 
large part of its growth in late July through August. 
Grazing should leave a 6-inch stubble to prevent loss 
of stand. 

This grass is palatable and nutritious in its early 
stages of growth. It withstands close grazing late in 
the season if it is protected from close grazing early 
in the season. Good hay may be made if harvested 
before seed heads emerge. Seed matures in late Sep- 
tember and October. 

Roundtree big bluestem was released by the Soil 
Conservation Service and the Missouri Agricultural 
Experiment Station in 1983. Other varieties of big 
bluestem are Champ, Kaw, and Pawnee. Other blue- 
stem varieties include Plains (Yellow Bluestem), re- 
leased by the Oklahoma Agricultural Experiment Sta- 
tion in 1970; King Ranch; and Caucasian. 

Indiangrass {Sorghastrum nutans) is a sod-forming 
grass with a deep, extensive root system with short 
rhizomes. It is adapted to deep soils that are not 
extremely wet. 

Indiangrass produces fair- to good-quality forage 
during the summer months. Grazing months are July 
through mid-September. Harvest indiangrass for hay 
at the early boot stage. Begin grazing after the plant 
reaches 18 inches in height. Graze to a minimum of 
a 10 -inch stubble. 

Varieties are Holt, from the Nebraska Agricultural 
Experiment Station; Osage, from the Kansas Agricul- 
tural Experiment Station; Oto, from the Nebraska 
Agricultural Experiment Station; and Rumsey, from a 
native stand in south central Illinois. 

Seedings should be made from mid-May to mid- 
June at 10 to 12 pounds of pure live seed (PLS) per 
acre. Seed at one-fourth inch deep, on a prepared 
seedbed that has been firmed with a corrugated roller. 
Use no nitrogen during the seeding year. See Table 
7.11 for a list of species and varieties. 

Eastern gamagrass {Tripsacum dactyloides [L]. L) is 



Table 7.11. Species and Varieties of Warm-Season 
Perennial Grasses at Dixon Springs 

Species/varietv" 1981 1990 Average 

dry matter, tons per acre 

Switchgrass/ 

Cave-in-Rock 4.50 6.43 5.47 

Eastern gamagrass/ 

Pete 8.25 6.14 7.20 

Big bluestem/ 

Roundtree 5.44 4.23 4.84 

Big bluestem/ 

Caucasian bluestem 3.73 3.42 3.58 

Indiangrass/ 

Rumsey 5.95 6.11 6.03 

' Each variety is harvested twice a year. 



related to corn. The seed heads have the female flowers 
on the lower portion and the male flowers above. It 
grows in large clumps in low areas, is quite palatable, 
and often is destroyed by close grazing. Eastern gam- 
agrass produces a large tonnage of forage and can be 
used for hay or silage. 

Caucasian bluestem or Old Word bluestems (Both- 
riochloa caucasica C.E. Hubb.), a perennial bunchgrass, 
is an introduction from Russia that shows promise as 
a pasture and hay grass in Illinois. It is easily estab- 
lished from seed and makes good growth even if 
moisture supplies are low. It bears an abundance of 
small, viable seed that shatter readily. 

Establishment of warm-season perennial grasses 

Establishment of warm-season perennial grasses is 
slow. Seedings need to be made early in the season, 
from April through June, to allow adequate time for 
the seedlings to become well established. Atrazine (at 
2 pounds of active ingredients per acre) may be applied 
to the surface after seeding big bluestem. Switchgrass 
and indiangrass seedlings are damaged by atrazine. 

Seeding rates of 5 to 6 pound PLS per acre of 
switchgrass and 10 to 12 pounds of PLS per acre of 
big bluestem and indiangrass are suggested rates. Do 
not graze until the plants are well estabhshed, at least 
one year old. Weeds may be reduced during the seeding 
year by clipping. The first clipping should be done at 
about 60 days after seeding and at a height of 3 inches. 
Later clippings should be at no less than 6-inch stubble 
height. Do not clip after August 1. 

Seedings should be made on prepared seedbeds 
that are very firm. The drill or seeder must be able to 
handle the seed, because seeds of indiangrass and big 
bluestem are light and feathery. Debearding will help 
to get the seed through the seeders. 

Seedings may be made into existing grass sods, but 
the grass must be destroyed. Roundup will remove 
most grasses when applied according to label instruc- 
tions. Atrazine also may be used when seeding big 
bluestem. A no-till drill is needed to place seeds into 
the soil surface and to obtain a good soil-seed contact. 



40 



Fertilization For establishment, fertilize with 30 to 40 pounds of 

Warm-season perennial grasses prefer fertile soils nitrogen, 24 to 30 pounds of phosphate, and 40 to 60 

but grow well in moderate fertility conditions. Warm- pounds of potash per acre. 

season perennials do not respond to nitrogen fertihza- For pasture or hay production of established stands, 

tion as much as cool-season perennials. Warm-season fertilize with 100 to 120 pounds of nitrogen, 50 to 60 

perennial grasses use minerals and moisture more poundsof phosphate, and 100 to 120 pounds of potash 

efficiently than cool-season perennial grasses. per acre. 



41 



Chapter 8. 
Seed Production 



Seed production of forage legumes 

Illinois is an important producer of red clover seed. 
Yields vary widely from year to year, with warm, dry 
summers favoring seed production. In part, low yields 
are caused by inadequate pollination by bees. Only 
during the clover's second growth period do honey 
bees visit red clover in numbers high enough to 
pollinate it while they collect pollen and nectar. In 
experiments on the Agronomy Farm at Urbana, honey 
bees collected 54 to 99 percent of their daily pollen 
intake from red clover between July 12 and August 3. 

Bumblebees also pollinate red clover, but they can- 
not be relied upon because they are not always present 
and their numbers are unpredictable. The presence of 
honey bees in the vicinity of red clover fields cannot 
be assured — because of insufficient numbers of hives 
in Illinois. 

To produce red clover seed, use the second growth 
period crop and at least two colonies of honey bees 
per acre within or beside the field. On large fields, 
place the hives in two or more groups. Do not rely 
on bees present in the neighborhood, because polli- 
nation and seed set decrease rapidly as distance be- 
tween the hives and the crop becomes greater than 
800 feet. Bring a sufficient number of hives to the field 
as soon as it comes into bloom. When all factors for 
seed production are favorable, proper pollination of 
red clover by honey bees has the potential of doubling 
or tripling seed yields. 

White and yellow sweet clovers are highly attractive 
to bees and other insects. Still, probably because of 
the large number of blossoms, their seed yields increase 
when colonies of honey bees are placed nearby. Yields 
up to 1,400 pounds per acre have been produced in 
the Midwest when using six colonies of bees per acre. 
One or two hives per acre will give reasonably good 
pollination. 

Crownvetch does not attract bees and requires 
special techniques to produce a commercial crop of 
seed. Best yields have been obtained by bringing 
strong, new hives of bees to the fields every 8 to 10 
days. Instead of such special provisions, one or more 



hives of honey bees per acre of crownvetch are of 
value. 

The effects of insect pollination on annual lespedeza, 
such as Korean, have not been investigated; but the 
perennial lespedezas require insect pollination to pro- 
duce a crop of seed, and honey bees can be used. 

Many legumes grown in Illinois for pasture or for 
purposes other than seed production are visited by 
honey bees and other bee pollinators. Alfalfa and 
birdsfoot trefoil — as well as alsike, white, and ladino 
clovers — all provide some pollen and nectar and, in 
turn, are pollinated to varying degrees. 

During their bloom in July and August, soybeans 
are visited by honey bees. The beans are a major 
source of honey in the state. In tests at Urbana, honey 
bee visits to soybeans did not increase seed yield over 
that of plants caged to exclude bees. Other studies 
have indicated that some varieties increase yields as a 
result of increasing honey bee visits during flowering. 



Plant Variety Protection Act 

Congress passed the Plant Variety Protection Act in 
1970. This law provides the inventor or owner of a 
new variety of certain seed-propagated crops the right 
to exclude others from selling, offering for sale, repro- 
ducing, exporting, or using the variety to produce a 
hybrid, different variety, or blend. 

These rights are not automatic. The owner must 
apply for a certificate of protection. If the owner does 
not choose to protect the variety, it is public property 
and anyone may legally reproduce it and sell the seed. 

Many varieties of the self-pollinated crops com- 
monly grown in Illinois — such as soybeans and 
wheat — that were developed by private industry since 
1970 are protected varieties. Many varieties developed 
at state experiment stations also are protected. 

Farmers who purchase a protected variety may use 
their production for seed on their own farm or market 
it as grain. An exemption has permitted limited mar- 
keting of seeds of protected varieties between farmers. 
This exemption may be changed in the future. Farmers 
should verify the legal marketing privileges of pro- 



42 



I 



tected varieties to avoid infringing the legal rights of 
the holder of the Plant Variety Protection Certificate. 

Under one provision of the act, the owner may 
stipulate that the variety be sold by variety name only 
as a class of Certified Seed. Seeds of a certified variety 
are produced according to the standards and proce- 
dures of an official Seed Certification Agency in the 
United States or Canada. In Illinois, this is the Illinois 
Crop Improvement Association. Selling uncertified seed 
by variety name of varieties protected in this manner 
is a violation of Seed Certification rules, the Federal 
Seed Act, and the State Seed Law. Violators are subject 
to prosecution. 

If the owner of a protected variety does not choose 
the Certified Seed provision of the act, a farmer whose 
primary occupation is producing food or feed may sell 
seed of the protected variety to another farmer whose 
primary occupation is producing grain for food or feed. 
The second farmer, however, may not sell as seed any 
of the crop that is produced. 

Even if the protected variety is not covered by the 
act's Certified Seed provision, any advertising of the 



sale of seed of that variety — including farm sale 
bills — usually is considered an infringement of the 
owner's rights. Therefore, any person who desires to 
sell the uncertified seed of a protected variety must 
also obtain permission from the variety's owner. Vi- 
olators are subject to civil lawsuits. 

The container in which seed of a protected variety 
is sold should carry a label identifying the seed as that 
of a protected variety. All seeds offered for sale in 
Illinois must be labeled according to the Illinois Seed 
Law. Requirements for labeling vary among the crop 
seeds. For current information, consult an Illinois Seed 
Law publication, available from the Illinois Department 
of Agriculture. 

Plant variety protection has greatly benefited U.S. 
agriculture. Many improved varieties of various crops 
have been developed that would not have been de- 
veloped without this protection. Farmers should not 
be reluctant to use "protected varieties" since many 
of these will be top performers, but they must be 
aware of the limitation of use of these crops for seed 
purposes. 



43 



I 



Chapter 9. 
Water Quality 



The protection of water quality is an important part 
of any crop production system. Illinois farmers have 
a great stake in protecting drinking water quality 
because they often consume the water that lies directly 
under their farming operation. Their domestic water 
wells are often in proximity to agricultural operations 
or fields and, therefore, must be safeguarded against 
contamination. The great majority of crop protection 
chemicals never reach groundwater. In Illinois, favor- 
able soil and geologic conditions help degrade or retard 
movement of pesticides. Vulnerable site conditions are 
found in some parts of Illinois, however. In these areas 
(described in detail later) appropriate chemical selec- 
tion and management decisions need to be made to 
ensure good water quality. 

Extensive well-water surveys are currently under 
way in Illinois. We will soon have more definitive 
information as to the extent of groundwater contam- 
ination. Smaller-scale water-testing projects in selected 
areas of Illinois have shown limited detections of 
agricultural chemicals and nitrate-nitrogen (sources of 
which are not always agricultural fertilizers). Atrazine 
is the most frequently detected herbicide. In some 
cases the levels of detection have exceeded recom- 
mended health advisory limits as established by the 
U.S. Environmental Protection Agency (EPA). The 
highest levels of detection are often from wells that 
are in proximity to chemical handling sites, or wells 
that are known to have been contaminated by an 
accidental point source introduction of the chemical 
directly to the well, such as back-siphoning. 

Protection of groundwater drinking sources is a 
critical and achievable task that can be accomplished 
by (1) preventing point source contamination of the 
well, (2) evaluating the groundwater contamination 
susceptibility as determined by soil and geologic con- 
ditions and the water management system, (3) selecting 
appropriate chemicals and chemical application strat- 
egies, and (4) practicing sound agronomy that uses 
integrated pest management principles and appropriate 
yield goals. 

Drinking water contaminants 

Many substances in the environment, whether re- 
lated to industry, agriculture, or of natural derivation, 



have been associated with health problems in humans 
and livestock. The scope of this chapter does not 
warrant a full discussion of all pollutants but rather 
focuses on the contaminants that are associated with 
agriculture and the rural farmer. The most frequent 
contaminant of rural wells is coliform bacteria, which 
are associated with livestock or human waste. These 
bacteria can enter wells laterally through a septic tank 
leach field or overland into a wellhead as runoff from 
livestock impoundments. Nitrate-nitrogen is the sec- 
ond most common substance that can occur in levels 
exceeding health advisories. Although the presence of 
nitrates (NO3) in drinking water is frequently blamed 
on agriculture, nitrates come from many sources, in- 
cluding septic tanks, livestock waste, and decaying 
organic matter. Bacteria and nitrates are often the "first 
to arrive" in a well with high potential for contami- 
nation. Together their presence suggests a possible 
pathway from a contaminating source to the well that 
has been established. 

A variety of herbicides have been detected in trace 
amounts in potable water supplies. A recently com- 
pleted nationwide survey found detectable levels of 
herbicides in 13 percent of the wells surveyed. Atrazine 
was detected in 12 percent of the wells surveyed and, 
therefore, constituted over 90 percent of the total 
detections. Although the herbicides were detected in 
a significant percentage of the wells, only 0.11 percent 
of the wells had herbicide concentrations above the 
health advisory levels. 



Point source prevention 

Control of point source contamination is the most 
important measure a farmer can take to protect a 
groundwater drinking source. A point source is a well- 
defined and traceable source of contamination such as 
a leaking pesticide container, a pesticide spill, or back- 
siphoning from spray tanks directly into a well. Because 
point sources involve high concentrations or direct 
movement of contaminants to the water source, the 
purifying ability of the soil is bypassed. The following 
handling practices, based largely on common sense, 



44 



will minimize the potential for groundwater contam- 
ination: 

• Never mix chemicals near (within 200 feet of) wells, 
ditches, streams, or other water sources. 

• Prevent back-siphoning of mixed pesticides from the 
spray tank to the well by always keeping the fill hose 
above the overflow of the spray tank. 

• Store pesticides downslope from well-water sources 
and a safe distance from both wells and surface 
waters. 

• Triple-rinse pesticide containers, and put rinsate back 
into the spray tank to make up the final spray mixture. 

•Avoid introducing pesticides or fertilizers into sink- 
holes or abandoned wells. Lateral movement of con- 
taminants in the groundwater to a drinking water 
well may be more rapid than vertical movement 
through the soil. 

• Seal abandoned wells to prevent connection between 
agricultural practices and the groundwater. 



Groundwater vulnerability 

Site characteristics, including the soil and geologic 
properties, water table depth, and depth of the well, 
will determine the potential of nonpoint contamination 
of the groundwater. Nonpoint sources of contamina- 
tion are difficult to pinpoint, originate from a variety 
of sources, and are affected by many processes. Con- 
taminants moving into groundwater from routine ag- 
ricultural use are an example of a nonpoint source. 
Producers applying pesticides in vulnerable areas should 
pay strict attention to chemical selection and manage- 
ment practices. 

Soil characteristics 

Water-holding capacity, permeability, and organic 
matter content are important soil properties that de- 
termine a soil's ability to detain surface-applied pes- 
ticides in the crop root zone. Fine-textured, dark prairie 
soils have large water-holding capacities, low perme- 
abilities, and large organic matter contents, all attri- 
butes that reduce pesticide leaching due to reduced 
water flow or increased binding of pesticides. The 
forest soils that dominate the landscape in western 
and southern Illinois are slightly lower in organic 
matter and, therefore, may be less effective at binding 
pesticides. 

The most vulnerable soils for groundwater contam- 
ination are the sandy soils that lie along the major 
river valleys of Illinois. Sandy soils are highly perme- 
able, have low organic matter contents, and often are 
irrigated. All of these factors represent increased risks 
to groundwater quality. Extra precautions in chemical 
selection and application method should be taken in 
these vulnerable soils. Irrigators in particular should 
pay attention to groundwater advisory warnings that 
restrict the use of some herbicides on sandy soils. 



Geology 

The geologic strata beneath a farming operation may 
be important in determining the risk of nonpoint 
contamination. In Illinois the most hazardous geology 
for groundwater pollution is the karst or limestone 
region that occurs along the margins of the Mississippi 
River and in the northwestern part of the state. Sink- 
holes and fractures that occur in the bedrock in these 
areas may extend to the soil surface, providing access 
for runoff directly to the groundwater. Water moving 
into these access points bypasses the natural treatment 
that is provided by percolation through soil. Karst 
areas should be farmed carefully with due attention 
to buffer zones around sinkholes to prevent runoff 
entry to the groundwater. Agronomic practices that 
minimize runoff are effective ways to reduce the 
potential for pesticide movement to the groundwater. 

Groundwater and well depths 

Deep aquifers that lie under impermeable geologic 
formations are the most protected from contamination 
by surface activities. Shallow water-table aquifers are 
more vulnerable to contamination because of their 
proximity to the surface. Shallow dug wells in water- 
table or shallow aquifers are also more vulnerable 
because of typically inadequate wellhead protection. 



Surface water contamination 

Although groundwater protection receives the ma- 
jority of media attention, surface water quaUty is 
generally at greater risk. Surface waters have a greater 
capacity for breaking down pesticides, because biolog- 
ical breakdown processes operate at a faster rate than 
in groundwater. A recent survey of surface waters in 
Illinois by the U.S. Geological Survey found detectable 
herbicide levels in 90 percent of the samples taken in 
May and June of 1989. Control of surface water 
contamination is best achieved by controlling runoff 
movement of water and sediment. Soil conservation 
practices and prudent use of buffer strips near stream 
banks generally reduce the probability of surface water 
contamination. 



Management practices 

Many effective management practices outlined in 
other sections of this handbook have been recom- 
mended with due consideration to water quality. Man- 
agement is most critical in areas that are the most 
vulnerable to contamination. 



Nutrient management 

Soil testing is a basic foundation for fertilizer rec- 
ommendations. Testing manures for nutrient content 
allows accurate crediting for fertilizer replacement. A 



45 



sound nitrogen management program for grain crops 
that emphasizes appropriate yield goals and credit for 
prior legumes will optimize the amount of fertilizer 
nitrogen introduced to the field. Splitting nitrogen 
applications on sandy irrigated soils is wise because it 
reduces the chances for excessive leaching that might 
occur if a single nitrogen application is used. 

Integrated pest management 

It is generally assumed that reduced pesticide use 
results in a reduced probability of groundwater con- 
tamination. The use of integrated pest management 
strategies reduces unnecessary use of pesticides. Two 
examples are the recommended practice of crop ro- 
tation that reduces the need for corn rootworm insec- 
ticides in continuous corn, and the use of crop rotation 
and tolerant varieties to control plant diseases. 

Conservation tillage 

Reducing tillage and retaining crop residues on the 
soil surface limits the runoff and overland flow that 
carries pesticides and nutrients out of the field. The 
effect of conservation tillage and no-till on ground- 
water quality is controversial and the subject of much 
research. Reduction of runoff and erosion is accom- 
plished by increasing infiltration of water. Increased 
infiltration, particularly through earthworm-formed 
macropores, offers a transport system to the subsoil 
that soil-applied pesticides can follow. Conversely, the 
macropores are not the primary routes of water flow 
unless heavy rainfall or flooding occurs and allows 
rapid movement of "clean" rainwater past the soil 
layers that contain pesticides. Conservation tillage 
methods are most important in controlling soil erosion 
on sloping land. Adopting more severe tillage to protect 
groundwater quality is not warranted based on our 
current knowledge. 

Cover crops 

A cover crop such as a small grain or legume may 
provide water quality benefits from several stand- 
points. The effectiveness of cover crops in controlling 
erosion is well documented, and controlling erosion is 
an important component of surface water quality pro- 
tection. Small-grain cover crops have shown some 
efficiency at retrieving residual nitrogen from the soil 
following fertilized corn or vegetable crops. This fea- 
ture may be important on sandy irrigated soils where 
winter rainfall leaches much of the residual nitrogen. 

Legumes may provide a source of nitrogen to sub- 
sequent crops. Refer to the chapter on cover crops in 
this handbook for further information. 



Chemical properties and selection 

The selection of agricultural chemicals is most critical 
for producers on vulnerable soil and geologic sites. 



Herbicide selection is a complex task that must take 
into account the crop, tillage system, target species, 
and a host of other variables. Chemical properties of 
the herbicide are important to consider when evalu- 
ating their potential to leach to the groundwater. The 
three most important characteristics of a pesticide that 
influence leaching potential are solubility in water, 
ability to bind with the soil (adsorption), and the rate 
at which it breaks down in the soil. High solubility 
(dissolves readily), low binding ability, and slow break- 
down all increase a pesticide's ability to move to the 
groundwater. Among the frequently used herbicides 
that have a greater potential to leach and are labeled 
with groundwater advisories are those that contain 
alachlor, atrazine, clopyralid, cyanazine, metribuzin, 
metolachlor, or simazine (Table 9.1). 



Precautions for irrigators 

Chemigation refers to the application of fertilizers 
and pesticides through an irrigation system and is a 
management tool that has benefits and potential draw- 
backs for groundwater protection. The greatest benefit 
of chemigation is for fertigation, which is the appli- 
cation of fertilizers, particularly nitrogen, through the 
irrigation system. Nitrogen application can be more 
carefully spread out in the vegetative growth period 
of grain crops, thereby minimizing the susceptibility 
of leaching. 

Chemigation systems should be equipped with back- 
flow prevention devices. These greatly reduce the 
threat of back-siphoning undiluted chemicals into the 
irrigation well. Back-flow prevention devices will likely 
become mandatory on irrigation systems by 1994 but 
should already be on every irrigation system that injects 



Table 9.1. Herbicide and Herbicide Premixes with 
Groundwater Advisories 

Trade name Common (generic) name 

AAtrex, Atrazine atrazine 

Bicep metolachlor + atrazine 

Bladex cyanazine 

Bronco alachlor + glyphosate 

Buctril/atrazine bromoxynil + atrazine 

Bullet alachlor + atrazine 

Cannon alachlor + trifluralin 

Canopy metribuzin + chlorimuron 

Dual metolachlor 

Extrazine cyanazine + atrazine 

Freedom alachlor + trifluralin 

Laddok bentazon + atrazine 

Lariat alachlor + atrazine 

Lasso EC, MT* alachlor 

Lexone metribuzin 

Marksman dicamba + atrazine 

Preview metribuzin + chlorimuron 

Princep, Simazine simazine 

Salute metribuzin + trifluralin 

Sencor metribuzin 

Stinger clopyralid 

Sutazine butylate + atrazine 

Turbo metribuzin + metolachlor 

• Lasso MT has shown reduced leaching tendency in initial experiments. 



f 



46 



chemicals. Reputable irrigation dealers do not sell 
irrigation systems without this important feature. 

Well water testing 

The most important step in well water testing is to 
contact the local health department and determine the 
procedure for sampling and submitting water for ni- 
trate and bacteria determinations. The service is pro- 
vided at no cost or a nominal fee in most counties. 



The presence of coliform bacteria with or without 
elevated nitrates is a sign that your well is contaminated 
by runoff or a septic system. Faulty well construction 
or improper wellhead protection is a major cause of 
contamination. Pesticide testing is expensive and re- 
quires sensitive analytical equipment. Several private 
water testing laboratories, certified by the Illinois En- 
vironmental Protection Agency, will perform water 
analyses for citizens. Contact your local Extension 
adviser for information on laboratories in your area. 



47 



Chapter 10. 

Soil Testing and Fertility 



Soil testing 

Soil testing is the most important single guide to the 
profitable application of fertilizer and lime. When soil 
test results are combined with information about the 
nutrients that are available to the various crops from 
the soil profile, the farmer has a reliable basis for 
planning the fertility program on each field. 

Traditionally, soil testing has been used to decide 
how much lime and fertilizer to apply. Today, with 
increased emphasis on the environment, soil tests are 
also a logical tool to determine areas where adequate 
or excessive fertilization has taken place. 

How to sample. A soil tube is the best implement 
to use for taking soil samples, but a spade or auger 
also can be used (Figure 10.1). One composite sample 
from every IVi acres is suggested. Five soil cores taken 
with a tube will give a satisfactory composite sample 
of about 1 to 2 cups in size. You may follow a regular 
pattern as indicated in Figure 10.2. This pattern is a 
change from the long-standing suggestion of 11 composite 
soil samples for a 40-acre field. It gives a better repre- 
sentation of all areas in the field. 

The most common mistake is taking too few samples 
to represent the fields adequately. Taking shortcuts in 
sampling may produce unreliable results and lead to 
higher fertilizer costs, lower returns, or both. 

It is important to collect soil samples to the proper 
depth — 7 inches. For fields in which reduced tillage 
systems have been used, proper sampling depth is 
especially important, as these systems result in less 
thorough mixing of lime and fertilizer than does a 





Soil slice 
Vz" thick 




Auger 



Soil tube 



Spade 



Figure 10.1. How to take soil samples with an auger, soil 
tube, and spade. 



s 2 



s 3 



s 7 



10 s 



11 s 



12 



16 s 



15 



14 



13 



Figure 10.2. Directions for collecting soil samples from 
a 40-acre field. Each step is a 3-foot distance. Each 
numbered area is a soil sample location 1 rod square. 
Five core samples 1 inch in diameter are collected from 
each square to a depth of 7 inches and mixed. 



tillage system that includes a moldboard plow. This 
stratification of nutrients has not adversely affected 
crop yields, but misleading soil test results may be 
obtained if samples are not taken to the proper depth. 

Under reduced tillage systems, it may be of interest 
to monitor surface soil pH by collecting samples to a 
depth of 2 inches from 3 separate areas in a 40-acre 
field. These areas should represent the low, interme- 
diate, and high ground of the field. 

When to sample. Sampling every 4 years is strongly 
suggested. Results from Iowa have indicated that pre- 
vious crops may influence the test values. Potassium 
tests following soybeans have consistently been slightly 
higher than following corn under the same fertility 
program. To improve the consistency of results, it is 



48 






suggested that samples be collected at the same time 
following the same crop. Therefore, if you are in a 3- 
year rotation, collect samples every 3 years instead of 
every 4 years. 

Late summer and fall are the best seasons for 
collecting soil samples from the field because potassium 
test results are most reliable during these times. Sam- 
pling frozen soil or within 2 weeks after the soil has 
thawed should be avoided. 

Where to have soil tested. Illinois has about 65 
commercial soil-testing services. Your county Extension 
adviser or fertilizer dealer can advise you about avail- 
ability of soil testing in your area. 

Information to accompany soil samples. The best 
fertilizer recommendations are those based on both 
soil test results and a knowledge of the field conditions 
that will affect nutrient availability. Because the person 
making the recommendation does not know the con- 
ditions in each field, it is important that you provide 
adequate information with each sample. 

This information includes cropping intentions for 
the next 4 years; the nature of the soil (clay, silty, or 
sandy; light or dark color; level or hilly; eroded; well 
drained or wet; tiled or not; deep or shallow; or if 
possible, the name of the soil type); fertilizer used 
(amount and grade); if the field was limed in the past 
2 years; and yield goals for all proposed crops. 

What tests to have made. Soil fertility problems in 
Illinois are largely associated with acidity, phosphorus, 
potassium, and nitrogen. Useful and recommended 
soil tests for making decisions about lime and fertilizer 
use are as follows: water pH test, which will show 
soil reaction as pH units; Bray P, test for plant-available 
soil phosphorus, which will commonly be reported as 
pounds of phosphorus per acre (elemental basis); and 
the potassium (K) test, which will commonly be re- 
ported as pounds of potassium per acre (elemental 
basis). Guides for interpreting these tests are included 
in this section. An organic-matter test made by some 
laboratories is particularly useful in selecting the proper 
rate of herbicide and agricultural limestone. 

Because nitrogen (N) can change forms or be lost 
from the soil, the use of soil testing to determine 
nitrogen fertilizer needs for Illinois field crops is not 
recommended in the same sense as testing for the 
need for lime, phosphorus, or potassium fertilizer. 
Testing the soil to predict the need for nitrogen fertilizer 
is complicated by the fact that nitrogen availability, 
both the release from soil organic matter and the loss 
by leaching and denitrification, is regulated by unpre- 
dictable climatic conditions. Under excessively wet 
conditions, both soil and fertilizer nitrogen may be 
lost by denitrification or leaching. Under dry condi- 
tions, the amount of nitrogen released from organic 
matter is low, but under ideal moisture conditions, it 
is high. Use of the organic-matter test as a nitrogen 
soil test, however, may be misleading and result in 
under fertihza tion . 

Scientists in Vermont and Wisconsin have identified 



nitrogen soil tests that work well under their condi- 
tions. These tests are now being evaluated under 
Illinois conditions. Specifics of the tests, along with an 
evaluation of their potential and limitations for Illinois, 
are discussed in the nitrogen section of this chapter. 
Guides for planning nitrogen fertilizer use are also 
provided. 

Tests are available for most of the secondary nu- 
trients and micronutrients, but interpretation of these 
tests is less reliable than the interpretation of tests for 
lime, phosphorus, or potassium. Complete field history 
and soil information are especially important in inter- 
preting the results. Even though these tests are less 
reliable, they may be useful in two ways: 

1 . Trouble shooting. Diagnosing symptoms of abnormal 
growth. Paired samples representing areas of good 
and poor growth are needed for analyses. 

2. "Hidden-hunger checkup." Identifying deficiencies 
before symptoms appear. Soil tests are of little value 
in indicating marginal levels of secondary nutrients 
and micronutrients when crop growth is apparently 
normal. For this purpose, plant analysis may yield 
more information. 

The rating of soil tests (given in Table 10.1) has 
been developed to put into perspective the reliability, 
usefulness, and cost effectiveness of soil tests as a 
basis for planning a soil fertility and liming program 
for field crops in Illinois. These subjective ratings are 
on a scale from to 100, for which a score of 100 is 
deemed very reliable, useful, and cost effective and a 
score of zero is deemed of little value. Additional 
research will undoubtedly improve some test ratings. 



Plant analysis 

Plant analyses can be useful in diagnosing problems, 
in identifying hidden hunger, and in determining 
whether current fertility programs are adequate. They 
often provide more reliable measures of micronutrient 
and secondary nutrient problems than do soil tests. 

How to sample. When making a plant analysis to 
diagnose a problem, select paired samples of compa- 
rable plant parts representing the abnormal and normal 
plants. Abnormal plants selected should represent the 
first stages of a problem. 

When using the technique to diagnose hidden hun- 
ger, for corn, sample several of the leaves opposite 
and below the ear at early tassel time. For soybeans, 
sample the most recent fully developed leaves and 
petioles at early podding. Samples taken later will not 
indicate the nutritional status of the plant. After you 
collect the samples, deliver them immediately to the 
laboratory. They should be air dried if they cannot be 
delivered immediately or if they are going to be shipped 
to a laboratory. 

Environmental factors may complicate the interpre- 
tation of plant analysis data. The more information 
one has concerning a particular field, the more reliable 



49 



the interpretation will be. Suggested critical nutrient 
levels are provided in Table 10.2. Lower levels may 
indicate a nutrient deficiency. 



Lime 

Soil acidity is one of the most serious limitations to 
crop production. Acidity is created by a removal of 
bases by harvested crops, leaching, and an acid residual 
that is left in the soil from nitrogen fertiUzers. Over 
the last several years, limestone use has tended to 
decrease while crop yields and nitrogen fertilizer use 
have increased markedly (Figure 10.3). 

At the present rate of limestone use, no lime is 
being added to correct the acidity that is created by 
the removal of bases nor the acidity created in prior 
years, which had not been corrected. A soil test every 
4 years is the best way to check on soil acidity levels. 

The effect of soil acidity on plant growth. Soil 
acidity affects plant growth in several ways. Whenever 
soil pH is low (that is, acidity is high), several situations 
may exist. 

1. The concentration of soluble metals may be toxic. 
Damage from excess solubility of aluminum and 
manganese due to soil acidity has been shown in 
field research. 

2. Populations and the activity of the organisms re- 
sponsible for transformations involving nitrogen, 
sulfur, and phosphorus may be altered. 

3. Calcium may be deficient. This usually occurs only 
when the cation-exchange capacity of the soil is 
extremely low. 

4. Symbiotic nitrogen fixation in legume crops is im- 



paired greatly. The symbiotic relationship requires 
a narrower range of soil reaction than does the 
growth of plants not relying on nitrogen fixation. 

5. Acidic soils are poorly aggregated and have poor 
tilth. This is particularly true for soils that are low 
in organic matter. 

6. Availability of mineral elements to plants may be 
affected. Figure 10.4 shows the relationship be- 
tween soil pH and nutrient availability. The vdder 
the white bar, the greater the nutrient availability. 
For example, the availability of phosphorus is great- 
est in the pH range between 6.0 and 7.5, dropping 
off sharply below 6.0. Because the availability of 
molybdenum is increased greatly as soil acidity is 
decreased, molybdenum deficiencies can usually be 
corrected by liming. 

Suggested pH goals. For cash-grain systems (no 
alfalfa or clover), maintaining a pH of at least 6.0 is 
a realistic goal. If the soil test shows that the pH is 
6.0 or less, apply limestone. After the initial invest- 
ment, it costs little more to maintain a pH at 6.5 than 
it does at 6.0. The profit over a 10 -year period will be 
affected very little because the increased yield will 
about offset the cost of the extra limestone plus interest. 

Research indicates that a profitable yield response 
from raising the pH above 6.5 in cash-grain systems 
is unlikely. 

For cropping systems with alfalfa and clover, aim 
for a pH of 6.5 or higher unless the soils have a pH 
of 6.2 or higher without ever being limed. In those 
soils, neutral soil is just below plow depth; and it will 
probably not be necessary to apply limestone. 

Liming treatments based on soil tests. The lime- 
stone requirements in Figure 10.5 assume: 



Table 10.1. Ratings of Soil Tests^ 



Soil test 



Rating 



Soil test 



Rating 



Water pH 100 

Salt pH 30 

Buffer pH 30 

Exchangeable H 10 

Phosphorus 85 

Potassium 80 

Boron (alfalfa) 60 

Boron (com and soybeans) 10 

Iron (pH > 7.5) 30 

Iron (pH < 7.5) 10 



Organic matter 75 

Calcium 40 

Magnesium 40 

Cation-exchange capacity 60 

Sulfur 40 

Zinc 45 



Manganese (pH 
Manganese (pH 



7.5). 
7.5). 



40 
10 



Copper (organic soils) 20 

Copper (mineral soils) 5 



^ On a scale of to 100, for which a score of 100 rates the test as very reliable, useful, and cost effective and a score of zero rates the test as having little 
value. 



Table 10.2. Suggested Critical Plant Nutrient Levels 



Crop 



Plant part 



N 



K 



Ca 



Mg 



Zn Fe Mn Cu B 



Com 



Soybeans 



Leaf opposite 
and below the 
ear at tasseling 

Fully developed 
leaf and petiole 
at early podding 



— percent 

2.9 0.25 1.90 0.40 0.15 0.15 

0.25 2.00 0.40 0.25 0.15 



15 25 



15 30 



ppm 
15 

20 



10 



25 



50 




pH 



1930 



1950 



1970 



1990 



Years 



Figure 10.3. Use of agricultural lime and commercial 
nitrogen fertilizer, 1930-1989. 



1. A 9-inch plowing depth. If plowing is less than 9 
inches deep, reduce the amount of limestone; if 
more than 9 inches, increase the lime rate propor- 
tionately. In zero-tillage systems, use a 3 -inch depth 
for calculations. 

2. Typical fineness of limestone. Ten percent of the 
particles are greater than 8-mesh; 30 percent pass 
an 8-mesh and are held on 30-mesh; 30 percent 
pass a 30-mesh and are held on 60-mesh; and 30 
percent pass a 60-mesh. 

3. A calcium carbonate equivalent (total neutralizing 
power) of 90 percent. The rate of application may 
be adjusted according to the deviation from 90. 
Instructions for using Figure 10.5 are as follows: 

1. Use Chart I for grain systems and Chart II for 
alfalfa, clover, or lespedeza. 

2. Decide which soil class fits your soil: 

a. Dark-colored silty clays and silty clay loams. 

b. Light- and medium-colored silty clays and silty 
clay loams; dark-colored silt and clay loams. 

c. Light- and medium-colored silt and clay loams; 
dark- and medium-colored loams; dark-colored 
sandy loams. 

d. Light-colored loams; light- and medium-colored 
sandy loams; sands. 

e. Muck and peat. 

Soil color is related to organic-matter level. Light- 
colored soils usually have less than 2.5 percent organic 
matter; medium-colored soils have 2.5 to 4.5 percent 
organic matter; dark-colored soils have more than 4.5 
percent organic matter; sands are excluded. 

Limestone quality. Limestone quality is measured 
by the neutralizing value and the fineness of grind. 
The neutralizing value of limestone is measured by its 
calcium carbonate equivalent: the higher this value, 
the greater the limestone's ability to neutralize soil 
acidity. Rate of reaction is affected by particle size; the 
finer that limestone is ground, the faster it will neu- 
tralize soil acidity. Relative efficiency factors have been 
determined for various particle sizes (Table 10.3). 




7.0 8.0 9.0 



Nitrogen 
Phosphorus " 



T — T 



Potassium 



i i y \ i... '.'.'.'.'■' 



Sulfur 



^^^^^Wf^^^^^ 



Calcium 



Iron 



Magnesium 

— i- ^ * I 



} i \ \ \ ^ 

Manganese ^ 

-.,.. ,. . I I I " 




Boron 



—I Copper and Zinc ' '*' 




] y { I" I i i 



^b^fcUA^^^ 



Molybdenum 

\ \ i \ 



Figure 10.4. Available nutrients in relation to pH. 



Table 10.3. Efficiency Factors for Various Limestone 
Particle Sizes 





Efficiency factor 


Particle sizes 


1 year after 4 years after 
application application 


Greater than 8-mesh 

8- to 30-mesh 


5 15 

20 45 


30- to 60-mesh 


50 100 


Passing 60-mesh 


100 100 



The quality of limestone is defined as its effective 
neutralizing value (ENV). This value can be calculated 
for any liming material by using the efficiency factors 
in Table 10.3 and the calcium carbonate equivalent for 
the limestone in question. The "typical" limestone on 
which Figure 10.5 is based has an ENV of 46.35 for 
1 year and 67.5 for 4 years. 

The Illinois Department of Agriculture, in cooper- 
ation with the Illinois Department of Transportation, 
collects and analyzes limestone samples from quarries 
that wish to participate in the Illinois Voluntary Lime- 
stone Program. These analyses, along with the cal- 
culated correction factors, are available from the Illinois 
Department of Agriculture, Division of Plant Industries 
and Consumer Services, P.O. Box 19281, Springfield, 
Illinois 62794-9281, in an annual publication entitled 
Illinois Voluntary Limestone Program Producer Informa- 
tion. To calculate the ENV for materials not reported 
in that publication, obtain the analysis of the material 
in question from the supplier and use the worksheet 
provided for your calculations. 

As an example, consider a limestone that has a 



51 



calcium carbonate equivalent of 86.88 percent, that 
the sample has 13.1 percent of the particles greater 
than 8-mesh, 40.4 percent that pass 8-mesh and are 
held on 30-mesh, 14.9 percent that pass 30-mesh and 
are held on 60-mesh, and 31.6 percent that pass 60- 
mesh. Assume that you need 3 tons of typical limestone 
per acre (according to Figure 10.5). 



At rates up to 6 tons per acre, if high initial cost is 
not a deterrent, you may apply the entire amount at 
one time. If cost is a factor and the amount of limestone 
needed is 6 tons or more per acre, apply it in split 
applications of about two-thirds the first time and the 
remainder 3 or 4 years later. 



Worksheet 

Evaluation for 1 year after application 

Efficiency factor 
% of particles greater 
than 8-mesh = x 5 



% of particles that 

Eass 8-mesh and are 
eld on 30-mesh 

% of particles that 
pass 30-mesh and are 
held on 60-mesh 

% of particles that 
pass 60-mesh 



100 



100 



100 



20 



50 



100 



100 

Total fineness efficiency 

ENV = total fineness efficiency 

% calcium carbonate equivalent 
^ 100 

Correction _ ENV of typical limestone (46.35) 
factor ENV of sampled limestone ( )_ 



Evaluation for 4 years after application 

Efficiency factor 
% of particles greater 



than 8-mesh 

% of particles that 
pass 8-mesh and are 
held on 30-mesh 



% of particles that 
pass 30-mesh and are 
held on 60-mesh 



% of particles that 
pass 60-mesh 



100 



100 



100 



15 



45 



100 



100 



100 

Total fineness efficiency 

ENV = total fineness efficiency 

% calcium carbonate equivalent 
^ 100 

Correction _ ENV of typical limestone (67.5) 
factor ENV of sampled limestone { )_ 



Correction factor x limestone requirement (from Figure 10.5) = 
tons of sampled limestone needed per acre 



Correction factor x limestone requirement (from Figure 10.5) 
tons of sampled limestone needed per acre 



Chart 1 
Grain farming 












systems 


y\ 


/ 




/ 


/ 






/ 


/ 


* 


V 




^ 


^ 




/ 


/ 


^C 


V 


/ 








A 


/ 




y 








^ 




/ 


/: 


y 


f 




.s 




/ 


T 




/ 


^ 


^ 


y 


.^* 


.^ 


E 


/ 


K 






A 






^ 




















T 






















r* n 



pH 6.5 6.0 

Slightly Moderately 
acid acid 



5.5 



5.0 

Strongly 
acid 



4.5 



Q. 
Q. 
CQ 

O 

c 
o 



Chart II 

Cropping systems with 

alfalfa, clover, or lespedza 



None needed If 
naturally pH 6.2 
or above 




Application 

Is 

optional 

h« >\ 



pH7.0 


6.5 


6.0 


Neutral 


Slightly 


Moderately 




acid 


acid 



strongly 
acid 



Figure 10.5. Suggested limestone rates based on soil type, pH, and cropping system. 
52 



Q. 
OL 
CO 

o 

(/> 

c 
o 



Fluid lime suspensions (liquid lime). These prod- 
ucts are obtained by suspending very finely ground 
limestone in water. Several industrial by-products that 
have liming properties also are being land-applied as 
suspensions, either because they are too fine to be 
spread dry or they are already in suspension. These 
by-product materials include residue from water treat- 
ment plants, cement plant stack dusts, paper mill 
sludge, and other waste products. These materials may 
contain as much as 50 percent water. In some cases, 
a small amount of attapulgite clay is added as a 
suspending agent. 

The chemistry of liquid hming materials is the same 
as that of dry materials. Research results have con- 
firmed that the rate of reaction and neutralizing power 
for liquid lime are the same as for dry materials when 
particle sizes are the same. 

Results collected from one research study indicate 
that application of liquid lime at the rate of material 
calculated by the following equation is adequate to 
maintain soil pH for at least a 4-year period at the 
same level as typical lime. 

ENV of typical limestone (use 46.35) 



100 (fineness % calcium carbonate o/ ^ 
efficiency x equivalent, dry x ° ^ 
factor) matter basis 



matter 



100 



100 



X tons of limestone needed per acre = 

tons of liquid lime needed per acre. 

During the first few months after application, the 
liquid material will provide a more rapid increase in 
pH than will typical lime, but after that the two 
materials will provide equivalent pH levels in the soil. 

As an example, assume a lime need of 3 tons per 
acre (based on Figure 10.5) and liquid lime that is 50 
percent dry matter and has a calcium carbonate equiv- 
alent of 97 percent on a dry matter basis. The rate of 
liquid lime needed would be calculated as follows. 



46.35 



X 3 = 2.87 tons of liquid lime per acre 



inn 97 50 

^oo^Ioo^T^ 



Lime incorporation. Lime does not react with acidic 
soil very far from the particle; but special tillage 
operations to mix lime with soil usually are not nec- 
essary in systems that use a moldboard plow. Systems 
of tillage that use a chisel plow, disk, or field cultivator 
rather than a moldboard plow, however, may not mix 
limestone deeper than 4 to 5 inches. 



Calcium-magnesium balance in Illinois soils 

Soils in northern Illinois usually contain more mag- 
nesium than those in central and southern Illinois 
because of the high magnesium content in the rock 
from which the soils developed and because northern 
soils are geologically younger. This relatively high level 



13.1% 

100 
40.4% 

100 
14.9% 

100 
31.6% 

100 



1 Year 

X 5 = 0.65 

X 20= 8.08 

X 50 = 7.45 

X 100 = 31.60 



Total fineness 
efficiency 47.78 

ENV = 47.78x^ = 41.51 

46.35 . . - -„_ 

., -, X 3 = 3.35 tons per acre 

41.51 ^ 



13.1% 
100 

40.4% 



4 Years 
X 15 = 1.96 

X 45 = 18.18 



100 
14.9% X 100 = 14.90 



100 
31.6% 



X 100 = 31.60 



100 

Total fineness 
efficiency 66.64 

ENV = 66.64 X -^^ = 57.9 

67.5 

57.9 X 3 = 3.5 tons per acre 



of magnesium has caused some speculation as to 
whether or not the level is too high. Although there 
have been reports of suggestions that either gypsum 
or low-magnesium hmestone should be applied, no 
one has put forth research data to justify concern over 
a too-narrow ratio of calcium to magnesium. 

On the other hand, concern is justified over a soil 
magnesium level that is low — because of its relation- 
ship with hypomagnesemia, a prime factor in grass 
tetany or milk fever in cattle. This concern is more 
relevant to forage production than to grain production. 
Very high potassium levels (more than 500 pounds 
per acre) combined with low soil magnesium levels 
contribute to low-magnesium grass forages. Research 
data to establish critical magnesium levels are very 
limited. However, levels of soil magnesium less than 
60 pounds per acre on sands and 150 pounds per acre 
on silt loams are regarded as low. 

Calcium and magnesium levels of agricultural lime- 
stone vary among quarries in the state. Dolomitic 
limestone (material with an appreciable magnesium 
content, as high as 21.7 percent MgO or 46.5 percent 
MgCOs) occurs predominantly in the northern three 



53 



tiers of Illinois counties, in Kankakee County, and in 
Calhoun County. Limestone occurring in the remainder 
of the state is dominantly calcitic (high calcium), 
although it is not uncommon for it to contain 1 to 3 
percent MgCOs. 

For grain farmers, there are no agronomic reasons 
to recommend either that farmers in northern Illinois 
bypass local limestone sources, which are medium to 
high in magnesium, and pay a premium for low- 
magnesium limestone from southern Illinois or that 
farmers in southern Illinois order limestone from north- 
ern Ilhnois quarries because of magnesium content. 

For farmers with a livestock program or who pro- 
duce forages in the claypan and fragipan regions of 
the south, where soil magnesium levels may be mar- 
ginal, it is appropriate to use a soil test to verify 
conditions and to use dolomitic limestone or magne- 
sium fertilization or to add magnesium to the feed. 



Nitrogen 

About 40 percent of the original nitrogen and 
organic-matter content has been lost from typical 
Illinois soils since farming began, by erosion and from 
increased oxidation of organic matter. Erosion reduces 
the nitrogen content of soils because the surface soil 
is richest in nitrogen and this erodes first. Farming 
practices that improved aeration of the soil, including 
improved drainage and tillage, have increased the rate 
of organic matter degradation. Further nitrogen losses 
occur as a result of denitrification and leaching. 

Since harvested crops remove more nitrogen than 
any other nutrient from Illinois soils, the use of nitrogen 
fertilizer is necessary if Illinois agriculture is to be 
competitive in the world market. Low grain prices, 
along with concern for the environment, make it 
imperative that all nitrogen fertilizers be used in the 
most efficient manner possible. Factors that influence 
efficiency of fertilizer use are discussed in the following 
sections. 

Nitrogen soil tests 

Total soil nitrogen. Since 5 percent of soil organic 
matter is nitrogen, some have theorized that organic 
matter content of a soil could be used as an estimate 
of the amount of supplemental N that would be needed 
for a crop. Attempts to use this procedure have been 
unsuccessful because mineralization of organic matter 
varies significantly over time due to variation in avail- 
able soil moisture. Additionally, soils high in organic 
matter usually have a higher yield potential due to 
their ability to provide a better environment for crop 
growth. 

Early spring nitrate nitrogen. This procedure has 
been used for several years in the more arid parts of 
the Corn Belt (west of the Missouri River) with rea- 
sonable success. It involves the collection of soil sam- 
ples in 1-foot increments to a 2- to 3-foot depth in 



early spring for analysis of nitrate nitrogen. While the 
use of the information varies somewhat from state to 
state, the general consensus is to reduce the normal 
nitrogen recommendation by the amount found in the 
soil. Results obtained by scientists in both Wisconsin 
and Michigan in the late 1980s have found this pro- 
cedure to work well, but work in Iowa indicated that 
the procedure did not accurately predict nitrogen needs. 

Since samples are collected in early spring, this 
procedure measures the potential for nitrogen car- 
ryover from the previous crop. Therefore, it will have 
the greatest potential for success on continuous com, 
especially in fields where adverse growing conditions 
have limited yields in the previous year. Additional 
work is needed to ascertain the sampling procedure 
that will best characterize the field conditions, espe- 
cially when nitrogen has been injected in prior years. 
When excessive precipitation is received in late spring 
or early summer, this procedure will not likely be 
successful as most of the nitrogen that is detected 
early may be leached or denitrified before the plant 
has an opportunity to absorb it from the soil. 

Late spring nitrate nitrogen. Success with this 
procedure was first observed with work in Vermont. 
Follow-up work in Iowa in the late 1980s also indicated 
that the procedure accurately characterized nitrogen 
needs. Soil samples are collected to a 1-foot depth 
when corn plants are 6 to 12 inches tall and analyzed 
for nitrate nitrogen. Iowa State University agronomists 
suggest that no additional nitrogen be applied when 
soil test levels exceed 21 parts per million (42 pounds 
per acre) and that full rate be applied if nitrate nitrogen 
levels are less than 10 parts per million. They suggest 
proportional adjustments in nitrogen rates when test 
levels are between 10 and 20 parts per million. Ver- 
mont, Connecticut, Pennsylvania, and Rhode Island 
all suggest that no nitrogen be applied when soil 
nitrate nitrogen levels in the top foot of soil are greater 
than 25 parts per million. 

By sampling later in the season, the test provides a 
measure of the mineralization of organic nitrogen that 
has occurred and the amount of residual carryover 
that is still present in the soil. Obvious limitations of 
this procedure include: (1) its use only on fields that 
receive sidedress application of nitrogen; (2) the short 
time available between sampling and the need to apply 
fertilizer — this could be especially critical in wet years 
and could result in corn plants becoming too large to 
use conventional application equipment; and (3) no 
existing correlation for use of the procedure on those 
fields that have received a banded nitrogen application. 

Since none of the nitrogen soil procedures have 
received adequate research to determine their reliability 
and usefulness under Illinois conditions, it is suggested 
that nitrogen rates be determined using the following 
materials as a guide. 

Rate of application 

Corn. Yield goal is one of the major considerations 
to use in determining the optimum rate of nitrogen 



54 



application for com. These goals should be established 
for each field, taking into account the soil type and 
management level under which the crop will grow. 

For Illinois soils, suggested productivity-index values 
are given in Illinois Cooperative Extension Service 
Bulletin 778, Soils of Illinois. Yield goals are presented 
for both basic and high levels of management. For 
fields that will be under exceptionally high manage- 
ment, a 15 to 20 percent increase in the values given 
for high levels of management would be reasonable. 
Annual variations in yield of 20 percent above or 
below the productivity-index values are common be- 
cause of variations in weather conditions. However, 
applying nitrogen fertiUzer for yields possible in the 
most favorable year will not result in maximum net 
return when averaged over all years. 

The University of lUinois Department of Agronomy 
has conducted research trials designed to determine 
the optimum nitrogen rate for com under varying soil 
and climatic conditions. 

The results of these experiments show that average 
economic optimum nitrogen rates varied from 1.22 to 
1.32 pounds of nitrogen per bushel of com produced 
when nitrogen was applied in the spring (Table 10.4). 
The lower rate of application (1.22 pounds) would be 
recommended at a corn-nitrogen price ratio (corn price 
per bushel to nitrogen price per pound) of between 
10:1 and 20:1, and the higher rate (1.32 pounds) at a 
price ratio of 20:1 or greater. 

As would be expected, the nitrogen requirement 
was lower at sites having a corn-soybean rotation than 
at sites with continuous com. (See the subsection about 
rate adjustments page 57.) 

With the exception of Dixon, which was based on 
limited data, Brownstown and DeKalb had the highest 
nitrogen requirement per bushel of corn produced. In 
part, this higher requirement may be the result of the 
higher denitrification losses that frequently have been 
observed at Brownstown and DeKalb. 

Based on these results. Table 10.5 gives examples 



of the recommended rate of nitrogen application for 
selected Illinois soils under a high level of management. 

Soybeans. Based on average Illinois corn and soy- 
bean yields from 1984-85 and average nitrogen content 
of the grain for these two crops, the total nitrogen 
removed per acre by soybeans was greater than that 
removed by com (soybeans, 148 pounds of nitrogen 
per acre; com, 96 pounds of nitrogen per acre). Re- 
search results from the University of Illinois, however, 
indicate that when properly nodulated soybeans were 
grown at the proper soil pH, symbiotic fixation was 
equivalent to 63 percent of the nitrogen removed in 
harvested grain. Thus, net nitrogen removal by soy- 
beans was less than that of com (com, 96; soybeans, 
55). 

This net removal of nitrogen by soybeans in 1984- 
85 was equivalent to 24 percent of the amount of 
fertilizer nitrogen used in Illinois. On the other hand, 
symbiotic fixation of nitrogen by soybeans in Illinois 
(420,000 tons of N) was equivalent to 55 percent of 
the fertilizer nitrogen used in Illinois. 

Even though there is a rather large net nitrogen 
removal from soil by soybeans (55 pounds of nitrogen 
per acre), research at the University of Illinois has 
generally indicated no soybean yield increase caused 
by either residual nitrogen remaining in the soil or 
nitrogen fertilizer applied for the soybean crop. 

1. Residual from nitrogen applied to corn (Table 10.6). 
Soybean yields at four locations were not increased 
by residual nitrogen remaining in the soil, even 
when nitrogen rates as high as 320 pounds per acre 
had been applied to com the previous year. 

2. Nitrogen on continuous soybeans (Table 10.7). After 
18 years of continuous soybeans at Hartsburg, 
yields were unaffected by applications of nitrogen 
fertilizer. 

3. High rates of added nitrogen (Table 10.8). In 1968 a 
study was started at Urbana using moderate rates 
of nitrogen. Rates were increased in 1969 so that 



Table 10.4. Economic Optimum Nitrogen Rate Experimentally Determined for Eight Locations as Affected 
by Corn-Nitrogen Price Ratios 



Corn-nitrogen price ratio 



Location and rotation 

Brownstown (continuous com) . 
Carthage (continuous corn) . . . . 

DeKalb (continuous com) 

Urbana (continuous com) 

Average of continuous com . . 

Dixon (corn-soybeans) 

Hartsburg (corn-soybeans) 

Oblong (corn-soybeans) 

Toledo (corn-soybeans) 

Average of corn-soybeans . . . 

Average of all locations 





10:1 




20:1 




Optimum yield, 
bu/acre 


Optimum N 
rate, Ib/bu 


Optimum yield, 
bu/acre 


Optimum N 
rate, Ib/bu 


83 




1.30 
1.22 
1.28 
1.17 

1.24 

1.37 
1.19 
1.11 
1.12 

1.20 

1.22 


86 
147 
143 
173 

134 
157 
126 
124 


1.47 


144 


1.29 


141 


1.31 


171 


1.24 




1.33 


131 


1.58 


156 


1.27 


123 


1.23 


123 


1.20 




1.32 




1.32 



55 



Table 10.5. Nitrogen Recommendations for Selected 
Illinois Soils Under High Level of Man- 
agement 

Corn-nitrogen price ratio 

Soil type 

^^ 10:1 20:1 

nitrogen recommendation, lb/acre 

Muscatine silt loam 205 220 

Ipava silt loam 200 215 

Sable silty clay loam 190 205 

Drummer silty clay loam 185 200 

Piano silt loam 185 200 

Hartsburg silty clay loam 175 190 

Fayette silt loam 155 170 

Clinton silt loam 155 170 

Cowden silt loam 145 160 

Cisne silt loam 140 150 

Bluford silt loam 125 135 

Grantsburg silt loam 115 125 

Huey silt loam 80 85 



Table 10.6. Soybean Yields at Four Locations as 
Affected by N Applied to Corn the 
Preceding Year (Four- Year Average) 



N applied to com, 
lb/acre 



Soybean yield 



Aledo Dixon Elwood Kewanee Average 



bushels per acre 

48 40 37 

80 49 40 36 

160 48 39 36 

240 48 42 36 

320 48 42 36 



Table 10.7. Yield of Continuous Soybeans with Rates 
of Added N at Hartsburg 



40 


41 


38 


41 


40 


41 


40 


41 


37 


41 



Nitrogen, Ib/acre/year 



Soybean yield 



1968-71 



1954-71 



bushels per acre 

43 37 

40 42 36 

120 43 37 



Table 10.8. Soybean Yields at Urbana as Affected 
by High Rates of Nitrogen 





Nitrogen, lb/acre 




Soybean 
1968 


yield, bu/c 
1969 


icre 


1968 


1969 


1970 


1970 











54 


53 


40 


40 


200 


200 


54 


57 


41 


80 


400 


400 


56 


57 


45 


120 


800 


800 


53 


55 


42 


160 


1,600 


1,600 


55 


34 


36 



the higher rates would furnish more than the total 
nitrogen needs of soybeans. Yields were not affected 
by nitrogen in 1968; but with 400 pounds per acre 
of nitrogen, a tendency toward a yield increase 
occurred in 1969 and 1970. However, the yield 
increase would not pay for the added nitrogen at 
current prices. 



Wheat, oats, and barley. The rate of nitrogen to 
apply on wheat, oats, and barley is dependent on soil 
type, crop and variety to be grown, and future cropping 
intentions (Table 10.9). Light-colored soils (low in 
organic matter) require the highest rate of nitrogen 
application because they have a low capacity to supply 
nitrogen. Deep, dark-colored soils require lower rates 
of nitrogen application for maximum yields. Estimates 
of organic-matter content for soils of Illinois may be 
obtained from Agronomy Fact Sheet SP-36, Average 
Organic Matter Content in Illinois Soil Types, or by 
using University of Illinois publication AG- 1941, Color 
Chart for Estimating Organic Matter in Mineral Soils. 

Nearly all modern varieties of wheat have been 
selected for improved standability; thus concern about 
nitrogen-induced lodging has decreased considerably. 
Varieties of oats, although substantially improved with 
regard to standability, will still lodge occasionally; and 
nitrogen should be used carefully. Barley varieties, 
especially varieties of spring barley, are prone to lodg- 
ing; thus rates of nitrogen application shown in Table 
10.9 should not be exceeded. 

Some wheat and oats in Illinois serve as a com- 
panion crop for legume or legume-grass seedings. On 
those fields, it is best to apply nitrogen fertilizer at 
well below the optimum rate because unusually heavy 
vegetative growth of wheat or oats competes unfa- 
vorably with the young forage seedlings (Table 10.9). 
Seeding rates for small grains should also be somewhat 
lower if used as companion seedings. 

The introduction of nitrification inhibitors and im- 
proved application equipment now provide two op- 
tions for applying nitrogen to wheat. Research has 
shown that when the entire amount of nitrogen needed 
is applied in the fall with a nitrification inhibitor, the 
resulting yields are equivalent to that obtained when 
a small portion of the total need was fall applied and 
the remainder was applied in early spring. Producers 
who are frequently delayed in applying nitrogen in 
the spring because of muddy fields may wish to 
consider fall application with a nitrification inhibitor. 
For fields that are not usually wet in the spring, either 
system of application will provide equivalent yields. 

The amount of nitrogen needed for good fall growth 
is not large because the total uptake in roots and tops 
before cold weather is not likely to exceed 30 to 40 
pounds per acre. 

Hay and pasture grasses. The species grown, period 
of use, and yield goal determine optimum nitrogen 
fertilization (Table 10.10). The lower rate of application 
is recommended on fields where inadequate stands or 
moisture limits production. 

Kentucky bluegrass is shallow rooted and suscep- 
tible to drought. Consequently, the most efficient use 
of nitrogen by bluegrass is from an early-spring ap- 
plication, with September application a second choice. 
September fertilization stimulates both fall and early- 
spring growth. 

Orchardgrass, smooth bromegrass, tall fescue, and 
reed canarygrass are more drought tolerant than blue- 
grass and can use higher rates of nitrogen more 



56 



Table 10.9. Recommended Nitrogen Application Rates for Wheat, Oats, and Barley 




Organic- Fields with alfalfa 
Soil sihiarion matter or clover seeding 


Fields with no alfalfa 
or clover seeding 


content Wheat Oats and barley 


Wheat Oats and barley 



Soils low in capacity to supply nitrogen: inherently 
low in organic matter (forested soils) <2% 

Soils medium in capacity to supply nitrogen: mod- 
erately dark-colored soils 2-3% 

Soils high in capacity to supply nitrogen: all deep, 
dark-colored soils >3% 



70-90 
50-70 
30-50 



— nitrogen, pounds per acre 
60-80 90-110 

40-60 70-90 

20-40 50-70 



70-90 

50-70 
30-50 



Table 10.10. Nitrogen Fertilization of Hay and Pas- 
ture Grasses 

Time of application 

Species Earlv ^^'^'' ^^^^^ l^^^^ 

s ine ^^^^ second Sep- 
f"^ ° harvest harvest temoer 

nitrogen, pounds per acre — 

Kentucky bluegrass 60-80 (see text) 

Orchardgrass 75-125 75-125 

Smooth bromegrass 75-125 75-125 50" 

Reed canarygrass 75-125 75-125 50" 

Tall fescue for winter use . . . 100-125 100-125 50" 

" Optional if extra fall growth is needed. 



effectively. Because more uniform pasture production 
is obtained by splitting high rates of nitrogen, two or 
more apphcations are suggested. 

If extra spring growth can be utilized, make the 
first nitrogen application in March in southern Illinois, 
early April in central Illinois, and mid-April in northern 
Illinois. If spring growth is adequate without extra 
nitrogen, the first application may be delayed until 
after the first harvest or grazing cycle to distribute 
production more uniformly throughout the summer. 
Total production likely will be less, however, if nitrogen 
is applied after first harvest rather than in early spring. 
Usually the second application of nitrogen is made 
after the first harvest or first grazing cycle; to stimulate 
fall growth, however, this application may be deferred 
until August or early September. 

Legume-grass mixtures should not receive nitrogen 
if legumes make up at least 30 percent of the mixture. 
Because the main objective is to maintain the legume, 
the emphasis should be on applying phosphorus and 
potassium rather than nitrogen. 

After the legume has declined to less than 30 percent 
of the mixture, the objective of fertilizing is to increase 
the yield of grass. The suggested rate of nitrogen is 
about 50 pounds per acre when legumes make up 20 
to 30 percent of the mixture. 

Rate adjustments 

In addition to determining nitrogen rates, consid- 
eration should be given to other agronomic factors 
that influence available nitrogen. These factors include 
past cropping history and the use of manure (Table 
10.11), as well as the date of planting. 



Corn following another crop consistently yields 
better than continuous corn. This is especially true for 
corn following a legume such as soybeans or alfalfa 
(Figure 10.6). This is due in part to residual nitrogen 
from the legumes as the differences in yield between 
rotations become smaller with increasing nitrogen rates. 
When no nitrogen was applied, the data indicate that 
soybeans and alfalfa contributed the equivalent of 65 
and 108 pounds of nitrogen per acre, respectively. At 
the optimum production level, soybeans contributed 
the equivalent of about 30 pounds of nitrogen per 
acre. The contribution of legumes, either soybeans or 
alfalfa, to wheat will be less than the contribution to 
corn because the oxidation of the organic nitrogen 
from these legumes will not be as rapid in early spring, 
when nitrogen needs of small grain are greatest, as it 
is in the summer, when nitrogen needs of corn are 
greatest. 

Corn following oats had a higher yield than con- 
tinuous corn (Figure 10.6). While oats are not a legume, 
a part of this yield differential may be due to nitrogen 
released from the soil after the oat crop had completed 
its nitrogen uptake and thus it was carried over to the 
next year's corn crop. 

Depending on the crop grown, the nitrogen credit 
from idled acres may be positive or negative. Plowing 
under a good stand of a legume that had good growth 
will result in a nitrogen contribution of 60 to 80 pounds 
of nitrogen per acre. If either stand or growth of the 
legume was poor or if corn was zero-tilled into a good 
legume stand that had good growth, the legume ni- 
trogen contribution could be reduced to 40 to 60 
pounds per acre. Because most of the net nitrogen 
gained from first-year legumes will be in the herbage, 
fall grazing will reduce the nitrogen contribution to 
30 to 50 pounds per acre. If sorghum residues are 
incorporated into the soil, an additional 30 to 40 
pounds of nitrogen should be applied per acre. 

Nutrient content of manure will vary, depending 
on source and method of handling (Table 10.12). 
Additionally, the availability of the total nitrogen con- 
tent will vary, depending on method of application. 
When incorporated during or immediately after ap- 
plication, about 50 percent of the total nitrogen in dry 
manure and 50 to 60 percent of the total nitrogen in 
liquid manure will be available for the crop that is 
grown during the year following manure application. 



57 



Table 10.11. Adjustments in Nitrogen Recommen- 
dations 

Factors resulting in reduced nitrogen requirement 



180 



Crop to 
be grown 



After 
soy- 
beans ■ 



1st year after 
alfalfa or clover 



2nd year after 
alfalfa or clover 



Plants/sq ft Plants/sq ft 



Ma- 
nure 



2-4 <2 



<5 



nitrogen reduction, lb/acre 

Com 40 100 50 30 5= 

Wheat 10 30 10 5^ 



' Nitrogen contribution in pounds per ton of manure. 



Table 10.12. Average Composition of Manure 



Nutrients (lb/ton) 



Kind of animal 



Nitrogen 
(N) 



Phosphorus 
(P2O5) 



Potassium 
(K2O) 



Dairy cattle 11 5 11 

Beef cattle 14 9 11 

Hogs 10 7 8 

Chicken 20 16 8 

Dairy cattle (liquid) 5(26)^ 2(11) 4(23) 

Beef cattle (liquid) 4(21) 1( 7) 3(18) 

Hogs (liquid) 10(56) 5(30) 4(22) 

Chicken (liquid) 13(74) 12(68) 5(27) 

^ Parenthetical numbers are pounds of nutrients per 1,000 gallons. 



Research at the Northern Illinois Research Center 
for several years showed that as planting was delayed, 
less nitrogen fertilizer was required for most profitable 
yield. Based upon that research, Illinois agronomists 
suggest that for each week of delay in planting after 
the optimum date for the area, the nitrogen rate can 
be reduced 20 pounds per acre down to 80 to 90 
pounds per acre as the minimum for very late planting 
in a corn-soybean cropping system. Suggested refer- 
ence dates are April 10 to 15 in southern Illinois, April 
20 to May 1 in central Illinois, and May 1 to 10 in 
northern Illinois. This adjustment is, of course, possible 
only if the nitrogen is sidedressed. 

Because of the importance of the planting date, 
farmers are encouraged not to delay planting just to 
apply nitrogen fertilizer: Plant, then sidedress. 



Reactions in tlie soil 

Efficient use of nitrogen fertilizer requires an un- 
derstanding of how nitrogen behaves in the soil. Key 
points to consider are the change from ammonium 
(NH4 ) to nitrate (NO3 ) and the movements and trans- 
formations of nitrate. 



20 




alfalfa 
soybeans 
oats 
corn 



80 160 

Nitrogen, pounds per acre 



240 



Figure 10.6. Effect of crop rotation and applied nitrogen 
on corn yield, DeKalb, 1980-83. 



A high percentage of the nitrogen applied in Illinois 
is in the ammonium form or converts to ammonium 
(anhydrous ammonia and urea, for example) soon 
after application. Ammonium nitrogen is held by the 
soil clay and organic matter and cannot move very far 
until it nitrifies (changes from ammonium to nitrate). 
In the nitrate form, nitrogen can be lost by either 
denitrification or leaching (Figure 10.7). 

Denitrification. Denitrification is believed to be the 
main process by which nitrate and nitrite nitrogen are 
lost, except on sandy soils, where leaching is the major 
pathway. Denitrification involves only nitrogen that is 
in the form of either nitrate (NO J) or nitrite (NO J). 

The amount of denitrification depends mainly on 
(1) how long the surface soil is saturated; (2) the 
temperature of the soil and water; (3) the pH of the 
soil; and (4) the amount of energy material available 
to denitrifying organisms. 

When water stands on the soil or when the surface 
is completely saturated in late fall or early spring, 
nitrogen loss is likely to be small because (a) much 
nitrogen is still in the ammonium rather than nitrate 
form; and (b) the soil is cool, and denitrifying orga- 
nisms are not very active. 

Many fields in east central Illinois and, to a lesser 
extent, in other areas have low spots where surface 
water collects at some time during the spring or early 
summer. The flat claypan soils also are likely to be 
saturated, though not flooded, during that time. Side- 
dressing would avoid the risk of spring loss on these 
soils but would not affect midseason loss. Unfortu- 
nately, these are the soils on which sidedressing is 
difficult in wet years. 

New scientific procedures now make it possible to 
directly measure denitrification losses. Results collected 
over the past few years indicated that when soils were 
saturated for 3 to 4 days, losses of 25 to 40 percent 



58 



of the nitrogen present as nitrate occurred even though 
water was ponded for only a few hours. These losses 
resulted in a yield loss of 10 to 20 bushels per acre. 
Increasing the time that soils were saturated to 6 days 
resulted in losses of 50 to 60 percent of the nitrogen 
present as nitrate. As more results are collected, agron- 
omists will be able to predict more accurately the 
nitrogen loss under specific conditions and, more im- 
portantly, to predict the response to added nitrogen. 

Leaching. In silt loams and clay loams, one inch of 
rainfall moves down about 5 to 6 inches, though some 
of the water moves farther in large pores through the 
profile and carries nitrates with it. 

In sandy soils, each inch of rainfall moves nitrates 
down about one foot. If the total rainfall at one time 
is more than 6 inches, little nitrate will be left within 
the rooting depth on sands. 

Between rains, some upward movement of nitrates 
occurs in moisture that moves toward the surface as 
the surface soil dries. The result is that it is difficult 
to predict how deep the nitrate has moved based only 
on cumulative rainfall. 

When trying to estimate the depth of leaching of 
nitrates in periods of very intensive rainfall, two points 
need to be considered. First, the rate at which water 
can enter the surface of silt and clay loams may be 
less than the rate of rainfall, which means that much 
of the water runs off the surface either into low spots 
or into creeks and ditches. Second, the soil may be 
saturated already. In either of these cases, the nitrates 
will not move down the 5 to 6 inches per inch of rain 
as suggested above. 




(Ammonium) 



(Nitrite) 



(Nitrate) 



Leaching 



Figure 10.7. Nitrogen reactions in the soil. 



Corn roots usually penetrate to 6 feet in Illinois 
soils. Thus, nitrates that leach only to 3 to 4 feet are 
well within normal rooting depth unless they reach 
tile lines and are drained from the field. 

Nitrification inhibitors 

As Figure 10.7 shows, nitrification converts am- 
monium nitrogen into the nitrate form of nitrogen and 
thereby increases the potential for loss of soil nitrogen. 
Use of nitrification inhibitors can retard this conversion. 
When inhibitors were properly applied in one exper- 
iment, as much as 42 percent of soil-applied ammonia 
remained in the ammonium form through the early 
part of the growing season, in contrast with only 4 
percent that remained when inhibitors were not used. 
Inhibitors can therefore have a significant effect on 
crop yields. The benefit from using an inhibitor will 
vary, however, with the soil condition, time of year, 
type of soil, geographic location, rate of nitrogen 
application, and weather conditions that occur after 
the nitrogen is applied and before it is absorbed by 
the crop. 

Considerable research throughout the Midwest has 
shown that only under wet soil conditions will inhib- 
itors significantly increase yields. When inhibitors were 
applied in years of excessive rainfall, increases in corn 
yield ranged from 10 to 30 bushels per acre; when 
moisture conditions were not as conducive to denitri- 
fication or leaching, inhibitors produced no increase. 

For the first 4 years of one experiment conducted 
by the University of Illinois, nitrification inhibitors 
produced no effect on grain yields because soil moisture 



-•- Fall-applied Nitrapyrin (0 lb/A) 
■O- Fall-applied Nitrapyrin (0.5 lb/A) 
-■- Spring-applied Nitrapyrin (0 lb/A) 

180 



0) 

u 

(0 

0) 
Q. 

V) 

0) 

(/> 

3 
£i 

]0 
> 



160 - 



140 



120 



100 



80 




60 

100 150 200 

Nitrogen, pounds per acre 

Figure 10.8. Effect of nitrification inhibitors on corn yields 
at varying nitrogen application rates, DeKalb, 1979. 



59 



levels were not sufficiently high. In early May of the 
fifth year, however, when soils were saturated with 
water for a long time, the application of an inhibitor 
in the preceding fall significantly increased corn yields 
(Figure 10.8). Furthermore, at a nitrogen application 
rate of 150 pounds per acre, the addition of an inhibitor 
increased grain yields more than did the addition of 
another 40 pounds of nitrogen (Figure 10.8). Under 
the conditions of that experiment, therefore, it was 
more economical to use an inhibitor than to apply 
more nitrogen. 

Because soils normally do not remain saturated with 
water for very long during the growing season after 
a sidedressing operation, the probability of benefiting 
from the use of a nitrification inhibitor with sidedressed 
nitrogen is less than from their use with either fall- 
or spring-applied nitrogen. Moreover, the short time 
between application and absorption by the crop greatly 
reduces the potential for nitrogen loss. 

The longer the period between nitrogen application 
and absorption by the crop, the greater the probability 
that nitrification inhibitors will contribute to higher 
yields. The length of time, however, that fall-applied 
inhibitors will remain in the soil is partly dependent 
on soil temperature. On one plot, a Drummer soil that 
had received an inhibitor application when soil tem- 
peratures were 55°F, retained nearly 50 percent of the 
applied ammonia in ammonium form for about 5 
months. When soil temperatures were 70°F, it retained 
the same amount of ammonia for only 2 months. Fall 
application of nitrogen with inhibitors should therefore 
be delayed until soil temperatures are no higher than 
60°F; and though temperatures may decrease to 60°F 
in early September, it is advisable to delay applications 
until the last week in September in northern Illinois 
and the first week in October in central Illinois. 

In general, poorly or imperfectly drained soils will 
probably benefit the most from nitrification inhibitors. 
Moderately well-drained soils that undergo frequent 
periods of 3 or more days of flooding in the spring 
will also benefit. Coarse-textured soils (sands) are likely 
to benefit more than soils with finer textures because 
the coarse-textured soils have a higher potential for 
leaching. 

Time of application and geographic location must 
be considered along with soil type when determining 
whether to use a nitrification inhibitor. Employing 
nitrification inhibitors can significantly improve the 
efficiency of fall-applied nitrogen on the loams, silts, 
and clays of central and northern Illinois in years when 
the soil is very wet in the spring. At the same time, 
presently available inhibitors will not adequately re- 
duce the rate of nitrification in the low organic-matter 
soils of southern Illinois when nitrogen is applied in 
the fall for the following year's corn. The lower 
organic-matter content and the warmer temperatures 
of southern Illinois soils, both in late fall and early 
spring, will cause the inhibitor to degrade too rapidly. 
Futhermore, applying an inhibitor on sandy soils in 
the fall will not adequately reduce nitrogen loss be- 



cause the potential for leaching is too high. Therefore, 
fall applications of nitrogen with inhibitors are not 
recommended for sandy soils or for soil with low 
organic-matter content, especially for those soils found 
south of Interstate Highway 70. 

In the spring, preplant applications of inhibitors 
may be beneficial on nearly all types of soil from 
which nitrogen loss frequently occurs, especially on 
sandy and poorly drained soils. Again, inhibitors are 
more likely to have an effect when subsoils are re- 
charged with water than when subsoils are dry at the 
beginning of spring. 

Nitrification inhibitors are most likely to increase 
yields when nitrogen is applied at or below the opti- 
mum rate. When nitrogen is applied at a rate greater 
than that required for optimum yields, benefits from 
an inhibitor are unlikely, even when moisture in the 
soil is excessive. 

Inhibitors should be viewed as soil management 
tools that can be used to reduce nitrogen loss. It is 
not safe to assume, however, that the use of a nitri- 
fication inhibitor will make it possible to reduce nitro- 
gen rates below those currently recommended, because 
those rates were developed with the assumption that 
no significant amount of nitrogen would be lost. 

Time of nitrogen application 

In recent years, farmers in central and northern 
Illinois have been encouraged to apply nitrogen in 
non-nitrate form in the late fall any time after the soil 
temperature at 4 inches was below 50°F, except on 
sandy, organic, or very poorly drained soils. 

The 50°F level for fall application is believed to be 
a realistic guideline for farmers. Applying nitrogen 
earlier involves risking too much loss (Figure 10.9). 
Later application involves risking wet or frozen fields, 
which would prevent application and fall tillage. Av- 
erage dates on which these temperatures are reached 
are not satisfactory guides because of the great vari- 
ability from year to year. Soil thermometers should be 
used to guide fall applications of nitrogen. 



c 

— * 

Z U 

CO a> 

O °- 

Z C 

<u o 

2 n 

.> E 

0) o 

oc < 



100 


^ 


80 


y^ 


60 


X 


40 


y/ 


20 


- ^^„^ 





.^ — r 1 1 1 1 



C 0° 
F 32° 



5° 
41 o 



10° 
50° 



15° 
59° 



20° 

68° 



25° 

77° 



Figure 10.9. Influence of soil temperature on the relative 
rate of NO3 accumulation in soils. 



60 



In Illinois, most of the nitrogen applied in late fall 
or very early spring will be converted to nitrate by 
corn-planting time. Though the rate of nitrification is 
slow (Figure 10.9), the soil temperature is between 
32°F and 40° to 45°F for a long period. 

The results from 18 experiments in central and 
northern Illinois (Figure 10.10) show that fall-applied 
ammonium nitrate (half ammonium, half nitrate) was 
less effective than spring-applied nitrogen. There are 
two ways to compare efficiency. For example, in Figure 
10.10, left, 120 pounds of nitrogen applied in the fall 
produced 92 percent as much increase as the same 
amount applied in the spring. But looked at another 
way, it requires 120 pounds of fall-applied nitrogen to 
produce as much yield increase as was produced by 
100 pounds applied in the spring (Figure 10.10, right). 
At higher nitrogen rates, the comparisons become less 
favorable for fall application because the yield leveled 
off 6 to 8 bushels below that from spring application. 

In consideration of the date at which nitrates are 
formed and the conditions that prevail thereafter, the 
difference in susceptibility to denitrification and leach- 
ing loss between late-fall and early-spring applications 
of ammonium sources is probably small. Both are, 
however, more susceptible to loss than is nitrogen 
applied at planting time or as a sidedressing. 

Anhydrous ammonia nitrifies more slowly than 
other forms and is slightly preferred for fall applica- 
tions. It is well suited to early-spring application, 
provided the soil is dry enough for good dispersion 
of ammonia and closure of the applicator slit. 

Sidedress application. Results collected from stud- 
ies in Illinois indicated that nitrogen injected between 
every other row was comparable in yield to injection 
between every row. This finding was true irrespective 
of tillage system (Table 10.13) or nitrogen rate (Table 
10.14). Furthermore, this outcome should be expected. 



as even with every-other row injection, each row will 
have nitrogen applied on one side or the other (Figure 
10.11). While all of the results to date were obtained 
with anhydrous ammonia, there is no reason to believe 
that the same results would not be obtained with 
injected nitrogen solutions. 

Use of wider injection spacing at sidedressing allows 
for a reduction in power requirement for a given 
applicator width or use of a wider applicator with the 
same power requirement. From a practical standpoint, 
the lower power requirement will frequently mean a 
smaller tractor and associated smaller tire, making it 
easier to maneuver between the rows and also giving 
less compaction next to the row. With this system, 
injector positions can be adjusted to avoid placing an 
injector in the wheel track. When matching the driving 
pattern for planters of 8, 12, 16, or 24 rows, the outside 
two injectors must be adjusted to half-rate application, 
as the injector will go between those two rows twice 
if one avoids the wheel track. To avoid problems of 
back pressure that might be created when applying at 
relatively high rates of speed, use a double-tube knife, 
with two hoses going to each knife; the outside knives 
would require only one hose to give the half-rate 
application. 

Winter application. Based on observations in 1986, 
the risk of nitrogen loss through volatilization asso- 
ciated with winter application of urea for corn on 
frozen soils is too great to consider the practice unless 
one is assured of at least one-half inch of precipitation 
occurring within 4 to 5 days after application. In most 
years, application of urea on frozen soils has been an 
effective practice for wheat. 

Aerial application. Recent research at the Univer- 
sity of Illinois has indicated that an aerial application 
of dry urea will result in increased yield. This practice 
should not be considered a replacement for normal 



a> 








Spring 






- 150 


r .----"""Fain 


1 


0) 

u 

(0 


(0 


'^ 


r — 






0) 


• ^X"^ 








»- 


Q. 










0) 
Q. 


0) 






-97% 




(0 


w 100 






- 92% 




-93% 


0) 


3 


// 










(/> 


A 


y 


-84% 








3 


■o 

0) 




Yield without fertilize 


;r 




•6 






• 




d) 


>- * 

1 


^ Nitrogen 

1 1 1 




>- 






60 



120 



180 



240 



Pounds of nitrogen 



150 r- 



Spring 
"Fall" 



100 




240 



Pounds of nitrogen 



Figure 10.10. Comparison of fall- and spring-applied ammonium nitrate, 18 experiments in central and northern 
Illinois, 1966-1969 (DeKalb, Carthage, Carlinville, and Hartsburg). Figure at left shows increased yield from fall 
fertilizer application as a percent of yield increases achieved when fertilizer was applied in the spring. Figure at right 
shows amount of fertilizer you need to apply in the fall to obtain a given yield as a percent of the fertilizer needed 
to obtain that same yield with spring application. 

61 



Table 10.13. Effect on Corn Yield of Ammonia Knife 
Spacing with Different Tillage Systems 
at Two Locations in Illinois 

Yield, bushels per acre 

Injector spacing, inches 

Plow Chisel Disk No-Till 

— -- DeKalb — 

30 159 157 163 146 

60 158 157 157 143 

Elwood — 

30 119 121 118 

60 117 125 121 



nitrogen application but rather an emergency treatment 
in situations where corn is too tall for normal applicator 
equipment. Aerial application of nitrogen solutions on 
growing corn is not recommended, as extensive leaf 
damage will likely result if the rate of application is 
greater than 10 pounds of nitrogen per acre. 

Which nitrogen fertilizer? 

Most of the nitrogen fertilizer materials available 
for use in Illinois provide nitrogen in the combined 
form of ammonia, ammonium, urea, and nitrate. For 
many uses on a wide variety of soils, all forms are 
likely to produce about the same yield — provided 
that they are properly applied. 

Ammonia. Nitrogen materials that contain free 
ammonia (NH3), such as anhydrous ammonia or low- 
pressure solutions, must be injected into the soil to 
avoid loss of ammonia in gaseous form. Upon injection 
into the soil, ammonia quickly reacts with water to 
form ammonium (NH4). In this positively charged 



form, the ion is not susceptible to gaseous loss because 
it is temporarily attached to the negative charges on 
clay and organic matter. Some of the ammonia reacts 
with organic matter to become a part of the soil humus. 

On silt loam or soils with finer textures, ammonia 
will move about 4 inches from the point of injection. 
On more coarsely textured soils such as sands, am- 
monia may move 5 to 6 inches from the point of 
injection. If the depth of application is shallower than 
the distance of movement, some ammonia may move 
slowly to the soil surface and escape as a gas over a 
period of several days. On coarse-textured (sandy) 
soils, anhydrous ammonia should be placed 8 to 10 
inches deep, whereas on silt-loam soils, the depth of 
application should be 6 to 8 inches. Anhydrous am- 
monia is lost more easily from shallow placement than 
is ammonia in low-pressure solutions. Nevertheless, 
low-pressure solutions contain free ammonia and thus 
need to be incorporated into the soil at a depth of 2 
to 4 inches. Ammonia should not be applied to soils 
having a physical condition that would prevent closure 
of the applicator knife track. Ammonia will escape to 
the atmosphere whenever there is a direct opening 
from the point of injection to the soil surface. 

You can damage seedlings if you do not take proper 
precautions when applying nitrogen materials that 
contain or form free ammonia. Damage may occur if 
you inject nitrogen material into soils that are so wet 
that the knife track does not close properly. If the soil 
dries rapidly, this track may open. You can also cause 
damage by applying nitrogen material to excessively 
dry soils, which allow the ammonia to move large 
distances before being absorbed. Finally, you can dam- 
age seedlings by using a shallower application than 




Figure 10.11. Schematic of every-other-row, sidedress nitrogen injection. Note that the outside two injectors are set at 
one-half rate because the injector will run between those two rows twice. 



62 



that suggested in the preceding paragraph. Generally, 
if you delay planting 3 to 5 days after you apply 
fertilizer, you will see little, if any, seedling damage. 
Under extreme conditions, however, seedling damage 
has been observed even when planting was delayed 
for 2 weeks after the fertilizer was applied. 

Ammonium nitrate. Half of the nitrogen contained 
in ammonium nitrate is in the ammonium form and 
half is in the nitrate form. The part present as am- 
monium attaches to the negative charges on the clay 
and organic-matter particles and remains in that state 
until it is utilized by the plant or converted to the 
nitrate ions by microorganisms present in the soil. 
Because 50 percent of the nitrogen is present in the 
nitrate form, this product is more susceptible to loss 
from leaching and denitrification. Thus, ammonium 
nitrate should not be applied to sandy soils because 
of the likelihood of leaching, nor should it be applied 
far in advance of the time when the crop needs the 
nitrogen because of possible loss by denitrification. 

Urea. The chemical formula for urea is CO(NH2)2. 
In this form, it is very soluble and moves freely up 
and down with soil moisture. After being applied to 
the soil, urea is converted to ammonia, either chemi- 
cally or by the enzyme urease. The speed with which 
this conversion occurs depends largely on temperature. 
At low temperatures, conversion is slow; but at tem- 
peratures of 55°F or higher, conversion is rapid. 

If the conversion of urea occurs on the soil surface 
or on the surface of crop residue or leaves, some of 
the resulting ammonia will be lost as a gas to the 
atmosphere. The potential for loss is greatest when: 

1. Temperatures are greater than 55°F. Loss is less 
likely with winter or early-spring applications, but 
results show that the loss may be substantial if the 
materials remain on the surface of the soil for 
several days. 

2. Considerable crop residue remains on the soil sur- 
face. 

3. Application rates are greater than 100 pounds of 
nitrogen per acre. 

4. The soil surface is moist and rapidly drying. 

5. Soils have a low cation-exchange capacity. 

6. Soils are neutral or alkaline in reaction. 
Research conducted at both the Brownstown and 

Dixon Springs research centers has shown that surface 
application of urea for zero-till corn did not yield as 
well as ammonium nitrate (Table 10.15) in most years. 
In years when a rain was received within 1 or 2 days 
after application, urea resulted in as good a yield 
increase as did ammonium nitrate (that is, compared 
to results from early-spring application of ammonium 
nitrate at Dixon Springs in 1975). In other studies, 
urea that was incorporated soon after application 
yielded as well as ammonium nitrate. 

Nitrogen solutions. The nonpressure nitrogen so- 
lutions that contain 28 to 32 percent nitrogen consist 
of a mixture of urea and ammonium nitrate. Typically, 



half of the nitrogen is from urea, and the other half 
is from ammonium nitrate. The constituents of these 
compounds will undergo the same reactions as de- 
scribed above for the constituents applied alone. 

Experiments at DeKalb have shown a yield difference 
between incorporated and unincorporated nitrogen so- 
lutions that were spring-applied (Table 10.16). This dif- 
ference associated with method of application is probably 
caused by volatilization loss of some nitrogen from the 
surface-applied solution containing urea. 



Table 10.14. Effect on Corn Yield of Injector Spacing 
of Ammonia Applied at Different Rates 
of Nitrogen, DeKalb 



Injector spacing, inches 




Nitrogen, lb/acre 




120 


180 


240 










30 

60 


. 171 

. 170 


176 
171 


181 
182 



Table 10.15. Effect of Source of 


^Jitrogen on Yield 




for Zero-Till Corn 






Nitrogen 










Date of 


Method 

of 
appli- 


Rate, 


^3^- Dixon 


Source 


appli- 
cation 


lb/ 
acre 


1974-77 Sprmgs 






cation 




avg. 










yield, bu/acre 


Control .... 









52 50 . . 


Ammonium 










nitrate . . . 


early spring 


surface 


120 


96 132 160 


Urea 


early spring 


surface 


120 


80 106 166 


Ammonium 










nitrate . . . 


early June 


surface 


120 


106 151 187 


Urea 


early June 


surface 


120 


99 125 132 



Table 10.16. Effect of Source, Method of Applica- 
tion, and Rate of Spring-Applied Ni- 
trogen on Corn Yield, DeKalb 

Carrier and method N, ^^^^ 

of application lb/acre 1976 1977 Avg. 

yield, bu/acre 

None 66 61 64 

Ammonia 80 103 138 120 

28 percent N solution, 

incorporated 80 98 132 115 

28 percent N solution, 

unincorporated 80 86 126 106 

Ammonia 160 111 164 138 

28 percent N solution, 

incorporated 160 107 157 132 

28 percent N solution, 

unincorporated 160 96 155 126 

Ammonia 240 112 164 138 

28 percent N solution, 

incorporated 240 101 164 132 

28 percent N solution, 

unincorporated 240 91 153 122 

FLSD.IO^ 9.1 5.2 

^ Differences greater than the FLSD value are statistically significant. 



63 



The effect on yield of postemergence application of 
nitrogen solutions and atrazine when corn plants are 
in the 3-leaf stage was evaluated in Minnesota. The 
results there indicated that yields were generally de- 
pressed when the nitrogen rate exceeded 60 pounds 
per acre. Leaf burn was increased by increasing the 
nitrogen rate, including atrazine with the nitrogen, 
and by hot, clear weather conditions. 



Phosphorus and potassium 

Inherent availability 

Illinois has been divided into three regions in terms 
of the inherent phosphorus-supplying power of the 
soil below the plow layer in dominant soil types (Figure 
10.12). 

High phosphorus-supplying power means that the 
soil test for available phosphorus (P, test) is relatively 
high and conditions are favorable for good root pen- 
etration and branching throughout the soil profile. 

Low phosphorus-supplying power may be caused 
by one or more of these factors: 

1. A low supply of available phosphorus in the soil 
profile because (a) the parent material was low in 
P; (b) phosphorus was lost in the soil-forming 
process; or (c) the phosphorus is made unavailable 
by high pH (calcareous) material. 

2. Poor internal drainage that restricts root growth. 




Figure 10.12. Phosphorus-supplying power. 



3. A dense, compact layer that inhibits root penetration 
or branching. 

4. Shallowness to bedrock, sand, or gravel. 

5. Droughtiness, strong acidity, or other conditions 
that restrict crop growth and reduce rooting depth. 
Regional differences in phosphorus-supplying power 

are shown in Figure 10.12. Parent material and degree 
of weathering were the primary factors considered in 
determining the various regions. 

The "high" region is in western Illinois, where the 
primary parent material was more than 4 to 5 feet of 
loess that was high in phosphorus content. The soils 
are leached of carbonates to a depth of more than Vk 
feet, and roots can spread easily in the moderately 
permeable profiles. 

The "medium" region is in central Illinois, with 
arms extending into northern and southern Illinois. 
The primary parent material was more than 3 feet of 
loess over glacial till, glacial drift, or outwash. Some 
sandy areas with low phosphorus-supplying power 
occur in the region. In comparison with the high- 
phosphorus region, more of the soils are poorly drained 
and have less available phosphorus in the subsoil and 
substratum horizons. Carbonates are likely to occur at 
shallower depths than in the "high" region. The soils 
in the northern and central areas are generally free of 
root-restrictions, while soils in the southern arm are 
more likely to have root-restricting layers within the 
profile. The phosphorus-supplying power of soils of 
the region is likely to vary with natural drainage. Soils 
with good internal drainage are Ukely to have higher 
levels of available phosphorus in the subsoil and 
substratum. If internal drainage is fair or poor, phos- 
phorus levels in the subsoil and substratum are likely 
to be low or medium. 

In the "low" region in southeastern Illinois, the 
soils were formed from IVi to 7 feet of loess over 
weathered Illinoisan till. The profiles are more highly 
weathered than in the other regions and are slowly 
or very slowly permeable. Root development is more 
restricted than in the "high" or "medium" regions. 
Subsoil levels of phosphorus may be rather high by 
soil test in some soils of the region, but this is partially 
offset by conditions that restrict rooting. 

In the "low" region in northeastern Illinois, the 
soils were formed from thin loess (less than 3 feet) 
over glacial till. The glacial till, generally low in avail- 
able phosphorus, ranges in texture from gravelly loam 
to clay in various soil associations of the region. In 
addition, shallow carbonates further reduce the phos- 
phorus-supplying power of the soils of the region. 
Further, high bulk density and slow permeability in 
the subsoil and substratum restrict rooting in many 
soils of the region. 

The three regions are delineated to show broad 
differences between them. Parent material, degree of 
weathering, native vegetation, and natural drainage 
vary within a region and cause variation in the soil's 
phosphorus-supplying power. It appears, for example. 



64 



that soils developed under forest cover have more 
available subsoil phosphorus than those developed 
under grass. 

Illinois is divided into two general regions for po- 
tassium, based on cation-exchange capacity (Figure 
10.13). Important differences exist, however, among 
soils within these general regions because of differences 
in the following six factors: 

1. The amount of clay and organic matter, which 
influences the exchange capacity of the soil. 

2. The degree of weathering of the soil material, which 
affects the amount of potassium that has been 
leached out. 

3. The kind of clay mineral. 

4. Drainage and aeration, which influence uptake of 
potassium (K). 

5. The parent material from which the soil was formed. 

6. Compactness or other conditions that influence root 
growth. 

Soils that have a cation-exchange capacity less than 
12 meq/100 gram are classified as having low cation- 
exchange capacity. These soils include the sandy soils 
because minerals from which these soils were devel- 
oped are inherently low in potassium. Sandy soils also 
have very low cation-exchange capacities and thus do 
not hold much reserve potassium. 

Silt-loam soils in the "low" area in southern Illinois 
(claypans) are relatively older soils in terms of soil 
development; consequently, much more of the potas- 
sium has been leached out of the rooting zone. Fur- 
thermore, wetness and a platy structure between the 
surface and subsoil may interfere with rooting and 
with potassium uptake early in the growing period, 
even though roots are present. 

Rate of fertilizer application 

Minimum soil-test levels required to produce opti- 
mum crop yields vary depending on the crop to be 
grown and the soil type (Figures 10.14 and 10.15). 
Near maximum yields of corn and soybeans will be 
obtained when levels of available phosphorus are 
maintained at 30, 40, and 45 pounds per acre for soils 
in the high, medium, and low phosphorus-supplying 
regions, respectively. Potassium soil-test levels at which 
optimum yields of these two crops will be attained 
are 260 and 300 pounds of exchangeable potassium 
per acre for soils in the low and high cation-exchange 
capacity regions, respectively. Because phosphorus, 
and on most soils also potassium, will not be lost from 
the soil system other than through crop removal or 
soil erosion and because these are minimum values 
required for optimum yields, it is recommended that 
soil-test levels be built up to 40, 45, and 50 pounds 
per acre of phosphorus for soils in the high, medium, 
and low phosphorus-supplying regions, respectively. 

Depending on the soil-test level, the amount of 
fertilizer recommended may consist of a buildup plus 
maintenance, maintenance, or no fertilizer suggestion. 




Figure 10.13. Cation-exchange capacity. The shaded areas 
are sands with low cation-exchange capacity. 







100 

■a 


^^^^^ 






0) 




.o^' 




•>,90 
E 
1 80 


- ^^jr* — Corn 







E70 


- /"^ 






o 


jT Wheat, oats, alfalfa, clover 




«rf 


• r 




i 60 


/* 








/ 






^ 


/ 






0- 50 


- / 






< 
P region 


y \ \ \ 


1 1 








Subsoil phosphorus 




High 7 15 20 40 60 


Medium 10 20 30 45 65 


Low 20 30 38 50 70 



Pl test, pounds per acre 

Figure 10.14. Relationship between expected yield and 
soil-test phosphorus. 



The buildup is the amount of material required to 
increase the soil test to the desired level. The main- 
tenance addition is the amount required to replace the 
amount that will be removed by the crop to be grown. 
Buildup plus maintenance. When soil-test levels 
are below the desired values, it is suggested that 
enough fertilizer be added to build the soil test to the 



65 



desired goal plus enough to replace what the crop will 
remove. At these test levels, the yield of the crop to 
be grown will be affected by the amount of fertilizer 
applied that year. 

Maintenance. When the soil-test levels are between 
the minimum and 20 pounds above the minimum for 
phosphorus (that is, 40 to 60, 45 to 65, or 50 to 70) 
or between the minimum and 100 pounds above the 
minimum for potassium (that is, 260 to 360 or 300 to 
400), apply enough to replace what the crop to be 
grown is expected to remove. The yield of the current 
crop may not be affected by the fertilizer addition that 
year, but the yield of subsequent crops will be adversely 
affected if the materials are not applied to maintain 
soil-test levels. 

No fertilizer. Although it is recommended that soil- 
test levels be maintained slightly above the level at 
which optimum yield would be expected, it would not 
be economical to attempt to maintain the values at 
excessively high levels. Therefore, it is suggested that 
no phosphorus be applied if Pi values are higher than 
60, 65, or 70, respectively, for soils in the high, medium, 
and low phosphorus-supplying regions. No potassium is 
suggested if test levels are above 360 or 400 for the low 
and high cation-exchange capacity regions, unless crops 
that remove large amounts of potassium (such as alfalfa 
or corn silage) are being grown. When soil-test levels 
are between 400 and 600 pounds per acre of potassium 
and corn silage or alfalfa is being grown, the soil 
should be tested every 2 years instead of 4 or main- 
tenance levels of potassium should be added to ensure 
that soil-test levels do not fall below the point of 
optimum yields. 



Phosphorus 

Buildup. Research has shown that, as an average 
for Illinois soils, 9 pounds of P2O5 per acre are required 
to increase the Pi soil test by 1 pound. Therefore, the 
recommended rate of buildup phosphorus is equal to 
nine times the difference between the soil-test goal 
and the actual soil-test value. The amount of phos- 
phorus recommended for buildup over a 4 -year period 
for various soil-test levels is presented in Table 10.17. 

Because the rate of 9 pounds of P2O5 to increase 
the soil test 1 pound is an average for Illinois soils, 
some soils will fail to reach the desired goal in 4 years 
with P2O5 applied at this rate, and others will exceed 
the goal. Therefore, it is recommended that each field 
be retested every 4 years. 

In addition to the supplying power of the soil, the 
optimum soil-test value also is influenced by the crop 
to be grown. For example, the phosphorus soil-test 
level required for optimum yields of wheat and oats 
(Figure 10.14) is considerably higher than that required 
for corn and soybean yields, partly because wheat and 
corn have different phosphorus uptake patterns. Wheat 
requires a large amount of readily available phosphorus 
in the fall, when the root system is feeding primarily 



Oats, wheat 



Soybeans 



100 






S 80 


""■" j""' 1 







/ // 1 




u 


/ // 1 




«> 


1 't I 1 




a. 


>l 1 




•a 


/' ' 1 













/ / ! ' 




> 60 


' / Crop yields . Subsequent 






' / dependent . crop yields 


Crop yields not 




/ on K (ertilizer dependent on 


dependent on 




'use 1 K fertilizer use 


lertllizer use 


40 


1 1 ! 1 1 


1 I 



40 


100 


200 260 300 
K lest, low CEC K region 


60 


120 


240 300 
K test, high CEC K region 



500 



Figure 10.15. Relationship between expected yield and 
soil-test potassium. 



Table 10.17. Amount of Phosphorus (P2O5) Required 
to Build Up the Soil (Based on Buildup 
Occurring over A 4- Year Period; 9 
Pounds of P2O5 per Acre Required to 
Change Pi Soil Test 1 Pound) 





Pounds of P2O5 to apply per acre 


each 


Pi test, 
lb/acre 


^ear for soils 


with supplying power rated 










Low 


Medium 


High 


4 


103 


92 


81 


6 


99 


88 


76 


8 


94 


83 
79 


72 


10 


90 


68 


12 


86 


74 


63 


14 


81 


70 


58 


16 


76 


65 
61 


54 


18 


72 


50 


20 


68 


56 


45 


22 


63 


52 


40 


24 


58 


47 


36 


26 


54 


43 


32 


28 


50 


38 


27 


30 


45 


34 


22 


32 


40 


29 


18 


34 


36 


25 


14 


36 


32 


20 


9 


38 


27 


16 


4 


40 


22 


11 





42 


18 


7 





44 


14 


2 





45 


11 








46 


9 








48 


4 








50 












from the upper soil surface. Phosphorus is taken up 
by corn until the grain is fully developed, so subsoil 
phosphorus is more important in interpreting the phos- 
phorus test for corn than for wheat. To compensate 
for the higher phosphorus requirements of wheat and 
oats, it is suggested that 1.5 times the amount of 
expected phosphorus removal be applied prior to seed- 
ing these crops. 

This correction has already been included in the 



66 



maintenance values listed for wheat and oats in Table 
10.18. 

Maintenance. In addition to adding fertilizer to 
build up the soil test, sufficient fertilizer should be 
added each year to maintain a specified soil-test level. 
The amount of fertilizer required to maintain the soil- 
test value is equal to the amount removed by the 
harvested portion of the crop (Table 10.18). The only 
exception to this guideline is that the maintenance 
value for wheat and oats is equal to 1.5 times the 
amount of phosphorus (P2O5) removed by the grain. 
This correction has already been accounted for in the 
maintenance values given in Table 10.18. 



Potassium 

As indicated, phosphorus will usually remain in the 
soil unless it is removed by a growing crop or by 
erosion; thus soil levels can be built up as described. 
Experience in the last several years indicates that on 
most soils potassium tends to follow the buildup 
pattern of phosphorus, but on other soils, soil-test 
levels do not build up as expected. Because of this, 
both the buildup-maintenance and the annual appli- 
cation options are provided. 

Producers who have one or more of the following 
conditions should consider the annual application op- 
tion: 

1. Soils for which past records indicate that soil-test 
potassium does not increase when buildup appli- 
cations are applied. 

2. Sandy soils that do not have a capacity large enough 
to hold adequate amounts of potassium. 

3. Producers who have an unknown or very short 
tenure arrangement. 

On all other fields, use of the buildup-maintenance 
option is suggested. 

Rate of fertilizer application 

Buildup. The only significant loss of soil-applied 
potassium is through crop removal or soil erosion. 
Therefore, it is recommended that soil-test potassium 
be built up to values of 260 and 300 pounds of 
exchangeable potassium, respectively, for soils in the 
low and high cation-exchange capacity region. These 
values are slightly higher than that required for max- 
imum yield, but as in the recommendations for phos- 
phorus, this will ensure that potassium availability will 
not limit crop yields (Figure 10.15). 

Research has shown that 4 pounds of K2O are 
required, on the average, to increase the soil test 1 
pound. Therefore, the recommended rate of potassium 
application for increasing the soil-test value to the 
desired goal is equal to four times the difference 
between the soil-test goal and the actual soil-test value. 

Tests on soil samples that are taken before May 1 
or after September 30 should be adjusted downward 



Table 10.18. Maintenance Fertilizer Required for 
Various Yields of Crops 

Yield, „ 

per acre ^ 2U5 K2O 

pounds per acre 

Corn grain 

90 bu 39 25 

100 43 28 

110 47 31 

120 52 34 

130 56 36 

140 $0 39 

150 64 42 

160 69 45 

170 73 48 

180 77 50 

190 82 53 

200 86 56 

Oats 

50 bu 19'' 10 

60 23 12 

70 27 14 

80 30 16 

90 34 18 

100 38 20 

110 42 22 

120 46 24 

130 49 26 

140 53 28 

150 57 30 

Soybeans 

30 bu 26 39 

40 34 52 

50 42 65 

60 51 78 

70 60 91 

80 68 104 

90 76 117 

100 85 130 

Corn silage 

90 bu; 18 tons 48 126 

100; 20 53 140 

110; 22 58 154 

120; 24 64 168 

130; 26 69 182 

140; 28 74 196 

150; 30 80 210 

Wheat 

30 bu 27'' 9 

40 36 12 

50 45 15 

60 54 18 

70 63 21 

80 72 24 

90 81 27 

100 90 30 

110 99 33 

Alfalfa, grass, or alfalfa-grass mixtures 

2 tons 24 100 

3 36 150 

4 48 200 

5 60 250 

6 72 300 

7 84 350 

8 96 400 

9 108 450 

10 120 500 

^ If the annual application option is chosen, then K application will be 1.5 

times the values shown below. 

''Values given are 1.5 times actual removal. (See this page.) 



67 



as follows: subtract 30 for the dark-colored soils in 
central and northern Illinois; subtract 45 for the light- 
colored soils in central and northern Illinois, and fine- 
textured bottomland soils; and subtract 60 for the 
medium- and light-colored soils in southern Illinois. 
Annual buildup rates of potassium application rec- 
ommended for a 4-year period for various soil test 
values are presented in Table 10.19. 

Wheat is not very responsive to potassium unless 
the soil test is less than 100. Because wheat is usually 
grown in rotation with corn and soybeans, however, 
it is suggested that soils be maintained at the optimum 
available potassium level for corn and soybeans. 

Maintenance. As with phosphorus, the amount of 
fertilizer required to maintain the soil-test value equals 
the amount removed by the harvested portion of the 
crop (Table 10.18). 

Annual application option. If soil-test levels are 
below the desired buildup goal, apply potassium fer- 
tilizer annually at an amount equivalent to 1.5 times 
the potassium content in the harvested portion of the 



Table 10.19. Amount of Potassium (K2O) Required 
to Build Up the Soil (Based on the 
Buildup Occurring over A 4-Year Pe- 
riod; 4 Pounds of K2O per Acre Re- 
quired to Change the K Test 1 Pound) 

Amount of K2O to apply per 
^ test^ acre each year for soils with 

pounds per cation exchange capacity: 

acre : ^ ' "^ — r 

Low" High" 

50 210 250 

60 200 240 

70 190 230 

80 180 220 

90 170 210 

100 160 200 

110 150 190 

120 140 180 

130 130 170 

140 120 160 

150 110 150 

160 100 140 

170 90 130 

180 80 120 

190 70 110 

200 60 100 

210 50 90 

220 40 80 

230 30 70 

240 20 60 

250 10 50 

260 40 

270 30 

280 20 

290 10 

300 

* Tests on soil samples that are taken before May 1 or after September 30 
should be adjusted downward as follows: subtract 30 pounds for dark-colored 
soils in central and northern Illinois; 45 pounds for light-colored soils in 
central and northern Illinois, and fine-textured bottomland soils; and 60 
pounds for medium- and light-colored soils in southern Illinois, 
"Low cation-exchange capacity soils are those with CEC less than 12 meq/ 
100 g soil; high capacity soils are those with CEC at least 12 meq/100 g 
soil. 



expected yield. If levels are only slightly below desired 
buildup levels, so that buildup and maintenance are 
less than 1.5 times removal, add the lesser amount. 
Continue to monitor the soil-test potassium level every 
4 years. 

If soil-test levels are within a range from the desired 
goal to 100 pounds above the desired potassium goal, 
apply enough potassium fertilizer to replace what the 
harvested yield will remove. 

Each of the proposed options (buildup-maintenance 
and annual) has advantages and disadvantages. In the 
short run, the annual option will likely be less costly. 
In the long run, the buildup approach may be more 
economical. In years of high income, tax benefits may 
be obtained by applying high rates of fertilizer. Also, 
in periods of low fertilizer prices, the soil can be built 
to higher levels that in essence bank the materials in 
the soil for use at a later date when the economy may 
not be as good for fertilizer purchases. Producers using 
the buildup system are insured against yield loss that 
may occur in years when weather conditions prevent 
fertilizer application or in years when fertilizer supplies 
are not adequate. The primary advantage of the buildup 
concept is the slightly lower risk of potential yield 
reduction that may result from lower annual fertilizer 
rates. This is especially true in years of exceptionally 
favorable growing conditions. The primary disadvan- 
tage of the buildup option is the high cost of fertilizer 
in the initial buildup years. 

Examples of how to figure phosphorus and potas- 
sium fertilizer recommendations follow. 

Example 1. Continuous corn with a yield goal of 
140 bushels per acre: 



(a) Soil-test results 



Soil region 



P, 30 
K 250 



high 
high 



(b) Fertilizer recommendation, pounds per acre per year 



P.O. 



K2O 



Buildup 22 (Table 10.17) 

Maintenance . . 60 (Table 10.18) 

Total 82 



50 (Table 10.19) 
39^(Table 10.18) 

89 



Example 2. Corn-soybean rotation with a yield goal 
of 140 bushels per acre for corn and 40 bushels per 
acre for soybeans: 

(a) Soil-test results Soil region 



Pi 20 
K 200 



low 
low 



(b) Fertilizer recommendation, pounds per acre per year 
P2O5 K2O 



Corn 



Buildup 68 

Maintenance . . 60 



Total 



.128 



60 
39 

99 



68 



Buildup 68 

Maintenance . . 34 



Soybeans 



Total 



.102 



60 

52 

112 



Note that buildup recommendations are indepen- 
dent of the crop to be grown, but maintenance rec- 
ommendations are directly related to the crop to be 
grown and the yield goal for the particular crop. 

Example 3. Continuous corn with a yield goal of 
150 bushels per acre: 



(a) Soil-test results 



Soil region 



P, 90 
K 420 



low 
low 



(b) Fertilizer recommendation, pounds per acre per year 



P.Os 



K2O 



Buildup 

Maintenance . . 



Total 







Note that soil-test values are higher than those 
suggested; thus no fertilizer is recommended. Retest 
the soil after 4 years to determine fertility needs. 

Example 4. Corn-soybean rotation with a yield goal 
of 120 bushels per acre for corn and 35 bushels per 
acre for soybeans: 

(a) Soil-test results Soil region 



Pi 20 
K 180 



low 

low (soil test 
does not increase 
as expected) 



(b) Fertilizer recommendation, pounds per acre per year 



p,o. 



K2O 



Buildup 68 

Maintenance . . 52 

Total 120 

Buildup 68 

Maintenance . . 30 

Total 98 



Corn 



Soybeans 



51 (34x1.5) 



69 (46x1.5) 



For farmers planning to double-crop soybeans after 
wheat, it is suggested that phosphorus and potassium 
fertilizer required for both the wheat and soybeans be 
applied before seeding the wheat. This practice will 
reduce the number of field operations necessary at 
planting time and will hasten the planting operation. 

The maintenance recommendations for phosphorus 
and potassium in a double-crop wheat and soybean 
system are presented in Tables 10.20 and 10.21, re- 
spectively. Assuming a wheat yield of 50 bushels per 



Table 10.20. Maintenance Phosphorus Required for 
Wheat-Soybean Double-Crop System 



Wheat yield, 




Soybean yield, bu/acre 




bu/acre 


20 


30 40 


50 


60 






P,n^ 1h 1 nrYP 
















30 


44 


53 61 


69 


78 


40 


53 


62 70 


78 


87 


50 


62 


71 79 


87 


96 


60 


71 


80 88 


96 


105 


70 


80 


89 97 


105 


114 


80 


89 


98 106 


114 


123 



Table 10.21. Maintenance Potassium Required for 
Wheat-Soybean Double-Crop System 



Wheat yield. 




Soyb 


ean 


yield, bu/acre 




bu/acre 


20 


30 




40 


50 


60 








K2O, Ih/acre 
















30 


35 


48 




61 


74 


87 


40 


38 


51 




64 


n 


90 


50 


41 


54 




67 


80 


93 


60 


44 


57 




70 


83 


96 


70 


47 


60 




73 


86 


99 


80 


50 


63 




76 


89 


102 



acre followed by a soybean yield of 30 bushels per 
acre, the maintenance recommendation would be 71 
pounds of P2O5 and 54 pounds of K2O per acre. 

Computerized recommendations 

Soil fertility recommendations have been incorpo- 
rated into a microcomputer program that utilizes the 
soil-test information, soil type and characteristics, crop- 
ping and management history, cropping plans and 
yield goals to develop recommendations for lime, 
nitrogen, phosphorus, and potassium. This program, 
called Soil Plan, groups together similar fertilizer rec- 
ommendations and provides a map showing where 
each recommendation should be implemented within 
the field. Users have the option of altering the map 
to adjust to the kind of spread pattern desired. Ad- 
ditionally, the user can change the different variables 
to determine their impact on fertilizer needed. 

Further information about this program may be 
obtained from lUinet Software, 330 Mumford Hall, 
1301 West Gregory Drive, Urbana, Illinois 61801. 

Time of application 

Although the fertilizer rates for buildup and main- 
tenance in Tables 10.17 and 10.19 are for an annual 
application, producers may apply enough nutrients in 
any one year to meet the needs of the crops to be 
grown in the succeeding 2- to 3-year period. 

Phosphorus and potassium fertilizers may be ap- 
plied in the fall to fields that will not be fall tilled, 
provided that the slope is less than 5 percent. Do not 
fall-apply fertilizer to fields that are subject to rapid 
runoff. When the probability of runoff loss is low. 



69 



soybean stubble need not be tilled solely for the 
purpose of incorporating fertilizer. This statement holds 
true when ammoniated phosphate materials are used 
as well because the potential for volatilization of 
nitrogen from ammoniated phosphate materials is in- 
significant. 

For perennial forage crops, broadcast and incorpo- 
rate all of the buildup and as much of the maintenance 
phosphorus as economically feasible before seeding. 
On soils with low fertility, apply 30 pounds of phos- 
phate (P2O5) per acre using a band seeder. If a band 
seeder is used, you may safely apply a maximum of 
30 to 40 pounds of potash (K2O) per acre in the band 
with the phosphorus. Up to 600 pounds of K2O per 
acre can be safely broadcast in the seedbed without 
damaging seedlings. 

Applications of phosphorus and potassium top- 
dressed on perennial forage crops may be made at 
any convenient time. Usually this will be after the first 
harvest or in September. 

High water-soiubility of phosphorus 

The water-solubility of the P2O5 Usted as available 
on the fertilizer label is of little importance under 
typical field crop and soil conditions on soils with 
medium to high levels of available phosphorus, when 
recommended rates of apphcation and broadcast place- 
ment are used. 

For some situations, water-solubility is important. 
These situations include the following: 

1. For band placement of a small amount of fertilizer 
to stimulate early growth, at least 40 percent of the 
phosphorus should be water-soluble for application 
to acidic soils and, preferably, 80 percent for cal- 
careous soils. As shown in Table 10.22, the phos- 
phorus in nearly all fertilizers commonly sold in 
Illinois is highly water-soluble. Phosphate water- 
solubility in excess of 80 percent has not been 
shown to give further yield increases above those 
that have water-solubility levels of at least 50 
percent. 

2. For calcareous soils, a high degree of solubility in 
water is desirable, especially on soils that are shown 
by soil test to be low in available phosphorus. 



Secondary nutrients 

The elements that are classified as secondary nutrients 
include calcium, magnesium, and sulfur. Crop yield 
response to application of these three nutrients has been 
observed on only a very limited basis in Illinois. There- 
fore, the data base necessary to correlate and calibrate 
soil-test procedures is very limited, and thus the reliability 
of the suggested soil-test levels for the secondary nu- 
trients presented in Table 10.23 is low. 

Deficiency of calcium has not been recognized in 
Illinois where soil pH is 5.5 or above. Calcium defi- 
ciency associated with acidic soils should be corrected 



Table 10.22. Characteristics of Some Common 
Processed-Phosphate Materials 



Material 



Percent 
P2O. 



Percent Percent ^^f- 
water- citrate- P*".; 
^ soluble soluble ^^^^j"" 



Ordinary superphosphate 

0-20-0 16-22 

Triple superphosphate 44-47 

Mono-ammonium phosphate 

11-48-0 46-48 

Diammonium phosphate 

18-46-0 46 

Ammonium polyphosphate 

10-34-0, 11-37-0 34-37 



78 
84 


18 
13 


96 
97 


100 




100 


100 
100 




100 
100 



Table 10.23. Suggested Soil-Test Levels for the Sec- 
ondary Nutrients 



Levels that are adequate 






Soil type ^o"" crop production 


Rating 


Sulfur 


Calcium Magnesium 






pounds per acre 




lb/acre 


Sandy .... 400 60-75 


Very low 


. . 0-12 


Silt loam 800 150-200 


Low 


. . 12-22 




Response unlikely . 


. . 22 



by the use of limestone that is adequate to correct the 
soil pH. 

Magnesium deficiency has been recognized in iso- 
lated situations in Illinois. Although the deficiency is 
usually associated with acidic soils, in some instances 
low magnesium has been reported on sandy soils 
where the soils were not excessively acidic. The soils 
most likely to be deficient in magnesium include sandy 
soils throughout Illinois and low exchange-capacity 
soils of southern Illinois. Deficiency will be more likely 
where calcific rather than dolomitic limestone has been 
used and where potassium test levels have been high 
(above 400). 

Recognition of sulfur deficiency has been reported 
with increasing frequency throughout the Midwest. 
These deficiencies probably are occurring because of 
(1) increased use of S-free fertilizer, (2) decreased use 
of sulfur as a fungicide and insecticide, (3) increased 
crop yields, resulting in increased requirements for all 
of the essential plant nutrients, and (4) decreased 
atmospheric sulfur supply. 

Organic matter is the primary source of sulfur in 
soils. Thus soils low in organic matter are more likely 
to be deficient than are soils with a high level of 
organic matter. Because sulfur is very mobile and can 
be readily leached, deficiency is more likely to be 
found on sandy soils than on finer-textured soils. 

A yield response to sulfur application was observed 
at 5 of 85 locations in Illinois (Table 10.24). Two of these 
responding sites, one an eroded silt loam and one a 
sandy soil, were found in northwestern Illinois (Whiteside 
and Lee counties); one site, a silty clay loam, was in 
central Illinois (Sangamon County); and two sites, one 



70 



a silt loam and one a sandy loam soil, were in southern 
Illinois (Richland and White counties). 

At the responding sites, sulfur treatments resulted 
in com yields that averaged 11.2 bushels per acre 
more than yields from the untreated plots. At the 
nonresponding sites, yields from the sulfur-treated 
plots averaged only 0.6 bushel per acre more than 
those from the untreated plots (Table 10.24). If one 
considers only the responding sites, the sulfur soil test 
predicts with good reliability which sites will respond 
to sulfur applications. Of the five responding sites, 
one had only 12 pounds of sulfur per acre, less than 
the amount considered necessary for normal plant 
growth, and three had marginal sulfur concentration 
(from 12 to 20 pounds of sulfur per acre). Sulfur tests 
on the 80 nonresponding sites showed 14 to be defi- 
cient and 29 to have a level of sulfur that is considered 
marginal for normal plant growth. Sulfur applications, 
however, produced no significant positive response in 
these plots. The correlation between yield increases 
and measured sulfur levels in the soil was very -low, 
indicating that the sulfur soil test did not reliably 
predict sulfur need. 

In addition to soil-test values, one should also 
consider organic-matter level, potential atmospheric 
sulfur contributions, subsoil sulfur content, and mois- 
ture conditions just before soil sampling in determining 
whether a sulfur response is likely. If organic-matter 
levels are greater than 2.5 percent or if the field in 
question is located in an area downwind from indus- 
trial operations where significant amounts of sulfur 
are being emitted, use sulfur only on a trial basis even 
when the soil-test reading is low. Because sulfur is a 
mobile nutrient supplied principally by organic-matter 
oxidation, abnormal precipitation (either high or low) 
could adversely affect the sulfur status of samples 
taken from the soil surface. If precipitation has been 
high just before sampling, some samples may have a 
low reading due to leaching. If precipitation were low 
and temperatures warm, some soils may have a high 
reading when, in fact, the soil is not capable of 
supplying adequate amounts of sulfur throughout the 
growing season. 



Micronutrients 

The elements that are classified as essential micro- 
nutrients include zinc, iron, manganese, copper, boron, 
molybdenum, and chlorine. These nutrients are class- 
ified as micronutrients because they are required in 
small (micro) amounts. Confirmed deficiencies of these 
micronutrients in Illinois have been limited to boron 
deficiency of alfalfa, zinc deficiency of corn, and iron 
and manganese deficiencies of soybeans. 

Similar to the tests for secondary nutrients, the 
reliability and usefulness of micronutrient tests are 
very low because of the limited data base available to 
correlate and calibrate the tests. Suggested levels for 
each of the tests are provided in Table 10.25. In most 



Table 10.24. 



Average Yields at Responding and Non- 
responding Zinc and Sulfur Test Sites, 
1977-79 



Number 

of 

sites 



Yield 

from 

untreated 

plots 



Yield 
from 
zinc- 
treated 
plots 



Yield 
from 
sulfur- 
treated 
plots 



Responding sites 

Low-sulfur soil 5 

Low-zinc soil 3 

Nonresponding sites 80 



bushels per acre 



140.0 
150.6 

147.6 



164.7 
146.2 



151.2 
148.2 



Adequate 



Table 10.25. Suggested Soil-Test Levels for Micro- 
nutrients 



Micronutrient Soil-test level 

and procedure Very low Low 

pounds per acre 

Boron 

(hot-water soluble) 0.5 1.0 

Iron (DTPA) <4.0 

Manganese (DTPA) <2.0 

Manganese (H3PO4) <10 

Zinc (.IN HCl) <7.0 

Zinc (DTPA) <1.0 



2.0 
>4.0 
>2.0 
>10 
>7.0 
>1.0 



cases, use of plant analysis will probably provide a 
better estimate of micronutrient needs than will the 
soil test. 

Manganese deficiency (stunted plants with green 
veins in yellow or whitish leaves) is common on high- 
pH (alkaline), sandy soils, especially during cool, wet 
weather in late May and June. Suggested treatment is 
to spray either manganese sulfate or an organic man- 
ganese formulation onto the leaves soon after the 
symptoms first appear; use the rate suggested by the 
manufacturer. Broadcast application on the soil is 
ineffective because the manganese becomes unavail- 
able in soils with a high pH. 

Wayne and Hark soybean varieties or lines devel- 
oped from them often show iron deficiency on soils 
with a very high pH (usually 7.4 to 8.0). The symptoms 
are similar to those shown with manganese deficiency. 
Most of the observed deficiencies have been on Harps- 
ter, a "shelly" soil that occurs in low spots in some 
fields in central and northern Illinois. This problem 
has appeared on Illinois farms only since the Wayne 
variety was introduced in 1964. 

Soybeans often outgrow the stunted, yellow ap- 
pearance of iron shortage. As a result, it has been 
difficult to measure yield losses or decide whether or 
how to treat affected areas. Sampling by United States 
Department of Agriculture (USDA) scientists in 1967 
indicated yield reductions of 30 to 50 percent in the 
center of severely affected spots. The yield loss may 
have been caused by other soil factors associated with 
a very high pH and poor drainage, rather than by iron 
deficiency itself. Several iron treatments were ineffec- 
tive in trials near Champaign and DeKalb in 1968. 



71 



Research in Minnesota has shown that time of iron 
apphcation is critical if a response is to be attained. 
Researchers recommend that a rate of 0.15 pound of 
iron per acre as iron chelate be applied to leaves within 
3 to 7 days after chlorosis symptoms develop (usually 
in the second-trifoliate stage of growth). Waiting for 
soybeans to grow to the fourth- or fifth -trifoliate stage 
before applying iron resulted in no yield increase. 
Because iron applied to the soil surface between rows 
does not help, directed applications directly over the 
soybean plants were preferred. 

A significant yield response to zinc applications was 
observed at 3 of 85 sites evaluated in Illinois (Table 
10.24). The use of zinc at the responding sites produced 
a corn yield that averaged 14.1 bushels per acre more 
than the check plots. Two sites were Fayette silt loams 
in Whiteside County, and one was a Greenriver sand 
in Lee County. 

At two of the three responding sites, tests showed 
that the soil was low or marginal in available zinc. 
The soil of the third had a very high zinc level but 
was deficient in available zinc, probably because of 
the excessively high phosphorus level also found at 
that site. 

The zinc soil-test procedures accurately predicted 
results for two-thirds of the responding sites. The same 
tests, however, incorrectly predicted that 19 other sites 
would also respond. These results suggest that the soil 
test for available zinc can indicate where zinc defi- 
ciencies are found but does not indicate reliably whether 
the addition of zinc will increase yields. 

To identify areas before micronutrient deficiencies 
become important, continually observe the most sen- 
sitive crops in soil situations in which the elements 
are likely to be deficient (Table 10.26). 

In general, deficiencies of most micronutrients are 
accentuated by one of five situations: (1) strongly 
weathered soils, (2) coarse-textured soils, (3) high-pH 
soils, (4) organic soils, and (5) soils that are inherently 
low in organic matter or low in organic matter because 
erosion or land-shaping processes have removed the 
topsoil. 

The use of micronutrient fertilizers should be limited 
to the application of specific micronutrients to areas 
of known deficiency. Only the deficient nutrient should 
be applied. An exception to this guideline would be 
situations in which farmers already in the highest yield 
bracket try micronutrients on an experimental basis in 
fields that are yielding less than would be expected 
under good management, which includes an adequate 
nitrogen, phosphorus, and potassium fertility program 
and a favorable pH. 



Method of fertilizer application 

With the advent of new equipment, producers have 
a number of options for placement of fertilizers. These 
options range from traditional broadcast application 
to injection of the materials at varying depths in the 



soil. Selection of the proper application technique for 
a particular field will depend at least in part upon the 
inherent fertility level, the crop to be grown, the land 
tenure, and the tillage system. 

On fields where the fertility level is at or above the 
desired goal, there is little research evidence to show 
any significant difference in yield that is associated 
with method of application. In contrast, on low-testing 
soils and in soils that "fix" phosphorus, placement of 
the fertilizer within a concentrated band has been 
shown to result in higher yields, particularly at low 
rates of application. On higher testing soils, plant 
recovery of applied fertilizer in the year of application 
will usually be greater from a band than a broadcast 
application although yield differences are unlikely. 

Broadcast fertilization. On highly fertile soils, both 
maintenance and buildup phosphorus and potassium 
will be efficiently utilized when broadcast and plowed 
or disked in. This system, particularly when the tillage 
system includes a moldboard plow every few years, 
distributes nutrients uniformly throughout the entire 
plow depth. As a result, roots growing within that 
zone have access to high levels of fertility. Because 
the nutrients are intimately mixed with a large volume 
of soil, opportunity exists for increased nutrient fixation 
on soils having a high fixation ability. Fortunately, most 
Illinois soils do not have high fixation rates for phos- 
phorus or potassium. 

Row fertilization. On soils of low fertility, place- 
ment of fertilizer in a concentrated band below and 
to the side of the seed has been shown to be an 
efficient method of apphcation, especially in situations 
for which the rate of application is markedly less than 
that needed to build the soil to the desired level. 
Producers who are not assured of having long-term 
tenure on the land may wish to consider this option. 
The major disadvantages of this technique are (1) the 
additional time and labor required at planting time, 

(2) limited contact between roots and fertiUzer, and 

(3) inadequate rate of apphcation to increase soil levels 
for future crops. 

Strip application. With this technique, phosphorus, 
potassium, or both are applied in narrow bands on 
approximately 30-inch centers on the soil surface, in 
the same direction as the primary tillage. The theory 
behind this technique is that, after moldboard plowing, 
the fertilizer will be distributed in a narrow vertical 
band throughout the plow zone. Use of this system 
reduces the amount of soil-to-fertilizer contact as com- 
pared with a broadcast application, and thus it reduces 
the potential for nutrient fixation. Because the fertiUzer 
is distributed through a larger soil volume than with 
a band application, the opportunity for root-fertilizer 
contact is greater. 

Deep fertilizer placement. Several terms have been 
used to define this technique. They include root-zone 
banding, dual placement, knife injection, and deep 
placement. With this system a mixture of N-P or N- 
P-K is injected at a depth ranging from 4 to 8 inches. 



72 



Table 10.26. Soil Situations and Crops Susceptible to Micronutrient Deficiency 



Micronutrient 



Sensitive crop 



Susceptible soil situations 



Season favoring 
deficiency 



Zinc (Zn) Young com 



Iron (Fe) Wayne soybeans, 

grain sorghum 

Manganese (Mn) Soybeans, oats 

Boron (B) Alfalfa 

Copper (Cu) Com, wheat 

Molybdenum (Mo) Soybeans 

Chlorine (CI) Unknov^n 



1. Low in organic matter, either inherently 
or because of erosion or land shaping 

2. High pH, that is, >7.3 

3. Very high phosphorus 

4. Restricted root zone 

5. Coarse-textured (sandy) soils 

6. Organic soils 



Cool, wet 





High pH 


Cool, wet 


1. 

2. 
3. 


High pH 

Restricted root zone 
Organic soils 


Cool, wet 


1. 
2. 
3. 

4. 


Low organic matter 
High pH 

Strongly weathered soils in south- 
central Illinois 
Coarse-textured (sandy) soils 


Drought 


1. 
2. 


Infertile sand 
Organic soils 


Unknown 




Strongly weathered soils in south- 
central Illinois 


Unknown 




Coarse-textured soils 


Excessive 
leaching by 
low-Cl water 



The knife spacings used may vary by crop to be grown, 
but generally they are 15 to 18 inches apart for close- 
grown crops such as wheat and 30 inches for row 
crops. Use of this technique provided a significantly 
higher wheat yield as compared with a broadcast 
application of the same rate of nutrients in some, but 
not all, experiments conducted in Kansas. Wisconsin 
research showed the effect of this technique to be 
equivalent to that of a band application for corn on a 
soil testing high in phosphorus but inferior to that of 
a band application for corn on a soil testing low in 
phosphorus. If this system is used on low-testing soils, 
it is advisable to apply a portion of the phosphorus 
fertilizer in a band with the planter. 

Dribble fertilizer. This technique involves the ap- 
plication of urea-ammonium nitrate solutions in con- 
centrated bands on 30-inch spacings on the soil surface. 
Results from several states have shown that this system 
reduces the potential for nitrogen loss of these mate- 
rials, as compared with an unincorporated broadcast 
application. However, it has not been shown to be 
superior to an injected or an incorporated application 
of urea-ammonium nitrate solution. 

'Top-up" fertilization. The term "pop-up" is a 
misnomer. The corn does not emerge sooner than it 
does without this kind of application, and it may come 
up 1 or 2 days later. The com may, however, grow 
more rapidly during the first 1 to 2 weeks after 
emergence. Pop-up fertilizer will make corn look very 
good early in the season and may aid in early culti- 
vation for weed control. But no substantial difference 
in yield is likely in most years due to a pop-up 
application as compared to fertilizer that is placed in 
a band to the side and below the seed. Seldom will 



there be a difference of more than a few days in the 
time the root system intercepts fertilizer placed with 
the seed as compared to that placed below and to the 
side of the seed. 

If used, pop-up fertilizer should contain all three 
major nutrients in a ratio of about 1-4-2 of N-P2O5- 
K2O (1-1.7-1.7 of N-P-K). Under normal moishire 
conditions, the maximum safe amount of N plus K2O 
for pop-up placement is about 10 or 12 pounds per 
acre in 40 -inch rows and correspondingly more in 30- 
and 20-inch rows. In excessively dry springs, even 
these low rates may result in damage to seedlings, 
reduction in germination, or both. Pop-up fertilizer is 
unsafe for soybeans. In research conducted at Dixon 
Springs, a stand was reduced to one-half by applying 
50 pounds of 7-28-14 and reduced to one-fifth with 
100 pounds of 7-28-14. 

Site-specific application. Equipment has recently 
been developed that uses computer technology to alter 
the rate of fertilizer application as the truck passes 
across the field. While this technology and the sup- 
porting research are still in their infancy, this approach 
offers the potential to improve yield while minimizing 
the potential for overfertilization. Yield improvement 
will result from applying the correct rate (not a rate 
based on average soil test) to the low-testing portions 
of the field. Overfertilization will be reduced by ap- 
plying the correct rate (in many cases this may be 
zero) to high-testing areas of the field. The combination 
of improved yield and reduced output will result in 
improved profit. 

Foliar fertilization. Researchers have known for 
many years that plant leaves absorb and utilize nu- 
trients sprayed on them. Foliar fertilization has been 



73 



used successfully for certain crops and nutrients. This 
n\ethod of application has had the greatest use with 
nutrients required in only small amounts by plants. 
Nutrients required in large amounts, such as nitrogen, 
phosphorus, and potassium, have usually been applied 
to the soil rather than the foliage. 

The possible benefit of foliarly applied nitrogen 
fertilizer was researched at the University of Illinois 
in the 1950s. Foliarly applied nitrogen increased corn 
and wheat yield, provided that the soil was deficient 
in nitrogen. Where adequate nitrogen was applied to 
the soil, additional yield increases were not obtained 
from foliar fertilization. 

Additional research in Illinois was conducted on 
foliar application of nitrogen to soybeans in the 1960s. 
This effort was an attempt to supply additional nitrogen 
to soybeans without decreasing nitrogen that was 
symbiotically fixed. That is, it was thought that if 
nitrogen application were delayed until after nodules 
were well established, then perhaps symbiotic fixation 
would remain active. Single or multiple applications 
of nitrogen solution to foliage did not increase soybean 
yields. Damage to vegetation occurred in some cases 
because of leaf "burn" caused by the nitrogen fertilizer. 

Although considerable research in foliar fertilization 
had been conducted in Illinois already, new research 
was conducted in 1976 and 1977. This new research 
was prompted by a report from a neighboring state 
indicating that soybean yields had recently been in- 
creased by as much as 20 bushels per acre in some 
trials. Research in that state differed from earlier work 
on soybeans in that, in addition to nitrogen, the foliar 
fertilizer increased yield only if phosphorus, potassium, 
and sulfur were also included. Researchers there 
thought that soybean leaves become deficient in nu- 
trients as nutrients are translocated from vegetative 
parts to the grain during grain development. They 
reasoned that foliar fertilization, which would prevent 
leaf deficiencies, should result in increased photosyn- 
thesis that would be expressed in higher grain yields. 

Foliar fertilization research was conducted at several 
locations in Illinois during 1976 and 1977 — ranging 
from Dixon Springs in southern Illinois to DeKalb in 
northern Illinois. None of the experiments gave eco- 
nomical yield increases. In some cases there were yield 



reductions, which were attributed to leaf damage caused 
by the fertilizer. Table 10.27 contains data from a study 
at Urbana in which soybeans were sprayed four times 
with various fertilizer solutions. Yields were not in- 
creased by foliar fertilization. 



Nontraditional products 

In this day of better informed farmers, it seems 
hard to believe that the number of letters, calls, and 
promotional leaflets about nontraditional products is 
increasing. The claim made is usually that "Product 
X" either replaces fertilizers and costs less, makes 
nutrients in the soil more available, supplies micro- 
nutrients, or is a natural product that does not contain 
strong acids that kill soil bacteria and earthworms. 

The strongest position that legitimate fertilizer deal- 
ers. Extension advisers, and agronomists can take is 
to challenge these peddlers to produce unbiased re- 
search results in support of their claims. Testimonials 
by farmers are no substitute for research. 

Extension specialists at the University of Illinois are 
ready to give unbiased advice when asked about 
purchasing new products or accepting a sales agency 
for them. 

In addition, each county Extension office has the 
publication Compendium of Research Reports on the Use 
of Nontraditional Materials for Crop Production, which 
contains data on a number of nontraditional products 
that have been tested in the Midwest. Check with 
your local Extension office for this information. 



Table 10.27. Yields of Corsoy and Amsoy Soybeans 
After Fertilizer Treatments Were 
Sprayed on the Foliage Four Times, 
Urbana 



Treatment per spraying, lb/acre 



Yield, bu/acre 



N 


P2O5 


K2O 


S 


Corsoy 


Amsoy 














61 


56 


20 











54 


53 





5 


8 


1 


58 


56 


10 


5 


8 


1 


56 


58 


20 


5 


8 


1 


55 


52 


30 


7.5 


12 


1.5 


52 


46 



74 



Chapter 11. 

Soil Management and Tillage Systems 



Selecting the most suitable tillage system for a partic- 
ular farming situation is an important management 
decision. Intensive use of a moldboard plow, disk, 
harrow, and cultivator was once the only practical 
tillage system that could assure crop producers of both 
establishing a crop and controlling weeds. With a wide 
variety of herbicides and tillage and planting imple- 
ments now available, producers have an opportunity 
to select a tillage system for their specific soil, crop, 
and climatic conditions. When selecting a tillage sys- 
tem, evaluate the various systems as they relate to soil 
type, slope, erosion control, drainage, moisture, tem- 
perature, timeliness, fertilizer distribution, and the 
potential of each for controlling weeds, insects, and 
disease. No single tillage system is clearly superior to 
the others for the wide array of soil, crop, and climatic 
conditions that occur in Illinois. 

The following five sections describe tillage systems 
used in Illinois and list some advantages and disad- 
vantages for each. 



Moldboard plow system 
(conventional clean tillage) 

Primary tillage is done with a moldboard plow. 
Secondary tillage includes one or more operations with 
a disk field cultivator, harrow, or similar implement. 

Advantages 

1. The uniform, fine seedbed gives good seed-soil 
contact and makes for easy planting. 

2. Survival of some insects, especially the European 
com borer, is reduced because cornstalk residues 
are buried. 

3. The system is flexible and adaptable to a wide range 
of soil and crop conditions. 

4. Use of labor and machinery is reasonably well 
distributed with fall plowing. 

5. Yields are as high as or higher than with alternative 
tillage systems over a wide range of soil and weather 
conditions. 



Disadvantages 

1. Bare soil is very susceptible to wind and water 
erosion. 

2. A uniform, fine seedbed is more susceptible to 
crusting. 

3. Fuel consumption, labor inputs, and machinery 
costs are high. 

Chisel plow system 

Primary tillage is usually done in the fall with a 
chisel plow, followed by use of a disk or field cultivator 
in the spring. 

Advantages 

1 . Machinery costs and time are slightly less than with 
moldboard plowing. 

2. The soil surface is rough and partially covered by 
crop residues that reduce raindrop impact and 
runoff. 

3. Soil roughness and residues protect the soil from 
water and wind erosion. This benefit may be lost 
in the spring if tillage is excessive. 

4. Yields are comparable to other tillage systems, 
especially on well-drained soils. 

Disadvantages 

1 . In heavy residue, a heavy planter with disk openers 
and a coulter in front of each row may be needed 
for planting. 

2. The lower soil temperatures, especially on poorly 
drained soils, can retard early corn growth in the 
northern two-thirds of Illinois. 

3. Stands are sometimes slightly lower than with clean 
tillage, although the newer planters may eliminate 
this problem. 

4. Slightly higher herbicide rates may be necessary 
for satisfactory weed control. 

5. Crop residue on the soil surface may harbor insects 
and disease-causing organisms. 



75 



Disk system 

A heavy disk or a tandem disk harrow is used for 
primary tillage in the fall or spring. A field cultivator 
or a light disk is used for secondary tillage. Advantages 
and disadvantages of the chisel plow system also apply 
to the disk system, provided that the disk produces a 
rough soil surface covered with some crop residues. 



Ridge-tillage system (till-plant) 

The ridge-tillage system is a one-pass, tillage plant- 
ing operation. Seed is planted in ridges formed during 
cultivation of the previous crop. A sweep or double- 
disk mounted in front of each planter unit pushes the 
top inch or so of crop residue from existing ridges 
between the rows. 



Advantages 

1. Soil roughness and residues protect the soil from 
wind erosion and raindrop impact. 

2. In the spring, soil temperature is higher in the ridge 
and soil moisture is lower. 

3. Machinery and, possibly, herbicide costs are lower 
than with other tillage systems. 

4. Wheel traffic is restricted to inter-row areas, causing 
less compaction in the rows. 

Disadvantages 

1 . Cultivation is required to rebuild ridges and is often 
necessary to control weeds. 

2. Because herbicides cannot be incorporated, the se- 
lection is limited. Contact herbicides may be nec- 
essary for adequate weed control. 

3. The wheel spacing of machinery should be modified 
to avoid driving on ridges. 

4. Narrow -row soybeans or small grains are not prac- 
tical planting options. 

5. Forming ridges in soybeans during cultivation may 
result in pod heights so close to the ground that 
harvest losses are higher. 

6. End rows are usually planted without ridges or are 
leveled with a disk before the entire field is har- 
vested. 



No-tillage system (zero-tillage) 

Seed is planted in previously undisturbed soil by 
means of a special heavy planter equipped to plant 
through residue into firm soil. Fertilizers and pesticides 
must be applied to the soil surface or in the narrow, 
tilled area of the row. Weeds growing at planting time 
are killed with a contact herbicide. Equipment is avail- 
able to apply anhydrous ammonia in no-hll. 



Advantages 

1 . Soil erosion is greatly reduced with no-till compared 
to other systems. 

2. Power, labor, and fuel costs are also greatly reduced 
compared to other tillage systems. 

3. The no-till planter is very adaptable to a wide range 
of soil and residue conditions. 

4. Firm soil may aid harvest operations in a wet year, 

but tillage may be needed to offset soil compaction ^ 
caused by wheel traffic. f 

Disadvantages 

1. Low soil temperatures often delay emergence and 
cause slow early growth. 

2. A special planter or planter attachments may be :^| 
needed. Care should be exercised when planting 

to ensure adequate seed-soil contact and that plant- 
ing depth and seed cover are as uniform as possible. 

3. Rodents and birds may reduce stands. 

4. Some insect and crop disease problems increase 
when crop residues are left on the soil surface. 

5. Without cultivation, weed control is entirely de- 
pendent on herbicides. 

6. Higher herbicide rates or more costly herbicide 
combinations may be needed for adequate weed 
control. 



Soil erosion, and residue management 

Bare, smooth soil left by moldboard plowing and 
intensive secondary tillage is extremely susceptible to 
soil erosion. Many Illinois soils have subsurface layers 
that restrict root development. Soil erosion slowly but 
permanently removes the soil that is most favorable 
for crop growth, resulting in gradually decreasing soil 
productivity and value. Even on soils without root- 
restricting subsoils, erosion removes nutrients that 
must be replaced with additional fertilizer to maintain 
yields. 

Sediment from eroding fields increases water pol- 
lution, reduces the storage capacity of lakes and res- 
ervoirs, and decreases the efficiency of drainage 
systems. Effective erosion control systems usually in- 
clude one or more of three features: 

1. The soil is protected with a cover of vegetation, 
such as a mulch of crop residue. 

2. The soil is tilled so that a maximum amount of 
water is absorbed with minimum runoff. 

3. Long slopes are divided into a series of short slopes 
so that the water cannot get "running room." 
Chisel plow, disk, ridge-till, and no-till systems may 

be classified as conservation tillage if a minimum 
residue cover of 20 to 30 percent remains on the soil 
surface after planting (Figure 11.1). This minimum 
amount of residue cover reduces erosion by approxi- 
mately 50 percent over cleanly tilled fields. A 20 to 



76 



30 percent residue cover should be maintained during 
the critical erosion period from early spring until the 
crop canopy is established. The amount of residue 
cover remaining on the soil surface after a single pass 
of tillage and planting implements can vary consid- 
erably (Table 11.1). In addition, soil type and moisture 
content, operating speed and depth, amount and con- 
dition of residue, sequence of tillage events, and crop 



c 
o 

o 

(0 
0) 

o 



o 

(A 



c 

4> 
O 

o 

Q. 



uu 




















^BH 


90 
80 
70 
60 
50 
40 
30 
20 
10 














A 


















J 


/^ 
















'^"-^■'^'JL 


/ 


















t 


















V 




















f 


















J 




















7 




















/ 





















10 



20 30 40 50 60 70 80 90 
Percent of surface crop residue 



100 



Figure 11.1. Percent of soil-loss reduction for various 
amounts of surface crop residue. 

Table 11.1. Influence of Field Operations on Surface 
Residue 

Percentage^ of 
Tillage and residue 

planting implements remaining after 

each operation 

Moldboard plow 3 to 5 

Chisel plow. 

Straight shovel points 50 to 75 

Twisted shovel points 30 to 60 

Anhydrous applicator 50 to 80 

Disk (tandem or offset), 

3 inches deep 40 to 70 

6 inches deep 30 to 60 

Field cultivator 50 to 80 

Planters, 

No coulter or smooth coulter 90 to 95 

Narrow-ripple coulter 

(less than 1.5' flutes) 85 to 90 

Wide-fluted coulter 

(greater than 1.5' flutes) 80 to 85 

Sweeps or double disk furrowers 

(till-plant) 60 to 80 

Drills, 

Disk openers 90 to 95 

Hoe openers 50 to 80 

Winter weathering 70 to 90 

* Use lower values for fragile residue such as soybeans. 



yields all affect the amount of residue left. With 
conservation tillage, the attachments used on an im- 
plement and the method of operation can be as 
important as the selection of the implement itself in 
retaining crop residue. Refer to the Cooperative Ex- 
tension fact sheet entitled The Residue Dimension, by 
R. Walker, M. Hirschi, and D. Peterson, for methods 
to estimate residue cover. 

The effectiveness of conservation tillage systems in 
reducing soil erosion on an 8 to 12 percent slope in 
simulated rainfall tests on Tama silt loam at Perry, 
Illinois, is illustrated in Figures 11.2 and 11.3. Nearly 
1.2 tons of soil per acre were eroded from an area 
that had been moldboard-plowed, planted on the 
contour, and subjected to 2.4 inches of intense rain 
(Figure 11.2). Under similar rainfall conditions, areas 
that were chisel-plowed and no-tilled following corn 
lost about 0.4 and 0.2 tons of soil per acre, respectively. 

Soil erosion after soybeans is very difficult to control 
with most tillage systems because only a small amount 
of residue is produced. Soil loss was about 3 tons per 
acre for both moldboard- and chisel-plowed areas that 
were planted on the contour and subjected to 2.4 
inches of intense rain (Figure 11.3). Soil erosion in the 
no-till area was reduced to 0.10 tons of soil per acre 
under similar rainfall conditions. No-till was the most 
effective tillage system in controlling soil erosion fol- 
lowing soybeans. 

Nevertheless, conservation tillage will not com- 
pletely control water erosion on all soils. On sloping 
soils, contouring is necessary for all tillage systems. 
Chisel plows, for example, often leave shallow furrows 
that can concentrate rainwater and erode severely if 
the tillage direction is uphill and down. Long or steep 
slopes may also require terraces or other practices. For 
technical assistance in developing erosion control sys- 
tems, consult your district conservationist or the Soil 
Conservation Service. 



Water runoff 

Immediately after operations like moldboard plow- 
ing, chisel plowing, and subsoiling, large amounts of 
rain can initiate runoff. After several rains, the soil 
surface often becomes sealed and runoff increases. 
Runoff is especially high when the soil surface is 
smooth in the spring after secondary tillage operations. 
Surface residue slows the velocity of water runoff. 



Crop production with conservation tillage 

Crop germination, emergence, and growth are largely 
regulated by soil temperature, moisture content, and 
nutrient placement. Tillage practices influence each of 
these components of the soil environment. Conser- 
vation tillage systems differ from conventional clean 
tillage in several respects. 

Soil temperature. Crop residue on the soil surface 



77 



0> 

« - 

Q. 

w 

c - 
o 



(0 — 
(0 

o 1 H 



o 



Moldboard 



T 



0.04 




0.08 1.2 1.6 2.0 

Rainfall, inches 



Figure 11.2. Soil loss after planting soybeans into corn 
residue on Tama silt loam, 8 to 12 percent slope, on 
contour. 



u 

(0 

& 2 

Q. 
CO 

c 
o 



o 
Z 1 



o 

CO 



Moldboard plow 
or chisel plow 



0.04 



— I — 
0.08 




1.2 1.6 2.0 

Rainfall, inches 



Figure 11.3. Soil loss after planting corn into soybean 
residue on Tama silt loam, 8 to 12 percent slope, on 
contour. 



insulates the soil from the sun's energy. In the spring, 
higher than normal soil temperatures are desirable for 
plant growth. Later in the season, cooler than normal 
temperatures are desirable, but a complete crop canopy 
at that time restricts the influence of crop residue on 
soil temperature. 

Minimum soil temperatures occur between 6 and 8 
a.m., and they are affected very little by tillage or crop 
residue. Maximum soil temperatures at a depth of 4 
inches occur between 3 and 5 p.m. During May, fields 
tilled by the fall-plow method have soil temperatures 
3° to 5°F warmer than those with a cornstalk mulch. 

Tillage affects soil temperature most from late April 
until the crop forms a canopy that shades the soil 
surface. During May and early June, the reduced soil 
temperatures caused by a mulch are accompanied by 
slower growth of corn and soybeans. Whether the 
lower soil temperature and subsequent slower early 



growth result in reduced yields depends largely on 
weather conditions during the summer, particularly 
during the tasseling and silking stages. Slower growth 
may delay this process until weather conditions are 
better, but best yields normally occur when corn tassels 
and silks early. ^ 

Soil moisture. Surface mulch reduces evaporation. 
Wetter soil is advantageous in dry summer periods, 
but it is disadvantageous at planting time and during 
early growth, especially on soils with poor internal 
drainage. 

Soil compaction. Interest in soil compaction has 
increased, probably because larger equipment is now 
being used and reduced tillage systems are more 
commonly used. Greater soil density or compaction 
restricts and slows root development and may cause 
yield declines. However, a complete understanding of 
the effects of soil compaction on plant growth is not 
available. 

Wet soils compact much more easily and to a greater 
extent than dry soils. If at all possible, wheel traffic 
and tillage operations should be restricted to times 
when the soil is dry. 

Measurements indicate increased soil compaction as 
tillage is reduced. The moldboard plow loosens soil 
uniformly to the plow's operating depth. The chisel 
plow and subsoilers loosen the soil where the points 
operate; but between points, just the upper few inches 
of soil are loosened. The disk loosens the soil only to 
the depth it operates. With no-till, of course, the soil 
is not loosened. 

Secondary tillage implements like disk harrows and 
field cultivators tend to increase the soil density when 
used on loose, tilled soil. These tools also break up 
the soil aggregates, making the soil more susceptible 
to compaction when it is wet and then dried. 

Traffic increases compaction when the soil strength 
is insufficient to support the load of the tire. The 
pressure applied to the soil is approximately equal to 
the tire pressure. If the load on a tire is increased, the 
tire deflects to maintain a constant pressure. Compac- 
tion due to traffic is most severe when the soil is wet. 

Stand establishment. Uniform planting depth, good 
contact between the seed and moist soil, and enough 
loose soil to cover the seed are necessary to produce 
uniform stands. Shallower than normal planting in 
the cool, moist soil common to many conservation 
tillage seedbeds may partially offset the disadvantage 
of lower temperatures, providing that a uniform depth 
is maintained and seeds are covered. Check planter 
adjustments frequently. 

Planters must be equipped to handle the large 
amounts of crop residue and firm soil in no-till and 
some other conservation tillage seedbeds. A coulter, 
disk blades, or other narrow-tillage equipment can be 
mounted ahead of the planter unit to handle residue 
in the row area and to open a slot in the soil for seed 
placement. Extra weight on the planter may be nec- 
essary to penetrate firm, undisturbed soil. 



78 



Fertilizer placement. Phosphorus and potassium 
fertilizers and limestone are relatively immobile in the 
soil; they remain where applied unless they are in- 
corporated by a tillage operation. Research has shown 
that surface-applied fertilizers (except nitrogen) remain 
in the upper 2 inches of soil with no-till, in the upper 
3 to 4 inches with chisel plow or disk tillage, and that 
they are uniformly distributed throughout the plowed 
layer when the tillage system includes moldboard 
plowing. Roots can use nutrients placed close to the 
surface with conservation tillage because the crop 
residue mulch tends to keep soil moist. Experiments 
in Illinois have not shown nonuniform fertilizer dis- 
tribution due to conservation tillage reduces yields, so 
this should not be a major consideration in deciding 
to adopt a conservation tillage system. 

Nitrogen may be applied to the soil surface or 
injected as anhydrous ammonia or low-pressure so- 
lutions. A coulter mounted ahead of the applicator 
knife may be needed if anhydrous ammonia is applied 
through heavy residue. Care must be taken to ensure 
a good seal behind the applicator; special packing 
wheels may be needed for the firm soil of no-till 
systems. Surface-applied solutions containing urea as 
the nitrogen carrier are subject to nitrogen loss unless 
they are incorporated or moved into the soil by rain. 
Large amounts of surface residue can interfere with 
soil entry and increase the potential for loss. Surface- 
applied ammonium nitrate has been shown to be 10 
to 20 percent more efficient than urea for no-till com 
in Illinois experiments. 

Research indicates that 10 to 20 percent more ni- 
trogen may be required for no-till than for conventional 
tillage. This need may result because the lower soil 
temperature reduces the rate of nitrogen release from 
organic matter and the wetter soils increase the po- 
tential for denitrification losses. 



Weed control 

Weed control is essential for profitable production 
with any tillage system. Cloddy soil surfaces and crop 
residues left by some tillage systems interfere with 
herbicide distribution and incorporation. Recom- 
mended herbicide rates should be used, especially with 
conservation tillage. (For specific herbicide recommen- 
dations, see the chapter entitled "1991 Weed Control 
for Corn, Soybeans, and Sorghum.") 

Problem weeds. Perennial weeds such as milkweed 
and hemp dogbane may be a greater problem with 
conservation tillage systems. Current programs for 
control of weeds such as johnsongrass and yellow 
nutsedge call for high rates of preplant herbicides that 
should be thoroughly incorporated. Wild cane is also 
best controlled by preplant incorporated herbicides. 
Volunteer corn is often a problem with tillage systems 
that leave the com relatively shallow. Unless control 
programs are monitored closely, surface-germinating 



weeds, such as fall panicum and crabgrass, may also 
increase with reduced tillage systems. 

Herbicide application. Surface-applied and incor- 
porated herbicides may not give optimum performance 
under tillage systems that leave large amounts of crop 
residue and clods on the soil surface. These problems 
interfere with herbicide distribution and thorough her- 
bicide incorporation. 

Herbicide incorporation is impossible in no-till sys- 
tems. Residual herbicides must be effective because 
mechanical cultivation is usually not done. Rates for 
residual herbicides may need to be higher with no-till 
and reduced tillage systems because of herbicide tie- 
up on crop residues and increased weed pressure. In 
the presence of heavy vegetation or surface residues, 
the performance of most herbicides may be improved 
by increasing the volume of spray per acre. 

Cultivation. Crops can be cultivated with all tillage 
systems except, possibly, no-till with heavy residue. 

High amounts of crop residues may interfere with 
some rotary hoes and sweep cultivators. Disk culti- 
vators will work, but they may tend to bury too much 
residue for effective erosion control. Rolling cultivators 
are effective across a wide range of soil and crop 
residue conditions. 

With the ridge-till system, special cultivation equip- 
ment is necessary to form a sufficiently high ridge and 
to operate through the inter-row residue. Weed control 
is also accomplished as ridges are rebuilt. 

Herbicide carryover. The potential for herbicide 
carryover is greater in conservation tillage systems 
because higher herbicide rates may be needed and 
because herbicides are diluted less in the soil when 
moldboard plowing is not done. Herbicide carryover 
is affected by climatic factors and soil conditions. 
Breakdown is faster in warm, wet weather and soils 
than in cool, dry conditions. Soils with a pH above 
7.4 tend to have greater problems with atrazine car- 
ryover than soils with pH values from 6.0 to 7.3. 

The carryover problem can be reduced by using 
lower rates of the more persistent herbicides in com- 
bination with other herbicides or by using less per- 
sistent herbicides altogether. Early application of 
herbicides reduces the potential for carryover. 

To detect harmful levels of persistent herbicide 
carryover, a sensitive species (bioassay) can be grown 
in soil samples from suspect fields. Carryover is not a 
problem if the same crop or a tolerant species is to be 
grown the next cropping season. 

No-till weed control. In conventional and most 
conservation tillage systems, the existing weeds are 
destroyed before planting begins. No-till systems re- 
quire a knockdown herbicide like paraquat or Roundup 
to control existing vegetation. The vegetation may be 
a grass or legume sod or early germinating annual and 
perennial weeds. Alfalfa, marestail, and certain peren- 
nial broadleaf weeds will not be controlled by paraquat 
or Roundup. It may be necessary to treat these weeds 
with Banvel or 2,4-D before paraquat application or 



79 



after regrowth. Do not apply these translocated her- 
bicides with paraquat because the contact action upon 
the foliage may prevent translocation. 



Insect control 

Insects should not preclude the adoption of con- 
servation tillage systems. In corn, most soil insect 
problems that might be magnified by conservation 
tillage practices can be controlled with soil insecticides 
applied at planting. Outbreaks of aboveground pests 
that feed on foliage can be controlled with properly 
timed sprays. Fields with insect outbreaks should be 
monitored closely. 

Insect populations are greatly affected by soil tex- 
ture, chemical composition, moisture content, temper- 
ature, and organisms in the soils. Tillage operations 
affect some of these soil conditions and change the 
environment in which the insects must survive. Some 
tillage operations favor specific pests while others tend 
to reduce pest problems. Because insect species differ 
in life cycles and habits, each must be considered 
separately. 

Northern and western corn rootworms are the 
primary soil insect pests of corn in Illinois. Damage is 
confined primarily to corn following corn. Research 
shows that none of the reduced tillage systems — 
whether no-till, chisel, or disk — increases corn root- 
worm damage. Although a specific tillage practice may 
affect corn rootworm populations in some fields in 
some years, none of the tillage systems seems to be 
an important factor in regulating corn rootworms. 
Moldboard plowing is not recommended as a control 
measure for corn rootworms. 

European corn borer larvae overwinter in cornstalk 
residues. Tillage systems that leave cornstalks on the 
surface can result in increased populations of first- 
generation moths and subsequent damage by the first 
brood in late June or early July. 

Black cutworm outbreaks in corn appear more often 
with conservation tillage systems than in convention- 
ally tilled fields, probably because cutworm moths 
deposit eggs on vegetation or surface debris. Recent 
research by the Illinois Natural History Survey indi- 
cates that egg laying occurs before planting. Chickweed 
and other winter annual weeds not buried by tillage 
serve as hosts for egg laying and promote cutworm 
survival. Thus, both weediness and reduced tillage 
practices may contribute to problems with cutworms. 



No-till pest problems 

Insect problems occur more frequently in no-till 
corn than in other conservation tillage systems and 
are often more serious. No-till systems give pests a 
stable environment for survival and development. Soil 
insecticides may be profitably applied to corn following 



grass sod or in any rotation where grass and weeds 
are prevalent. It does not generally pay to apply a soil 
insecticide to no-till corn following com, except in 
rootworm-infested areas; nor will it generally benefit 
soybeans or small grain following corn. A diazinon 
planter-box seed treatment should, however, be used 
to protect against damage by seed-corn beetles and 
seed-corn maggots. 

Table 11.2 illustrates the effects of tillage practices 
on pest problems in corn, based on estimates of 
Extension entomologists. 

Disease control. The potential for plant disease is 
greater when mulch is present than when fields are 
clear of residue. With clean tillage, residue from the 
previous crop is buried or otherwise removed. Because 
buried residue is subject to rapid decomposition, in- 
fected residue is likely to disappear though decay. 

Volunteer corn may be a problem unless the soil is 
moldboard-plowed in the fall or the zero-till system 
is used. If the volunteer corn is a hybrid that is 
susceptible to disease, early infection with diseases 
such as southern corn leaf blight, for instance, will 
increase. 

Although the potential for plant disease is greater 
with mulch tillage than with clean tillage, disease- 
resistant hybrids and varieties can help reduce this 
problem. The erosion control benefit of reduced tillage 
must be balanced against the increased potential for 
disease. Crop rotation or modification of the tillage 
practice may be justified if a disease problem appears 
likely. 



Crop yields 

Tillage research is conducted at the seven University 
of Illinois Agricultural Research and Demonstration 



Table 11.2. Estimate of the Effect of Different Tillage 
Practices on Insect Populations in Corn^ 

Pest ^P""8 /^" ■^fS""^'^ S chScTl 

plowing plowing tillage till" ^.o^trol^ 

Seed-corn beetles. ... ? + Yes 

Seed-corn maggots . . ? + Yes 

Wireworm — ? -♦-(sod) Yes 

White grubs — ? -H(sod) Yes 

Corn root aphids .... — — ? -l-(sod) ? 

Corn rootworm -(-(com) Yes 

Black cutworms ? ? ? + Yes 

Billbugs — — — -H(sod) Yes 

European corn borer — — + + Yes 

True armyworms .... — — — -)-(sod) Yes 

Common stalk borer — — — + Yes 

Slugs — — — + No 

' + = The practice will increase the populations or potential for damage by 
the pest. 

- = It will reduce the population or potential for damage. 

= No effect on the pest. 

? = Effect on the pest unknown. 
*" The preceding crop will have a direct influence on the pest problem(s) in 
no-till com. 

'^ More specific information on insect pest management is presented in Chapter 
1 of the 1993 Illinois Pest Control Handbook, "Insect Pest Management for 
Field and Forage Crops." 



* 



80 



Centers (see figure on inside front cover) to evaluate 
crop yield response to different tillage systems under 
a wide variety of soil and climatic conditions. Con- 
servation tillage systems have produced yields com- 
parable to those from moldboard plowing on most 
Illinois soils when stands are adequate and pests are 
controlled. Yields on poorly drained, fine-textured soils 
such as silty clay loam, silty clay, or clay have been 
consistently higher when soils are moldboard plowed 
after corn. Soils with root-restricting claypan or fra- 
gipan subsoils, or coarse-textured sandy soils, on the 
other hand, have frequently produced higher corn 
yields where conservation tillage is used to retain soil 
moisture. The ridge-till system is most suited to nearly 
level, dark-colored soils with restricted drainage. 

Com and soybean yields for different tillage systems 
obtained from the Research and Demonstration Cen- 



ters are summarized in Table 11.3. Tillage experiments 
at all locations are ongoing, with the exception of the 
Champaign location where the experiment was ter- 
minated in 1989. 

Drummer silty clay loam and Flanagan silt loam 
are poorly and somewhat poorly drained, respectively. 
They are moderately heavy-textured, dark-colored soils 
that developed under prairie vegetation. They are 
sticky and compact easily if tilled when wet. When 
corn follows soybeans, corn yields using chisel and 
spring disk systems are similar to yields produced by 
moldboard-plow tillage. Yields for continuous corn 
generally decrease as tillage decreases. 

Bloomfield fine sand is a somewhat excessively 
drained, coarse-textured soil developed under forest 
vegetation. Tillage systems that retain residue on the 



Table 11.3. Corn and Soybean Yields with Moldboard Plow, Chisel Plow, Disk, No-Till, and Ridge-Till 
Systems 



Tillage system 



Flanagan silt 

loam and 

Drummer silty 

clay loam 



Flanagan silt 

loam and 

Drummer silty 

clay loam 



Soil type 



Bloomfield 
fine sand 



Cisne 
silt loam 



Downs-Fayette 
silt loam 



Tama 
silt loam 



Moldboard plow' 129" 1 78^ 

Chisel plow 142^ .. 166 

Disk 142 129 172 

No-till 135 108 168 

Ridge-till 144 115 

Ro-till' 

Moldboard plow' 44' 44'' 50 

Chisel plow 46 

Disk 43 42 44 

No-till 41 41 45 

Ridge-till 

Ro-till' 

* Champaign, corn-soybean rotation, 1980-89. 

" Champaign, continuous com, 1980-89. 

■^ DeKalb, corn-soybean rotation, 1985-89. 

^ Kilboume, corn-soybean rotation, 1987-89. 

' Brownstown, corn-soybean rotation, 1985-89. 

'Perry, corn-soybean rotation, 1980-89. 

8 Monmouth, corn-soybean rotation, 1986-89. 

I* Monmouth, continuous com, 1987-89. 

I Moldboard plowed in the fall, except Cisne moldboard plowed in the spring. 

' Row spacing was 10 inches. 

^ Row spacing was 30 inches. 

' Ro-till performed in spring. 



corn yield, bushels per acre 

113" 
130" 122 

145 124 

141 118 



-soybean yield, bushels per acre 

32 
32 33 

37 34 

37 36 



131' 
130 
130 
121 



37 
38 
37 
32 



1448 

147 

166 

143 

152 

153 



46 
45 
43 
43 
43 
44 



112h 
109 

Vo 

ll'4 



Table 11.4. Estimated Production Costs with Different Tillage Systems 

Cost 

Tillage system 

Machinery^ Labor" Pesticide 

dollars per acre 

Moldboard and chisel 51.51 8.99 14-19 

Chisel 48.01 7.73 14-19 

Disk 43.11 7.95 14-19 

No-till 31.55 4.84 15-30^ 

Ridge-till 35.78 6.47 7-19'^ 

"Machinery and labor costs calculated from Farm Machinery Selection Program (Siemens, Hamburg, and Tyrrell, 1990). 

" Labor assumed to cost $7.50 per hour. 

*^ No-till herbicide program options include early preplant, preemergent, or postemergent and knockdown. 

^ Ridge-till herbiciae program options include band or broadcast applications. 

* No-till nitrogen application options include anhydrous ammonia or UAN. 



Fertilizer 



Total 



29-35 


103.5-114.5 


29-35 


98.74-109.74 


29-35 


94.06-105.06 


29-40" 


80.39-106.39 


29-35 


78.25-96.25 



81 



soil surface reduce soil blowing, conserve soil moisture, 
and typically result in higher yields. 

Cisne silt loam is a very slowly permeable, poorly 
drained soil that is common in south central Illinois. 
A strongly developed argillic horizon (claypan) restricts 
root development and water use by the crop. Reduced 
evaporation with the cornstalk mulch of chisel plow, 
disk, and ridge-till systems conserves water for crop 
use, frequently producing higher yields. 

Downs silt loam and Fayette silt loam are moderately 
well-drained and well-drained, respectively, medium- 
textured, light-colored soils developed under prairie- 
forest and forest vegetation. Yields with chisel plow 
and disk systems are similar to yields from the mold- 
board plow tillage system. 

Tama silt loam is a well- to moderately well-drained, 
medium-textured, dark-colored soil developed under 
prairie vegetation. Yields for all tillage systems are 
quite similar when com follows soybeans, but yields 
for no-till and ridge-till systems are reduced with 
continuous com. 

For more local sources of yield data for different 
tillage systems, contact your local county Extension 
personnel. Soil and Water Conservation District, and 
tillage groups or clubs about tillage system demon- 
strations in your county. 



Production costs 

Will the switch from a conventional moldboard 
plow system to a conservation tillage system be prof- 
itable? The answer depends on how one weighs the 
importance of three primary factors: yield, cost, and 
erosion control. The relation of yield and soil erosion 
to tillage system was discussed in the preceding section. 

Machinery investment is one of the major produc- 
tion costs affected by the choice of tillage system. If 
new machinery must be purchased, the capital in- 
vestment and the depreciation and interest costs of 
the equipment needed for conservation tillage will be 
less than for moldboard plow tillage (Table 11.4). 
Conservation tillage implements are l#ss expensive, 
and the necessary power units may be smaller. If 
conservation tillage is used on only a part of the land 
farmed, larger equipment will still be needed for the 
other portions, so there will be no savings. 

With a conservation tillage system, some labor costs 
will be reduced because fall or spring tillage operations 
are reduced or eliminated. The labor saved in this way 



Table 11.5. Estimated Soil Losses with Different 
Tillage Systems, Crop Rotations, and 
Conservation Practices 

Soil loss^ 

Tillage systems 2 percent 5 percent 5 percent 

and rotations slope, no slope, no K 

conservation conservation ^ ^ ' j 

practices practices ^oi^toured 

tons per acre 

Corn-soybean rotation 

Moldboard and chisel 6.4 25.1 12.6 

Chisel 4.5 17.1 8.6 

Disk 3.8 14.5 7.3 

No-till 3.4 1.7 

Ridge-till 3 12.5 5.2 

Combination: moldboard 

on flat ground, no-till 

on sloping land 6.4'' 3.4' 1.7'^ 

Corn-soybean-oats-meadow rotation 

Moldboard 2.5 9.6 4.8 

' Soil loss calculated for Catlin and Flanagan soil series using formulas and 
data from Estimating Your Soil Erosion Losses with the Universal Soil Loss 
Equation (USEE), Circular 1220, R.D. Walker and R.A. Pope, 1983. 
^ Only moldboard plow used. 
■^ Only no-till used. 



has value only if it reduces the cost of hired labor or 
if the saved costs of hired labor are directed into other 
productive activities, such as raising livestock, farming 
more acres, or reducing machinery costs by substituting 
smaller equipment. 

An extra cost of additional or more expensive 
pesticides and fertiUzers also may be associated with 
conservation tillage systems. For example, contact 
herbicides may be needed with no-till and ridge-tillage 
systems. These increases must be weighed against the 
reduced fuel and machinery repair costs necessary to 
perform fewer operations. Often, the reduced 
machinery costs associated with conservation tillage 
are offset by increased herbicide cost. Ridge-till can 
be cost effective if a contact herbicide is not required 
and a band application of herbicide is used. Fertilizer 
costs, especially nitrogen costs, can be more expensive 
with no-till if anhydrous ammonia is not used. 

A major advantage of reduced tillage is improved 
erosion control (Table 11.5). With an appropriate soil 
conservation practice, such as contouring, soil losses 
can be reduced to the tolerance level with reduced 
tillage systems. If the aim is to reach that level, a 
conservation tillage system such as no-till will be more 
profitable on grain farms than an alternate method 
such as a rotation of com, soybeans, oats, and meadow. 



82 



Chapter 12. 

Water Management 



A superior water management program seeks to pro- 
vide an optimum balance of water and air in the soil 
that will allow full expression of genetic potential in 
plants. The differences among poor, average, and 
record crop yields generally can be attributed to the 
amount and timing of soil water supply. 

Improving water management is an important way 
to increase crop yields. By eliminating crop-water 
stress, you will obtain more benefits from improved 
cultural practices and realize the full yield of the 
cultivars now available. 

To produce maximum yields, the soil must be able 
to provide water as it is needed by the crop. But the 
soil seldom has just the right amount of water for 
maximum crop production; a deficiency or a surplus 
usually exists. A good water management program 
seeks to avoid both extremes through a variety of 
measures. These measures include draining water- 
logged soils; making more effective use of the water- 
holding capacity of soils so that crops will grow during 
periods of insufficient rainfall; increasing the soil's 
ability to absorb moisture and conduct it down through 
the soil profile; reducing water loss from the soil 
surface; and irrigating soils with low water-holding 
capacity. 

In Illinois, the most frequent water management 
need is improved drainage. Initial efforts in the nine- 
teenth century to artificially drain Illinois farmland 
made our soils among the most productive in the 
world. Excessive water in the soil limits the amount 
of oxygen available to plants and thus retards growth. 
This problem occurs where the water table is high or 
where water ponds on the soil surface. Removing 
excess water from the root zone is an important first 
step toward a good water management program. A 
drainage system should be able to remove water from 
the soil surface and lower the water table to about 12 
inches beneath the soil surface in 24 hours and to 21 
inches in 48 hours. 

The benefits of drainage 

A well-planned drainage system will provide a 
number of benefits: better soil aeration, more timely 



field operations, less flooding in low areas, higher soil 
temperatures, less surface runoff, better soil structure, 
better incorporation of herbicides, better root devel- 
opment, higher yields, and improved crop quality. 

Soil aeration. Good drainage ensures that roots 
receive enough oxygen to develop properly. When the 
soil becomes waterlogged, aeration is impeded and the 
amount of oxygen available is decreased. Oxygen 
deficiency reduces root respiration and often the total 
volume of roots developed. It also impedes the trans- 
port of water and nutrients through the roots. The 
roots of most nonaquatic plants are injured by oxygen 
deficiency; and prolonged deficiency may result in the 
death of some cells, entire roots, or in extreme cases 
the whole plant. Proper soil aeration also will prevent 
rapid losses of nitrogen to the atmosphere through 
denitrification. 

Timeliness. Because a good drainage system in- 
creases the number of days available for planting and 
harvesting, it can enable you to make more timely 
field operations. Drainage can reduce planting delays 
and the risk that good crops will be drowned or left 
standing in fields that are too wet for harvest. Good 
drainage may also reduce the need for additional 
equipment that is sometimes necessary to speed up 
planting when fields stay wet for long periods. 

Soil temperature. Drainage can increase soil surface 
temperatures during the early months of the growing 
season by 6° to 12°F. Warmer temperatures assist 
germination and increase plant growth. 

Surface runoff. By enabling the soil to absorb and 
store rainfall more effectively, drainage reduces runoff 
from the soil surface and thus reduces soil erosion. 

Soil structure. Good drainage is essential in main- 
taining the structure of the soil. Without adequate 
drainage the soil remains saturated, precluding the 
normal wetting and drying cycle and the corresponding 
shrinking and swelling of the soil. The structure of 
saturated soil will suffer further damage if tillage or 
harvesting operations are performed on it. 

Herbicide incorporation. Good drainage can help 
avoid costly delays in applying herbicide, particularly 



83 



of postemergence herbicides. Because some herbicides 
must be applied during the short time that weeds are 
still relatively small, an adequate drainage system may 
be necessary for timely application. Drainage may also 
help relieve the cool, wet stress conditions that increase 
crop injury by some herbicides. 

Root development. Good drainage enables plants 
to send roots deeper into the soil so they can extract 
moisture and plant nutrients from a larger volume of 
soil. Plants with deep roots are better able to withstand 
drought. 

Crop yield and quality. All these benefits previ- 
ously mentioned contribute to greater yields of higher- 
quality crops. The exact amount of the yield and quality 
increases depends on the type of soil, the amount of 
rainfall, the fertility of the soil, crop management 
practices, and the level of drainage before and after 
improvements are made. Of the few studies that have 
been conducted to determine the benefits of drainage, 
the most extensive in Illinois was initiated at the 
Agronomy Research Center at Brownstown. This study 
evaluated drainage and irrigation treatments with Cisne 
and Hoyleton silt loams. 



Drainage methods 

A drainage system may consist of surface drainage, 
subsurface drainage, or some combination of both. 
The kind of system you need depends in part upon 
the abihty of the soil to transmit water. The selection 
of a drainage system ultimately should be based on 
economics. Surface drainage, for example, would be 
most appropriate where soils are impermeable and 
would therefore require too many subsurface drains 
to be economically feasible. Soils of this type are 
common in southern Illinois. 

Surface drainage 

A surface drainage system is most appropriate on 
flat land with slow infiltration and low permeability 
and on soils with restrictive layers close to the surface. 
This type of system removes excess water from the 
soil surface through improved natural channels, man- 
made ditches, and shaping of the land surface. A 
properly planned system eliminates ponding, prevents 
prolonged saturation, and accelerates the flow of water 
to an outlet without permitting siltation or soil erosion. 

A surface drainage system consists of a farm main, 
field laterals, and field drains. The farm main is the 
outlet serving the entire farm. Where soil erosion is a 
problem, a surface drain or waterway covered with 
vegetation may serve as the farm main. Field laterals 
are the principal ditches that drain adjacent fields or 
areas on the farm. The laterals receive water from 
field drains, or sometimes from the surface of the field, 
and carry it to the farm main. Field drains are shallow, 
graded channels (with relatively flat side slopes) that 
collect water within a field. 



A surface drainage system sometimes includes di- 
versions and interceptor drains. Diversions are chan- 
nels constructed across the slope of the land to intercept 
surface runoff and prevent it from overflowing bot- 
tomlands. Diversions are usually located at the bases 
of hills. These channels simplify and reduce the cost 
of drainage for bottomlands. 

Interceptor drains collect subsurface flow before it 
resurfaces. These channels may also collect and remove 
surface water. They are used on long slopes that have 
grades of one percent or more and on shallow, perme- 
able soils overlying relatively impermeable subsoils. 
The location and depth of these drains are determined 
from soil borings and the topography of the land. 

The principal types of surface drainage configura- 
tions are the random and parallel systems (Figure 
12.1). The random system consists of meandering field 
drains that connect the low spots in a field and provide 
an outlet for excess water. This system is adapted to 
slowly permeable soils with depressions too large to 
be eliminated by smoothing or shaping the land. 

The parallel system is suitable for flat, poorly 
drained soils with many shallow depressions. In a field 
that is cultivated up and down a slope, parallel ditches 
can be arranged to break the field into shorter lengths. 
The excess water thus erodes less soil because it flows 
over a smaller part of the field before reaching a ditch. 
The side slopes of the parallel ditches should be flat 
enough to permit farm equipment to cross them. The 
spacing of the parallel ditches will vary according to 
the slope of the land. 

For either the random or parallel systems to be fully 
effective, minor depressions and irregularities in the 
soil surface must be eliminated through land grading 
or smoothing. 

Bedding is another surface drainage method that 
is used occasionally. The land is plowed to form a 
series of low, narrow ridges separated by parallel, dead 
furrows. The ridges are oriented in the direction of 
the steepest slope in the field. Bedding is adapted to 
the same conditions as the parallel system, but it may 
interfere with farm operations and does not drain the 
land as completely. It is not generally suited for land 
that is planted in row crops because the rows adjacent 
to the dead furrows will not drain satisfactorily. Bed- 
ding is acceptable for hay and pasture crops, although 
it will cause some crop loss in and adjacent to the 
dead furrows. 

Subsurface drainage 

Many of the deep, poorly drained soils of central 
and northern Illinois respond favorably to subsurface 
drainage. A subsurface drainage system is used in soils 
permeable enough that the drains do not have to be 
placed too closely together. If the spacing is too narrow, 
the system will not be economical. By the same token, 
the soil must be productive enough to justify the 
investment. Because a subsurface drainage system 
functions only as well as the outlet, a suitable one 



84 



Random 




Parallel 



Figure 12.1. Types of surface drainage systems 



must be available or constructed. The topography of 
the fields also must be considered because the instal- 
lation equipment has depth limitations and a minimum 
amount of soil cover is required over the drains. 

Subsurface systems are made up of an outlet or 
main, sometimes a submain, and field laterals. The 
drains are placed underground, although the outlet is 
often a surface drainage ditch. Subsurface drainage 
conduits are constructed of clay, concrete, or plastic. 

There are four types of subsurface systems: the 
random, the herringbone, the parallel, and the double- 
main (Figure 12.2). A single system or some combi- 
nation of systems may be chosen according to the 
topography of the land. 

For rolling land, a random system is recommended. 
With this system, the main drain is usually placed in 
a depression. If the wet areas are large, the submains 
and lateral drains for each area may be placed in a 
gridiron or herringbone pattern to achieve the required 
drainage. 

With the herringbone system, the main or submain 
is often placed in a narrow depression or on the major 
slope of the land. The lateral drains are angled up- 
stream on either side of the main. This system some- 
times is combined with others to drain small or irreg- 
ular areas. Because two laterals intersect the main at 



the same point, however, more drainage than necessary 
may occur at that intersection point. The herringbone 
system may also cost more because it requires more 
junctions. Nevertheless, it can provide the extra drain- 
age needed for the heavier soils that are found in 
narrow depressions. 

The parallel system is similar to the herringbone 
system, except that the laterals enter the main from 
only one side. This system is used on flat, regularly 
shaped fields and on uniform soil. Variations are often 
used with other patterns. 

The double-main system is a modification of the 
parallel and herringbone systems. It is used where a 
depression, frequently a natural watercourse, divides 
the field in which drains are to be installed. Sometimes 
the depression may be wet due to seepage from higher 
ground. A main placed on either side of the depression 
intercepts the seepage water and provides an outlet 
for the laterals. If only one main were placed in the 
center of a deep and unusually wide depression, the 
grade of each lateral would have to be changed at 
some point before it reaches the main. A double-main 
system avoids this situation and keeps the gradelines 
of the laterals uniform. 

The advantage of a subsurface drainage system is 
that it usually drains soil to a greater depth than 



85 



Field lateral 




Farm main 




Field lateral 



Farm main 



Random 



Herringbone 



Field 
lateral 



Farm main 



I 



Parallel 



Farm main- 



7 



Field lateral 



II 



r 



// 

Double Main 



Figure 12.2. Types of subsurface drainage systems. The arrows indicate the direction of water flow. 



86 



surface drainage. Subsurface drains placed 36 to 48 
inches deep and 80 to 100 feet apart are suitable for 
crop production on many medium-textured soils in 
Illinois. When properly installed, these drains require 
little maintenance, and because they are underground, 
they do not obstruct field operations. 

For more specific information about surface and 
subsurface drainage systems, obtain the Extension 
Circular 1226, Illinois Drainage Guide, from your county 
Extension adviser. This publication discusses the plan- 
ning, design, installation, and maintenance of drainage 
systems for a wide variety of soil, topographic, and 
climate conditions. 



The benefits of irrigation 

During an average year, most regions of Illinois 
receive ample rainfall for growing crops; but, as shown 
in Figure 12.3, rain does not occur when the crops 
need it the most. From May to early September, 
growing crops demand more water than is provided 
by precipitation. For adequate plant growth to continue 
during this period, the required amount of water must 
be supplied by stored soil water or by irrigation. During 
the growing season, crops on deep, fine-textured soils 
may draw upon moisture stored in the soil, if the 
normal amount of rainfall is received throughout the 
year. But if rainfall is seriously deficient or if the soil 
has little capacity for holding water, crop yield may 
be reduced. Yield reductions are likely to be most 
severe on sandy soils or soils with claypans. Claypan 
soils restrict root growth, and both types of soils often 
cannot provide adequate water during the growing 
season. 

To prevent crop-water stress during the growing 
season, more and more producers are using irrigation. 
It may be appropriate where water stress can substan- 
tially reduce crop yields and where a supply of usable 
water is available at reasonable cost. Irrigation is still 
most widely used in the arid and semi-arid parts of 



7r 



Potential water loss 
Precipitation 



(A 

0) 



u 

c 




Jan. Mar. May July Sept. Nov. 

Figure 12.3. Average monthly precipitation and potential 
moisture loss from a growing crop in central Illinois. 



the United States, but it can be beneficial in more 
humid states such as Illinois. Almost every year, Illinois 
corn and soybean yields are limited by drought to 
some degree, even though the total annual precipita- 
tion exceeds the water lost through evaporation and 
transpiration (ET). 

With current cultural practices, a good crop of corn 
or soybeans in Illinois needs at least 20 inches of 
water. All sections of the state average at least 15 
inches of rain from May through August. Thus satis- 
factory yields require at least 5 inches of stored subsoil 
water in a normal year. 

Crops growing on deep soil with high water-holding 
capacity, that is, fine-textured soil with high organic- 
matter content, may do quite well if precipitation is 
not appreciably below normal and if the soil is filled 
with water at the beginning of the season. 

Sandy soils and soils with subsoil layers that restrict 
water movement and root growth cannot store as 
much as 5 inches of available water. Crops planted 
on these soils suffer from inadequate water every year. 
Most of the other soils in the state can hold more than 
5 inches of available water in the crop rooting zone. 
Crops on these soils may suffer from water deficiency 
when subsoil water is not fully recharged by about 
May 1 or when summer precipitation is appreciably 
below normal or poorly distributed throughout the 
season. 

The probability of getting one inch or more of rain 
in any week is shown in Figure 12.4. One inch of rain 
per week will not replace ET losses during the summer, 
but it can keep crop-water stress from severely limiting 
final grain yields on soils that can hold water reason- 
ably well. This probability is lowest in all sections of 
Illinois during July, when corn normally is pollinating 
and soybeans are flowering. 

Water stress delays the emergence of corn silks and 
shortens the period of pollen shedding, thus reducing 
the time of overlap between the two processes. The 
result is incomplete kernel formation, which can have 
disastrous effects on corn yields. 

Corn yields may be reduced as much as 40 percent 
when visible wilting occurs on four consecutive days 
at the time of silk emergence. Studies have also shown 
that severe drought during the pod-filling stage causes 
similar yield reductions in soybeans. 

Increasing numbers of farmers are installing irri- 
gation systems to prevent the detrimental effects of 
water deficiency. Some years of below-normal summer 
rainfall and other years of erratic rainfall distribution 
throughout the season have contributed to the increase. 
As other yield-limiting factors are eliminated, adequate 
water becomes increasingly important to assure top 
yields. 

Most of the development of irrigation systems has 
occurred on sandy soils or other soils with correspond- 
ingly low levels of available water. Some installations 
have been made on deeper, fine-textured soils, and 
other farmers are considering irrigation of such soils. 



87 




10 20 
March 



Figure 12.4. Chance of at least one inch of rain in one week. 



10 20 
September 



10 20 
October 



The decision to irrigate 

The need for an adequate water source cannot be 
overemphasized when one is considering irrigation. If 
a producer is convinced that an irrigation system will 
be profitable, an adequate source of water is necessary. 
Such sources do not now exist in many parts of the 
state. Fortunately, underground water resources are 
generally good in the sandy areas where irrigation is 
most likely to be needed. A relatively shallow well in 
some of these areas may provide enough water to 
irrigate a quarter section of land. In some areas of 
Illinois, particularly the northern third, deeper wells 
may provide a relatively adequate source of irrigation 
water. 

Some farmers pump their irrigation water from 
streams, which can be a relatively good and economical 
source, providing the stream does not dry up in a 
droughty year. Impounding surface water on an in- 
dividual farm is also possible in some areas of the 
state, but this water source is practical only for small 
acreages. However, an appreciable loss may occur both 
from evaporation and from seepage into the substrata. 
Generally, 2 acre-inches of water should be stored for 
each acre-inch actually applied to the land. 

To make a one-inch application on one acre (one 
acre-inch), 27,000 gallons of water are required. A 



flow of 450 gallons per minute will give one acre-inch 
per hour. Thus a 130-acre, center-pivot system with a 
flow of 900 gallons per minute can apply one inch of 
water over the entire field in 65 hours of operation. 
Because some of the water is lost to evaporation and 
some may be lost from deep percolation or runoff, the 
net amount added will be less than one inch. 

The Illinois State Water Survey and the Illinois State 
Geological Survey at Urbana can provide information 
about the availability of irrigation water. Submit a 
legal description of the site planned for development 
of a well and request information regarding its suita- 
bihty for irrigation well development. Once you decide 
to drill a well, the Water Use Act of 1983 requires you 
to notify the local Soil and Water Conservation District 
office if the well is planned for an expected or potential 
withdrawal rate of 100,000 gallons or more per day. 
There are no permit requirements or regulatory pro- 
visions. 

An amendment passed in 1987 allows Soil and 
Water Conservation districts to limit the withdrawals 
from large wells if domestic wells meeting state stan- 
dards are affected by localized drawdown. The legis- 
lation currently affects Kankakee, Iroquois, Tazewell, 
and McLean counties. 

The Riparian Doctrine, which governs the use of 
surface waters, states that one is entitled to a reasonable 



88 



use of the water that flows over or adjacent to his or 
her land as long as one does not interfere with someone 
else's right to use the water. No problem results as 
long as water is available for everybody. But when 
the amount of water becomes limited, legal determi- 
nations become necessary as to whether one's water 
use interferes with someone else's rights. It may be 
important to establish a legal record to verify the date 
on which the irrigation water use began. 

Assuming that it will be profitable to irrigate and 
that an assured supply of water is available, how do 
you find out what type of equipment is available and 
what is best for your situation? University represen- 
tatives have discussed this question in various meetings 
around the state, although they cannot design a system 
for each individual farm. Your county Extension adviser 
can provide Usts of dealers located in and serving 
Illinois. This list includes the kinds of equipment each 
dealer sells, but it will not supply information about 
the characteristics of those systems. 

We suggest that you contact as many dealers as you 
wish to discuss your individual needs in relation to 
the type of equipment they sell. You will then be in 
a much better position to determine what equipment 
to purchase. 



Subsurface irrigation 

Subirrigation can offer the advantages of good 
drainage and irrigation using the same system. During 
wet periods, the system provides drainage to remove 
excess water. For irrigation, water is forced back into 
the drains and then into the soil. 

This method is most suitable for land areas where 
the slope is less than 2 percent, with either a relatively 
high water table or an impermeable layer at 3 to 10 
feet below the surface. The impermeable layer ensures 
that applied water will remain where needed and that 
a minimum quantity of water will be sufficient to raise 
the water table. 

The free water table should be maintained at 20 to 
30 inches below the surface. This level is controlled 
and maintained at the head control stands, and water 
is pumped accordingly. In the event of a heavy rainfall, 
pumps must be turned off quickly and the drains 
opened. As a general rule, to irrigate during the 
growing season, you must deliver a minimum of 5 
gallons per minute per acre. 

The soil should be permeable enough to allow rapid 
water movement, so that plants are well supplied in 
peak consumption periods. Tile spacing is a major 
factor in the cost of the total system and perhaps the 
most important single variable in its design and effec- 
tiveness. Where subirrigation is suitable, the optimum 
system will have closer drain spacings than a traditional 
drainage system. 



Irrigation for double-cropping 

Proper irrigation can eliminate the most serious 
problem in double-cropping: inadequate water to get 
the second crop off to a good start. No part of Illinois 
has better than a 30 percent chance of getting an inch 
or more of rain during any week in July and most 
weeks in August. With irrigation equipment available, 
double-crop irrigation should be a high priority. If one 
is considering irrigating, the possibility of double- 
cropping should be taken into account in making the 
decision about irrigation. Soybeans planted at Urbana 
on July 6 following a wheat harvest have yielded as 
much as 38 bushels per acre with irrigation. In Mason 
County, soybeans planted the first week in July have 
yielded as much as 30 bushels per acre with irrigation. 

While it may be difficult to justify investing in an 
irrigation system for double-cropping soybeans alone, 
the potential benefits from irrigating other crops may 
make the investment worthwhile. Some farmers report 
that double-cropping is a top priority in their irrigation 
programs. 



Fertigation 

The method of irrigation most common in Illinois, 
the overhead sprinkler, is the one best adapted to 
applying fertilizer along with water. Fertigation permits 
nutrients to be applied to the crop as they are needed. 
Several applications can be made during the growing 
season with little if any additional application cost. 
Nitrogen can be applied in periods when the crop has 
a heavy demand for both nitrogen and water. Corn 
uses nitrogen and water most rapidly during the 3 
weeks before tasseling. About 60 percent of the nitro- 
gen needs of corn must be met by silking time. 
Generally, nearly all the nitrogen for the crop should 
be applied by the time it is pollinating, even though 
some uptake occurs after this time. Fertilization through 
irrigation can be a convenient and timely method of 
supplying part of the plant's nutrient needs. 

In Illinois, fertigation appears to be best adapted to 
sandy areas where irrigation is likely to be needed 
even in the wettest years. On finer-textured soils with 
high water-holding capacity, nitrogen might be needed 
even though water is adequate. Neither irrigating just 
to supply nitrogen nor allowing the crop to suffer for 
lack of nitrogen is an attractive alternative. Even on 
sandy soils, only part of the nitrogen should be applied 
with irrigation water; preplant and sidedress applica- 
tions should provide the rest of it. 

Other problems associated with fertigation can only 
be mentioned here. These include (1) possible lack of 
uniformity in application, (2) loss of ammonium ni- 
trogen by volatilization in sprinkling, (3) loss of nitro- 
gen and resultant groundwater contamination by 
leaching if overirrigation occurs, (4) corrosion of equip- 
ment, and (5) incompatibility and low solubihty of 
some fertilizer materials. 



89 



Cost and return 

The annual cost of irrigating field corn with a center- 
pivot system in Mason County was estimated in 1987 
to vary from $95 to $140 per acre. The lower figure 
is for a leased low-pressure system with a 50-horse- 
power electric motor driving the pump. The higher 
figure is for a purchased high-pressure system with a 
130-horsepower diesel engine. Additional costs asso- 
ciated with obtaining a yield large enough to offset 
the cost of irrigation were estimated to be about $30 
per acre per year, for a total irrigation cost of $125 to 
$170 per acre per year. The total investment for the 
purchased high-pressure irrigation system, including 
pivot, pump and gear head, diesel engine, and a 100- 
foot well, amounted to $450 per acre. If the low- 
pressure system were purchased, the total investment 
for the system, including pivot, pump, electric motor, 
and a 100-foot well, would be $400. 

Irrigation purchases should be based on sound 
economics. The natural soil-water storage capacity for 
some soils in Illinois is too good to warrant supple- 
mental irrigation. Based on the assumed fixed and 
variable costs of about $110 per acre per year, it would 
require an annual yield differential of about 50 bushels 
of corn ($2.20 a bushel) or 18 bushels of soybeans 
($6.00 a bushel) to break even (Table 12.1). For irri- 
gation to pay off, these yield differentials would have 
to be met on the average, over the 10- to 15 -year life 
of the irrigation system. Some of the deep, fine-textured 
soils in Illinois simply would not regularly support 
these yield increases. 



Irrigation scheduling 

Experienced irrigators have developed their own 
procedures for scheduhng applications, whereas be- 
ginners may have to determine timing and rates of 
application before they feel prepared to do so. Irrigators 
generally follow one of two basic scheduling methods, 
each of which has many variations. 

The first method involves measuring soil water and 
plant stress by (1) taking soil samples at various depths 
with a soil probe, auger, or shovel and then measuring 
or estimating the amount of water available to the 
plant roots; or (2) inserting instruments such as ten- 



Table 12.1. Break-Even Yield Increase Needed to Cover 
Fixed and Variable Irrigation Costs 

Com price Yield increase Soybean price Yield increase 
per bushel in bushels per bushel in bushels 

$1.50 67 $4.75 21 

1.70 59 5.00 20 

1.90 53 5.25 19 

2.10 48 5.50 18 

2.30 43 5.75 17 

2.50 40 6.00 17 

2.70 37 6.25 16 

2.90 34 6.50 15 



90 



siometers or electrical resistance blocks into the soil to 
desired depths and then taking readings at intervals; 
or (3) measuring or observing some plant characteristics 
and then relating them to water stress. 

Although in theory the crop can utilize 100 percent 
of the water that is available, the last portion of that 
water is not actually as available as the first water that 
the crop takes from the soil. Much like a half-wrung- 
out sponge, the remaining water in the soil following 
50 percent depletion is more difficult to remove than 
the first half of the plant-available water. 

The 50 percent depletion figure is often used to 
schedule irrigation. For example, if a soil holds 3 inches 
of plant-available water in the root zone, then we 
could allow IV2 inches to be used by the crop before 
replenishing the soil water with irrigation. 

Soil samples 

Estimating when the IV2 inches is used, or when 
50 percent depletion occurs, can be done by a number 
of methods. One of the simplest is to estimate the 
amount of depletion by the "feel" method, which 
involves taking a sample from various depths in the 
active root zone with a spade, soil auger, or soil probe. 
It is important to dig a shallow hole to see how the 
soil looks at 6 to 12 inches early in the irrigation 
season. As the rooting depth extends to 3 feet, it may 
be wise to inspect a soil sample from the 9- to 18- 
inch level and another from the 24- to 30-inch level. 
Observing only the surface can be misleading on sandy 
soils because the top portion dries fairly quickly in the 
summer. To use this method of sampling, follow the 
guidelines shown in Table 12.2 to identify the depletion 
range you are in. 

Tenslometers 

Tensiometers are most suitable for sandy or loamy 
soils because the changes in soil-water content can be 
adequately described by the range of soil moisture 
tension (SMT) in which they operate. As plant roots 
dry the soil, SMT increases and water is pulled from 
the tensiometer into the surrounding soil, thereby 
increasing the reading on the vacuum gauge. After 
irrigation or rainfall, water replenishes the dry soil and 
SMT decreases. The vacuum developed in the ten- 
siometer pulls water back through the porous ceramic 
tip, and the dial gauge reading decreases. By respond- 
ing to both wetting and drying, a tensiometer can 
yield information on the effect of crop transpiration 
or water additions to soil-water status. 

A tensiometer must be installed carefully to ensure 
meaningful readings. Improper use may be worse than 
not using a tensiometer — because false readings can 
result in poorly timed irrigation. Before use, each 
tensiometer assembly must be soaked in water over- 
night; then the bubbles and dissolved gases must be 
removed from the water within the tube and ceramic 
cup. This procedure can be done by using boiled water 



I 



Table 12.2. Behavior of Soil at Selected Soil-Water Depletion Amounts 



Available water remaining 
in the soil 



Soil type 



Sands 



Loamy sand/sandy loam 



Saturated, wetter than 
field capacity 

100% available 
(field capacity) 

75 to 100% 

50 to 75% 

Less than 50% 



Free water appears when soil ball is squeezed 

When soil ball is squeezed, wet outline on 
hand, but no free water 

Sticks together slightly 

Appears dry; will not form a ball 

Flows freely as single grains 



Free water appears when soil ball is squeezed 

When soil ball is squeezed, wet outline on hand, 
but no free water 

Forms a ball that breaks easily 

Appears dry; will not form a ball 

Flows freely as grains with some small 
aggregates 



and a small suction pump that is available from 
tensiometer manufacturers. 

The tensiometer should be installed by creating a 
hole with a soil probe to within 3 to 4 inches of the 
desired depth, then pounding a rod with a rounded 
end to the final depth. The rod tip should be shaped 
like the tensiometer tip to ensure a good, porous cup- 
to-soil contact. Placement of tensiometers should be 
made according to two principles: (1) the tensiometer 
should be readily accessible if it is to be used; and (2) 
field placement of tensiometers should be made to 
stagger the readings throughout the irrigation cycle. 

Tensiometers are available in lengths ranging from 
6 inches to 4 feet. The length required depends on 
the crop grown, with lengths chosen to gain accurate 
information in the active root zone. For shallow-rooted 
vegetable crops, a single tensiometer per station, at a 
6- to 9 -inch depth, may be sufficient. Multiple-depth 
stations for corn or soybeans will allow you to track 
the depletion and recharge of soil water at several 
depths throughout the season. Because the active root 
zone shifts as the plant matures, water extraction 
patterns change as well. If you want to go with a 
single depth station, refer to Table 12.3 for the proper 
depths of placement. 

Tensiometers may require servicing if SMT increases 
to more than 80 centibars. At this tension, air enters 
the porous cup and the vacuum is broken. Tensiometers 
that have failed in this manner can be put back into 
service by filling them with deaerated water. Servicing 
can be done without removing the tensiometer from 
the soil. If proper irrigation levels are maintained, the 
SMT should not rise to levels sufficient to break the 
vacuum. 

Moisture blocks 

Moisture blocks (sometimes referred to as electrical 
resistance blocks or gypsum blocks) are small blocks 
of gypsum with two embedded electrodes. The block 
operates on the principle that the electrical resistance 
of the gypsum is affected by water content. 

When saturated, the gypsum block has low electrical 
resistance. As it dries, the electrical resistance increases. 
The moisture blocks are placed in the soil and electrical 
leads coming from the embedded electrodes are al- 
lowed to protrude from the soil surface. These leads 



Table 12.3. 


Tensiometer Placement 
Selected Crops 


Depth for 




Depth, inches 


Depth, centimeters 


Soybeans. . . . 

Corn 

Snap beans . . 
Cucumbers . . 


18 

12 

9 

9 


46 
30 
23 
23 



are connected to a portable instrument that includes 
an electrical resistance meter and a voltage source. 

When a reading is desired, a voltage is applied and 
the resulting reading is recorded. The reading is con- 
verted to a soil-water content by using a predetermined 
calibration curve relating resistance to water content. 
Soil moisture blocks work well in fine- and medium- 
textured soils and are not recommended for sandy 
soils. The increase in fine-textured soil irrigation in 
Illinois, particularly for seed corn, may prompt an 
increase in the use of moisture blocks. As with ten- 
siometers, a good soil contact is absolutely necessary 
for meaningful readings. Soil water must be able to 
move in and out of the blocks as if the blocks were 
part of the soil. Any gap between the block and the 
surrounding soil will prevent this movement. 

Another method of scheduhng, frequently called 
the "checkbook method," involves keeping a balance 
of the amount of soil water by measuring the amount 
of rainfall and then measuring or estimating the amount 
of water lost from crop use and evaporation. When 
the water drops to a certain level, the field is irrigated. 
Computer techniques are also available for estimating 
water loss, computing the water balance, and predict- 
ing when irrigation is necessary. 



Management requirements 

Irrigation will provide maximum benefit only when 
it is integrated into a high-level management program. 
Good seed or plant starts of proper genetic origin 
planted at the proper time and at an appropriate 
population, accompanied by optimum fertilization, good 
pest control, and other recommended cultural practices 
are necessary to assure the highest benefit from irri- 
gation. 



91 



Farmers who invest in irrigation may be disap- 
pointed if they do not manage to irrigate properly. 
Systems are so often overextended that they cannot 
maintain adequate soil moisture when the crop requires 
it. For example, a system may be designed to apply 2 
inches of water to 100 acres once a week. In two or 
more successive weeks, soil moisture may be limiting, 
with potential evapotranspiration equaling 2 inches 
per week. If the system is used on one 100-acre field 
one week and another field the next week, neither 
field may receive much benefit, especially if water 
stress comes at a critical time, such as during pollination 
of corn or soybean seed development. Inadequate 
production of marketable products may result. 



Currently we suggest that irrigators follow the cul- 
tural practices they would use for the most profitable 
yield in a year of ideal rainfall. In many parts of the 
state, 1975, 1981, and 1982 were such years. If a 
farmer's yield is not already appreciably above the 
county average for that particular soil type, he or she 
needs to improve management of other cultural factors 
before investing in an irrigation system. 

The availability of irrigation on the farm permits 
the use of optimum production practices every year. 
If rains come as needed, the investment in irrigation 
equipment will have been unnecessary that year, but 
no operating costs will be involved. When rainfall is 
inadequate, however, the yield potential can still be 
realized with irrigation. 



I 



92 



Chapter 13. 

1991 Weed Control 

for Corn, Soybeans, and Sorghum 



This guide is based on the resuhs of research conducted 
by the University of Illinois Agricultural Experiment 
Station, other experiment stations, and the United 
States Department of Agriculture (USDA). The soils, 
crops, and weed problems of Illinois have been given 
primary consideration. 

The user should have an understanding of cultural 
and mechanical weed control. These practices change 
little from year to year, so this text will focus on 
making practical, economical, and environmentally 
sound decisions regarding herbicide use. 



Precautions 

Use herbicides if the weed infestation is a threat to 
the crop and other methods of weed control are not 
practical. The benefits of chemical weed control must 
be weighed against the potential risks to crops, people, 
and the environment. Discriminate use should mini- 
mize exposure of humans or livestock, as well as 
desirable plants. Risks can be reduced by observing 
current label precautions. 

• Current label. Precautions and directions for use 
may change. Herbicides classified as restricted-use 
pesticides (RUP) must be applied by certified appli- 
cators (Table 13.1). Their use may be restricted be- 
cause of toxicity or environmental hazards. Toxicity 
is indicated by the signal word on the label. 

• Signal word. Heed the accompanying precautions. 
The signal word for herbicides discussed in this guide 
is given in Table 13.1. "Danger-Poison" or "Danger" 
indicate high toxicity hazards, while "Warning" in- 
dicates moderate toxicity. Always use protective 
equipment for handling and apphcation as specified 
in the label. Be sure that persons or animals not 
directly involved in the operation are not in the area. 
Use special precautions near residential areas. 

•Environmental hazards. Groundwater advisories 
(Table 13.1) must be observed, especially on sandy 
soils with a high water table. The threat of toxicity 



to fish and wildlife are indicated under "Environ- 
mental Hazards" on the label. Hazards to endangered 
species may be indicated. 

• Proper herbicide use. Apply only to approved crops 
at the proper rate and time. Illegal residues can result 
from overapplication or wrong timing. Observe the 
recommended harvesting or grazing intervals after 
treatment. 

• Proper equipment use. Make sure that spray tanks 
are clean and free of other pesticide residues. Many 
herbicide labels provide cleaning suggestions, which 
are particularly important when spraying different 
crops with the same sprayer and using postemergence 
herbicides. Correctly calibrate and adjust the sprayer 
before adding the herbicide to the tank. 

• Proper drift precautions. Spray only on calm days 
or when the wind is very light. Make sure the wind 
is not moving toward areas of human activity or 
susceptible crops or ornamental plants. Nearby res- 
idential areas or fields of edible, horticultural crops 
deserve particular attention to prevent injury or illegal 
residues. Use special precautions with Command, di- 
camba, and 2,4-D as symptoms of injury have occurred 
far from the application site. 

• Precautions to protect the crop. Avoid applying a 
herbicide to crops under stress or predisposed to 
injury. Crop sensitivity varies with size and climatic 
conditions, as well as previous injury from plant 
diseases, insects, or chemicals. 

• Proper recropping interval. Faliure to observe the 
proper recropping intervals may result in carryover 
injury to the present crop. Soil texture, organic matter, 
and pH may affect herbicide persistence. Atrazine 
(see "Preplant or preemergence herbicides [corn]") 
can carry over and injure susceptible follow crops. 
Many soybean herbicides have special recropping 
restrictions (Table 13.9). Check the labels for current 
restrictions. 

• Proper storage. Promptly return unused herbicides 
to a safe storage place. Pesticides should be stored 



93 



Table 13.1. Herbicide and Herbicide Premix Names and Restrictions 



Trade name 



Common (generic) name(s) 



RUP^ 



GWA" 



Signal word"^ 



AAtrex, atrazine 

Accent 

Assure 

Banvel 

Basagran 

Beacon 

Bicep 

Bladex 

Blazer 

Bronco 

Buctril 

Buctril/atrazine 

Bullet 

Butyrac 200 

Cannon 

Canopy 

Classic 

Cobra 

Command 

Commence 

Cycle 

Dual 

Eradicane 

Eradicane Extra 

Evik 

Extrazine 

Freedom 

Fusilade 2000 

Galaxy 

Gramoxone Extra 

Laddok 

Lariat 

Lasso EC 

Lasso MT 

Lexone 

Lorox 

Lorox Plus 

Marksman 

Many trade names 

Many trade names 

Option 

Passport 

Pinnacle 

Poast 

Poast Plus 

Preview 

Princep, Simazine 

Prowl 

Pursuit 

Pursuit Plus 

Ramrod/atrazine 

Reflex 

Rescue 

Roundup 

Salute 

Scepter 

Sencor 

Sonalan 

Squadron 

Stinger 

Storm 

Sutan+ 

Sutazine 

Treflan,Tri-4, Trific, Trilin 

Tri-Scept 

Turbo 



atrazine 
nicosulfuron 

auizalofop 
icamba 
bentazon 
primisulfuron 
metolachlor + atrazine 
cyanazine 
acifluorfen 

alachlor + glyphosate 
bromoxynil 
bromoxynil + atrazine 
alachlor + atrazine 
2,4-DB 

alachlor + trifluralin 
metribuzin + chlorimuron 
chlorimuron 
lactofen 
clomazone 

clomazone + trifluralin 
metolachlor + cyanazine 
metolachlor 
EPTC + safener 
EPTC + safener + extender 
ametryn 

cyanazine + atrazine 
alachlor + trifluralin 
fluazifop 

bentazon + acifluorfen 
paraquat 

bentazon + atrazine 
alachlor + atrazine 
alachlor 
alachlor 
metribuzin 
linuron 

linuron + chlorimuron 
dicamba + atrazine 
2,4-D dimethylamine 
2,4-D ester 
fenoxaprop 

trifluralin + imazethapyr 
thifensulfuron 
sethoxydim 
sethoxydim 

metribuzin + chlorimuron 
simazine 
pendimethalin 
imazethapyr 

pendimethalin + imazethapyr 
propachlor + atrazine 
fomesafen 
naptalam + 2,4-DB 
glyphosate 

metribuzin + trifluralin 
imazaquin 
metribuzin 
ethalfluralin 

imazaquin + pendimethalin 
clopyralid 

bentazon + acifluorfen 
butylate + safener 
butylate + atrazine 
trifluralin 

imazaquin + trifluralin 
metribuzin + metolachlor 



Yes 



Yes 
Yes 

Yes 
Yes 
Yes 
Yes 

Yes 



Yes 



Yes 
Yes 



Yes 
Yes 
Yes 
Yes 
Yes 



Yes 



Yes 



Yes 



Yes 


Caution 


— 


Caution 


— 


Caution 


— 


Warning 
Caution 


— 


Caution 


Yes 


Caution 


Yes 
Yes 
Yes 


Warning 

Danger 

Danger 

Warning 

Caution 


Yes 


Caution 


Yes 
Yes 


Danger 

Warning 

Caution 


— 


Caution 


Yes 


Danger 
Warning 
Danger 
Caution 


Yes 


Caution 


— 


Caution 


— 


Caution 


— 


Caution 


Yes 
Yes 


Warning 
Warning 
Caution 


Yes 
Yes 
Yes 
Yes 


Danger 

Danger-Poison 

Danger 

Warning 

Danger 

Caution 


Yes 


Caution 


— 


Caution 


Yes 


Warning 
Caution 


— 


Danger 
Caution 


— 


Warning 

Danger 

Caution 


— 


Warning 
Caution 


Yes 


Caution 


Yes 


Caution 


— 


Warning 
Caution 


— 


Caution 


Yes 

Yes 


Warning 
Warning 
Warning 
Warning 
Caution 


— 


Caution 


Yes 


Caution 


Yes 


Warning 

Danger 

Caution 


— 


Danger 
Caution 


Yes 

Yes 


Danger 
Warning 
Danger 
Caution 



I 



I 



' RUP = Restricted-use pesticide to be applied by licensed applicator. 

^ GWA = Groundwater advisory; special precautions in sanay soils. 

'^ Signal word = Toxicity signal; indicates need for extra precautions. The signal words "Danger" and "Warning" often indicate pesticides that can irritate skin 

ancf eyes, necessitating protective clothing, gloves, and goggles or face shield. 



94 



in their original, labeled containers in a secure place 
away from unauthorized people (particularly chil- 
dren) or hvestock and their food or feed. 
• Proper container disposal. Liquid containers should 
be pressure- or triple-rinsed. Properly rinsed con- 
tainers can be handled at approved sanitary landfills 
or possibly recycled. Haul paper containers to a 
sanitary landfill or burn them in an approved manner. 
This guide has been developed to help you use 
herbicides as effectively and safely as possible. Because 
no guide can remove all the risk involved, however, 
the University of Illinois and its employees assume no 
responsibility for the results of using herbicides, even 
if they have been used according to the suggestions, 
recommendations, or directions of the manufacturer 
or any governmental agency. 



Cultural and mechanical control 

Good cultural practices that aid in weed control 
include adequate seedbed preparation, adequate fer- 
tilization, crop rotation, planting on the proper date, 
use of the optimum row width, and seeding at the 
rate required for optimum stands. 

Planting in relatively warm soil can help the crop 
emerge quickly and compete better with weeds. Good 
weed control during the first 3 to 5 weeks is extremely 
important for both corn and soybeans. If weed control 
is adequate during that period, corn and soybeans will 
usually compete quite well with most of the weeds 
that begin growing later. 

Narrow rows will shade the centers faster and help 
the crop compete better with the weeds. If herbicides 
alone cannot give adequate weed control, however, 
then keep rows wide enough to allow for cultivation. 

If a preemergence or preplant herbicide does not 
appear to be controlling weeds adequately, use the 
rotary hoe while weeds are still small enough to be 
controlled. Use the rotary hoe after weed seeds have 
germinated but before most weeds have emerged. 
Operate it at 8 to 12 miles per hour, and weight it 
enough to stir the soil and kill the tiny weeds. Rotary 
hoeing also aids crop emergence if the soil is crusted. 

Row cultivators also should be used while weeds 
are small. Throwing soil into the row can help smother 
small weeds. Cultivate shallowly to prevent injury to 
crop roots. 

Herbicides can provide a convenient and economical 
means of early weed control and allow for delayed 
and faster cultivation. Furthermore, unless the soil is 
crusted, it may not be necessary to cultivate some 
fields if herbicides are controlling weeds adequately. 



Herbicide incorporation 

Soil-applied herbicides are incorporated to minimize 
surface loss, reduce dependence upon rainfall, and 
provide appropriate placement of the herbicide. Her- 



bicides such as Sutan-I-, Eradicane, and Command are 
incorporated soon after application to minimize surface 
loss from volatilization. Treflan and Sonalan are in- 
corporated to minimize loss due to photodecomposition 
and volatilization. Triazine herbicides such as atrazine 
and Bladex and acetamide herbicides such as Lasso 
and Dual may be incorporated to minimize dependence 
upon timely rainfall; but because these herbicides are 
not lost as quickly from the soil surface, the timing of 
incorporation is less critical. 

Incorporation should place the herbicide uniformly 
throughout the top 1 or 2 inches of soil for the best 
control of small-seeded annual weeds that germinate 
at shallow depths. Slightly deeper placement may 
improve the control of certain weeds from deep- 
germinating seed under relatively dry conditions. In- 
corporating too deeply, however, tends to dilute the 
herbicide and may reduce the effectiveness. The field 
cultivator and tandem disk place most of the herbicide 
at about one-half the depth of operation. Thus for 
most herbicides, the suggested depth of operation is 
3 to 4 inches for most tillage tools. 

Thorough incorporation with ground-driven imple- 
ments usually requires two passes. If the first pass 
sufficiently covers the herbicide to prevent surface loss, 
the second pass can be delayed until immediately 
before planting. Single-pass incorporation may be ad- 
equate with some herbicides and some equipment, 
especially if rotary hoeing, cultivation, or subsequent 
herbicide treatments are used to improve weed control. 

The depth and thoroughness of incorporation de- 
pend upon the type of equipment used, the depth and 
speed of operation, the texture of the soil, and the 
amount of soil moisture. Field cultivators and tandem 
disks are commonly used for incorporation; however, 
disk-chisels and other combination tools are being 
used in some areas. 

Field cultivators 

Field cultivators are frequently used for herbicide 
incorporation. They should have three or more rows 
of shanks with an effective shank spacing of no more 
than 8 to 9 inches (a spacing of 24 to 27 inches on 
each of three rows). The shanks may be equipped 
with points or sweeps. Sweeps usually give better 
incorporation, especially when soil conditions are a 
little too wet or dry for optimum soil flow and mixing. 
Sweeps for C-shank cultivators should be at least as 
wide as the effective shank spacing. 

The recommended operating depth for the field 
cultivator is 3 to 4 inches. It is usually sufficient to 
operate the field cultivator only deep enough to remove 
tractor tire depressions. The ground speed should be 
at least 6 miles per hour. The field cultivator must be 
operated in a level position so that the back shanks 
are not operating in untreated soil, which would result 
in streaked weed control. Two passes are recommended 
to obtain uniform weed control. If single-pass incor- 
poration is preferred, the use of wider sweeps or 



95 



narrower spacing with a 3- to 5 -bar harrow or rolling 
baskets pulled behind will increase the probability of 
obtaining adequate weed control. 

Tandem disks 

Tandem disk harrows invert the soil and usually 
place the herbicide deeper in the soil than most other 
incorporation tools. Tandem disks used for herbicide 
incorporation should have disk blade diameters of 20 
inches or less and blade spacings of 7 to 9 inches. 
Larger disks are considered primary tillage tools and 
should not be used for incorporating herbicides. Spher- 
ical disk blades give better herbicide mixing than do 
conical disk blades. 

Tandem disks usually place most of the herbicide in 
the top 50 to 60 percent of the operating depth. For 
most herbicides, the suggested operating depth is from 
3 to 4 inches. Two passes are recommended to obtain 
uniform mixing with a double disk. A leveling device 
(harrow or rolling baskets) should be used behind the 
disk to obtain proper mixing. Recommended ground 
speeds are usually between 4 and 6 miles per hour. 
The speed should be sufficient to move the soil the 
full width of the blade spacing. Lower speeds can 
result in herbicide streaking. 

Combination tools 

Several new tillage tools combine disk gangs, field 
cultivator shanks, and leveling devices. Many of these 
combination tools can handle large amounts of surface 
residue without clogging and yet leave considerable 
crop residue on the soil surface for erosion control. 
Results indicate that these combination tools may 
provide more uniform one-pass incorporation than 
does a disk or field cultivator, but one pass with them 
is generally no better than two passes with the disk 
or field cultivator. 



Chemical weed control 

Plan your weed-control program to fit your soils, 
tillage program, crops, weed problems, and farming 
operations. Good herbicide performance depends on 
the weather and on wise selection and application. 
Your decisions about herbicide use should be based 
on the nature and seriousness of your weed problems. 
The herbicide selectivity tables in this guide indicate 
the susceptibility of our most common weed species 
to herbicides. 

Corn or soybeans may occasionally be injured by 
some of the herbicides registered for use on these 
crops. To reduce injury to crops, apply the herbicide 
uniformly, at the time specified on the label, and at 
the correct rate. (See the section entitled "Herbicide 
rates.") Crop tolerance ratings for various herbicides 
are also given in the tables in this guide. Unfavorable 
conditions such as cool, wet weather, delayed crop 
emergence, deep planting, seedling diseases, soil in 



96 



poor physical condition, and poor-quality seed may 
contribute to crop stress and herbicide injury. Hybrids 
and varieties also vary in their tolerance to herbicides 
and environmental stress factors. Once injured by a 
herbicide, plants are prone to disease. 

Crop planting intentions for next season must also 
be considered. Where atrazine or simazine are used, 
you should not plant spring-seeded small grains, small- 
seeded legumes and grasses, or vegetables the follow- 
ing year. Be sure that the application of Treflan or 
similar herbicides for soybeans is uniform and suffi- 
ciently early to reduce the risk of injury to wheat or 
corn following soybeans. Refer to the herbicide label 
for information about cropping sequence and appro- 
priate intervals to allow between different crops. Table 
13.9 provides a summary of some of the recropping 
restrictions. 

Some herbicides have different formulations and 
concentrations under the same trade name. No en- 
dorsement of any trade name is implied, nor is discrim- 
ination against similar products intended. 



Herbicide combinations 

Herbicide combinations can control more weed spe- 
cies, reduce carryover, or reduce crop injury. Numerous 
combinations of herbicides are sold as premixes, and 
some are tank-mixed. Registered tank-mixes are shown 
in Tables 13.2, 13.8, and 13.11. Tank-mixing allows 
you to adjust the ratio of herbicides to fit local weed 
and soil conditions, while premixes may overcome 
some of the compatibility problems found with tank- 
mixing. When using a tank-mix, you must follow 
restrictions on all products used in the combination. 

Problems may occur when mixing emulsifiable con- 
centrate (EC) formulations with wettable powder (W), 
liquid flowable (L), or dry flowable (DF) formulations. 
These problems can sometimes be prevented by using 
proper mixing procedures. If using liquid fertilizers, 
check compatibility in a small lot before mixing a 
tankful. Fill tanks at least one- fourth full with water 
or liquid fertilizer before adding herbicides that are 
suspended. The addition of compatibility agents may 
be necessary. Wettable powders, dry flowable, or liquid 
flowable concentrations should be added to the tank 



Table 13.2. Registered Herbicide Combinations for 
Preplant Incorporated, Preemergence, or 
Early Postemergence Application in Corn 

Atrazine Bladex Extrazine II ^stan 

Used alone 1,2,3^ 1,2,3 1,2,3 2,3 

Eradicane 1 1 1 — * 

Sutan + 1 1 1 — 

Dual 1,2,3 1,2 1,2 2,3 

Lasso 1,2,3 1,2 1,2 2,3 

Prowl 2,3 2,3 - 2,3 

' 1 = Preplant incorporated; 2 = Preemergence; 3 = Early postemergence; 
— = Not registered. 



I 
I 



and thoroughly mixed before adding emulsifiable con- 
centrates. Emulsify concentrates by mixing with equal 
volumes of water before adding them to the tank. 
Empty and clean spray tanks often enough to prevent 
accumulation of material on the sides and the bottom 
of the tank. 

The user can apply two treatments of the same 
herbicide (split application) or can use two different 
herbicides, provided such uses are registered. The use 
of one herbicide after another is referred to as a 
sequential or overlay treatment. 



Herbicide rates 

Herbicide rates vary according to the time of appli- 
cation, soil conditions, the tillage system used, and the 
seriousness of the weed infestation. Rates of individual 
components within a combination are usually lower 
than rates for the same herbicides used alone. 

The rates for soil-applied herbicides usually vary 
with the texture of the soil and the amount of organic 
matter the soil contains. For instance, medium-textured 
soils that have little organic matter require lower rates 
of most herbicides than do fine-textured soils that have 
medium to high organic-matter content. For sandy 
soils, the herbicide label may specify reducing the rate 
or not to use at all if crop tolerance to the herbicide 
is marginal. Postemergence rates often vary depending 
upon the size and species of the weeds and whether 
or not an adjuvant is specified. 

The rates given in this guide are, unless otherwise 
specified, broadcast rates for the amount of formulated 
product. If you plan to band or direct herbicides, adjust 
the amount per crop acre according to the percent of 
the area actually treated. Herbicides may have several 
formulations with different concentrations of active 
ingredient. Be sure to read the label and make nec- 
essary adjustments when changing formulations. 



Postemergence herbicide principles 

Postemergence herbicides applied to growing weeds 
generally have foliar rather than soil action; however, 
some may have both. The rates and timing of appli- 
cations are based on weed size and climatic conditions. 
Weeds can usually be controlled with a lower appli- 
cation rate when they are small and tender. Larger 
weeds often require a higher herbicide rate or the 
addition of a spray additive, especially if the weeds 
have developed under droughty conditions. Herbicide 
penetration and action are usually greater with warm 
temperature and high relative humidity. Rainfall oc- 
curring too soon after application (1 to 8 hours, de- 
pending on the herbicide) can cause poor weed control. 

Translocated herbicides are most effective at lower 
spray volumes (5 to 20 gallons per acre), whereas 
contact herbicides require more complete coverage. 
Foliar coverage increases as water volume and spray 



pressure are increased. Spray nozzles that produce 
small droplets also improve coverage. For contact 
herbicides, 20 to 40 gallons of water per acre are often 
recommended for ground application, and a minimum 
of 5 gallons per acre is recommended for aerial ap- 
plication. Spray pressures of 30 to 60 psi are often 
suggested with flat-fan or hollow-cone nozzles to 
produce small droplets and improve canopy penetra- 
tion. These small droplets are quite subject to drift. 

The use of an adjuvant such as a surfactant, crop- 
oil concentrate, or fertilizer solution may be recom- 
mended to improve spray coverage and herbicide 
uptake. These spray additives will usually improve 
weed control but may increase crop injury. Spray 
additives may be needed, especially under droughty 
conditions or on larger weeds. 

Crop size limitations may be specified on the label 
to minimize crop injury and maxinuze weed control. 
If weeds are smaller than the crop, basal-directed 
sprays may minimize crop injury because they place 
more herbicide on the weeds than on the crop. If the 
weeds are taller than the crop, rope-wick applicators 
or recirculating sprayers may be used to place the 
herbicide on the top of the weeds and minimize contact 
with the crop. Follow the label directions and precau- 
tions for each herbicide. 



Conservation tillage and weed control 

Conservation tillage allows crop production while it 
reduces soil erosion by protecting the soil surface with 
plant residue. Minimum or reduced tillage refers to 
any tillage system that leaves crop residue on the soil 
surface. These include primary tillage with chisel plows 
or disks and the use of field cultivators, disks, or 
combination tools for secondary tillage. Mulch tillage 
is reduced tillage that leaves at least 30 percent of the 
soil surface covered with plant residue. 

Ridge tillage and zero tillage are conservation tillage 
systems with no major tillage prior to planting. In 
ridge tillage, conditions are often ideal for banding of 
preemergence herbicides. Cultivation is a part of the 
system. "No-till" is actually slot tillage for planting 
with no overall primary tillage. No-till planting con- 
serves moisture, soil, and fuel. It also allows timely 
planting of soybeans or sorghum after winter wheat 
harvest. 

If tillage before planting is eliminated, undesirable 
existing vegetation at planting must be controlled with 
herbicides. The elimination or reduction of herbicide 
incorporation and row cultivation puts a greater stress 
and reliance on chemical weed control. Soil conditions 
must be ideal for single-pass herbicide incorporation 
to be uniform. Greater emphasis may be placed on 
preplant or postplant soil-applied herbicides that are 
not incorporated or on foliar-applied herbicides. 

Where primary tillage is minimized, soil residual 
herbicides applied several weeks before planting may 
reduce the need for a "knockdown" herbicide. How- 



97 



ever, early preplant (EPP) application may require 
additional preemergence or postemergence herbicides 
or cultivation for satisfactory weed control after plant- 
ing. See the sections on corn and soybean in this 
chapter under "Preplant not incorporated" for more 
details. 

Corn and soybeans are the primary crops in Illinois, 
and they are often planted in a corn and soybean 
rotation. Modern equipment allows successful no-till 
planting in corn or soybean stubble. The use of a disk 
or chisel plow on corn stubble may still provide 
adequate crop residue to allow minimum tillage. Her- 
bicides are also available to allow a "total postemer- 
gence" weed control program, especially for soybeans. 

Soybean stubble is often ideal for zero or minimum 
tillage. Primary tillage is rarely needed and the crop 
residue should not interfere with herbicide distribution. 
Early preplant application of preemergence herbicides 
or the use of postemergence herbicides can often 
provide adequate weed control. 

The existing vegetation in corn and soybean stubble 
is often annual weeds. If the weeds are small, they 
can often be controlled before planting with herbicides 
that have both foliar and soil residual activity. For 
corn, these include atrazine or Bladex and their pre- 
mixes. For soybeans, metribuzin (Sencor or Lexone), 
linuron (Lorox), and their premixes with chlorimuron 
(Preview, Canopy, or Lorox Plus), as well as Pursuit 
can be used. Foliar activity is enhanced with the 
addition of crop-oil concentrate (COC) or surfactant. 

Sod planting requires a different approach. If minimum 
or zero tillage is to be used in perennial grass or legume 
sods, the sod should be controlled prior to planting. Late 
control of sod may deplete soil moisture, making crop 
establishment difficult when soil moisture is low. Some 
grass sods may require the use of Roundup in the fall 
when there is adequate foliage and translocation for 
effective control. Bluegrass or clover may be controlled 
by atrazine alone or combined with Bladex. Clover sods 
can be controlled by Banvel or 2,4-D applied in the fall 
before planting soybeans or com or in the spring for 
com only. Alfalfa may be controlled with Banvel or 
Banvel plus 2,4-D. Do not plan to take a spring cutting 
before planting into forage sods. Regrowth rarely provides 
sufficient foliage for active herbicide uptake to kill the 
sod prior to planting com. 

Winter cover crops of wheat or rye can be controlled 
by Roundup prior to planting corn or soybeans, or 
Gramoxone plus atrazine may be used prior to planting 
corn. 

Annual vegetation over 2 to 3 inches tall at planting 
time may require a burndown or translocated herbicide. 
Gramoxone, Roundup, or Bronco can be used with 
most preemergence herbicides to control vegetation 
that is already present. 

Gramoxone Extra (paraquat) can be used to control 
existing vegetation before planting. Gramoxone Extra 
2.5S is used at 1.5 to 3 pints per acre. It should be 
applied with a nonionic surfactant in at least 20 gallons 
of spray per acre. Gramoxone alone often fails to 



provide adequate control of smartweed, giant ragweed, 
"marestail" and fall panicum. Gramoxone is a restricted- 
use pesticide. 

Roundup (glyphosate) can be used at 3 to 8 pints 
per acre to control existing vegetation prior to planting. 
Roundup at the higher rates can translocate to the 
roots to control some perennials. Spray volume per 
acre should be 20 to 40 gallons. Small annual weeds 
can be controlled with 0.75 to 1 pint of Roundup in 

5 to 10 gallons of water per acre plus 0.5 percent 
nonionic surfactant. Do not mix Roundup with Lasso 
Micro Tech or Bullet. 

Bronco (glyphosate plus alachlor) contains the 
equivalent of 2.6 quarts of Lasso EC and and 1.4 
quarts of Roundup per gallon. Bronco is used at 6 to 
10 pints per acre applied in 10 to 30 gallons of water. 
Application can also be made in urea ammonium 
nitrate (UAN) solutions if annual weeds are less than 

6 inches tall. Bronco is a restricted-use pesticide. 
Banvel (dicamba) may be used in the fall or spring 

before planting corn or only in the fall before planting 
soybeans. Banvel can control annual and some per- 
ennial broadleaved plants including clovers and alfalfa. 
A combination of Banvel plus 2,4-D can often control 
more weeds at lower costs. 

2,4-D can be used in the fall or spring before planting 
com to control broadleaved weeds. The status of 2,4-D 
prior to planting soybeans is somewhat controversial. 
See the "Preplant not incorporated" portion in the 
soybean section. 



Herbicides for corn 

Herbicides mentioned in this section are registered 
for use on field corn. Some are also registered for 
silage corn. See Table 13.2 for registered combinations. 
Herbicide suggestions for sweet corn and popcorn may 
be found in Chapter 11, Weed Control for Commercial 
Vegetable Crops, which appears in the 1991 Illinois Pest 
Control Handbook. Growers producing hybrid seed corn 
should check with the contracting company or the 
producer of inbred seed about tolerance of the parent 
lines. See Tables 13.3 and 13.4 for weeds controlled 
by the herbicides used in corn. 

Preplant not incorporated (corn) 

Early preplant application allows control of existing 
vegetation and early germinating weeds. Atrazine, 
Bladex, and Banvel act on leaves as well as in the soil. 

Atrazine, Bicep, Bullet, or Cycle can be used within 
30 days before planting as a single, full-rate application 
or within 45 days if application is split before planting 
and at planting. Atrazine, Bicep, Bullet, and Cycle are 
restricted-use pesticides. 

Bladex or Extrazine can be applied 15 to 30 days 
before planting corn. Apply before weeds germinate 
or seedlings are more than 3 inches tall. Bladex and 
Extrazine are restricted-use pesticides. 



98 



Table 13.3. Corn Herbicides: Grass and Nutsedge Control 



Herbicide 


BYG 


CBG 


FLP 


GFT 


YFT 


WCG 


SBR 


SHC 


WPM 


YNS 


CRN 


Soil-applied 
























Atrazine 


8 


5 


3 


7 


8 


4 


7 


2 


3 


5 





Bladex 


7 


7 


8 


8 


8 


6 


6 


2 


6 


3 


2 


Dual 


8+ 


9 


8+ 


9 


9 


7 


7 


6 


7 


7+ 


2 


Eradicane 


9 


8 


9 


9 


9 


7 


8 


6 


7 


7 


1 + 


Eradicane Extra 


9 


9 


9 


9 


9 


8 


9 


8 


8+ 


8 


2 


Lasso 


8+ 


9 


8 


9 


9 


7 


7 


5 


7 


7 


2 


Marksman 


4 


3 


2 


3 


3 


2 


1 


1 


1 


4 


2 


Princep 


8 


6 


5 


7 


7 


4 


5 


4 


4 


2 





Prowl 


8 


8 


8 


8 


8 


7 


7 


6 


7 





2 


Sutan+ 


9 


9 


9 


9 


9 


8 


9 


7 


7 


7 


1 


Foliar-applied 
























Accent 


8 


4 


8+ 


9 


8 


8 


5 


9+ 


8 


3 


1 


Atrazine/oil 


8 


5 


5 


7 


7 


6 


7 


2 


4 


6 


1 + 


Beacon 





2 


7 


6 


5 


2 


6 


9+ 


2 


4 


1 + 


Bladex 


8 


7 


7 


8 


8 


5 


6 


2 


6 


5 


1 + 


Buctril 





























2 


1 + 


Buctril/atrazine 
LaddoK 


2 


2 





3 


3 














5 


1 + 


2 


2 





3 


3 





2 








8 


1 


Marksman 


2 


2 





2 


2 


2 


2 


1 





3 


1 + 



Note: BYG = bamyardgrass, CBG = crabgrass, FLP = fall panicum, GFT = giant foxtail, YFT = yellow foxtail, WCG = woolly cupgrass, SBR = sandbur, 
SHC = shattercane, WPM = wild proso millet, YNS = yellow nutsedge, and CRN = com response. 

Rating Scale: 

10 = 95 to 100 percent, 9 = 85 to 95 percent, 8 = 75 to 85 percent, 7 = 65 to 75 percent, 6 = 55 to 65 percent, and 5 = 45 to 55 percent. 



Table 13.4. Corn Herbicides: Broadleaf Weed Control 



Herbicide 


AMG 


CCB 


JMW 


LBQ 


BNS 


PGW 


CRW 


GRW 


SMW 


SFR 


VLV 


Soil-applied 
























Atrazine 


9 


9 


10 


9 


9 


9 


9 


8 


9 


8 


8 


Bladex 


8 


8 


8 


9 


8 


6 


9 


7 


9 


7 


7 


Dual 








4 


6 


7+ 


8 


5 


2 


5 








Eradicane 


4 


2 


2 


7 


4 


7 


4 


3 


4 





5 


Lasso 








5 


7 


7+ 


9 


6 


2 


5 








Marksman 


8 


8 


8 


8 


8 


9 


9 


8 


9 


8 


7+ 


Princep 


9 


9 


9 


9 


9 


9 


9 


7 


9 


8 


7 


Prowl 








2 


8 





9 


2 





3 





4 


Sutan+ 


4 


2 


2 


4 


2 


7 


4 


3 


3 





4 


Foliar-applied 
























Accent 


8+ 


2 


7 


5 





9 


3 


3 


8 


6 


3 


Atrazine/oil 


9 


9 


9 


9 


9 


10 


9 


8 


10 


9 


9 


Banvel 


9 


9 


9 


9 


8 


9 


9 


9 


10 


8 


7 


Beacon 


4 


8 


8 


6 


7 


9 


9 


9 


8 


8 


7 


Bladex 


7 


8 


8 


9 


9 


7 


9 


7 


9 


7 


7 


Buctril 


8 


9 


9 


9 


9 


7+ 


9 


8 


8+ 


9 


8 


Buctril/atrazine 


9 


9 


10 


10 


10 


10 


9 


9 


10 


10 


9 


2,4-D 


9 


9 


7 


9 


7 


9 


9 


9 


6 


8 


8 


Laddok 


8 


9 


10 


9 


9 


9 


9 


9 


10 


10 


9 


Marksman 


9 


9 


10 


10 


10 


10 


9 


9 


10 


9 


9 



Note: AMG = annual momingglory, CCB = cocklebur, JMW = jimsonweed, LBQ = lambsquarters, BNS = black nightshade, PGW = pigweed, 
CRW = common ragweed, GRW = giant ragweed, SMW = smartweed, SFR = wild sunflower, and VLV = velvetleaf. 

Rating Scale and Approximate Weed Control 

10 = 95 to 100 percent, 9 = 85 to 95 percent, 8 = 75 to 85 percent, 7 = 65 to 75 percent, and 6 = 55 to 65 percent. 
Weed control of 5 or less is rarely significant. Corn injury of 1 or less is rarely significant. 
For ratings on herbicide combinations (tank-mix or premix), see the component parts. 



Premix: 


Grass 


+ 


Broadleaf 


Bicep: 


Dual 


+ 


atrazine 


Bullet: 


Lasso 


+ 


atrazine 


Cycle: 


Dual 


+ 


Bladex 


Extrazine: 


Bladex 


+ 


atrazine 


Lariat: 


Lasso 


+ 


atrazine 


Sutazine: 


Sutan+ 


+ 


atrazine 



Premix: 



Broadleaf 



Broadleaf 



Buctril/atrazine: 

Laddok: 

Marksman: 



Buctril 

Basagran 

Banvel 



+ atrazine 
+ atrazine 
+ atrazine 



99 



Banvel or Marksman can be applied before planting 
no-till corn on soils with more than 2 percent organic 
matter. Marksman is a restricted-use pesticide. 

2,4-D can be used to control existing vegetation 
before planting reduced-tillage corn. Some preplant 
tank-mixes allow for 1 to 2 pints of 2,4-D LV ester 
per acre. See the specific label for the instructions. 

Buctril, or a tank-mix or premix of Buctril and 
atrazine can control some existing vegetation before 
planting field corn. Buctril and atrazine are restricted- 
use pecticides. 

Roundup may be used before planting at 12 to 16 
fluid ounces per acre alone or with 2,4-D or Banvel 
to control small, annual weeds. Use 5 to 10 gallons 
of water plus a nonionic surfactant. 

Preplant incorporated herbicides (corn) 

Sutan-h (butylate), Eradicane or Eradicane Extra 

(EPTC) require incorporation because they are volatile. 
Apply within 2 weeks of the expected planting date. 
If possible, application and incorporation should be 
done at the same time. Do not delay incorporation more 
than 4 hours. 

Eradicane Extra is used primarily for late weed 
species such as shattercane as it contains an extender. 
Sutan-t- and Eradicane control annual grass weeds 
(Table 13.3) and are both used at 4% to 7V3 pints per 
acre. The rate for Eradicane Extra 6E is 5% to 8 pints 
per acre. Use the higher rates for heavy weed infes- 
tations or to suppress certain problem weeds. 

Sutan+ or Eradicane may be tank-mixed with atra- 
zine, Bladex, or Extrazine II to improve broadleaf 
control. Rates per acre are 2 to 3 pints atrazine 4L or 
3 to 4 pints Bladex or Extrazine 4L or equivalent rates 
of 90DF formulations. Sutazine, a premix of butylate 
(Sutan-h) and atrazine, is used at 5.5 to 10.5 pints 
6ME or 11.7 to 22.7 pounds 18-6G per acre. Sutazine 
is a restricted-use pesticide. 

Preplant or preemergence herbicides (corn) 

AAtrex, Atrazine (atrazine) or Princep (simazine) 

are often incorporated before planting because of low 
solubility. Princep plus atrazine can be tank-mixed 
with the total rate being the same as for atrazine alone. 
Atrazine alone is used at 4 to 6 pints 4L or 2.2 to 3.3 
pounds 90DF per acre. The rate is 2 to 3 pints 4L or 
1.1 to 1.8 pounds 90DF per acre for broadleaf control 
in tank-mixes with other herbicies to control grass 
weeds. All products containing atrazine are restricted- 
use pesticides because of the risk of groundwater contam- 
ination. No more than 3 pounds active ingredient of 
atrazine may be applied to any one site per year and 
fall application is no longer allowed. 

Atrazine and simazine can persist to injure follow 
crops. Carryover can be minimized by mixing and 
applying the herbicides accurately, by applying them 
early, and by using the lowest rate consistent with 
good weed control. The risk of carryover is greater 



after a cool, dry season and on soils with a pH over 
7.3. Soybeans planted the next year may show injury 
from atrazine carryover. If you apply atrazine after 
June 10, plant only corn or sorghum the next year. Do 
not plant small grains, clovers, alfalfa, or vegetables in 
the fall or the next spring after using atrazine. 

Bladex (cyanazine) controls most annual grass weeds 
(Table 13.3) but is weaker than atrazine on broadleaf 
weeds (Table 13.4). Bladex has shorter persistence than 
atrazine, but atrazine is less likely to injure corn. 
Extrazine II is a 3:1 premix of cyanazine (Bladex) and 
atrazine used at rates and times similar to those of 
Bladex. 

Select rates of Bladex or Extrazine accurately on the 
basis of soil texture and organic matter content to 
reduce the possibility of corn injury. Used alone, Bladex 
rates are 1.3 to 5.3 pounds of 90DF or 2V2 to 9% pints 
of 4L per acre, while Extrazine rates are 1.4 to 5.8 
pounds 90DF or 2V2 to IOV2 pints 4L per acre. They 
may be tank-mixed at reduced rates with "grass" 
herbicides (Table 13.2) for broadleaf weed control. 
Bladex and Extrazine are restricted-use pesticides. 

Cycle 4L, a 1:1 premix of metolachlor (Dual) and 
cyanazine (Bladex), can be applied up to 14 days prior 
to planting and incorporated or used preemergence 
after planting. The rate is 5 to 9 pints per acre. Cycle 
is a restricted-use pesticide. 

Lasso (alachlor) or Dual (metolachlor) primarily 
control annual grasses and some small broadleaf weeds 
(Tables 13.3 and 13.4). To improve broadleaf control, 
they can be combined with atrazine or Bladex. Dual 
may be applied and shallowly incorporated within 45 
days before planting, or it may be used after planting. 
The rates are IV2 to 4 pints of Dual 8E or 6 to 16 
pounds of Dual 25G per acre. 

Lasso may be applied and shallowly incorporated 
within 7 days of planting corn, or it may be used 
immediately after planting. The rates are 4 to 8 pints 
of Lasso 4E or 4L (Micro Tech) or 16 to 26 pounds of 
Lasso 15G per acre. Arena, Judge, Stall, Saddle, and 
Confidence are distributor brands of alachlor. Products 
containing alachlor are restricted-use pesticides. 

Lasso or Dual plus atrazine may be applied pre- 
plant or after planting until corn is 5 inches tall and 
grass weeds have not passed the 2-leaf stage. Do not 
use liquid fertilizer as a carrier after the corn emerges. 
The rate is 3 to 8 pints Lasso or 1 V4 to 2y2 pints Dual 
8E plus atrazine at 2 to 4 pints 4L, 1.1 to 2.2 pounds 
90DF, or 1.5 to 2.5 pounds 80W per acre. 

Bicep 6L is a 5:4 premix of metolachlor (Dual) plus 
atrazine used at 3 to 6 pints per acre. Lariat 4L and 
Bullet 4L are 5:3 mixes of alachlor (Lasso) plus atrazine 
used at 5 to 12 pints per acre. Bicep, Bullet, and Lariat 
are restricted-use pesticides. 

Preemergence herbicides (corn) 

Banvel (dicamba) or Marksman (dicamba + atra- 
zine) can be applied right after planting on many 
medium- to fine-textured soils. The preemergence rate 



100 



is 1 pint of Banvel or Vk pints of Marksman per acre. 
Do not apply preemergence to soils containing less than 
2 percent organic matter or to coarse-textured soils. Banvel 
or Marksman can be tank-mixed with several other 
herbicides (Table 13.2) and applied preemergence or 
early postemergence. 

Prowl (pendimethalin) can be used only after corn 
planting. Do not incorporate. Corn should be planted 
at least 1.5 inches deep. The Prowl rate per acre is 
IV2 to 4 pints alone or IV2 to 3 pints in most tank- 
mix combinations. Most Prowl tank-mixes for corn can 
also be apphed early postemergence (Table 13.2). See 
labels for limitations to corn size if the herbicide is 
applied postemergence. 

Postemergence herbicides (corn) 

Several preemergence herbicide tank-mixes or pre- 
mixes may also be applied early postemergence to 
com (Table 13.2). Most require the grass weeds .to be 
less than 1.5 to 2 inches tall for effective control. Use 
water and not liquid fertilizer as the carrier when 
applying postemergence herbicides. Some herbicides 
will control grass weeds; others will control broadleaf 
weeds (see Tables 13.3 and 13.4). Several combinations 
of postemergence herbicides are registered (see Table 
13.5). 

Postemergence grass control in corn 

Accent, Beacon, atrazine, Bladex, or Extrazine II can 
be used to control certain grass weeds. Atrazine, Bladex, 
or Extrazine II must be applied before annual grass 
weeds are over 1.5 inches tall. These herbicides also 
control several broadleaf weeds. 

Accent and Beacon are used for postemergence grass 
control in field corn. Both can control shattercane and 
johnsongrass but Accent is better for giant foxtail and 
fall panicum control. Do not use Accent or Beacon if the 
insecticide Counter is applied for corn. Check the current 
labels for restrictions in tank-mixing or sequencing 
with other herbicides. Do not use if Basagran or Laddok 
have been applied to the corn. Accent or Beacon are 
considered rainfast within 4 to 6 hours. 

Accent 75DF (nicosulfuron) can be applied to field 
com from the 2- to 6-leaf stage at Va ounce of product 
per acre in a minimum of 10 gallons of water per 
acre. A second application may be made until the 10- 
leaf stage of com. Add 1 quart of nonionic surfactant 
or 1 gallon of crop-oil concentrate per 100 gallons of 



spray. Urea ammonium nitrate (UAN) can also be 
added at 4 gallons per 100 gallons of spray. 

Weed height limitations when using Accent are 1 to 
4 inches for giant foxtail, 4 to 10 inches for shattercane, 
8 to 12 inches for rhizome johnsongrass, and 2 to 4 
inches for quackgrass. Accent can also provide some 
control of relatively small pigweed, smartweed, jim- 
sonweed, and annual morningglories. Observe recrop- 
ping restrictions on the labels. 

Beacon 75DF (primisulfuron) can be applied to 
corn that is 4 to 20 inches tall. A 1.52 ounce packet 
treats 2 acres. Split applications at half rate will provide 
better control of johnsongrass and quackgrass. Weed 
height limitations when using Beacon are 4 to 12 
inches for shattercane, 8 to 16 inches for rhizome 
johnsongrass, 4 to 8 inches for quackgrass, and 1 to 
2 inches for fall panicum. Beacon can control several 
broadleaf weeds. 

If Beacon is tank-mixed with Buctril, Banvel, or 2,4- 
D, use nonionic surfactant (NIS) and not crop-oil 
concentrate (COC). Use NIS at 1 quart per 100 gallons 
of spray or COC at 1 to 4 pints per acre; UAN can 
also be added at 1 to 2 pints per acre. Use a minimum 
of 10 gallons of spray per acre. Observe label restric- 
tions for recropping. 

Atrazine may be applied before corn is 12 inches 
tall. Use 2.2 pounds 90DF or 4 pints 4L plus one quart 
crop-oil concentrate (COC) per acre to control annual 
grass weeds less than 1.5 inches tall. Many annual 
broadleaf weeds up to 4 inches tall are controlled with 
1.3 pounds 90DF or 2.4 pints 4L plus a quart of COC 
per acre. 

Atrazine plus COC may injure corn that has been 
under stress from prolonged cold, wet weather or other 
factors. Do not add 2,4-D with the atrazine plus COC. 
Mix the atrazine with water first and then add the 
COC. If atrazine is applied after June 10, plant only 
corn or sorghum the next year. Atrazine is a restricted- 
use pecticide. 

Bladex (cyanazine) or Extrazine II (cyanazine -I- 
atrazine) may be apphed until the 5 -leaf stage in field 
corn and before grass weeds exceed 1.5 inches in 
height. The rate per acre is 1.1 to 2.2 pounds 90DF 
or 2.2 to 4 pints 4L. Use 4L formulations only under 
warm, dry, sunny conditions of low humidity. Do not 
apply Bladex or Extrazine II to corn that is stressed or 
growing under cold, wet weather. Under dry, arid 
conditions, a surfactant or vegetable oil may be added 
to 90DF (not 4L) formulations. Do not use petroleum- 



Table 13.5 Postemergence Herbicide Tank-Mixes for Corn 



Herbicide 



Buctril 



Basagran 



Laddok 



Banvel 



Marksman 



2,4-D 



Atrazine 



Accent 

Atrazine 

Beacon 

Bladex 

2,4-D 



X? 
X? 



Note: X = registered; X? = check current label; - = not registered. 



101 



based crop oils or apply with liquid fertilizer. Extrazine 
II and Bladex are restricted-use pesticides. 

Postemergence broadleaf control (corn) 

Banvel, Stinger and 2,4-D are plant hornnone her- 
bicides that control broadleaf weeds in corn. Observe 
drift precautions with these herbicides. Buctril, Buctril 
plus atrazine, and Laddok are contact herbicides, so 
good spray coverage is essential. 

Banvel (dicamba) or Marksman (dicamba + atra- 
zine) may be applied from spike to 5 -leaf stage in 
corn. Use 1 pint of Banvel or 3V2 pints of Marksman 
per acre except on coarse-textured soils, when the rate 
to use is Vi pint of Banvel or 2 pints of Marksman. 
Banvel may also be applied at Vi pint to corn that is 
8 to 36 inches tall or 15 days before tassels emerge, 
whichever comes first. Use drop nozzles on corn over 
8 inches tall to reduce the risk of corn injury, improve 
spray coverage, and to reduce drift. To minimize the 
risk of injury from drift, do not apply Banvel to corn over 
24 inches tall if nearby soybeans are over 10 inches tall 
or have begun to bloom. 

Observe all label precautions to minimize the risk 
of Banvel or Marksman drifting to susceptible crop or 
ornamental plants nearby. If weeds are drought- 
stressed, the addition of an approved agricultural 
surfactant to Banvel or Marksman will improve cov- 
erage and control. The Banvel label calls for directed 
application if applied with a surfactant or with 2,4-D. 
Do not use petroleum or crop oils. 

Stinger (clopyralid) can be used on field corn up 
to 24 inches in height. The rate per acre is Vi to Vi 
pint for ragweeds, cocklebur, sunflower, and jimson- 
weed up to the 5 -leaf stage and V3 to % pint for 
Canada thistle. Its price will limit its use in corn. 

2,4-D amine or ester can be used from emergence 
to tassehng of corn. Apply with drop nozzles if corn 
is more than 8 inches tall. The rate is Va to V2 pint of 
2,4-D ester or 1 pint of 2,4-D amine if the active 
ingredient is 3.8 pounds per gallon. 2,4-D ester can 
vaporize and injure susceptible plants nearby if tem- 
peratures exceed 85°F. Spray particles of either 2,4-D 
ester or amine can drift and cause injury to susceptible 
plants. 

Corn is often brittle for 1 to 2 weeks after application 
of 2,4-D and may be susceptible to stalk breakage 
from high winds or cultivation. Other symptoms of 
2,4-D injury are stalk lodging, abnormal brace roots, 
and failure of leaves to unroll. Corn hybrids differ in 
their sensitivity to 2,4-D. High humidity and temper- 
ature increase the potential for 2,4-D injury to corn. 

After the hard dough to dent stage in corn, certain 
2,4-D labels specify preharvest use to control or sup- 
press broadleaf weeds that may interfere with harvest. 
Do not use for forage or fodder for 7 days after 
treatment. 

Buctril G>romoxynil) is used at 1 to IV2 pints per 
acre in corn from the 3- to 4-leaf stage up to tassel 
emergence and while weeds are in the 3- to 8-leaf 



stage. Larger pigweed and velvetleaf may require the 
higher rate or a combination with atrazine. 

Buctril/atrazine 3L is used at IV2 to 3 pints per 
acre or Buctril can be tank-mixed with 1 to 2.4 pints 
atrazine 4L or 0.6 to 1.3 pounds atrazine 90DF. The 
herbicide may be applied when corn is at the 3- to 4- 
leaf stage up to 12 inches tall. Surfactants or crop-oil 
concentrate can be added to the spray mix but the 
potential for injury may increase. Buctril and Buctril/ 
atrazine are restricted-use pesticides. 

Laddok G'entazon -I- atrazine) is used at 2 to 3V2 
pints per acre until corn is 12 inches tall. Always add 
one gallon of UAN or one quart of crop-oil concentrate 
(COC) per acre for ground application. Use the COC 
for Canada thistle or yellow nutsedge. Laddok is a 
restricted-use pesticide. 

Postemergence soil-applied herbicides (corn) 

Some herbicides that are normally applied to the 
soil may be used postemergence in com to back up 
herbicides that had been applied earlier and to keep 
late-emerging weeds from becoming problems. Drop 
nozzles should be used if corn foliage prevents uniform 
application to the soil. 

Prowl (pendimethalin) or Treflan (trifluralin) may 
be applied after field corn is 4 inches tall (for Prowl) 
or from the 2-leaf stage (for Treflan) up to last culti- 
vation. Prowl or Treflan plus atrazine can be used but 
do not apply after corn is 12 inches tall. Apply the 
herbicide and then incorporate with a sweep-type or 
rolling cultivator. Prowl may not require incorporation 
if rainfall occurs soon after application. These treat- 
ments are used to help control late-emerging grasses 
such as shattercane, wild proso millet, fall panicum, 
or woolly cupgrass. Do not use Prowl in corn more than 
once per crop season. Observe recropping restrictions, 
especially for wheat. 

Dual (metolachlor) plus atrazine as a tank-mix or 
premix (Bicep) can be used postemergence to control 
weeds in corn up to 12 inches high, especially in seed 
corn, where late emerging weeds become problems. 
See the current label for rate and timing restrictions. 

Directed postemergence herbicides for emergencies 
(corn) 

Directed (not over-the-top) sprays of Lorox, Evik, or 
Gramoxone can be used for emergencies if weed and 
crop size limits are met. Early cultivation may allow 
for the proper height differential between the crop 
and weeds. Direct the spray to the base of the com 
plants to minimize injury to the corn while covering 
the weeds as much as possible. Adjust the rate of Lorox 
or Evik for banded applications. 

Lorox (linuron) may be used in field corn at least 
15 inches tall (freestanding) but before weeds are 5 
inches tall. Use Lorox at 1.25 to 3 pounds 50DF or at 
IV4 to 3 pints 4L per acre depending upon the weed 
size and soil type. Add 1 pint of surfactant per 25 
gallons of spray. 



102 



Evik SOW (ametryn) can be used as a directed spray 
in field com more than 12 inches tall but before weeds 
are taller than 6 inches. Use 2 to 2.5 pounds Evik 
SOW per acre plus 2 quarts of surfactant per 100 
gallons of spray. Do not graze or harvest within 30 
days after apphcation. Do not apply within 3 weeks of 
corn tasseling. 

Gramoxone Extra (paraquat) may be applied as a 
directed spray after corn is 10 inches tall but before 
weeds are 4 inches tall. Use 12.8 fluid ounces of 
Gramoxone Extra in 20 to 40 gallons of water per 
acre. Add 1 quart of nonionic surfactant per 100 gallons 
of spray. A tank-mix with atrazine can increase broad- 
leaf control. Observe current label precautions. Gra- 
moxone is a restricted-use pesticide. 



Herbicides for sorghum 

Atrazine, Dual, Bicep, and 2,4-D are registered for 
use in grain or "forage" sorghums. Several other corn 
herbicides can also be used in grain sorghum or milo, 
although the application rates may be lower. Check 
the labels for the relevant information. 

Gramoxone Extra (paraquat) or Roundup (gly- 
phosate) can be used to control existing vegetation 
before planting grain sorghum in reduced-tillage sys- 
tems. Bronco (glyphosate + alachlor) can also be used 
if the seed is treated with Screen. Gramoxone Extra and 
Bronco are restricted-use pesticides. 

Atrazine may be applied to medium-textured soils 
with more than 1 percent organic matter, but the rates 
are lower than for corn. Atrazine can also be applied 
postemergence at 4 to 6 pints 4L per acre without 
crop-oil concentrate (COC) or at 2.4 pints per acre 
with COC for broadleaf control only. Use equivalent 
rates of atrazine 90DF. Atrazine is a restricted-use 
pesticide. 

Ramrod (propachlor) alone or with atrazine or 
Bladex can be used only preemergence in grain 
sorghum. Do not graze or feed forage to dairy animals. 

Lasso (alachlor) or Lariat (alachlor + atrazine) can 
be used if grain sorghum seed is treated with Screen. 
Lasso Micro Tech and Bullet are not registered for use 
in grain sorghum. Lasso and Lariat are restricted-use 
pesticides. 

Dual (metolachlor), Bicep (metolachlor + atrazine), 
or Cycle (metolachlor -f- cyanazine) can be used if 
grain sorghum seed has been treated with Concep II. 
Bicep and Cycle are restricted-use pesticides. 

2,4-D may be applied for broadleaf control in 
sorghum that is 4 to 24 inches tall. Use drop pipes if 
sorghum is taller than 8 inches. 

Banvel (dicamba) or Marksman (dicamba -I- atra- 
zine) can be applied to grain sorghum after the 3-leaf 
stage. Marksman can be applied only until sorghum 
has 5 leaves or is 12 inches tall, while Banvel can be 
applied to sorghum up to 15 inches tall. Rates are 
lower than for use in corn; see the label for instructions. 
Do not graze or feed treated forage to animals before 



the mature grain stage. Marksman is a restricted-use 
pesticide. 

Laddok (bentazon + atrazine) can be used post- 
emergence to control broadleaf weeds in grain sorghum 
if apphed before the crop is 12 inches tall. Laddok is 
a restricted-use pesticide. 

Buctril (bromoxynil) applied alone can be used 
from the 3-leaf to boot stage, while Buctril that has 
been tank-mixed or premixed with atrazine can only 
be applied to grain sorghum up to 12 inches in height. 
Buctril and atrazine are restricted-use pesticides. 

Roundup (glyphosate) may be applied as a spot 
treatment in grain sorghum prior to heading. 



Herbicides for soybeans 

Consider the kinds of weeds expected when you 
plan a herbicide program for soybeans. The herbicide 
selectivity table lists herbicides and their relative weed 
control ratings for various weeds. (See Tables 13.6, 
13.7, 13.10, and 13.12 for soybean herbicides.) 

Although soybeans may be injured by some herbi- 
cides, they usually outgrow early injury with little or 
no effect on yield if stands have not been significantly 
reduced. Significant yield decreases can result when 
injury occurs during the bloom to pod-fill stages. 
Excessively shallow planting can increase the risk of 
injury from some herbicides. Accurate rate selection 
for soil type is essential for herbicides containing 
metribuzin (Canopy, Lexone, Preview, Salute, Sencor, 
or Turbo) or linuron (Linex, Lorox, or Lorox Plus). Do 
not apply these herbicides after soybeans begin to 
emerge, or severe injury can result. Always follow 
label instructions. See Table 13.8 for some preplant 
and preemergence tank-mix combinations. 

Preplant not incorporated (soybeans) 

Early preplant application of herbicides can be used 
in minimum tillage programs to minimize existing 
vegetation problems at planting and reduce the need 
for a knockdown herbicide. Preemergence herbicides 
for early application before planting soybeans include 
Dual and Prowl for grass control and Canopy, Lexone, 
Lorox Plus, Preview, Pursuit, Pursuit Plus, Sencor, and 
Scepter for broadleaf control. All except Dual and 
Prowl have both soil and foliar activity, so they may 
sometimes control small annual weeds prior to planting 
soybeans, especially if a nonionic surfactant or crop- 
oil concentrate is added to the spray mix. However, if 
weeds are over 1 to 2 inches tall, add either Gramox- 
one, Roundup, or Bronco to the spray mix within label 
guidelines to control existing vegetation. (See the sec- 
tion on "Conservation tillage and weed control.") 

Dual can be applied up to 30 days prior to planting 
or as a split application within 45 days of planting 
soybeans. The split application rate is a full rate with 
two-thirds applied preplant and one-third at planting. 

Canopy, Lorox Plus, or Preview can be applied 



103 



Table 13.6. Soybean Soil-Applied Herbicides: Grass and Nutsedge Control 



Herbicide 




BYG 


CBG 


FLP 


GFT 


YFT 


WCG 


SBR 


SHC 


VCN 


YNS 


Soil-applied 


"grass" 






















Command 




9 


9 


9 


9 


9 


8 


7 


7 


5 


3 


Dual 




8+ 


9 


8+ 


9 


9 


7 i 


7 


5 





7+ 


Lasso 




8+ 


8 


8 


9 


9 


7 


7 


5 





7 


Prowl 




9 


9 


9 


9 


9 


9 


8 


8 


4 





Sonalan 




9 


8 


9 


9 


9 


8 


8 


7 


4 





Trifluralin 




9 


9 


9 


9 


9 


9 


8 


8 


5 





Soil-applied 


"broadleaf" 






















Canopy 




6 


5 


6 


6 


6 


5 


5 


2 


3 


3 


Lexone 




6 


5 


6 


6 


6 


5 


5 


2 


2 


2 


Lorox 




6 


6 


6 


6 


6 


6 


4 


4 


3 


2 


Lorox Plus 




6 


6 


6 


6 


6 


6 


4 


4 


4 


2 


Preview 




6 


5 


6 


6 


6 


5 


5 


2 


3 


2 


Pursuit 




6 


7 


7 


7 


6 


6 


5 


7 


5 


4 


Scepter 




6 


6 


6 


6 


6 


5 


5 


5 


7 


6 


Sencor 




6 


5 


6 


6 


6 


5 


5 


2 


2 


2 



Note: BYG = bamyardgrass, CBG = crabgrass, FLP = fall panicum, GFT = giant foxtail, YFT = yellow foxtail, WCG = woolly cupgrass, SBR = sandbur, 
SHC = shattercane, VCN = volunteer com, and YNS = yellow nutsedge. 

Rating Scale: 

10 = 95 to 100 percent, 9 = 85 to 95 percent, 8 = 75 to 85 percent, 7 = 65 to 75 percent, 6 = 55 to 65 percent, and 5 = 45 to 55 percent. 



Table 13.7. Soybean Soil- 


-Applied 


Herbicides: 


Broadleaf Control 














Herbicide 


AMG 


CCB 


JMW 


LBQ 


BNS 


PGW 


CRW 


GRW 


SMW 


SFR 


VLV 


SBN 


Soil-applied "grass" 


























Command 





6 


8 


9 


6 


6 


8 


5 


8 


4 


9+ 


1 


Dual 








4 


6 


7+ 


8 


5 


2 


4 








1 


Lasso 








5 


7 


7+ 


9 


6 


2 


5 








1 


Prowl 


4 





2 


9 





9 


2 





4 





4 


1 


Sonalan 


4 





2 


9 


5 


9 


2 





4 





3 


2 


Trifluralin 


4 





2 


9 





9 


2 





4 





2 


1 


Soil-applied "broadleaf" 


























Canopy 


6 


9 


9 


9 


6 


9 


9 


7 


9 


8 


9 


2 


Lexone 


3 


6 


7 


9 


4 


9 


8 


6 


9 


7 


8 


2 


Lorox 


4 


6 


5 


9 


7 


9 


8 


6 


9 


6 


6 


2 


Lorox Plus 


6 


8 


7 


9 


7 


9 


9 


7 


9 


7 


7 


2 


Preview 


6 


8 


9 


9 


6 


9 


9 


7 


9 


8 


9 


2 


Pursuit 


6 


7 


8 


9 


8 


9 


7 


6 


9 


8 


8 


1 


Scepter 


6 


9 


8 


9 


8+ 


9 


9 


7 


9 


9 


7 


1 


Sencor 


3 


6 


7 


9 


4 


9 


8 


6 


9 


7 


8 


2 



Note: AMG = annual morningglory, CCB = cocklebur, JMW = jimsonweed, LBQ = lambsquarters, BNS = black nightshade, PGW = pigweed, 
CRW = common ragweed, GRW = giant ragweed, SMW = smartweed, SFR = wild sunflower, VLV = velvetleaf, and SBN = soybean tolerance. 

Rating Scale and Approximate Weed Control 

10 = 95 to 100 percent, 9 = 85 to 95 percent, 8 = 75 to 85 percent, 7 = 65 to 75 percent, and 6 = 55 to 65 percent. 

Weed control of 5 or less is rarely significant. 

For ratings for combinations (tank-mix and premix), see the component parts. 

Premix: "Grass" + "Grass" Premix: "Grass" + "Broadleaf" 



Cannon: 


Lasso 


+ Treflan 


Pursuit Plus: 


Prowl 


+ 


Pursuit 


Commence: 


Treflan 


+ Command 


Salute: 


Treflan 


+ 


Sencor 


Freedom: 


Lasso 


+ Treflan 


Squadron: 


Prowl 


+ 


Scepter 








Tri-Scept: 


Treflan 


+ 


Scepter 








Turbo: 


Dual 


+ 


Sencor 








Passport: 


Treflan 


+ 


Pursuit 



early preplant up to 30 days before planting soybeans. 
However, if applied with Dual, this is reduced to 14 
days and with Lasso, to 7 days. 

Prowl may be applied up to 60 days before planting 
soybeans. It should be incorporated if rainfall does 
not occur within 14 days. 

Sencor plus Lasso or Dual may be applied up to 
30 days before planting soybeans if applied as a split 
preplant and at-planting application. Turbo is a premix 
of Sencor and Dual. 



Pursuit, Pursuit Plus, Scepter, and Squadron can 

be applied up to 45 days before planting soybeans. 
However, if sufficient rain does not occur before plant- 
ing, then mechanical incorporation is required. 

Roundup or Poast can be also be used before 
planting soybeans. Roundup may be used preplant in 
soybeans to control small annual weeds. The rate is 
0.75 to 1 pint per acre in 5 to 20 gallons of water 
with the addition of a surfactant. Poast can be used 
at 0.5 pint per acre before planting soybeans to control 



104 



Table 13.8. Herbicide Tank-Mixes for PPI or PRE Use in Soybeans 



Herbicide 


Sencor or 
Lexone 


Canopy or 
Preview 


Scepter* 


Pursuit 


Command 




PPI 














Cannon 

Command 

Commence 

Freedom 

Salute 

Sonalan 

Treflan 


1 
1 
1 

1 

1 
1 


1 

1 
1 
1 

1 

1 


1 


1 


1 

1 
1 
1 

1 




PPI or Pre 














Dual 
Lasso 
Prowl 
Turbo 


1,2 
1,2 

1,2 
1,2 


1,2 
1,2 
1,2 


1,2 
1,2 
1,2 
1,2 


1,2 
1,2 
1,2 


1 
1 
1 
1 






Sencor + 
Scepter* 


Sencor + 
Command 


Command + 
Scepter* 


Lorox 
or Linex 


Lorox 
Plus 


Treflan 


PP7 Only 














Sonalan 
Treflan 


1 


1 

1 


1 


— 


1 
1 


— 


PPI or Pre 














Dual 

Lasso 
Prowl 


1,2 

1,2 
1,2 


1 

1 

1 


1 

1 
1 


2 

2 
2 


1,2 

1,2 
2 


1 
1 



Note: 1 = preplant incorporated, 2 = preemergence, and 
• Only in Scepter label's "southern use area." 



not registered. 



small annual grasses. Always add crop-oil concentrate 
or Dash with Poast. 

2,4-D application prior to planting soybeans is con- 
troversial. Poast labeling allows preplant application 
with 2,4-D LVE, but the label states, "Do not plant 
soybeans for 3 months after treatment or until the 
2,4-D LVE has disappeared from the soil." Canopy, 
Lorox Plus, Preview, Sencor, and Turbo labels allow 
tank-mixing with 2,4-D LVE when applied 30 days 
before planting soybeans. Yet, these labels allow twice 
the rate of 2,4-D as on the Poast label. A residue 
tolerance for 2,4-D in soybeans has not been estab- 
lished. There is no 2,4-D label allowing use in the spring 
prior to planting soybeans. The legality of these treat- 
ments as used is questionable. 

Butyrac 200 (2,4-DB) may be used alone or in 
combination with Roundup for preplant through pre- 
emergence for soybeans. For no-till or reduced- 
tillage systems, 2,4-DB can help to control such weeds 
as emerged annual morningglories, cocklebur, and 
"marestail' (horseweed). The application rate of Bu- 
tyrac 200 is 0.7 to 0.9 pint per acre when used alone 
or V2 to % pint with 1 to IV2 pints of Roundup plus 
nonionic surfactant. 

Soil-applied "grass" herbicides (soybeans) 

Treflan, Sonalan, and Command are soil-applied 
herbicides for grass control which require mechanical 
incorporation, while Prowl, Lasso, and Dual can be 
used preemergence or preplant incorporated. Incor- 
poration improves herbicide performance if rainfall is 
limited. For more information, see the section entitled 
"Herbicide incorporation." 



Treflan, Sonalan, and Prowl are dinitroaniline 
(DNA) herbicides which control annual grasses, pig- 
weed, and lambsquarters. Control of additional broad- 
leaf weeds requires combinations (see Tables 13.7 and 
13.8) or sequential treatments with other herbicides. 

Soybeans are sometimes injured by DNA herbicides. 
Symptoms are stunting, swollen hypocotyls, and short, 
swollen lateral roots. Usually, such injuries are not 
serious. If incorporation is too shallow or Prowl is 
used preemergence, soybean stems may be calloused 
and brittle, leading to lodging or stem breakage. 

DNA herbicides can sometimes carry over and injure 
rotational crops of corn or sorghum. Symptoms appear 
as reduced stands and stunted, purple plants with 
poor root systems. Under good growing conditions, 
corn typically recovers from this early season injury. 
Accurate, uniform incorporation is needed to minimize 
potential carryover. 

Treflan, Trilin, Tri-4, or Trifle (trifluralin) may be 
applied alone anytime in the spring prior to planting. 
However, tank-mixes may specify application closer 
to soybean planting. Incorporate trifluralin within 24 
hours after application or within 8 hours if the soil is 
warm and moist. The rate per acre is 1 to 2 pints of 
4E or equivalent rates of Pro-5, lOG, or Trific 60DF. 
A slightly higher rate and deeper incorporation may 
be specified for shattercane control. 

Sonalan 3E (ethalfluralin) may be applied at 1.5 to 
3 pints per acre within 3 weeks before planting and 
should be incorporated within 2 days after application. 
There is a greater risk of soybean injury from Sonalan 
than with trifluralin, so incorporation must be uniform. 



105 



Sonalan is less likely than trifluralin to carry over and 
injure com the following year. 

Prowl 4E (pendimethalin) may be applied at 1 to 
3 pints per acre up to 60 days (less for some tank- 
mixes) before planting soybeans. Preplant treatments 
should be incorporated within 7 days unless adequate 
rainfall occurs to incorporate the herbicide. South of 
Interstate 80, Prowl may be applied preemergence up 
to 2 days after planting. Do not use Prowl preemergence 
north of Interstate 80. 

Command 4E (clomazone) is used at 1.5 to 2 pints 
per acre to control annual grasses, velvetleaf, and 
several other broadleaved weeds. Use the higher rate 
if Command is applied more than 30 days prior to 
planting. Command is also used at lower rates in some 
tank-mixes for velvetleaf control (see Table 13.10). 
Commence 5.25L is a premix of Command and Treflan 
used at 1.75 to 2.67 pints per acre. 

Incorporate Command or Commence immediately 
if the soil is moist or within 8 hours after application 
if the soil is dry. You must minimize drift (spray or 
vapor) to sensitive plants. Avoid applying within 100 
feet of trees, ornamentals, vegetables, alfalfa, or small 
grains or within 1,000 feet of subdivisions or towns, 
nurseries, greenhouses, and commercial fruit or veg- 
etable (except sweet com) production areas. 

Minimum recropping intervals are 9 months for field 
corn or sorghum and 12 months for wheat. See Table 
13.9 or the label for more information. Carryover 
injury will appear as whitened or bleached plants after 
emergence. Com has usually outgrown modest injury 
v^th little effect on yield. However, injury may be 
severe if application or incorporation is not uniform. 
Com hybrids vary in tolerance to clomazone. 

Dual (metolachlor) and Lasso (alachlor) can be 
apphed preplant or preemergence to control annual 
grasses and pigweed. Use the higher rates to improve 
black nightshade control and incorporate to improve 
yellow nutsedge control. They can be combined with 
other herbicides to improve broadleaf control (see 
Tables 13.7 and 13.8). Dual can be applied up to 30 



days prior to planting soybeans. The rate per acre is 
1.5 to 3 pints of 8E or 6 to 12 pounds of 25G. Lasso 
can be applied up to 7 days prior to planting soybeans. 
The rate per acre is 2 to 4 quarts of 4E or 4L (Micro 
Tech), or 16 to 26 pounds of 15G. Arena, Judge, Stall, 
Saddle, and Confidence are private brands of alachlor 
All herbicides containing alachlor are restricted-use pes- 
ticides. 

Cannon and Freedom are premixes of alachlor 
(Lasso) and trifluralin (Treflan). They control the same 
weeds as Lasso (see Tables 13.6 and 13.7), but require 
incorporation within 24 hours because of the trifluralin. 
Cannon 3E is for darker, heavier soils at a rate of 3 to 
5 quarts per acre. Freedom 3E is for lighter soils such 
as occur in southern Illinois, and the rate is 2.75 to 
4.5 quarts per acre. Cannon and Freedom are restricted- 
use pesticides. 

Soil-applied "broadleaf" herbicides (soybeans) 

Canopy, Command, Lexone, Lorox, Lorox Plus, Pre- 
view, Pursuit, Scepter, and Sencor are soil-applied 
herbicides used for broadleaf weed control in soybeans. 
Lorox is not to be incorporated and Command must 
be incorporated (Command is discussed in the "grass" 
herbicide section). The others can be used preplant 
incorporated or preemergence after planting soybeans. 

Timely rainfall or incorporation is needed for uni- 
form herbicide placement in the soil. Incorporation 
may improve control of deep-germinating (large-seeded) 
weeds especially when soil moisture is limited. Ac- 
curate and uniform application and incorporation are 
essential to minimize potential soybean injury. Except 
for Command, these herbicides are photosynthetic 
inhibitors (PSI), meristematic inhibitors (MSI), or pre- 
mixes of MSI (chlorimuron) and PSIs (metribuzin or 
linuron). 

Photosynthetic inhibitors (PSI) 

Metribuzin (Sencor or Lexone) and linuron (Lorox 
or Linex) are photosynthetic inhibitors (PSI). Preview, 



Table 13.9. Soybean 


Herbicides and 


Crop Rotation Restrictions 












Herbicide 


pH 


FC 


SC 




GS 


WT 


OT 


RY 


ALF 


CLO 








-—Months 


after 


application before 


planting rotationa 


/ rTHTI 








I tfUU 






Canopy 


<6.8 


10 


18 




12 


4 


18 


18 


10 


12 


Classic 


- 


9 


*• 




9 


3 


3 


3 


9 


9 


Command 


— 


9 


9-12 




9 


12 


16 


16 


16 


16 


Commence 


- 


9 


9 




9 


12 


16 


16 


16 


16 


Lorox Plus 


<6.8 


10 


18 




10 


4 


4 


4 


** 


12 


Preview 


<6.8 


10 


18 




12 


4 


18 


18 


10 


12 


Reflex 


- 


10 


10 




18 


4 


4 


4 


18 


18 


Pursuit## 


— 


9.5 


18 




18 


4 


18 


18 


18 


18 


Scepter (northern area) 


- 


11* 


18 




11 


4 


4 


18 


18 


18 


(Vs pint/ A post) 






















Scepter (northern area)# 


— 


18 


18 




11 


16 


16 


16 


18 


18 


(Vs pint/ A) 






















Scepter (southern area)# 


— 


11* 


18 




11 


4* 


11 


18 


18 


18 



Note: pH = soil pH restrictions, FC = field com, SC = seed com, GS = grain sorghum, WT = wheat, OT = oats, RY = rye, ALF = alfalfa, and CLO = clover. 

# Applies also to Squadron and Tri-Scept. 
## Apphes also to Pursuit Plus and Passport. 

* 15 inch rainfall restriction. 
•• Bioassay after 9 months. 



106 



Salute, and Canopy are premixes which contain me- 
tribuzin while Lorox Plus is a premix which contains 
linuron. These PSI herbicides can cause soybean injury 
from fohar or soil uptake, so do not apply them after 
soybeans emerge. 

PSI herbicide injury symptoms are yellowing (chlo- 
rosis) and dying of lower soybean leaves, usually 
appearing about the first trifoliolate stage. Atrazine 
and simazine carryover can intensify these symptoms. 
Soybeans usually recover from moderate PSI injury 
that occurs early. Metribuzin injury may be greater on 
soils with pH over 7.5. Soybean varieties differ in their 
sensitivity to metribuzin. 

Sencor or Lexone (metribuzin) may be applied 
anytime within 14 days before planting soybeans. The 
Sencor or Lexone rate per acre used in tank-mixes is 
V2 to 1 pint of 4L or Va to % pound of 75DF. Accurately 
adjust the rates according to soil texture and organic 
matter content. Do not apply to sandy soil that is low 
in organic matter Reduced rates minimize soybean 
injury but lessen weed control. Spht preplant and 
preemergence applications allow higher rates to im- 
prove weed control. Sencor or Lexone can control 
several annual broadleaves (see Table 13.7) and can 
be tank-mixed with many herbicides to broaden the 
spectrum of control (see Table 13.8). 

Turbo 8E, a premix of metribuzin (Sencor) plus 
metolachlor (Dual), can be applied preplant incorpo- 
rated or preemergence. The rate per acre is 1.5 to 3.5 
pints. 

Salute 4E, a premix of metribuzin (Sencor) plus 
trifluralin (Treflan), is applied preplant at 1.5 to 3 pints 
per acre and must be incorporated within 24 hours. 

Preview 75DF and Canopy 75DF are premixes of 
metribuzin (Lexone) and chlorimuron (Classic) while 
Lorox Plus 60DF is a premix of linuron (Lorox, see 
next entry) and chlorimuron (Classic). These premixes 
may be applied preemergence or preplant incorporated. 
They control cocklebur, velvetleaf, and wild sunflower 
better than metribuzin or linuron alone (see Table 
13.7). Combinations with the grass herbicides can 
improve grass control (see Tables 13.6 and 13.8). 
Preview and Canopy contain significant amounts of 
chlorimuron (Classic) as well as metribuzin, so they 
can provide some burndown of small weeds as well 
as residual control for minimum tillage systems. 

Broadcast rates per acre are 6 to 10 ounces of Preview 
75DF, 4 to 7 ounces of Canopy 75DF, and 12 to 18 
ounces of Lorox Plus 60DF. Do not apply Preview, 
Canopy, or Lorox Plus to soils with pH greater than 6.8. 
High soil pH may occur in localized areas in a field. 
Correct rate selection for the soil plus uniform, accurate 
application and incorporation are essential to minimize 
soybean injury and potential follow crop injury. See 
PSI injury symptoms (above) and MSI injury symptoms 
(next column). 

Minimum recropping intervals for Preview, Canopy, 
and Lorox Plus are 4 months for wheat and 10 months 
for field corn. If Classic, Pursuit, or Scepter is applied 
the same year as Preview, Canopy, or Lorox Plus, the 



risk of carryover can increase so labels should be 
checked carefully for rotational guidelines. 

Lorox or Linex (linuron) is used after planting 
soybeans and before the crop emerges. Lorox is best 
suited to the silt loam soils of southern Illinois that 
contain 1 to 3 percent organic matter where the rate 
per acre is 1 to 1% pounds of 50DF or 1 to 1% pints 
of 4L per acre. Do not apply to very sandy soils or soils 
containing less than 0.5 percent organic matter. 

Command (clomazone) is often used as a broadleaf 
herbicide in tank-mixes, but it also controls annual 
grasses. Command is a pigment inhibitor and not a 
true photosynthesis inhibitor. See discussion under 
soil-applied "grass" herbicides. 

Meristematic inhibitors (MSI) 

Imazethapyr (Pursuit), imazaquin (Scepter), and 
chlorimuron (in Canopy, Preview, and Lorox Plus; see 
above) are meristematic inhibitors (MSI). 

MSI herbicide injury symptoms include temporary 
yellowing of upper leaves (golden tops) and shortened 
internodes of soybeans. Although plants may be 
stunted, yield is generally not affected. These MSI 
herbicides may carry over and injure certain sensitive 
follow crops. Symptoms on corn or grain sorghum are 
stunted growth, inhibited roots, and interveinal chlo- 
rosis or purpling of leaves. Symptoms on small grains 
are stunted top growth and excess tillering. 

Pursuit 2E (imazethapyr) is used at 4 fluid ounces 
per acre (1 gallon per 32 acres) to control broadleaved 
weeds, (see Table 13.7). Velvetleaf and jimsonweed 
control are more consistent with incorporation. Grass 
control is improved by tank-mixing Pursuit with a 
grass herbicide (see Table 13.8). Pursuit Plus and 
Passport are both premixes of Pursuit and Prowl or 
trifluralin, respectively. Both are used at 2.5 pints per 
acre, which is equivalent to 0.25 pint of Pursuit, 1.75 
pint of Prowl, or 1.5 pints of trifluralin, respectively. 

Pursuit and Pursuit Plus can be applied up to 45 
days prior to planting soybeans. If sufficient rain does 
not occur before planting, then mechanically incor- 
porate. South of Interstate 80, Pursuit Plus can be 
surface-applied up to 2 days after soybean planting. 
Do not apply Pursuit Plus after soybean planting north 
of Interstate 80. Minimum recropping intervals for 
Pursuit, Pursuit Plus, and Passport are 4 months for 
wheat, 9.5 months for field corn, and 18 months for 
grain sorghum. Pursuit has less potential than Scepter 
to injure corn the next season on high organic matter 
soils, and it provides better control of velvetleaf. Thus, 
Pursuit is more adapted than Scepter to most soils of 
central and northern Illinois. 

Scepter (imazaquin) is used at % pint 1.5E or 2.8 
ounces of 70DG per acre and is applied within 45 
days (less with many tank-mixes) before planting or 
immediately after planting. Scepter controls many 
broadleaf weeds such as pigweed and cocklebur (see 
Table 13.7) with adequate soil moisture, but it is 
somewhat weak on velvetleaf. Incorporation can 



107 



improve weed control under low-rainfall conditions, 
and nnay improve control of velvetleaf and giant 
ragweed. Grass control is improved by mixing with 
"grass" herbicides (see Table 13.8). 

Squadron and Tri-Scept are premixes of imazaquin 
(Scepter) plus pendimethalin (Prowl), or trifluralin, 
respectively. The rate per acre is 3 pints of Squadron 
or 2.33 pints of Tri-Scept. This is the equivalent of % 
pint of Scepter plus 1.5 pints of Prowl or 1.5 pints of 
trifluralin per acre. Incorporate Squadron within 7 
days unless sufficient rain occurs. Tri-Scept must be 
incorporated within 24 hours. 

A line across Peoria, extending west along Illinois 
Route 116 and east along U.S. Route 24, presently 
delineates Scepter, Squadron, or Tri-Scept rotational 
crop restrictions (see Table 13.9). 

There have been significant problems with carryover 
of Scepter and related premixes and tank-mixes in 
Illinois. Soil and climatic conditions plus lack of uni- 
formity in application and incorporation are associated 
with the carryover problem. The potential for carryover 
is greater on soils with high organic matter and low 
pH. Research and field results indicate that in Illinois, 
Scepter, Squadron, and Tri-Scept are best adapted to the 
soils and weeds south of Interstate 70. Reduced rates, 
which can reduce potential carryover, are allowed for 
postemergence use of Scepter and in tank-mixes with 
several other products. 

Postemergence herbicides (soybeans) 

Postemergence (foliar) herbicides are more effective 
when used in a planned program so that application 
is timely and not just an emergency or rescue treatment. 
Foliar treatments allow the user to identify the problem 
weed species and choose the most effective herbicide. 
Climatic conditions greatly affect foliar herbicides as 
penetration and action are usually greater with warm 
temperatures and high relative humidity. Rainfall soon 
after application can cause poor weed control. Weeds 
growing under droughty conditions are more difficult 
to control. 

Rates and timing for foliar treatments are based on 
weed size. Early application when weeds are young 
and tender may allow the use of lower herbicide rates. 
Treatment of oversized weeds may only suppress 
growth temporarily and regrowth may occur. A cul- 
tivation 7 to 14 days after application but before 
regrowth can often improve weed control. However, 
cultivation during or within 7 days of a foliar appli- 
cation may cause erratic weed control. 

Crop-oil concentrates (COC) or nonionic surfactants 
(NIS) are usually added to the spray mixture to improve 
effectiveness of postemergence soybean herbicides. 
Dash is a special surfactant primarily for use with 
Poast. Fertilizer adjuvants such as 28-0-0 (UAN) or 
10-34-0 may be specified on the label to increase 
control of certain weed species, such as velvetleaf. Do 
not use brass or aluminum nozzles with fertilizer adju- 
vants. All fertilizer adjuvants should be rinsed from the 
tank before final cleanup with chlorine bleach. 



Postemergence herbicides for soybeans are either 
contact or translocated in action. Contact herbicides 
affect only the leaf tissue covered by the spray, so 
thorough spray coverage is critical. Contact herbicides 
should be applied to small weeds. Injury symptoms 
are usually noticeable within a day. Translocated her- 
bicides do not require complete spray coverage as they 
move to the growing points (meristems) after foliar 
penetration. Their action is slow and symptoms may 
not appear for about a week. 

Contact broadleaf herbicides (soybeans) 

Basagran, Blazer, Reflex, Cobra, Galaxy, and Storm 
are contact broadleaf herbicides. See Table 13.10 for 
weeds controlled. Spray volumes for ground applica- 
tion are 20 to 30 gallons per acre and spray pressure 
should be 40 to 60 psi. Hollow cone or flat-fan nozzles 
provide much better coverage than flood nozzles. 

Low temperatures and humidity will reduce contact 
activity. Soybean leaves may show contact burn under 
conditions of high temperature and humidity. This leaf 
burn is intensified by crop-oil concentrate or Dash. 
Soybeans usually recover within 2 to 3 weeks after 
application. A rain-free period of several hours is 
required for most effective control with most contact 
herbicides. 

Smaller weeds that are actively growing may allow 
the use of reduced herbicide rates. Most contact her- 
bicides have little soil residual activity, so do not apply 
too early. Apply 2 to 3 weeks after soybean emergence 
or when soybeans are in the 1- to 2-trifoliolate stage. 
Larger weeds not only require increased rates, but the 
weeds may recover and regrow. Contact herbicides 
should not be applied after soybeans begin to bloom. 
Preharvest intervals are generally 50 to 90 days. 

Basagran (bentazon) is used at 1 to 2 pints per acre. 
See the label for specifics on weed sizes and rates. 
Most weeds should be small (1 to 3 inches) and actively 
growing. Basagran controls cocklebur, smartweed, jim- 
sonweed, and velvetleaf. Velvetleaf control is improved 
if 28-0-0 (UAN) is added to the spray mixture. Crop- 
oil concentrate is preferred if the major weed species 
are common ragweed or lambsquarters. Split appli- 
cations can improve control of lambsquarters, giant 
ragweed, wild sunflower, and yellow nutsedge. Adding 
2,4-DB can improve annual morningglory control. Do 
not spray if rain is expected within 8 hours. 

Blazer (acifluorfen) is used at 1 to 3 pints per acre 
when broadleaf weeds are 2 to 4 inches tall and 
actively growing. See the label for specifics on adju- 
vants and weed sizes. Weeds controlled include pig- 
weed, annual morningglory, jimsonweed, and black 
nightshade. Velvetleaf control is improved with the 
use of fertilizer adjuvants or the addition of Basagran. 
Adding 2,4-DB can improve cocklebur and morning- 
glory control. Blazer may cause soybean leaf burn, 
especially if applied with crop-oil concentrate instead 
of surfactant or fertihzer adjuvants. However, the crop 
usually recovers within 2 to 3 weeks. Do not spray if 
rain is expected within 4 to 6 hours. 



108 



Table 13.10. Soybean Postemergence Herbicides: Broadleaf Weed Control 



Herbicide 


AMG < 


2CB 


JMW 


LBQ 


BNS 


PGW 


CRW 


GRW 


BMW 


SFR 


PSI 


VLV 


SBN 


Contact postemergence broadleaf 


























Basagran 


4 


9+ 


9 


6 


3 


4 


7 


8 


9 


8 


8 


8+ 





Blazer 


8 


7 


9 


5 


8 


9+ 


9 


8 


9 


7 


2 


6 


2 


Galaxy 


6 


9 


9 


6 


6 


9 


8 


8 


9 


8 


7 


8+ 


1 


Storm 


7 


8+ 


9 


5 


7 


9 


9 


8 


9 


8 


6 


8 


1 + 


Cobra 


7 


8+ 


9 


4 


8 


9+ 


9 


8 


6 


8 


6 


7 


3 


Reflex 


7 


7 


9 


5 


7 


9 


8 


7 


7 


7 


2 


6 


1 


Systemic postemergence broadlea] 


r 
























Classic 


7 


9+ 


8+ 


2 





9 


8 


7 


8 


9 


4 


8 


1 + 


Pinnacle 


4 


6 


4 


8+ 





8+ 


4 


4 


8 


6 


4 


8+ 


2 


Classic and Pinnacle 


6 


9+ 


8+ 


8+ 





9 


6 


5 


8 


8 


4 


8+ 


2 


Pursuit 


7 


8+ 


7 


4 


8 


9 


6 


8 


8 


9 


6 


8+ 


1 


Scepter 


2 


9+ 


4 


3 


5 


10 


6 


3 


6 


7 


2 


3 


1 


Rescue 


7 


8 


4 


4 


3 


4 


3 


7 


5 


6 


2 


3 


4 



Note: AMG = annual momingglory, CCB = cocklebur, JMW = jimsonweed, LBQ = lambsquarters, BNS = black nightshade, PGW = pigweed, CRW = common 
ragweed, GRW = giant ragweed, SMW = smartweed, SFR = wild sunflower, PSI = prickly sida, VLV = velvetleaf, and SBN = soybean response. 

Rating Scale: 

10 = 95 to 100 percent, 9 = 85 to 95 percent, 8 = 75 to 85 percent, 7 = 65 to 75 percent, 6 = 55 to 65 percent, and 5 = 45 to 55 percent. 



Basagran plus Blazer improves control of pigweed 
and momingglory over Basagran alone and of vel- 
vetleaf and cocklebur over Blazer alone. Rates vary 
depending upon weed species and size. Fertilizer ad- 
juvants can improve velvetleaf control. Storm 4S and 
Galaxy 3.67S are premixes of Basagran and Blazer. 
Storm at 1.5 pints per acre is equivalent to 1 pint of 
Basagran plus 1 pint of Blazer. Galaxy at 2 pints per 
acre is equivalent to 1.5 pints of Basagran plus 0.67 
pint of Blazer. See the labels for adjuvant specifics. 

Cobra 2E (lactofen) is applied at 12.5 fluid ounces 
per acre v^th crop-oil concentrate (COG) at 0.5 to 1 
pint per acre. One gallon per acre of 28-0-0 (UAN) 
may be substituted for COG under favorable growing 
conditions. Weeds controlled include cocklebur, pig- 
weed, jimsonweed, common ragweed, and velvetleaf. 
Cobra usually causes soybean leaf bum, but soybeans 
usually recover within 2 to 3 weeks. Cobra can be 
tank-mixed wdth Basagran, Classic, Scepter, or 2,4-DB. 
Apply Cobra only once during the season and no later 
than 90 days before harvest. Do not apply if rain is 
expected within 30 minutes. 

Reflex 2LC (fomesafen) is used at 0.75 to 1 pint 
per acre north of Interstate 70 and at 1.25 pints south 
of Interstate 70. Add either crop-oil concentrate at 1 
gallon or nonionic surfactant at 1 to 2 quarts per 100 
gallons of spray. Reflex controls pigweed, black night- 
shade, jimsonweed, smartweed, and common ragweed 
up to the 4-leaf stage. Reflex can be tank-mixed with 
Basagran, Classic, or Scepter to broaden the spectrum 
of control. Do not spray if rain is expected within 4 
hours of application. Do not apply Reflex after the first- 
bloom stage. There is a potential for carryover, so be 
sure that applications are accurate and even. Recrop 
intervals are 4 months for small grains, 10 months for 
com, and 18 months for other crops. 

Translocated herbicides for control of broadleaf weeds 
(soybeans) 

Classic, Pinnacle, Pursuit, and Scepter are translo- 
cated herbicides which primarily control broadleaf 



weeds in soybeans. See Table 13.10 for weeds con- 
trolled. All four have the same mode of action and 
some soil residual activity. Weeds should be actively 
growing (not moisture- or temperature-stressed). Do 
not make applications when weeds are in the cotyledon 
(very early seedling) stage. Annual weeds are best 
controlled when less than 3 to 5 inches tall (within 2 
to 4 weeks after soybean emergence). A one-hour rain- 
free period is usually adequate for these herbicides. 

These herbicides inhibit growth of new meristems 
so symptoms of weed injury may not be exhibited for 
3 to 7 days. Injury symptoms are yellowing of leaves 
followed by death of the growing point. Death of leaf 
tissue in susceptible weeds is usually observed in 7 to 
21 days. Less susceptible plants may be suppressed, 
remaining green or yellow but stunted for 2 to 3 
weeks. 

Soybeans may show temporary leaf yellowing (golden 
tops) and/or growth retardation (stunting), especially 
if the soybeans are under stress. Under favorable 
conditions, affected soybeans may recover with only 
a shght reduction in height and no loss of yield. 

Total spray coverage is not critical for translocated 
herbicides. A minimum spray volume of 10 gallons 
per acre may be used for ground application using 
flat-fan nozzles at 20 to 40 psi or hollow cone nozzles 
at 40 to 60 psi. Nonionic surfactants (NIS) are usually 
specified at 1 to 2 pints per 100 gallons of spray. Crop- 
oil concentrate (COC) may improve weed control but 
may increase crop injury. Fertilizer additives (28-0-0 
or 10-34-0) improve control of some weeds and are 
specified for velvetleaf control on the Classic, Pinnacle, 
and Pursuit labels. Tank-mixing these herbicides with 
postemergence herbicides for grass may reduce grass 
control, so sequential applications are often specified. 
(Table 13.11) 

Classic 25DF (chlorimuron) is used at 0.5 to 0.75 
ounce per acre plus 1 quart of surfactant or 1 gallon 
of crop-oil concentrate per 100 gallons. Fertilizer ad- 
juvants improve velvetleaf control. Classic can control 
cocklebur, jimsonweed, wild sunflower, and yellow 



109 



Table 13.11. Postemergence Herbicide Tank-Mixes for Soybeans 



Basagran 



Blazer 



Reflex 



Cobra 



Classic 



Registered for broadleaf weed control in soybeans 

Basagran - 

Classic X 

Scepter X 

Pinnacle X 

Rescue - 

2,4-DB X 



Registered for grass 

Assure 

Fusilade 

Option 

Poast Plus 

Pursuit 



broadleaf weed control in soybeans* 
X 
X 
X 
X 
X 



Note: X = registered and - = not registered. 

• Check labels for special instructions. Sequential application may be preferable. 



nutsedge. Pigweed control varies with rate and species. 
Check the label for weed sizes and rates. Split apph- 
cations can improve control of burcucumber, giant 
ragweed, and annual morningglory. Do not apply 
Classic within 60 days of harvest. Recrop intervals are 
3 months for small grains and 9 months for field corn, 
sorghum, alfalfa, or clover. If Classic is applied after 
Preview, Canopy, Lorox Plus, Pursuit, or Scepter, check 
the label for recrop intervals as carryover injury to 
corn can occur, especially if soil pH is above 6.8. Corn 
will appear stunted with interveinal chlorosis or pur- 
pling of leaves and inhibition of roots. 

Pinnacle 25DF (thifensulfuron) is used at 0.25 
ounce per acre to control lambsquarters, pigweed, 
smartweed, and velvetleaf. The addition of 1 gallon 
of UAN (28-0-0) per acre improves velvetleaf control. 
Tank-mixing with 0.25 ounce of Classic 25DF per acre 
with Pinnacle can improve control of cocklebur, jim- 
sonweed, and wild sunflower. Add nonionic surfactant 
at 1 pint per 100 gallons. Do not use crop-oil concentrate. 
Pinnacle has less persistence than Classic. Any crop 
may be planted 45 days after application of Pinnacle 
alone. Classic recropping intervals apply only for the 
tank-mix. 

Pursuit 2E (imazethapyr) is used at 0.25 pint per 
acre plus surfactant at 1 quart per 100 gallons of spray. 
Add 1 quart per acre of 28-0-0 or 10-34-0. Most 
broadleaf weeds should be less than 3 inches tall, but 
cocklebur and pigweed may be controlled up to 8 
inches tall. Lambsquarters, common ragweed, and 
annual morningglory control may be poor. It may also 
provide some control of foxtails and shattercane but 
not volunteer corn. Do not apply Pursuit within 85 
days of soybean harvest. Recropping intervals are 4 
months after application for wheat, 9.5 months for 
field corn, and 18 months for other field crops including 
grain sorghum. See Table 13.9. Do not apply products 
containing chlorimuron or imazaquin the same year 
as Pursuit since such combinations increase the po- 
tential for injury to subsequent crops. 

Scepter (imazaquin) can be used postemergence to 
control pigweed, cocklebur, wild sunflower, and vol- 
unteer corn in soybeans. The low rate is Vs pint of 



1.5E or 1.4 ounces of 70DG. A higher rate is labeled, 
but rotational guidelines change. Scepter is better on 
cocklebur and volunteer corn than Pursuit, but Pursuit 
is better on velvetleaf and shattercane. Use a nonionic 
surfactant at 1 quart per 100 gallons. Do not apply 
Scepter within 90 days of soybean harvest. Follow 
rotational guidelines on the Scepter label or see Table 
13.9. Also see the recrop discussion on Scepter in the 
section on "Soil-applied 'broadleaf herbicides (soy- 
beans)." 

Rescue (naptalam plus 2,4-DB), a premix of two 
translocated herbicides, is used at 2 to 3 quarts per 
acre for midseason control of cocklebur, giant ragweed, 
and wild sunflower. Apply after soybeans are 14 inches 
tall or after first bloom. Rescue can be tank-mixed 
with Blazer to control more weeds and provide faster 
action on the weeds. Add crop-oil concentrate or 
surfactant at the manufacturer's recommended rate. 
Effectiveness may be reduced if rain occurs within 6 
hours. Crop injury often occurs as leaf twisting and 
drooping tops. Do not apply Rescue to soybeans under 
stress from drought, disease, or injury from another 
herbicide. Do not apply Rescue within 60 days of 
harvest. 

Translocated herbicides for control of grass weeds 

Poast, Assure, Fusilade, and Option can control 
many annual and perennial grasses in soybeans (see 
Table 13.12). Pursuit also has some postemergence 
grass control. Grasses should be actively growing (not 
stressed or injured) and not tillering or forming seed- 
heads. Cultivation within 5 to 7 days before or after 
application may decrease grass control. Addition of 
crop-oil concentrate is usually specified, especially if 
the weeds are somewhat droughty or label limitations 
on weed size are approached. 

Rates vary by weed size and species, so consult the 
label before applying. Rate reductions may be optional 
on small weeds while rate increases may be needed 
for larger weeds. Crabgrass, field sandbur, and barn- 
yardgrass control vary with herbicide and size. Control 
of johnsongrass and quackgrass often requires foUow- 



110 



Table 13.12. Soybean Postemergence Herbicides and Their Grass Control 



Herbicide 


BYG 


CBG 


FLP 


GFT 


YFT 


WCG 


SBR 


SHC 


VCN 


VCL 


JHG 


QKG 


WSM 


Assure 


8+ 


9 


9+ 


9+ 


9 


9 


9 


10 


10 


9 


9 


9 


9 


Fusilade 


8+ 


8 


8 


9 


8 


9 


9 


10 


10 


9 


9 


9 


9 


Option 


8 


7 


8+ 


8+ 


8 


8 


8 


9 


10 


6 


8 





8 


Poast Plus 


9 


8 


9+ 


9+ 


9 


9 


7 


8 


8 


7 


7 


7+ 


8 


Pursuit 


6 


7 


7 


7+ 


6 


5 


4 


7 


4 


3 


3 





2 



Note: Annual grasses are BYG = bamyardgrass, CBG = crabgrass, FLP = fall panicum, GFT = giant foxtail, YFT = yellow foxtail, WCG = woolly cupgrass, 
SBR = sandbur, SHC = shattercane, VCN = volunteer corn, and VCL = volunteer cereal (wheat, oats, rye). 
Perennial grasses are JHG = johnsongrass, QKG = quackgrass, and WSM = wirestem muhly. 

Rating Scale: 

10 = 95 to 100 percent, 9 = 85 to 95 percent, 8 = 75 to 85 percent, 7 = 65 to 75 percent, 6 = 55 to 65 percent, and 5 = 45 to 55 percent. 



up applications for control of regrowth. Volunteer ce- 
reals such as wheat and rye can be controlled by 
Assure, Fusilade, or Poast if the plants have not tillered 
or overv^intered. 

Specified spray volume per acre is 10 to 20 gallons 
for ground application or 3 to 5 gallons for aerial 
application. A one-hour rain-free period after appli- 
cation is needed. Avoid drift to sensitive crops such 
as corn, sorghum, or wheat. Apply before bloom stage 
of soybeans and at least 80 to 90 days before harvest. 

These herbicides do not control broadleaved weeds. 
Most labels allow tank-mixing with certain broadleaf 
herbicides, but limitations are made as to rate, timing, 
and spray coverage. Check the label before applying 
grass and broadleaf herbicide tank-mixes or sequences as 
control of grass weeds may be reduced. 

Poast 1.5E (sethoxydim) is used at 1 pint per acre 
to control most annual grasses including foxtails, fall 
panicum, volunteer corn, or shattercane. See label for 
w^eed sizes and special rates for smaller or larger weeds. 
Fertilizer adjuvants are specified for control of vol- 
unteer corn and shattercane. Always add 2 pints per 
acre of Dash or crop-oil concentrate. Poast Plus IE 
has extra additives to improve performance. The rate 
is 1.5 pints instead of 1 pint per acre to compensate 
for the change of active ingredients. Poast or Poast 
Plus can be tank-mixed with Basagran and/or Blazer. 
See the label for more information on rates and weed 
sizes. See the "Problem perennial weeds" section for 
control of perennial grasses. 

Assure 0.8E (quizalofop) is used at 14 fluid ounces 
per acre to control foxtails and fall panicum. Use 10 
fluid ounces per acre to control volunteer corn or 
shattercane. Refer to the label for weed sizes. Add 
either 1 gallon of crop-oil concentrate or 2 quarts of 
nonionic surfactant per 100 gallons of spray. Assure 
can be tank-mixed with Basagran or Classic. Refer to 
the label for rates and weed sizes. See the "Problem 
perennial weeds" section for perennial grass control. 

Fusilade 2000 IE (fluazifop) is applied at 1.5 pints 
per acre to control giant foxtail and other annual 
grasses. Use 0.75 pint per acre for volunteer corn or 
shattercane. Refer to the label for weed sizes and rates. 
Add either 1 gallon of crop-oil concentrate or 1 quart 
of nonionic surfactant per 100 gallons of spray. Fusilade 
can be tank-mixed with Reflex, Basagran, or Blazer. 
See the label for rates and weed sizes. See the "Problem 



perennial weeds" section for control of perennial 
grasses. 

Option IE (fenoxaprop) is used at 0.8 pint per acre 
to control giant foxtail, volunteer corn, or shattercane. 
Use 1.2 pints per acre for fall panicum or bamyardgrass 
control. Crop-oil concentrate is required for yellow 
foxtail and crabgrass but is optional for shattercane. 
See the "Problem perennial weeds" section for control 
of perennial grasses. Option can be tank-mixed with 
Basagran or Blazer. See the label for instructions. 

Roundup (glyphosate) may be applied through rope- 
wick applicators to control volunteer corn, shattercane, 
and johnsongrass. Hemp dogbane and common milk- 
weed may also be suppressed. Weeds should be at 
least 6 inches taller than the soybeans to avoid contact 
with the crop. Adjust the height of the rope-wick 
apphcator so that the wiper contact is at least 2 inches 
above the soybean plants. Mix 1 gallon of Roundup 
with 2 gallons of water for rope-wick applicators. Spot 
treatment can be made on a spray-to-wet basis using 
a 2 percent solution of Roundup in water. Motorized 
spot treatment may provide less complete spray cov- 
erage of weeds, so use a 5 percent solution of Roundup. 
Minimize spray contact with the soybeans. 

Soybean harvest aid 

Gramoxone Extra (paraquat) may be used for drying 
weeds in soybeans just before harvest. For indeter- 
minate varieties (most of the varieties planted in Illi- 
nois), apply when 65 percent of the seed pods have 
reached a mature brown color or when seed moisture 
is 30 percent or less. For determinate varieties, apply 
when at least one-half of the leaves have dropped 
and the rest of the leaves are turning yellow. 

The rate is 12.8 ounces of Gramoxone Extra 2.5S. 
The total spray volume per acre is 2 to 5 gallons for 
aerial application and 20 to 40 gallons for ground 
application. Add 1 quart of nonionic surfactant per 
100 gallons of spray. Do not pasture livestock within 
15 days of treatment, and remove livestock from 
treated fields at least 30 days before slaughter. Gra- 
moxone is a restricted-use pesticide. 

Problem perennial weeds 

Perennial weeds are on the increase throughout most 
of Illinois because of reduced tillage, less crop rotation, 
and reduced competition from annual weeds. 



111 



Perennial weeds are often found in dense localized 
infestations or lightly scattered within fields. Even 
small populations, however, can cause reductions in 
crop yield, grain quality, and harvesting efficiency and 
can develop into very serious infestations if left un- 
treated. 

Control of most perennials is often difficult. This is 
mostly due to the fact that perennials reproduce both 
by vegetative propagation and by seed. Light tillage, 
such as the use of a chisel plow or field cultivator, 
may drag root sections about the field where new 
shoots emerge and the problem spreads. If tillage is 
to be beneficial, root sections displaced by tillage must 
be exposed to the freeze-thaw cycle of winter weather 
or left on the soil surface to desiccate. Repeated 
mowings, where possible, or row cultivation can de- 
plete food reserves these plants store in the roots. 

Effective control of perennial weeds will often rely 
on a combination of mechanical control methods and 
the use of translocated (systemic) herbicides. Tillage 
and herbicide applications used in combination will 
weaken the vegetative regeneration of plant parts and 
suppress seedling development. Since no program is 
completely effective, elimination of perennial weeds 
from a single location may take years of treatment. 
When using systemic herbicides, control of perennials 
is often more effective when low dosage, multiple 
treatments are applied. This results in better movement 
of the herbicide into the roots and a more complete 
kill of perennial plant parts. Contact herbicides, which 
do not move within the plant, will not be effective in 
preventing regrowth from plant roots. 



Table 13.13 lists common herbicides that are rec- 
ommended for control or suppression of many per- 
ennial weeds. Although not indicated in this table, it 
should be emphasized that isolation of an infested 
area is often necessary to effectively treat perennial 
weeds. This can be done by rotating the affected field 
to small grains or forage legumes, government set- 
aside, or to a crop for which herbicides or mecharucal 
controls can be used. 

With any perennial weed infestation, if the affected 
area is small enough or if plants are lightly scattered 
through a field, spot treatment with a 2 percent solution 
of Roundup (3 ounces in 1 gallon) in a hand-held 
sprayer is highly effective. Although Roundup is non- 
selective and must be kept from contacting desirable 
vegetation, it can be applied to perennial weeds almost 
any time they are actively growing and have sufficient 
foliage to absorb and translocate the herbicide. 

Roundup can also be used in rope-wick applicators 
and applied to weeds that exceed the height of the 
crop by 6 inches or more. For wick applicators, dilute 
1 gallon of Roundup in 2 gallons of water. Do not till 
the soil for 5 days before or after any Roundup 
application. 

Table 13.13 includes recommendations for control 
of many of the most common perennial weeds in 
Illinois. Observe all precautions regarding drift and 
crop injury when applying any of the herbicides 
mentioned. These precautions can be found on the 
herbicide labels. 



112 



Table 13.13. Problem Perennial Weeds 



Weed 



Crop 



Herbicide 



Remarks 



Bindweed 



Corn 



2,4-D ester 0.5 pt/A or 
amine 1 pt/A of 3.8 a.e.* 



Banvel 0.5 to 1 pt/A 



Apply in spring when leaves are fully expanded or apply 
preharvest after brown silk stage in corn. The ester formu- 
lation is preferred. Use drop nozzles when com is over 8 
inches tall. 

Use the 0.5 pt rate of Banvel on sandy soils and on corn 
taller than 8 inches or up to 2 weeks before tasseling, 
whichever comes first. 



Soybeans 



Blazer, Cobra, Basagran 
(rates on label) 



Vines may be suppressed by applications. Control can be 
improved by adding 2 fluid ounces/A of Butyrac 200. 



Bigroot 
morningglory 



Corn 



2,4-D amine 1 pt/A or ester 
0.5 pt/A of 3.8 a.e. 



Use on actively growing plants that have sufficient vine 
growth to which to apply the herbicide (10 to 24 inches). 



Canada thistle 



Corn 



Banvel 0.5 to 1 pt/A or 2,4- 
D amine 1 pt/A or ester 
0.5 pt/A of 3.8 a.e. 

Laddok 3.5 pt/A 

Buctril 1.5 pt/A or 
Buctril/atrazine 
2 to 3 pt/A 

Stinger Va to % pt/A 



Use the 0.5 pt rate of Banvel on sandy soils and on corn 
taller than 8 inches or up to 2 weeks before tasseling, 
whichever comes first. Use drop nozzles when corn is over 
8 inches tall. 

Suppression only. Apply when Canada thistle is 8 to 10 
inches tall. Use with 2 pt/A COC. 

Suppression only. Apply to weeds from 8 inches tall to the 
bud stage or up to tassel emergence on corn. Do not add 
spray additives. 

Apply as broadcast spray from 4-inch rosette to before bud 
stage. Do not apply after the corn is 24 inches tall; do not 
apply more than Va pt/A per year. 



Corn/Soybeans 



Roundup 2 to 3 qt/A 



Basagran 1 qt/A 



Apply after harvest and prior to tillage in the fall. Do not 
till for 3 days after application. Weeds should be actively 
growing. 

Will suppress thistle growth. Retreatment 7 to 14 days later 
with Basagran, or cultivation may be necessary to maintain 
suppression. 



Common milkweed 
and Hemp dogbane 



Corn 



2,4-D amine 1 to 2 pt/A 
or ester 1 to 2 pt/A of 3.8 
a.e. 



Apply mid- to late-season after corn silks have turned brown 
and plants are actively growing and have adequate foliage. 



Soybeans 



Blazer, Cobra (rates on la- 
bel) 



Suppresses common milkweed only. 



Honeyvine 
milkweed 



Corn 



2,4-D ester 0.5 pt/A or 2,4- 
D amine 1 pt/A of 3.8 a.e. 
or Banvel 0.5 to 1 pt/A or 
2,4-D + Banvel at half rates 



The ester formulation of 2,4-D is preferred; however, a 
combination of 2,4-D and Banvel may be better than 2,4-D 
used alone. Check Banvel label for restrictions. 



Jerusalem 
artichoke 



Corn 



Banvel 0.5 to 1 pt/A or 
Banvel + 2,4-D at half rates 



Stinger 'A to Vi pt/A 



Treat weeds when they are 8 to 16 inches tall. Use the 0.5 
pt rate of Banvel on sandy soils and on corn taller than 8 
inches or up to 2 weeks before tasseling, whichever comes 
first. Use drop nozzles when corn is over 8 inches tall. 

Apply 'A to V2 pt/A on weeds up to the 5-leaf stage. Do not 
apply more than Vs pt/A per year if retreatment is necessary. 
Do not apply to corn taller than 24 inches. 



Soybeans 



Pursuit 4 fluid oz/A or 
Classic 0.75 oz/A 



Pursuit should be applied to plants that are 6 to 10 inches 
tall and Classic to plants less than 8 inches tall. Small weeds 
just emerging may have sufficient root or tuber reserves to 
begin regrowth after treatment and a cultivation may be 
required. Use a surfactant at 0.25 percent, or 1 qt in 100 
gallons of spray. 



Swamp smartweed Corn 



Banvel 0.5 to 1 pt/A 



Use the higher rate on corn shorter than 8 inches. Use the 
lower rate on taller corn up to 36 inches or up to 2 weeks 
before tasseling, whichever comes first, or on sandy soils. 
Use drop nozzles if the corn is more than 8 inches tall. 



113 



Table 13.13. (continued) 



Weed 



Crop 



Herbicide 



Remarks 



Yellow nutsedge 



Com 



Sutan+, Eradicane (labeled 
rate for soil) 

Laddok 3.5 pt/A 



Apply preplar\t incorporated. 
Suppression only. Add 2 pt/A COC. 



Corn/Soybeans Lasso, Dual 



Use higher rate for soil type and incorporate thoroughly. 



Soybeans 



Scepter 0.6 pt/A 
Basagran 2 pt/A 

Classic Vi oz/A to % oz/A 



Thoroughly incorporate for best control. 

Apply 1.5 to 2 pt/A when plants are 6 to 8 inches tall. 
Reapply 7 to 10 days later if needed. Add 2 pt/A COC with 
each application. 

Apply Classic at the 4- to 6-leaf stage. Use a nonionic 
surfactant at 1 qt per 100 gallons of spray. 



Rhizome or 

seedling 

johnsongrass 



Com 



Accent Vs oz/A 



Beacon '^k oz/A 



Apply to 4- to 10-inch tall seedling johnsongrass or apply 
up to IV3 oz (in split application) on rhizome johnsongrass 
8 to 12 inches tall. Use a nonionic surfactant at 1 qt per 100 

Gallons of spray or COC at 4 qts per 100 gallons of spray. 
ee label for restrictions. 

Apply to seedling johnsongrass when 4 to 12 inches tall and 
rhizome johnsongrass when 8 to 16 inches tall. Add nonionic 
surfactant at 1 at per 100 gallons of spray or COC at 1 to 4 
pts/A. See label for restrictions. 



Soybeans 



Assure 1.25 oz/A 



Poast 1 pt/A or Poast Plus 
1.5 pt/A 

Fusilade 1.5 pt/A 



Option 1.2 pt/A 



Apply 1.25 pt/A to johnsongrass when 10 to 24 inches tall. 
For regrowth apply additional % pt/A to regrowth 6 to 10 
inches tall. 

Apply to johnsongrass 15 to 25 inches tall. Use Dash or 
COC at 2 pt/A. Retreat regrowth with same rate. 

Fusilade can be used at 1.5 pt/A on 8- to 18-inch johnsongrass 
and applied to 6- to 12-inch regrowth at 1 pt/A. Use COC 
or nonionic surfactant. 

Apply to 10- to 20-inch johnsongrass. Do not add COC. 
Apply 0.8 pt/A to regrowth. 



Quackgrass 



Corn 



Accent V3 oz/A 



Beacon ¥4 oz/A 



Eradicane Extra 4 qt/A or 
Eradicane 6.7E 7.3 pt/A 



Apply to 2- to 4-inch tall quackgrass or apply up to IVs oz 
(in split application) on quackgrass up to 6 inches tall. Use 
a nonionic surfactant at 1 qt per 100 gallons of spray or 
COC at 4 qts per 100 gallons of spray. See label for restrictions. 

Apply to quackgrass when 4 to 8 inches tall. Control of this 
species is not immediate and symptoms may take several 
aays to develop. Add nonionic surfactant at 1 qt per 100 
gallons of spray or COC at 1 to 4 pts/A. See label for 
restrictions. 

A lighter rate may be used on lighter infestations. Use a 
tank-mix with atrazine to improve control. 



Corn/Soybeans Roundup 1 to 2 qt/A 



Apply prior to spring tillage or after harvest in the fall. Do 
not till for 3 days before or after application. Weeds should 
be actively growing and greater than 8 inches tall. 



Soybeans 



Assure 1.25 to 2.25 pt/A 



Fusilade 1.5 pt/A 



Poast 1.5 pt/A or Poast 
Plus 2.25 pt/A 



Apply 1.25 pt/A when quackgrass is 6 to 10 inches tall. For 
regrowth apply 78 pt/A when quackgrass is 4 to 8 inches 
tafl. 

Fusilade can be used at 1.5 pt/A on 6- to 10-inch quackgrass 
and applied to regrowth at 1 pt/A. Use COC or nonionic 
surfactant. 

Apply to quackgrass 6 to 8 inches tall and retreat at V3 listed 
rate for regrowth. Use Dash or COC at 2 pt/A. 



Wirestem 
muhly 



Soybeans 



Assure 1.25 pt/A 
Fusilade 1.5 pt/A 



Poast 1.25 pt/A or Poast 
Plus Vk pt/A 

Option 1.2 pt/A 



Apply 1.25 pt/A when wirestem muhly is 4 to 6 inches tall. 
For regrowth, apply '/s pt/A. 

Fusilade can be used at 1.5 pt/A on 4- to 12-inch wirestem 
muhly and applied to regrowth at 1.5 pt/A. Use COC or 
nonionic surfactant. 

Apply to wirestem muhly up to 6 inches tall and retreat at 
same rate for regrowth. Use Dash or COC. 

Apply 1.2 pt/A of Option to 3- to 6-inch wirestem muhly. 
Use COC at 1 qt/A. 



* a.e. = acid equivalent. If not 3.8 lb/gal, use equivalent amount. 



114 



Chapter 14. 

1991 Weed Control for Small Grains, 
Pastures, and Forages 



Good weed control is necessary for maximum pro- 
duction of high-quality small grains, pastures, and 
forages in Illinois. When properly established, these 
crops can usually compete effectively with weeds so 
that the need for herbicide applications is minimized. 
Weeds, however, can sometimes become significant 
problems and warrant control. For example, wild garlic 
is considered the worst weed problem in wheat in 
southern Illinois. Because its life cycle is similar to that 
of winter wheat, wild garlic can establish itself with 
the wheat, grow to maturity, and produce large quan- 
tities of bulblets by wheat-harvest time. Economic 
considerations make it necessary to attempt some 
control of wild garlic in winter wheat. 

In pastures, woody and herbaceous perennials can 
become troublesome. Annual grasses and broadleaf 
weeds such as chickweed and henbit may cause prob- 
lems in hay crops. Through proper management, many 
of these weed problems can be controlled effectively. 

Several herbicide labels carry the following ground- 
water warnings under either the environmental hazard 
or the groundwater advisory section. "X is a chemical 
that can travel (seep or leach) through soil and enter 
groundwater which may be used as drinking water. X 
has been found in groundwater as a result of its use 
as a herbicide. Users of this product are advised not 
to apply X where the soils are very permeable (that 
is, well-drained soils such as loamy sands) and the 
water table is close to the surface." See Table 14.1 for 
a list of herbicides that carry this warning. 



Small grains 

Good weed control is critical for maximum produc- 
tion of high-quality small grains. Often, problems with 
weeds can be dealt with before the crop is established. 
For example, some broadleaf weeds are controlled 
effectively in the late fall, after corn or soybean has 
been harvested, with 2,4-D, Banvel (dicamba), or 
Roundup (glyphosate). 



Tillage helps control weeds. Although generally 
limited to preplant and postharvest operations, tillage 
can destroy many annual weeds and help suppress 
certain perennials. Good cultural practices such as 
proper seeding rate, optimum soil fertility, and timely 
planting help to ensure the establishment of an ex- 
cellent stand and a crop that is better able to compete 
with weeds. 

Winter annual grasses such as downy brome and 
cheat are very competitive in winter wheat. Illinois 
wheat producers are often limited to preplant tillage 
operations for control of these species as few herbicides 
have label clearances for annual grass control in winter 
wheat. If a severe infestation of downy brome or cheat 
exists, planting an alternative crop or spring crop may 
be best for that field. 

A decision to use postemergence herbicides for 
broadleaf weed control in small grains should be based 
on several considerations: 

1. Nature of the weed problem. Identify the species 
present and consider the severity of the infestation. 
Also note the size of the weeds. Weeds are usually 
best controlled while small. 

2. Stage of the crop. Most herbicides are applied after 
full tiller until the boot stage. Do not apply her- 
bicides from the boot stage to the hard-dough stage 
of most small grains. (See Figure 14.1 for a descrip- 
tion of growth stages of small grains.) 

3. Presence of a legume underseeding. Usually 2,4-D 
ester formulations and certain other herbicides listed 
in Table 14.3 should not be applied because they 
may damage the legume underseeding. 

4. Herbicide activity. Determine crop tolerance and 
weed susceptibility to herbicides by referring to 
Tables 14.2 and 14.3. The lower rates in Table 14.3 
are for more easily controlled weeds and the higher 
rates for the more difficult to control species. Tank- 
mixes may broaden the weed spectrum and thereby 
improve control; check the herbicide label for reg- 
istered combinations. 

5. Economic justification. Consider the treatment cost 



115 



Table 14.1. List of Herbicides, Formulations, and Special Statements 











Groundwater 




Trade name 


Common name 


Formulation 


Restricted use 


advisory 


Key word 


Ally 60 DF 


metsulfuron methyl 


60% 


no 


no 


caution 


Balan 1.5E 


benefin 


1.5 lb/gal 


no 


no 


danger 


Banvel 


dicamba 


4 lb a.e.Vgal 


no 


no 


warning 


Buctril 


bromoxynil 


2 lb/gal 


yes 


no 


danger 


Butyrac 200 


2,4-DB 


2 lb a.e./gal 


no 


no 


caution 


Butyrac Ester 


2,4-DB 


2 lb a.e./gal 


no 


no 


caution 


Crossbow 


2,4-D + tridopyr 


2 + 1 lb a.e./gal 


no 


no 


caution 


Eptam 7E, lOG 


EPTC 


7 lb/gal, 10% 


no 


no 


caution 


Fusilade 2000 


fluazifop 


1 lb a.e./gal 


no 


no 


caution 


Gramoxone Extra 


paraquat 


2.5 lb/gal 


yes 


no 


danger 


Harmony Extra 75 DF 


thifensulfuron + bensulfuron 


75% 


no 


no 


warning 


Kerb SOW 


pronamide 


50% 


? 


no 


caution 


Lexone 4L 


metribuzin 


4 lb/gal 


no 


yes 


caution 


Lexone 75DF 


metribuzin 


75% 


no 


yes 


caution 


MCPA 


MCPA 


several 


no 


no 


warning 


Option 


fenoxaprop 


1 lb a.e./gal 


no 


no 


warning 


Poast 


sethoxydim 


1.5 lb/gal 


no 


no 


warning 


Prowl 


pendimethalin 


4 lb/gal 


no 


no 


warning 


Roundup 


glyphosate 


3 lb a.e./gal 


no 


no 


warning 


Sencor 4L 


metribuzin 


4 lb/gal 


no 


yes 


caution 


Sencor 75DF 


metribuzin 


75% 


no 


yes 


caution 


Sinbar SOW 


terbacil 


80% 


no 


no 


caution 


Spike 20P 


tebuthiuron 


20% 


no 


no 


warning 


Spike 40P 


tebuthiuron 


40% 


no 


no 


caution 


Stinger 


clopyralid 


3 lb a.e./gal 


no 


yes 


caution 


Treflan 


trifluralin 


4 lb/gal 


no 


no 


warning 


Velpar L 


hexazinone 


2 lb/gal 


no 


no 


danger 


2,4-D amine 


2,4-D 


3.8 lb a.e./gal 


no 


no 


danger 


2,4-D ester 


2,4-D 


3.8 lb a.e./gal 


no 


no 


caution 



' a.e. = Acid equivalent for these herbicides. All others are active ingredient (a.i.) formulations. 



in terms of potential benefits such as the value of 
increased yield, improved quality of grain, and ease 
of harvesting the crop. 

Table 14.3 outlines current suggestions for weed 
control options in wheat and oats, the two small grains 
most commonly grown in Illinois. Always consult the 
herbicide label for specific information about the use 
of a given product. 

For annual broadleaf weeds postemergence herbi- 
cides such as 2,4-D, MCPA, Banvel, and Buctril 
(bromoxynil) can provide good control of susceptible 
species (Table 14.2). Herbicides must be applied during 
certain growth stages of the crop to avoid crop injury 
and for optimum weed control. Refer to Figure 14.1 
for a description of the growth stages of small grains. 

Some perennial broadleaf weeds may not be con- 
trolled satisfactorily with the low herbicide rates used 
in small grains; and higher rates are not advisable 
because they can cause serious injury to crops. To 
control perennial weeds, translocated herbicides such 
as 2,4-D, Banvel, or Roundup, in combination with 
tillage after small grain harvest or after soybean harvest 
but before establishing small grains, may be the best 
approach. 

Stinger (clopyralid) may be used to control broadleaf 
weeds in wheat, oats, and barley. Stinger controls 
Canada thistle as well as a number of annual broadleaf 
weeds (Table 14.2). 

Wild garlic continues to be a serious weed problem 
in winter wheat. Harmony Extra (thifensulfuron -I- 



bensulfuron), applied in the spring at 0.3 to 0.6 ounce 
of 15 DF per acre, effectively controls wild garlic aerial 
bulblets and some underground bulbs as well. Har- 
mony Extra also helps control chickweed, henbit, 
common lambsquarters, smartweed, and several spe- 
cies of mustard. See Tables 14.2 and 14.3 for additional 
information on controlling weeds in small grains. 



Grass pastures 

Unless properly managed, broadleaf weeds can be- 
come a serious problem in grass pastures. They can 
compete directly with forage grasses and reduce the 
nutritional value and longevity of the pasture. Certain 
species, such as white snakeroot and poison hemlock, 
are also poisonous to livestock and may require special 
consideration. 

Perennial weeds are probably of greatest concern. 
They can exist for many years, reproducing from both 
seed and underground parent rootstocks. Occasional 
mowing or grazing helps control certain annual weeds, 
but perennials can grow back from underground root 
reserves unless long-term control strategies are imple- 
mented. 

Certain biennials can also flourish in grass pastures. 
The first year, they exist as a prostrate rosette, so that 
even close mowing does little to control their growth. 
The second year, biennials produce a seedstalk and a 
deep taproot. If these weeds are grazed or mowed at 
this stage, root reserves can sometimes enable the 



116 



Wheat 





stage 1 
Seedling 



Stages 4 to 5 
Tillering 



Stage 7 
Joint 



Stage 10 Stages 10.1 to 10.5 

Boot Heading 



Figure 14.1. Growth stages of small grains. 



Seedling 

Stage 1. The coleoptile, a protective sheath that 
surrounds the shoot, emerges. The first leaf emerges 
through the coleoptile, and other leaves follow in 
succession from within the sheath of the previously 
emerging leaf. 

Tillering 

Stages 2 to 3. Tillers (shoots) emerge on opposite 
sides of the plant from buds in the axils of the first 
and second leaves. The next tillers may arise from the 
first shoot at a point above the first and second tillers 
or from the tillers themselves. This process is repeated 
until a plant has several shoots. 

Stages 4 to 5. Leaf sheaths lengthen, giving the 
appearance of a stem. The true stems in both the main 
shoot and in the tillers are short and concealed within 
the leaf sheaths. 

Jointing 

Stage 6. The stems and leaf sheaths begin to elongate 
rapidly, and the first node (joint) of the stem is visible 
at the base of the shoot. 

Stage 7. Second node (joint) of stem is visible. The 
next-to-last leaf is emerging from within the sheath 
of the previous leaf but is barely visible. 

Stage 8. Last leaf, the "flag leaf," is visible but still 
rolled. 

Stage 9: Preboot stage. Ligule of flag leaf is visible. 
The head begins to enlarge within the sheath. 



Stage 10: Boot stage. Sheath of flag leaf is completely 
emerged and distended because of enlarging but not 
yet visible head. 

■Heading 

Stages 10.1 to 10.5. Heads of the main stem usually 
emerge first, followed in turn by heads of tillers in 
order of their development. Heading continues until 
all heads are out of their sheaths. The uppermost 
internode continues to lengthen until the head is raised 
several inches above the uppermost leaf sheath. 

Flowering 

Stages 10.5.1 to 10.5.3. Flowering progresses in 
order of head emergence. Unpollinated flowers result 
in barren kernels. 

Stage 10.5.4: Premilk stage. Flowering is complete. 
The inner fluid is abundant and clear in the developing 
kernels of the flowers pollinated first. 

Ripening 

Stage 11.1: Milk stage. Kernel fluid is milky white 
because of accumulating starch. 

Stage 11.2: Dough stage. Kernel contents are soft 
and dry (doughy) as starch accumulation continues. 
The plant leaves and stems are yellow. 

Stage 11.3. The kernel is hard, difficult to divide 
with the thumbnail. 

Stage 11.4. Ripe for cutting. Kernel will fragment 
when crushed. The plant is dry and brittle. 



117 



Table 14.2. Effectiveness of Herbicides on Weeds in Small Grains 

This table compares the relative effectiveness of herbicides on individual weeds. Ratings are based on labeled application rate and weed 
size or growth stage. Performance may vary due to weather and soil conditions, or other variables. Weed control rating: 10 = 95 to 100%, 
9 = 85 to 95%, 8 = 75 to 85%, 7 = 65 to 75%, 6 = 55 to 65%, 5 = 45 to 55%, and = less than 45% control or not labeled. 



Weed 






Susceptibility 


to herbicide 






2,4-D 


MCPA 


Banvel 


Buctril 


Harmony Extra 


Stinger 


Winter annual 














Buckwheat, wild 


5 


8 


10 


9 


8 


8 


Chickweed, common 


5 


5 


6 


6 


9 





Henbit 


5 


5 


6 


8 


9 





Horseweed (marestail) 
Lettuce, prickly 
Mustard spp., annual 


8 
10 
10 


8 

9 

10 


10 
8 
6 


6 
6 
9 


7 
8 
9 


9 
9 



Pennycress, field 
Shepherdspurse 


10 
10 


10 
10 


6 

8 


8 
8 


9 
9 






Summer annual 














Lambsquarters, common 
Pigweed spp. 
Ragweed, common 
Ragweed, giant 
Smartweed, Pennsylvania 


10 
10 
10 
10 
6 


10 

10 

9 

9 

7 


10 
10 
10 
10 
9 


10 
7+ 
9 
8 
9 


8 
9 


9 




9 
10 
6 


Perennial 














Dandelion 


9 


8 


8 





6 


9 


Garlic, wild 














aerial bulblets 


6» 


5 


5 





9 





underground bulbs 
Thistle, Canada 




7 




7 




8 



6 


5 

7 



9 



^ 2,4-D ester at maximum use rate. 



plant to grow again, thereby increasing its chance of 
surviving to maturity. 

In general, the use of good cultural practices such 
as maintaining optimum soil fertility, rotational grazing, 
and periodic mowing can help keep grass pastures in 
good condition and more competitive with weeds. 
Where broadleaf weeds become troublesome, however, 
2,4-D, Banvel, or Stinger may be used. Roundup 
may also be used as a spot treatment, and Crossbow 
(2,4-D plus triclopyr) or Ally (metsulfuron methyl) 
are labeled for control of broadleaf and woody plant 
species in grass pastures. Certain formulations of Spike 
(tebuthiuron) may also be used in grass pastures for 
brush and woody plant control. (See Tables 14.4 and 
14.5 for additional information.) 

Proper identification of target weed species is im- 
portant. As shown in Table 14.4, weeds vary in their 
susceptibility to herbicides. Timing of herbicide appli- 
cation may also affect the degree of weed control. 
Annuals and biennials are most easily controlled while 
young and relatively small. A fall or early spring 
treatment works best if biennials or winter annuals 
are the main weed problem. Summer annuals are most 
easily controlled in the spring or early summer. Apply 
translocated herbicides to control established peren- 
nials when the weeds are in the bud to bloom stage. 
Perennials are most susceptible at this reproductive 
phase because translocated herbicides can move down- 
ward with food reserves to the roots, potentially killing 
the entire plant. 

For control of woody brush, apply 2,4-D, Banvel, 
or Crossbow when the plants are fully leafed and 
actively growing. Where regrowth occurs, a second 



treatment may be needed in the fall. During the 
dormant season, oil-soluble formulations of 2,4-D, 
Banvel or Crossbow may be used in fuel oil. Spike 
controls many woody perennials and should be applied 
to the soil in the spring. Spike requires rainfall to move 
it into the root zone of target species. Ally controls 
multiflora rose, Canada thistle, and blackberry {Rubus 
sp.) as a spot treatment or suppresses these weeds and 
controls several annual broadleaf weeds when applied 
as a broadcast treatment at the lower rate range. 

The weed control options in grass pastures are shown 
in Table 14.5. Be cautious with any pesticide and 
always consult the herbicide label for specific infor- 
mation about the use of a given product. 



Forage legumes 

Weed control is very important in managing forage 
legumes. Weeds can severely reduce the vigor of 
legume stands and thus reduce yield and forage quality. 
Good management begins with weed control practices 
that prevent weeds from becoming serious problems. 

Establishment 

To minimize problems, prepare the seedbed properly 
so that it is firm and weed-free. Select an appropriate 
legume variety. If you use high-quality seed and follow 
the recommendations for liming and fertility, the leg- 
ume crop may crowd out many weeds and reduce the 
need for herbicides. 

In fields where companion crops such as oats are 



118 



Table 14.3. Weed Control in Small Grains 



Herbicide 



Broadcast 
rate/acre 



Remarks 



Restrictions 



Oats and wheat 

2,4-D, 3.8 lb a.i. 
(amine) 



MCPA (amine) 



Banvel, 4 lb a.i. 



Buctril 2E 



Stinger 3 lb a.e. 



Wheat only 

2,4-D, 3.8 lb a.i. 
(ester) 



Harmony Extra 
75DF 



'A to V/i pt Winter wheat more tolerant than oats. Apply in spring 
after full tiller but before boot stage. Do not treat in fall. 
Use lower rate of amine if underseeded with legume. 
Some legume damage may occur May be used as pre- 
harvest treatment at 1 to 2 pints per acre during hard- 
dough stage. 

Vi to 3 pt Less likely than 2,4-D to damage oats and legume un- 

derseeding. Apply from 3-leaf stage to boot stage. Rate 
varies with crop and weed size and presence of legume 
underseeding. 

4 fl oz Do not apply to small grains with legume underseeding. 

In fall-seeded wheat, apply before jointing stage. In 
spring-seeded oats, apply before oats exceed 5-leaf stage. 

1 to 2 pt Apply Buctril alone to fall-seeded small grains in the fall 

or spring, but before the boot stage. Weeds are best 
controlled before the 3- to 4-leaf stage. Buctril may be 
applied at 1 to IV2 pints per acre to small grains under- 
seeded with alfalfa. 

'/i to Va pt Apply to small grains from the 3-leaf stage up to the 

early boot stage. For control of Canada thistle, Va pint 
per acre should be used. For control of additional weeds, 
Buctril, Banvel, Harmony, MCPA, or 2,4-D may be tank- 
mixed with Stinger. 



Vi to ¥4 pt Do not apply to wheat with legume underseeding. Apply 

in spring after full tiller but before boot stage. For pre- 
harvest treatment, apply 1 to 2 pints per acre during 
hard-dough stage. For control of wild garlic or wild onion, 
apply 1 to 2 pints in the spring when wheat is 4 to 8 
inches high, after tillering but before jointing; these rates 
may injure the crop. 

0.3 to 0.6 oz Apply to the crop after the 2-leaf stage, but before the 
third node is detectable. Wild garlic should be less than 
12 inches tall, with 2 to 4 inches of new growth. Annual 
broadleaf weeds should be past the cotyledon stage, 
actively growing, and less than 4 inches tall or across. 
Nonionic surfactant at 0.25% v/v should be included in 
the spray mixture. When liquid fertilizer is used as the 
carrier, use V\f,-^k% v/v surfactant. Temporary stunting 
and yellowing may occur when Harmony Extra is applied 
using liquid fertilizer solution as the carrier. These symp- 
toms will be intensified with the addition of surfactant. 
Without surfactant addition, wild garlic control may be 
erratic. 



Do not forage or graze within 2 weeks 
after treatment. Do not feed treated straw 
to livestock following a preharvest treat- 
ment. 



Do not graze dairy animals on treated 
areas for 7 days after treatment. 



Do not graze or harvest for dairy feed 
before ensilage (milk) stage. 

Do not graze treated fields for 30 days 
after application. 



Do not forage or graze dairy or meat 
animals on treated fields within 1 week 
after treatment. Do not harvest treated 
fields for hay. Do not apply to small 
grains with legume underseeding. 



Do not forage or graze within 2 weeks 
after treatment. See current label for ad- 
ditional restrictions. 



Do not plant to any crop other than 
wheat or barley within 60 days after 
application. Do not apply to cereals un- 
derseeded with legumes. 



used to reduce weed competition, seed the small grain 
at half the rate for grain production to ensure that the 
legumes will become established with minimum stress. 
If the legume is seeded without a companion crop 
(direct seeded), the use of an appropriate herbicide is 
suggested. 

Preplan! incorporated herbicides. Balan (benefin) 
and Eptam (EPTC) are registered for preplant incor- 
poration for legumes that are not seeded with grass 
or small-grain companion crops. These herbicides will 
control most annual grasses and some broadleaf weeds. 
In fall plantings, the weeds controlled include winter 
annuals such as downy brome and cheat. In spring 
legume plantings, the summer annual weeds controlled 
include foxtails, pigweeds, lambsquarters, crabgrass, 
and fall panicum. 



Eptam can help suppress johnsongrass, quackgrass, 
yellow nutsedge, and shattercane, in addition to con- 
trolling many annual grasses and some broadleaf weeds. 
Neither one will effectively control mustards, smart- 
weed, or established perennials. Balan and Eptam must 
be thoroughly incorporated soon after application to 
avoid herbicide loss. They should be applied shortly 
before the legume is seeded, so they remain effective 
as long as possible into the growing season. 

Weeds that emerge during crop establishment should 
be evaluated for their potential to become problems. 
If they do not reduce the nutritional value of the 
forage or if they can be controlled by mowing, they 
should not be the primary target of a postemergence 
herbicide. For example, winter annual weeds do not 
compete vigorously with the crop after the first spring 



119 



Table 14.4. Effectiveness of Herbicides on Weeds in Grass Pastures 

This table compares the relative effectiveness of herbicides on individual weeds. Ratings are based on labeled application rate and weed 
size or growth stage. Performance may vary due to weather and soil conditions, or other variables. Weed control rating: 10 = 95 to 100%, 
9 = 85 to 95%, 8 = 75 to 85%, 7 = 65 to 75%, 6 = 55 to 65%, 5 = 45 to 55%, and = less than 45% control or not labeled. 



Weed 






Susceptibility 


to herbicide 






2,4-D 


Ally 


Banvel 


Crossbow 


Roundup" 


Stinger 


Winter annual 














Horseweed (marestail) 


9 


9 


10 


10 


10 


9 


Pennycress, field 


10 





8 


9 


10 





Summer annual 














Ragweed, common 


10 





10 


10 


10 


9 


Ragweed, giant 


10 





10 


10 


10 


10 


Biennial 














Burdock, common 


10 





10 


10 


9 


8 


Hemlock, poison 


9 





10 


10 


9 





Thistle, bull 


10 





10 


10 


10 


9 


Thistle, musk 


10 


9 


9 


9 


10 


9 


Perennial'' 














Daisy, oxeye 


8 





10 


10 


9 


9 


Dandelion 


10 





8 


10 


8 


9 


Dock, curly 


7 





10 


10 


9 


8 


Goldenrod spp. 


8 





9 


8 


10 





Hemlock, spotted water 


9 





10 


10 


9 





Ironweed 


8 





10 


9 


10 





Milkweed, common 


6 





8 


8 


8 





Nettle, stinging 


9 





9 


9 


9 





Plantain spp. 


10 





8 


10 


9 





Rose, multiflora'' 


8 


9 


9 


9 


9 





Snakeroot, white 


8 





9 


9 


8 





Sorrel, red 


5 





10 


10 


8 


6 


Sowthistle, perennial 


8 





9 


10 


9 


7 


Thistle, Canada 


8 


9 


9 


9 


8 


10 



" Spot treatment. 

^ Perennial weeds may require more than one application. 

"^ Spike is also an effective herbicide for multiflora rose control (weed susceptibility = 10). 



cutting. Unless they are unusually dense or production 
of weed seed becomes a concern, these weeds may 
not be a significant problem. Some weeds such as 
dandelions are palatable and may not need to be 
controlled if the overall legume stand is dense and 
healthy; but undesirable weeds must be controlled 
early to prevent their establishment. 

Postemergence herbicides. Poast (sethoxydim) may 
be applied to seedling alfalfa for control of annual 
and some perennial grass weeds after weed emergence. 
Grasses are more easily controlled when small, and 
alfalfa is tolerant to Poast at all stages of growth. 
Butyrac (2,4-DB) controls many broadleaf weeds and 
n\ay be applied postemergence in many seedling forage 
legumes. Buctril (bromoxynil) may also be used to 
control broadleaf weeds in seedling alfalfa. Be sure to 
apply Buctril while weeds are small. (See Table 14.7 
for specific weed control ratings.) 

Established legumes 

The best weed control in established forage legumes 
is maintenance of a dense, healthy stand via proper 
management techniques. Chemical weed control in 
established forage legumes is often limited to late fall 
or early spring applications of herbicide. Sencor or 
Lexone (metribuzin), Sinbar (terbacil), and Velpar 
(hexazinone) are applied after the last cutting in the 



fall or in the early spring. These herbicides control 
many broadleaf weeds and some grasses, too. Kerb 
(pronamide) is used for grass control and is applied 
in the fall after the last cutting. 2,4-DB controls many 
broadleaf weeds in established alfalfa; it should be 
apphed when the weeds are small and actively grow- 
ing. Refer to Tables 14.6 and 14.7 for additional 
remarks and weed control suggestions. 

Once grass weeds have emerged, they are particu- 
larly difficult to control in established alfalfa. Poast 
herbicide may be used in established alfalfa for control 
of annual and some perennial grasses. Optimum grass 
control is achieved if Poast is applied when grasses 
are small and before the weeds are mowed. 

Table 14.6 outlines current suggestions for weed 
control options in legume forages. The degree of 
control will often vary with weed size, apphcation 
rate, and environmental conditions. Be sure to select 
the correct herbicide for the specific weeds to be 
controlled (Table 14.7). Always consult the herbicide 
label for specific information about the use of a given 
product. 

Acreage Conservation Reserve Program 

Investing in good weed control on Acreage Conser- 
vation Reserve (ACR) land will help alleviate some 



120 



Table 14.5. Broadleaf Weed Control in Grass Pastures 



Herbicide 



Rate/acre 



Remarks 



Restrictions 



2,4-D, 3.8 lb a.e. 
(amine or low- 
volatile ester) 



Ally 60 DF 



Banvel, 4 lb a.e. 



Crossbow 



Roundup 



Spike 20P 
Spike 40P 



2 to 4 pt 



'/lO to ^10 oz 



Annuals: Vi to 

Wi pt 
Biennials: Vi to 

3 pt 
Perennials: 1 to 

2pt 

(suppression) 
Perennials: 1 to 

6 qt 

(control) 
Woody brush: 1 

to 2 pt 

(suppression) 
Woody brush: 1 

to 8 qt 

(control) 

Annuals: 1-2 qt 
Biennials and 

herbaceous 

perennials: 

2 to 4 qt 
Woody perennials: 

6 qt 

2% solution 
(spot 
treatment) 



10 to 20 lb 
5 to 10 lb 



Stinger, 3 lb a.e. Vs to I'A pt 



Broadleaf weeds should be actively growing. Higher rates 
may be needed for less susceptible weeds and some 
perennials. Spray bull or musk thistles in the rosette stage 
(spring or fall) while they are actively growing. Spray 
perennials such as Canada thistle in the bud stage. Spray 
susceptible woody species in spring when leaves are fully 
expanded. 

Apply to weeds when actively growing in the spring or 
early summer, before annual broadleaf weeds are 4 inches 
tall. As a spot application for control of multiflora rose, 
blackberry, or Canada thistle, apply Ally at 1 ounce per 
100 gallons of water and spray foliage to runoff. Include 
a surfactant of at least 80% active ingredient at 1 pint to 
1 quart per 100 gallons spray solution (Vs to '74% v/v) 
unless applying in liquid nitrogen fertilizer. When Ally is 
applied using liquid nitrogen fertilizer solution as the 
spray carrier, crop injury is more likely. 



Use lower rates for susceptible annuals when they are 
small and actively growing and for susceptible biennials 
in the early rosette stage. Use higher rates for larger 
weeds, for less susceptible weeds, for established peren- 
nials in dense stands, and for certain woody brush species. 



Apply to foliage during warm weather when brush and 
broadleaf weeds are actively growing. When applying as 
a spot spray, thoroughly wet all foliage. See herbicide 
label for more specific rate recommendations. 



Controls a variety of herbaceous and woody brush species 
such as multiflora rose, brambles, poison ivy, and quack- 
grass. Spray foliage of target vegetation completely and 
uniformly, but not to point of runoff. Avoid contact with 
desirable nontarget vegetation. Consult label for recom- 
mended timing of application for maximum effectiveness 
on target species. 

For control of brush and woody plants in rangeland and 
grass pastures. Requires sufficient rainfall to move her- 
bicide into root zone. May kill or injure desirable legumes 
and grasses where contact is made. Injury is minimized 
by applying when grasses are dormant. 



Apply when weeds are young and actively growing. 
Grasses are tolerant, but new grass seedlings may be 
injured. 



Do not graze dairy animals within 7 days 
after treatment. Do not apply to newly 
seeded areas or to grass when it is in 
boot to milk stage. Be cautious of spray 
drift. 



Ally has no grazing restrictions. Blue- 
grass, bromegrass, orchardgrass, and 
timothy are tolerant, but should be es- 
tablished for at least 6 months at the 
time of application. Applications to fes- 
cue may result in stunting and seedhead 
suppression. Do not apply to ryegrass or 
pastures containing desirable alfalfa or 
clovers. Ally is persistent in soil and crop 
rotation guidelines must be followed. Refer 
to product label for specific rotation 
guidelines as well as other restrictions. 

Refer to label for specific timing restric- 
tions for lactating dairy animals. Remove 
meat animals from treated areas 30 days 
before slaughter. Be cautious of spray 
drift. 



Remove livestock from treated forage at 
least 3 days before slaughter during the 
year of treatment. Do not graze lactating 
dairy animals on treated areas for one 
year following treatment. Do not harvest 
grass for hay from treated areas for one 
year following treatment. Be cautious of 
spray drift. 

No more than Vio of any acre should be 
treated at one time. Further applications 
may be made in the same area at 30- 
day intervals. Allow 14 days after ap- 
plication before grazing or harvesting 
forage. 

Do not apply on or near field crops or 
other desirable vegetation. Do not apply 
where soil movement is likely. Grazing 
allowed in areas treated with 20 lb or 
less Spike 20P and 10 lb or less Spike 
40P. At these rates, grass may be cut for 
hay 1 year after application. Refer to 
label for additional restrictions. 

Do not spray pastures containing desir- 
able forbs, such as alfalfa or clover, unless 
injury can be tolerated. Do not use hay 
or straw from treated areas for com- 
posting or mulching on susceptible 
broadleaf crops. Refer to product label 
for additional precautions. 



121 



Table 14.6. Weed Control in Legume Forages 



Herbicide 



Legume 



Time of 
application 



Broadcast 
rate/acre 



Seedling year 

Balan 1.5EC 



Eptam 7E,10G 



Alfalfa, birdsfoot 
trefoil, red clover, 
ladino clover, 
alsike clover 

Alfalfa, birdsfoot 
trefoil, lespedeza, 
clovers 



Gramoxone Extra Alfalfa only 



Preplant 
incorporated 


3 to 4 qt 


Preplant 
incorporated 


3 'A to 4 '72 pt 
30 lb (lOG) 


Between 
cuttings 


12.8 fluid oz 



Buctril 2E 



Alfalfa only 



Postemergence 1 to IV2 pt 



Butyrac 200 

or 

Butyrac 

Ester 



Kerb SOW 



Poast 1.5E 



Alfalfa, birdsfoot 
trefoil, ladino clover, 
red clover, alsike 
clover, white clover 



Alfalfa, birdsfoot 
trefoil, crown vetch, 
clovers 



Postemergence 



1 to 3 qt 
(amine) 

2 to 4 pt 
(ester) 



Alfalfa only 



Postemergence 1 to 3 lb 



Postemergence ^k to I'A pt 



Established stands 

Butyrac 200 Alfalfa only 



Growing 



1 to 3 qt 
(amine) 



Kerb SOW 



Alfalfa, birdsfoot 
trefoil, crown vetch, 
clovers 



Growing or 
dormant 



1 to 3 lb 



Remarks 



Restrictions 



Apply shortly before seeding. 
Do not use with any compan- 
ion crop of small grains. 

Apply shortly before seeding. 
Do not use with any compan- 
ion crop of small grains. 

Apply within 5 days of cutting 
and before alfalfa regrowth is 
2 inches. Add surfactant ac- 
cording to label instructions. 

Apply in the fall or spring to 
seedling alfalfa with at least 4 
trifoliate leaves. Apply to 
weeds at or before the 4-leaf 
stage or 2 inches in height 
(whichever is first). May be 
tank-mixed with 2,4-DB for 
improved control of kochia and 
pigweed. Eptam, previously 
used, may enhance Buctril bum 
to alfalfa. 



Use amine or ester formulation 
when weeds are less than 3 
inches tall or less than 3 inches 
across if rosettes. Use higher 
rates for seedling smartweed 
or curly dock. May be tank- 
mixed with Poast. 

In fall-seeded legumes, apply 
after legumes have reached tri- 
foliate stage. In spring-seeded 
legumes, apply next fall. 

Alfalfa is tolerant of Poast at 
all stages of growth. Best grass 
control is achieved when ap- 
plications are made prior to 
mowing. If tank-mixed with 
2,4-DB, follow 2,4-DB harvest 
and grazing restrictions. 



Spray when weeds are less 
than 3 inches tall or less than 
3 inches wide if rosettes. Fall 
treatment of fall-emerged 
weeds may be better than 
spring treatment. May be tank- 
mixed with Poast. 

Apply in the fall after last cut- 
ting, when weather and soil 
temperatures are cool. 



Do not use on soils high 
in organic matter. 



Do not use on white 
Dutch clover. 

Do not harvest or graze 
within 30 days after ap- 
plication. Do not apply 
more than twice during 
seedling year. 

A restricted-use herbi- 
cide. Do not apply when 
temperatures are likely 
to exceed 70°F at ap- 
plication or for the 3 
days following appli- 
cation or when the crop 
is stressed. Do not add 
a surfactant or crop oil. 
Do not harvest or graze 
spring-treated alfalfa 
within 30 days and fall- 
treated alfalfa within 60 
days following treat- 
ment (60 days if tank- 
mixed with 2,4-DB). 

Do not harvest or graze 
for 60 days following 
treatment. Do not use 
on sweet clover. 



Do not graze or harvest 
for 120 days following 
application. 

Do not apply Poast 
within 7 days of graz- 
ing, feeding, or har- 
vesting undried forage, 
or within 20 days of 
harvesting dry hay. Do 
not apply more than a 
total of S pints of Poast 
per acre in one season. 
Apply by ground equip- 
ment only. 



Do not harvest or graze 
for 30 days following 
application. Do not ap- 
ply to sweet clover. 



Do not harvest or graze 
for 120 days. 



122 



618,^ .61 



f io?l 



li 



Table 14.6. (continued) 



Herbicide 


Legume 


Time of 
application 


Broadcast 
rate/acre 


Remarks 


Restrictions 


Sencor or 
Lexone 


Alfalfa and 

alfalfa-grass 

mixtures 


Dormant 


% to 2 pt 
(4L) 

Vi to IVa lb 
(75 DF) 


Apply once in the fall or spring 
before new growth starts. Rate 
is based upon soil type and 
organic-matter content. Higher 
rates may injure grass com- 
ponent. 


Do not use on sandy 
soils or soils with pH 
greater than 7.5. Do not 
graze or harvest for 28 
days. 


Sinbar SOW 


Alfalfa only 


Dormant 


1/2 to I'/j lb 


Apply once in the fall or spring 


Do not use on sandy 



Velpar L 



Alfalfa only 



Dormant 



Poast 1.5E 



Alfalfa only 



Roundup 



Alfalfa, clover, 
and alfalfa or 
clover-grass 
mixtures 



Growing 



before new growth starts. Use 
lower rates for coarser soils. 



1 to 3 qt Apply iri the fall or spring be- 

fore new growth exceeds 2 
inches in height. Can also be 
applied to stubble after hay 
crop removal but before re- 
growth exceeds 2 inches. 



Postemergefice ¥4 to Vh pt 



Gramoxone 


Alfalfa only 


Dormant 


Vh to 2 pt 


Extra 




Between 
cutting 


12.8 fl oz 



Alfalfa is tolerant of Poast at 
all stages of growth. Best grass 
control is achieved when ap- 
plications are made prior to 
mowing. If tank-mixed with 
2,4-DB, follow 2,4-DB grazing 
and harvest restrictions. 



For dormant season, apply after 
last fall cutting or before spring 
growth is 1 inch tall. Weeds 
should be succulent and grow- 
ing at the time of application. 
Between cutting treatments 
should be applied immediately 
after hay removal within 5 days 
after cutting. Weeds germinat- 
ing after treatment will not be 
controlled. Add surfactant as 
label indicates. 



2% solution Apply to actively growing, 
(spot susceptible weeds. Avoid con- 

treatment) tact with desirable, nontarget 

vegetation because damage 
may occur. Refer to label for 
recommended timing of appli- 
cation for maximum effective- 
ness on target species. 



soils with less than 1 
percent organic matter. 
Do not plant any crop 
for 2 years. 

Do not plant any crop 
except corn within 2 
years of treatment. Com 
may be planted 12 
months after treatment, 
provided deep tillage is 
used. Do not graze or 
harvest for 30 days. 

Do not apply Poast 
within 7 days of graz- 
ing, feeding, or har- 
vesting undried forage, 
or within 20 days of 
harvesting dry hay. Do 
not apply more than a 
total of 5 pints of Poast 
per acre in one season. 
Apply by ground equip- 
ment only. 

A restricted-use herbi- 
cide. Do not apply if fall 
regrowth following the 
last fall cutting is more 
than 6 inches tall. Do 
not cut, harvest, or graze 
for 60 days following a 
dormant season appli- 
cation and for 30 days 
between cutting appli- 
cations. 

No more than Ko of any 
acre should be treated 
at one time. Further ap- 
plications may be made 
in the same area at 30- 
day intervals. Do not 
graze or harvest for 14 
days. 



problem weeds when rotating back to row crops. For 
example, perennial broadleaf weeds such as hemp 
dogbane and common milkweed may be controlled or 
suppressed under small-grain production or when a 
perennial grass or legume species is grown. In addition, 
mowing or alternative herbicide options may be avail- 
able. Whether using tillage, mowing, herbicides, or 
combinations, the best approach is to remain flexible 
and use cost-effective methods that fit your weed 
problems and management system. 

Clover, alfalfa, or other forage legumes may be one 
of the best options for ACR acres. The cover helps 
conserve soil, improves soil structure, and adds nitro- 



gen. Clover and alfalfa can be very economical, par- 
ticularly if grown for at least two consecutive years. 
The use of a herbicide for legume establishment can 
allow a vigorous legume stand and alleviate the need 
for weed control measures later. If annual broadleaf 
weeds become a problem, applying 2,4-DB or mowing 
is another helpful option. Herbicides for use on forage 
legumes on ACR acres include those registered for 
commercial production fields and are listed in Table 
14.6. In addition, Treflan (trifluralin) or Prowl (pen- 
dimethalin) may be used preplant incorporated to 
control annual grasses and some small-seeded broad- 
leaf weeds. Some stand reduction may occur with 



123 



Table 14.7. Effectiveness of Herbicides on Weeds in Legume and Legume-Grass Forages 

This table compares the relative effectiveness of herbicides on individual weeds. Ratings are based on labeled application rate and weed 
size or growth stage. Performance may vary due to weather and soil conditions, or other variables. Weed control rating: 10 = 95 to 100%, 
9 = 85 to 95%, 8 = 75 to 85%, 7 = 65 to 75%, 6 = 55 to 65%, 5 = 45 to 55%, and = less than 45% control or not labeled. 













Gramox- 






Round- 


Sencor/ 






Weed 


Balan 


Buctril 


Butyrac 


Eptam 


one 


Kerb 


Poast 


up^'' 


Lexone^ 


Sinbar 


Velpar 


Winter annual 
























Brome, downy 


9 








9 


9 


9 


9 


9 


9 


9 


8 


Chickweed, common 


8 


6 


6 


7 


9 


8 





10 


9 


9 


9 


Henbit 


5 


8 


6 


9 


9 


8 





8 


9 


9 


8 


Mustard, wild 





8 


10 


6 


9 


5 





9 


9 


9 


9 


Pennycress, field 





9 


9 


6 


9 


5 





10 


9 


9 


9 


Shepherdspurse 





9 


9 


7 


9 


5 





9 


9 


9 


9 


Summer annual 
























Bamyardgrass 


9 








9 


8 


8 


10 


10 


6 


6 


7 


Crabgrass spp. 


9 








9 


6 


8 


10 


9 


5 


7 


7 


Foxtail spp. 


9 








9 


9 


8 


10 


10 


6 


7 


7 


Lambsquarters, common 


9 


10 


8 


9 


9 


6 





9 


9 


9 


9 


Nightshade spp." 





9 


8 


8 


9 


6 





9 


5 


6 


6 


Panicum, fall 


9 








9 


9 


6 


10 


10 


6 


6 


6 


Pigweed sp. 


9 


8 


8 


9 


9 


6 





10 


9 


8 


9 


Ragweed, common 





9 


9 


5 


9 


5 





9 


8 


8 


8 


Smartweed, Pennsylvania 





9 


6 


5 


9 


5 





9 


9 


8 


8 


Perennial 
























Dandelion 








8 














8 


7 


6 


8 


Dock, curly 








5 














9 


6 


6 


6 


Nutsedge, yellow 











8 











7 











Orchardgrass 


5 








6 


5 


7 


6 


8 


5 


5 


6 


Quackgrass 


5 








8 


5 


8 


7 


9 


5 


5 


5 



' Lexone, Sencor, and Roundup are labeled for use in mixed legume-grass forages. No other herbicides are cleared for this use. 

^ Spot treatment. 

'^ Control of different species may vary. 



Treflan or Prowl, but good weed control can compen- 
sate to allow for good establishment of the legume. 
Fusilade (fluazifop), Option (fenoxaprop), and Poast 
(sethoxidim) may be used for grass control postemer- 
gence on forage legumes on ACR land. With many of 
these products, haying and grazing are not allowed, 
therefore be sure to follow all restrictions imposed by 
the pesticide label. 

Oats are commonly grown as a cover crop on set- 
aside acres. Oat seed is inexpensive and easy to obtain. 
If the Agricultural Stabilization and Conservation Ser- 
vice (ASCS) does not require clipping before seed 
maturity, oats can reseed themselves for fall cover. 
Wheat, rye, and barley are other small-grain cover 
crop possibilities. 

Sowing clean oat, wheat, rye, or barley seed is the 
first step to minimizing weed problems. Small grains 
generally provide relatively good cover until they 
mature or the area is mowed; then weeds can soon 
proliferate. However, winter wheat or rye may be 
sown in the spring, and without the overwintering 
period (vernalization), httle or no seed production 
occurs and a dense cover remains. Annual broadleaf 
weeds can be controlled by mowing and by the use 



of the herbicides listed in Table 14.3. Tilling before 
small-grain planting will help control established weeds. 

Planting a small-grain/legume combination is an- 
other option for set-aside. Using the small grain as a 
nurse or companion crop may help reduce weed 
pressure and alleviate the need for herbicides. If weeds 
become a problem, refer to Table 14.6 for more infor- 
mation in selecting the appropriate herbicide. In ad- 
dition to those herbicides listed in Table 14.6, Buctril 
may also be used to control broadleaf weeds in seedling 
alfalfa-grass mixes on Conservation Reserve Program 
acres. Refer to current label rates and restrictions. 

Sorghum-sudan grass can make a rapid, vigorous 
cover that also effectively suppresses many weeds. 
Although herbicides are rarely needed in sorghum- 
sudan grass stands, mowing and tillage may be diffi- 
cult; and viable seed sometimes causes weed problems 
the next year. 

Acreage Conservation Reserve land may offer an 
opportunity for controlling certain problem weeds such 
as perennials and may keep other, more common 
weeds in check. By managing ACR land this year, 
controlling weeds in future row crops will be less 
difficult and more economical. 



124 



Selected Publications 



Readers interested in reading more about a particular topic are referred to these publications, which were 
mentioned in the handbook. The publications are available from your county Extension office. Many of them 
are also available for purchase from the Office of Agricultural Communications and Education (OACE), 69 
Mumford Hall, 1301 West Gregory Drive, Urbana, Illinois 61801. Addresses for publications from other sources 
are also indicated. 



Chapter 1. 

Soils of lUinois, B778 (available from OACE). 

Performance of Commercial Corn Hybrids in Illinois — 
annual report on hybrid performance, available each 
year after harvest, AG-2056 (available from Depart- 
ment of Agronomy, N-307 Turner Hall, University of 
Illinois, 1102 South Goodwin Avenue, Urbana, Illinois 
61801 or your county Extension office). 

Chapter 2. 

Narrow-Row Soybeans: What to Consider, CI 161 
(available from OACE). 

Soybean Replanting Considerations for Maximizing 
Returns, CI 265 (available from OACE). 

Double-Cropping in Illinois, CI 106 (available from 
OACE). 

Performance of Commercial Soybeans in Illinois, AG- 
2055 (available from Department of Agronomy or your 
county Extension office). 



Chapter 3. 

Wheat Performance in Illinois Trials — 1990, AG-2054 
(available from Department of Agronomy or your 
county Extension office). 



Chapter 7. 

1991 Illinois Pest Control Handbook, IPC 1991 (avail- 
able from OACE). 



Chapter 8. 

Illinois Seed Law publications — updated as there are 
changes to the law (available from Illinois Department 
of Agriculture, Division of Plant Industries and Con- 
sumer Services, P.O. Box 19281, Springfield, Illinois 
62794-9281). 



Chapter 10. 

Illinois Voluntary Limestone Program Producer Infor- 
mation — annual publication (available from the Illi- 
nois Department of Agriculture, Division of Plant 
Industries and Consumer Services). 

Average Organic Matter Content in Illinois Soil Types, 
Agronomy Fact Sheet SP-36 (available from the De- 
partment of Agronomy). 

Color Chart for Estimating Organic Matter in Mineral 
Soils, AG-1941 (available from OACE). 

Soil Plan (available from Illinet Software, 330 Mum- 
ford Hall, 1301 West Gregory Drive, Urbana, Illinois 
61801). 



125 



Compendium of Research Reports on the Use of 
Nontraditional Materials for Crop Production (avail- 
able from Publications Distribution, Printing and Pub- 
lications Building, Iowa State University, Ames, Iowa 
50011 or your county Extension office). 



Chapter 11. 

The Residue Dimension — Managing Residue to Con- 
trol Erosion (CES fact sheets. Land & Water Series No. 
9, June 1989. This ongoing series covers a wide range 
of water quality and soil conservation issues. For more 
information, write to Land & Water Publications, 305 



Mumford Hall, 1301 West Gregory Drive, Urbana, 
Illinois 61801). 

A Farm Machinery Selection and Management Pro- 
gram — J. Siemens, K. Hamburg, and T. Tyrrell (J. 
Prod. Agric, 3:212-219, April-June 1990). 

Estimating Your Soil Erosion Losses with the Universal 
Soil Loss Equation (USLE), CI 220 (available from 
OACE). 



Chapter 12. 

Illinois Drainage Guide, CI 226 (available from OACE). 






126 



New^ 



Revised for 1991! 



1991 Illinois Pest Control Handbook 



Protect your crops with timely recommendations from Illinois 
pesticide specialists. The 1991 Illinois Pest Control Handbook 
contains guidelines for insect, weed, and disease management and 
provides information on pesticide application and equipment. 



The 1991 Illinois Pest Control Handbook includes 

• Insect management for crops, livestock & 
stored crops 

• Weed control for field & forage crops 

• Insect, weed & disease control for commercial 
vegetable, turf & ornamental production 

^ Alternatives in insect management 

• Pesticide toxicities, formulations & environ- 
mental hazards 

^ Specific recommendations developed 
especially for Illinois 



IPC-91 

1991 Illinois Pest Control 

Handbook. 

$14.00. 




See your county 
Extension adviser or 
use the order form 
to order your copy 
today. 



Publication Title 


Pub.# 


No. of Copies 


Price per Copy 


Total Cost 


1991 Illinois Pest Control Handbook 


IPC-91 




$14.00 




The 65th Annual Summary of Illinois Farm Business Records 


CI 304 




4.00 






























Amt. Enclosed 





No credit sales are permitted for orders totalling less than 
$10.00. For credit orders, please provide your organization's 
federal identification number (FEIN) or your Social Security 
number. International orders must be prepaid by checks 
cleared through a U.S. clearing bank. 

Please bill to # 

Make checks payable to the University of Illinois. 



Please print name and address in space below. 
Ship to: 



Mail to: 

Your County Extension Office 

OR: University of Illinois 

Office of Agricultural Communications 

and Education 

69E Mumford Hall 

1301 West Gregory Drive 

Urbana, Illinois 61801 

(217)333-2007 



A Comprehensive Look at 
Farm Performance 

The 65th Annual Summary of Illinois Farm 
Business Records presents 1989 income and 
expenses reported by over 7,000 participating 
Illinois farmers — including nearly 20 percent of 
all farms of 500 acres or more. 

The summary includes an analysis of recent 
changes in farm income for grain and livestock 
enterprises throughout Illinois. Comprehensive 
tables show average 1989 results by farm size, 
region, type of operation, and soil fertility rating. 



Designed for Easy Comparison 

You can use these results to compare your own 
operation with hundreds of others similar to yours. 
Complete, detailed tables show total and per-acre 
average costs and investments for a wide range of 
expenses, including 

•Seed, pesticide, and fertility 
•Power and equipment 
•Land and buildings 
•Labor and interest 

And there's space in each table to insert your 
own figures for comparison. 



Information You Can Use 

By putting your results next to the averages from 
participating farms, you can 

• Identify your strengths. When you see where 
you're doing better than average, you can more 
confidently continue doing those things that have 
made you successful. 

• Detect potential problem areas. By comparing your 
operation with others that are similar to yours, you 
can identify trouble spots where changes may have 
the greatest effect on your profitability. 

• Evaluate possible changes. Other farmers' results 
can help you judge how a change in your operation 
could affect your net income. 



Order Your Copy Today 

The 1989 Summary of Illinois Farm Business 
Records is an important source of farm manage- 
ment information. Use the order form or call 
(217)333-2007 to order your copy today. 

C1304. 1990. 40 pages, soft cover, 
8 1/2" X 11". $4.00. 






Useful Facts and Figures 



To convert 
column 1 
into column 2, 
multiply by 



0.621 
1.094 
0.394 
16.5 



0.386 
247.1 
2.471 



0.028 

1.057 

0.333 

0.5 

0.125 

29.57 

2 

16 



1.102 
2.205 
0.035 



0.446 
0.891 
0.891 
0.016 

0.015 



Column 1 



Length 



kilometer, km 
meter, m 
centimeter, cm 
rod, rd 



Area 



kilometer-, km- 
kilometer-, km- 
hectare, ha 



Volume 



Column 2 



mile, mi 
yard, yd 
inch, in. 
feet, ft 



To convert 
column 2 
into column 1, 
multiply by 



1.609 
0.914 
2.54 
0.061 



liter 
liter 

teaspoon, tsp 
fluid ounce 
fluid ounce 
fluid ounce 
pint 
pint 

Mass 

ton (metric) 
kilogram, kg 
gram, g 

Yield 

ton (metric)/hectare 
kg/ha 

quintal/hectare 
kg/ha-com, sorghum, rye 
kg/ha-soybean, wheat 



mile^ mi^ 2.59 

acre, acre 0.004 

acre, acre 0.405 



bushel, bu 35.24 

quart (liquid), qt 0.946 

tablespoon, tbsp 3 

tablespoon, tbsp 2 

cup 8 

milliliter, ml 0.034 

cup 0.5 

fluid ounce 0.063 



ton (English) 0.907 

pound, lb 0.454 

ounce (avdp.), oz 28.35 



ton (English)/acre 2.24 

lb/acre 1.12 

hundredweight/acre 1.12 

bu/acre 62.723 

bu/acre 67.249 



Temperature 



(9/5C) + 32 Celsius 



Fahrenheit 



5/9(F-32) 



Plant Nutrition Conversion 



P(phosphorus) x 2.29 = P^Os 
K(potassium) x 1.2 = K:0 



P:Os X .44 = P 
K.O X .83 = K 



ppm X 2 = lb/A (assumes that an acre plow depth of 6^3 inches weighs 
2 million pounds) 



Speed (mph) = 



Useful Equations 

distance (ft) x 60 

time (seconds) x 88 

1 mph = 88'/min 



Area = a x b 



Area = 1/2 (a x b) 




Area = irr- 
ir = 3.1416 



lb/ 100 ft= = 



Example: 10 tons/acre = 



lb/acre 
435.6 
20,000 lb 



435.6 



= 46 lb/ 100 ft= 



ib/acre 

oz/100 ft- =— X 16 

^ 435.6 

100 

Example: 100 lb/acre = x 16 = 4 oz/100 ft= 

^ ' 435.6 ^ 

gal /acre 

tsp/100 ft- = ^-^ X 192 

^' 435.6 

Example: 1 gal/acre = x 192 = .44 tsp/100 ft" 

Water weight = 8.345 lb/gal 
Acre-inch water = 27,150 gal 



iff ' ' '^ '^ 



3Iers.tyof.luho.s-urb2 




3 0112 027501961 



I 



I 



I 

I 



I