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630.7 
IL63AG 


Univ;        y  of 

III  in'  3rary 

at  Urbai.     ..  *i.mpaign 

ACES 


Atf-   .•^' -■.«r    v^Stf-M,  . 


ACES  yp'-^'^^y 

Aub  1  2  2010 


•s 

n. 


■.^ 


UNIVERSITY  OF  ILLINOIS 


Volume  III 


Issued  by  Agronomy  Department,  University  of  Illinois 
During  the  Period  September  5^  1955^  to  June  l8,  1956 


AGITI^ 


ACES  LIBRARY 
UNIVERSITY  OF  ILLINOIS 
1101  S.  GOODWIN  AVE. 
URBANA.IL  61801 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://www.archive.org/details/agronomyfacts03univ 


TABLE  OF  CONTENTS 


Miscellaneous 


Pollination  and  Fertilization M-13 

The  Function  of  CO  in  Crop  Production K-l4 

Radiation  and  Plant  Breeding K-15 

The  Yellow  Dwarf  (Red  Leaf)  Disease  of  Oats M-I6 


Corn 


Corn  Hybrids  for  Specialized  Farm  and  Market  Uses C-7 

Tomorrow's  Hybrid  Corn C-8 

Temperature  and  Other  Interrelated  Factors  in  Drought  Damage 

to  the  Corn  Plant C-9 

How  to  Estimate  Hail  Losses  to  Corn C-10 


Forage  Crops 


Identifying  Common  Legume  Seedlings F-IT 

Selecting  Alfalfa  Varieties F-I8 

How  Hybrid  Sorghums  Were  Developed  and  Are  Being  Produced F-I9 

Sudangrass  in  Illinois F-20 

Orchardgrass  and  Its  Management F-21 


Small  Grains 


Winter  Barley  in  Illinois G-I3 

Winter  Wheat G-lU 

"Blast"  in  Oats G-I5 

Winter  Rye  in  Illinois^ G-I6 

Soybeans 

Root  and  Stem  Rot  of  Soybeans E-5 

Estimating  Hail  Losses  to  Soybeans S-6 

Soil  Fertility  and  Testing 

Chemistry  of  Organic  Nitrogen  in  Soils  SF-37 

1955  Wheat  Yields--Illinois  Soil  Experiment  Fields  SF-38 

Earthworms SF-39 

Band  Application  of  Fertilizers  in  Illinois — Part  1 SF-40 

Band  Application  of  Fertilizers  in  Illinois — Part  2 SF-4l 

Progress  Report  on  a  Green-Manuring  Project SF-U2 

Composts SF-i|-3 

The  Nature  of  Exchangeable  Calcium  and  Magnesium  and  Their 

Relation  to  Soil  Acidity  and  Lime  Requirement SF-^ij- 


-2- 

Soil  Management  and  Conservation 

Objectives  of  Crop  Rotations — Introduction  and  Erosion  Control  .  .  .SM-12 

Effect  of  Crop  Rotations  on  Soil  Physical  Condition SM-I3 

Crop  Rotations  and  Insects 5M-1^ 

An  Analysis  of  the  Nitrogen  Status  of  the  Agronomy  South 

Farm  Rotations SM-I5 

Economic  Ohjectives  of  Crop  Rotations £M-l6 

Continuous  Corn SM-IT 

Soil  Properties 

The  Productivity  of  Some  Important  Southern  Illinois  Soils SP-9 

Corn  Root  Distribution  in  Fertilized  and  Unfertilized  Flanagan 

Silt  Loam SP-10 

The  Productivity  of  Dark,  Till-Derived  Soils  in  Northeastern 

Illinois SP-11 

Bottomland  Soils  of  Illinois SP-12 

Organic  Soils  in  Illinois SP-I3 

Fragipans  in  Illinois  Soils SP-1^ 

Basis  for  Separating  and  Classifying  Soils SP-I5 

Weed  Control 

Controlling  Wild  Garlic  and  Wild  Onion W-6 

Reaction  of  Various  Weeds  and  Brush  to  2,4-1  and  2,k,'^-T V-J 


J.-/P:  sc 
Aug.  1955 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M-13 


POLLINATION  AND  FERTILIZATION 


The  pollen  that  we  see  flying  in  fields 
of  corn  in  July  and  August  plays  an  im- 
portant pai-t  in  the  production  of  the 
corn  crop.  These  tiny  grains  are  essen- 
tial for  the  formation  of  the  kernel; 
■without  them  the  cob  vciold  he  hare  and 
useless.  Pollination  is  essential  not 
only  in  producing  corn,  hut  in  producing 
all  other  crops.  Without  this  process, 
almost  all  of  the  seed  plants  would 
disappear,  leaving  only  those  that  repro- 
duce by  cuttings  or  other  special  mechan- 
isms. 

Pollen  is  produced  by  the  male  flowers 
of  the  corn  tassel.  The  female  flowers 
are  borne  on  the  ear.  Plants  of  this 
sort,  in  which  the  flowers  are  carried 
separately,  are  said  to  have  imperfect 
flowers.  Most  plants  have  perfect 
flowers;  that  is,  the  male  and  female 
parts  are  carried  within  a  single  flower, 
as  in  wheat,  oats  and  soybeans.  Plants 
that  have  perfect  flowers  are  often 
self -fertilized,  while  those  that  have 
imperfect  flowers  are  usually  cross- 
fertilized.  In  many  species  with  per- 
fect flowers,  stray  pollen  is  usually 
excluded  because  pollination  occurs  be- 
fore the  flower  actually  opens.  This 
makes  it  virtually  certain  that  self- 
pollination  will  take  place. 

At  the  time  of  sexual  maturity,  matiure 
pollen  is  released  from  anthers  in  large 
amounts.  It  has  been  estimated  that  a 
single  corn  tassel  will  produce  as  much 
as  25, 000, ceo  pollen  grains.  This  esti- 
mate is  probably  high,  but  even  the  most 
conservative  estimate  would  be  that  each 
silk  produces  at  least  9^000  pollen 
grains , 

Mature  pollen  is  transferred  from  the 
anther  to  a  receptive  surface,  called  a 
stigma,  by  wind,  gravity,  or  insects. 
Upon  alighting,  the  pollen  grain  germi- 
nates, and  the  pollen  tube  grows  down 
the  style  (silk  in  corn)  until  it  reaches 
the  ovary. 


Fertilization  in  Typical  Grass 
Species   (Schematic) 


,Silk  (stigma) 


Polar 
Nuclei 


Germinated 
Pollen     I 

Pollen  Tube 


Sperm 


In  corn  this  process  usually  takes  2k- 
to  26  hours.  Two  sperm  move  down  the 
pollen  tube  and  enter  the  ovary.  One  of 
these  sperm  unites  with  the  egg  and  the 
other  unites  with  two  polar  nuclei.  The 
egg  and  sperm  union  produces  the  embryo 
(the  new  plant),  and  the  polar  nuclei- 
sperm  \inion  produces  the  endosperm. 
This  process  is  called  fertilization. 
Cell  division  proceeds  in  these  tissues 
\intil  the  mature  seed  is  produced. 

Endosperm  in  corn  consists  of  the  aluerone 
layer  and  the  soft  and  horny  starch  of 
the  kernel.  In  soybeans  the  endosperm 
is  microscopic,  and  the  food  for  the  new 
embryo  is  stored  in  stinctiires  called 
cotyledons.  Cotyledons  are  a  part  of  the 
embryo  itself,  and  in  young  soybean  seed- 
lings they  look  much  like  two  thickened 
leaves , 


Envirorment  plays  an  important  part  in 
the  success  of  pollination.  For  ex- 
ample, high  humidity  quickly  bursts  pol- 
len of  red  clover.  The  higher  seed  set 
of  this  species  in  dry  climates  is  doubt- 
less due  to  the  lower  humidity.  High 
temperatures  usually  reduce  the  time 
that  pollen  will  live.  Species  vary  in 
the  length  of  time  pollen  remains  via- 
able.  Barley  pollen  is  particularly 
short-lived  if  removed  from  the  flower. 
In  contrast,  wheat  pollen  can  be  col- 
lected and  stored  at  room  temperatures 
for  as  long  as  six  hovirs  and  still  ef- 
fect fertilization.  Corn  pollen  remains 
viable  for  a  shorter  period,  possibly  no 
longer  than  two  or  three  hours  under 
ordinary  field  conditions.  Viability  is 
lost  much  more  quickly  when  temperatures 
are  high  than  when  they  are  low. 

Under  Illinois  conditions,  pollen  via- 
bility rarely  limits  corn  production. 


In  100°  temperatures,  pollen  remains  via- 
ble for  only  a  short  time.  During  early 
morning  hours  when  temperatures  are 
lower,  enough  pollen  is  usually  shed  to 
insure  a  satisfactory  seed  set.  How- 
ever, extremely  high  planting  rates  or 
drouth  often  causes  late  silking  and  many 
ears  may  not  be  adequately  pollinated. 

The  pollination  habits  of  a  crop  species 
largely  determine  the  methods  that  plant 
breeders  may  use  in  improving  that  crop. 
In  corn,  the  male  and  female  flowers  are 
widely  separated,  and  hybrids  may  be 
produced  easily  and  inexpensively.  Thus 
their  large-scale  use  is  practical. 
Oats,  wheat,  and  soybeans,  however,  can- 
not be  easily  hybridized  because  the 
flowers  are  perfect  and  tiny.  Hybrids 
of  these  crop  plants  will  therefore  prob- 
ably never  be  ccmmercially  available. 

D.  E.  Alexander 
10-17-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M-14 


THE  FUNCTION  OF  CO2  IN  CROP  PRODUCTION 


Carbon  constitutes  kO-k-^  percent  of  the 
dry  weight  of  most  crop  plants.  Wo 
other  element  contributes  as  many  atoms 
to  the  formation  of a  plant.  Carbon  mol- 
ecules linked  one  to  another  form  the 
basic  skeleton  of  the  carbohydrates^ 
fats^  proteins,  and  other  substances 
that  make  up  a  plant.  The  oxidation  or 
"burning"  of  the  reduced  carbon  in  fat 
and  sugar  provides  the  energy  for  plant 
growth.  Obviously,  an  adequate  supply 
of  carbon  is  imperative  for  good  crop 
production. 

The  basic  supply  of  carbon  for  plants  is 
in  the  form  of  a  gas,  carbon  dioxide,  or 
CO2.  Carbon  in  this  form  is  at  its  low- 
est energy  level — completely  oxidized 
or  burned--and  is  very  stable.  The  nor- 
mal CO2  concentration  of  the  atmosphere 
is  about  three  parts  in  10,000  parts  of 
air,  or  O.O3  percent.  Except  in  the  vi- 
cinity of  the  soil  or  photosynthesizing 
plants,  this  figure  is  relatively  con- 
stant. The  constancy  is  maintained  by  a 
vast  reservoir  of  CO2  dissolved  in  the 


oceans,  both 


as  the  gas  and  as  carbon- 


ates (the  reaction  product  of  CO2  and 
H2O).  Air  passing  over  the  oceans  gains 
or  loses  CO2  until  the  normal  concentra- 
tion is  re-established,  and  large  m.asses 
of  air  continually  move  from  oceans  to 
land  and  off  to  the  oceans  again. 

The  plant  absorbs  nearly  all  of  the  CO2 
it  requires  frcm  the  atm.osphere,  the  gas 
diffusing  in  through  small  pores  in  the 
leaves.  Some  CO2  is  absorbed  by  the 
roots  and  is  translocated  to  the  leaves 
in  the  upward-moving  sap,  but  the  amount 
so  supplied  is  believed  to  be  of  minor 
importance  (about  5  percent  at  most). 

Plant  leaves  are  amazingly  efficient  in 
absorbing  CO2.  They  can  remove  as  much 
as  50  percent  of  the  CO2  from  a  layer  of 
air  which  is  rapidly  passed  over  photo- 
synthesizing  corn  leaves .   If  it  were 


not  for  this  high  absorption  efficiency, 
plants  would  make  very  poor  gro-vrth,  since 
the  concentration  of  CO2  in  the  air  is 
so  very  small. 

The  CO2  that  is  absorbed  by  the  leaf  is 
transformed  to  sugars  in  the  chloro- 
plasts,  which  are  small,  more  or  less 
rounded  bodies  to  be  found  in  the  cells 
of  all  green  tissue.  The  chlorophyll  of 
the  chloroplasts  absorbs  light  (prin- 
cipally the  red  and  blue  wave  lengths, 
leaving  the  familiar  green  color)  and 
uses  the  light  energy to  split  off  hydro- 
gen from  water.  The  hydrogen  thus 
gained  is  used  to  "reduce"  carbon  diox- 
ide to  a  higher  energy  state — the  state 
in  which  it  occurs  in  sugars  and  starch. 
This  reduction  to  a  higher  energy  state 
is  an  extremely  ccmplicated  biochemical 
process,  but  it  can  be  summarized  as 
follows : 

1.  The  CO2  absorbed  by  the  chloroplasts 
is  added  by  an  enzyme  to  aphosphory- 
lated  5-carbon  sugar.  This  forms  an 
unstable  6-carbon  compound,  which 
immediately  splits  to  give  two  phos- 
phorylated  S-cs^^'bcn  acids. 

2.  The  hydrogen  produced  by  the  split- 
ting of  water  is  added  to  the  3-carbon 
acids,  which  then  condense  to  give  a 
stable  6-carbon  sugar,  a  phosphory- 
lated  glucose.  The  phosphorylated 
glucose  is  a  key  compound  that  can 
be  readily  transformed  to  starch, 
cane  sugar,  fat,  amino  acids,  etc. 
The  figure  on  the  back  schematica3J.y 
depicts  the  photosynthetic  process. 

Greenhouse  and  laboratory  experiments 
have  shown  that  the  concentration  of  CO2 
in  the  atmosphere  is  far  frcm  optimal 
for  photosynthesis.  By  increasing  the 
CO2  concentration  about  2.5  times,  the 
photosynthetic  rate  of  plants  in  bright 
sunlight  can  be  doubled.   There  is  some 


question,  however,  about  the  effect  of 
still  higher  concentrations  of  COg. 
While  short-time  photosynthesis  con- 
tinues to  increase,  the  higher  concentra- 
tions of  CO2  have  a  toxic  effect  that 
reduces  grovth. 

Many  investigators  have  grown  crop  plants 
to  maturityin  C02-enriched  air  in  green- 
houses, and  with  few  exceptions  they  re- 
port yield  increases  of  20  to  200  percent. 
Exceptions  apparently  occur  when  the  CO2 
concentration  is  raised  too  high.  There 
is  no  accurate  evaluation  of  just  what 
concentration  of  CO2  would  produce  maxi- 
mum photosynthesis  without  injuring  the 
plant,  hut  it  appears  that  a  50-100  per- 
cent increase  in  concentration  would  he 
nearly  optimal,  depending  on  the  species 
concerned. 

Field  studies  on  the  effect  of  CO2  en- 
richment have  also  been  carried  out, 
and  for  the  most  part  these  results  also 
shew  yield  increases.  Field  studies 
are  much  more  difficult  to  make  than 


greenhouse  studies,  "because  the  gas  is 
not  contained  and  winds  will  carry  it 
away.  However,  CO2  is  a  heavy  gas,  and 
if  released  near  the  soil  it  will  tend  to 
"hang"  in  the  vegetation  in  high  concen- 
tration if  there  is  not  excessive  turbu- 
lence due  to  winds.  Even  though  marked 
yield  increases  of  such  crops  as  sugar 
beets  have  been  obtained  by  CO2  enrich- 
ment of  the  air,  such  "fertilization"  is 
not  commercially  practical  because  of  the 
excessive  cost  of  supplying  the  gas. 

Actually  it  appears  that  sizable  yield 
increases  could  be  obtained  if  one 
could  only  maintain  the  normal  concen- 
tration of  CO2  around  the  crop  during 
the  daylight  hours.  As  it  is,  the  CO2 
concentration  in  a  field  of  rapidly 
growing  corn  during  the  daylight  hours 
will  average  about  25  percent  less  than 
normal.  Measurements  made  at  Ames, 
Iowa,  show  that  even  at  5OO  feet  above 
the  cornfield  the  concentration  will  be 
reduced  10  percent.  Such  depletions 
occur  on  windy  as  well  as  still  days 


light 


-3- 


and  leave  no  doubt  that  the  crop  can  ah- 
sorh  CO2  more  rapidly  than  it  can  be 
brought  down  from  the  upper  atmosphere. 

The  upper  atmosphere  is  not  the  only 
source  of  CO2  for  the  plant ^  however. 
The  respiration  of  microorganisms  and 
plant  roots  produces  large  amounts  of  CO 2 
in  the  soil^  which  diffuses  up  into  the 
atmosphere  about  the  leaves  of  the  crop. 
A  fertile^  warm,  moist  soil,  well  sup- 
plied with  organic  matter,  will  give  off 
as  much  as  3OO  pounds  of  CO2  per  acre 
during  the  daylight  hours.  Inasmuch  as 
a  very  rapidly  growing  acre  of  corn  will 
absorb  about  400  pounds  of  CO2  in  the 
same  period,  it  can  be  seen  that  the  soil 
can  do  much  to  maintain  favorable  concen- 
trations of  CO2  about  the  leaves.  If  it 
were  not  for  this  evolution  of  CO2  from 
the  soil,  the  concentration  of  the  gas  in 
the  cornfield  during  the  day  would  un- 
doubtedly be  reduced  more  than  the  25 
percent  below  normal  previously  quoted. 

The  point  bears  emphasizing,  however, 
that,  if  the  soil  is  to  be  effective  in 
this  respect,  it  must  be  fertile,  moist. 


and  warm,  with  a  high  organic  matter  con- 
tent and  a  structure  conducive  to  rapid 
gas  exchange.  In  short, production  of  CO2 
by  the  soil  will  be  maximal  in  those 
soils  that  have  long  been  recognized  as 
producing  excellent  crops.  But  just 
what  share  of  the  yield  is  to  be  at- 
tributed to  increased  COo  concentration 
about  the  leaves?  Experimental  evidence 
does  not  permit  this  question  to  be 
answered  with  exactitude,  although  an  ex- 
periment conducted  in  Sweden  with  sugar 
beets  30  years  ago  suggests  that  it 
might  be  appreciable. 

In  this  experiment,  manure,  instead  of 
being  worked  into  the  soil,  was  allowed 
to  ferment  in  troughs  between  the  beet 
rows.  This  fermentation  prevented  the 
roots  from  obtaining  the  nutritive  ele- 
ments, but  the  air  around  the  leaves  was 
enriched  by  the  escaping  C02.  A  19  per- 
cent increase  in  yield  over  controls  was 
obtained  by  this  treatment.  Such  results 
suggest  that  an  appreciable  part  of  record 
corn  yields  may  be  due  to  increased  CO2 
coming  from  the  heavily  manured  soils 
that  seem  to  be  an  invariable  part  of 
such  yields. 


J.  B.  Hanson 
1-16-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


M-15 


RADIATION  AND  PLANT  BREEDING 


In  1927  and  1928  Dr.  H.  J.  Muller,  now 
of  Indiana  University,  and  the  late  Dr. 
L.  J.  Stadler,  of  the  University  of 
Missouri,  reported  that  X-ray  and  ultra- 
violet radiation  "brought  about  heritable 
changes  (mutations)  in  living  organisms. 
(Doctor  Muller  was  awarded  the  Eobel 
prize  in  Medicine  in  19^6  for  this  work. ) 
Since  the  rate  of  mutation  was  thousands 
of  times  greater  in  irradiated  material 
than  in  untreated  material  and,  further, 
since  some  of  the  mutants  appeared  to 
have  qualities  that  plant  breeders  were 
looking  for,  it  was  immediately  suggested 
that  plant  breeders  use  this  new  tech- 
nique. 

At  that  time  corn  breeders  were  perfect- 
ing hybrid  corn,  and  other  breeders  were 
convinced  that  the  new  tool  was  not  well 
adapted  to  their  programs.  Most  breeders 
and  geneticists  were  impressed  with 
the  fact  that  the  vast  majority  of  the 
mutations  were  deleterious,  i.e.,  the 
plant  that  possessed  the  new  character 
yielded  lower  or  was  otherwise  less  de- 
sirable than  already  existing  strains. 
Hence  the  use  of  irradiation  in  breeding 
was  largely  neglected. 

If  we  examine  critically  the  changes 
brought  about  in  the  hereditary  material 
of  an  irradiated  individual,  we  can  make 
some  interesting  observations.  Muller 
and  Stadler  found  that  these  changes 
could  be  roughly  placed  into  three 
classes: 


1.  Intra-genic  changes,  i.e.,  changes 
within  the  gene  itself  that  are  simi- 
larto  those  found  in  nature.  These 
changes  behaved  in  a  Mendelian  fash- 
ion. No  differences  in  viability  of 
pollen  or  egg  were  evident  and  normal 
segregation  occurred  in  the  F2.  Un- 
fortunately, these  changes  are  the 
least  common  ones  that  are  induced 
by  radiation. 


2.  Deletion,  i.e.,  destruction  of  a 
small  part  of  the  chromosome  itself. 
Critical  studies  by  Stadler  revealed 
that  many  of  these  changes  were  so 
small  as  to  be  undetactable  when  he 
looked  at  the  chromosome  under  a 
microscope,  but  genetic  studies 
showed  that  a  number  of  genes  had 
been  destroyed. 

3.  Structural  rearrangement  of  chromo- 
somes. Many  of  the  mutations  in- 
volved the  translocation  of  part  of 
one  chromosome  to  another  chromosome, 
or  the  inversion,  or  change  in  gene 
order,  of  a  single  chromosome.  These 
changes  produced  varying  degrees  of 
sterility,  either  on  the  female  or 
male  side,  or  on  both. 

Swedish  plant  breeders,  however,  started 
irradiation  breeding  in  barley  and  other 
cereal  crops  and  were  able  to  show  that 
mutants  could  be  produced  that  matured 
earlier  and  had  stiffer  and  shorter 
straw,  greater  resistance  to  certain 
diseases  and,  in  a  few  cases,  higher 
yield.  However,  these  useful  mutants 
were  very  rare.  Swedish  workers  esti- 
mate that  only  one  in  a  thousand  of 
these  mutations  may  be  of  value  in  a 
breeding  program. 

An  increase  in  radiation  breeding  oc- 
curred after  World  War  II  in  the  U.S., 
largely  because  of  the  financial  support 
of  the  Atomic  Energy  Commission.  Radia- 
tion breeding  in  corn,  wheat,  oats,  soy- 
beans, rye,  peanuts,  cotton,  and  several 
other  field  crop  species  is  currently 
under  way  in  agricultural  experiment 
stations  throughout  this  country.  It  is 
still  too  early  to  anticipate  the  even- 
tual outcome  of  all  this  work,  but  the 
conclusions  on  the  following  page  appear 
to  the  justified  as  of  now. 


2. 


It  is  improbable  that  the  mutants 
produced  in  a  strain  by  irradiation 
will  be  used  directly  by  farmers. 
It  is  more  probable  that  the  new 
quality  will  be  incorporated  into 
new  varieties  by  conventional  plant 
breeding  methods  and  that  these  va- 
rieties will  be  released  only  if 
they  possess  advantages  over  exist- 
ing varieties. 

The  use  of  radiation  does  not  appear 
to  be  a  profitable  venture  for  plant 
breeders  unless  a  desired  quality 
does  not  exist  or  cannot  be  found  in 
the  species  under  improvement. 


3.  No  drastically  new  and  completely 
superior  varieties  can  be  expected 
through  irradiation  treatment  alone. 
Since  the  discovery  of  the  mutational 
effect  of  ionizing  radiation  in  I926, 
millions  of  individual  seeds,, plants, 
and  pollen  grains  have  been  treated 
with  X-rays,  neutrons,  and  ultra- 
violet rays.  Some  heritable  changes 
have  been  wrought.  All  of  them  are 
more  or  less  similar  to  the  changes 
that  occur  at  rarer  intervals  without 
man's  intervention,  and  most  of  them 
are  deleterious  to  the  individual 
that  inherits  them. 

D.  E.  Alexander 
3-26-56 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M-16 


THE  YELLOW  DWARF  (RED  LEAF)  DISEASE  OF  OATS 


The  red  leaf  (yellov  dvarf )  disease  of 
oats  probably  has  been  present  in  the 
U.S.  for  many  years.  Excellent  descrip- 
tions of  what  appear  to  be  the  eame 
disease  were  published  as  far  back  as 
1898.  Since  19^5:)  however^  the  disease 
has  become  increasingly  more  prevalent. 
The  reason  for  this  increase  is  not 
known,,  but  it  does  not  appear  to  be  as- 
sociated with  the  continual  change-over 
in  oat  varieties. 

Red  leaf  is  caused  by  a  virus  that  can 
be  transmitted  by  at  least  five  species 
of  aphids  commonly  infesting  small  grain 
and  grasses.  The  virus  cannot  be  trans- 
mitted mechanically,  in  the  seed,  or 
through  the  soil. 

The  virus  has  been  sho-vm  to  be  identical 
with  the  one  causing  yellow  dwarf  dis- 
ease of  small  gi-ain  in  California.  The 
name  "yellow  dwarf"  was  selected  by  Cali- 
fornia workers  on  the  basis  of  outstand- 
ing symptoms  produced  by  the  virus  on 
barley  and  wheat. 

The  disease  usually  appears  first  on  the 
edges  of  a  field  and  in  "spots"  or  cir- 
cular areas  varying  from  a  few  feet  to 
30  or  more  feet  in  diameter.  Sometimes 
these  areas  may  overlap,  and  in  years 
when  aphids  are  very  abimdant  a  field 
may  be  uniformly  affected.  Farmers  fre- 
quently have  failed  to  associate  earlier 
aphid  infestations  with  the  disease, 
since  the  first  symptoms  usually  appear 
in  about  ik  days.  Sometimes  nearly  all 
aphids  have  disappeared  by  the  time  the 
first  symptoms  can  be  seen. 

The  first  symptom  of  the  disease  in  oats 
is  the  appearance,  usually  near  the  leaf 
tip,  of  faint  yellowish-green  blotches 
that  can  best  be  seen  by  holding  the 
leaf  blade  up  to  the  light.   V/hen  first 


formed,  the  blotches  are  somewhat  vari- 
able in  size  and  shape  and  are  usually 
less  than  a  few  centimeters  in  size.  The 
blotches  enlarge  rather  rapidly,  merge, 
and  turn  various  shades  of  red,  broim, 
and  yellow- orange.  Cool  temperatures 
(70°  F.  and  lower)  favor  the  appearance 
of  red  pigments  in  the  affected  leaves, 
whereas  temperatures  of  75°  F.  and  above 
suppress  their  appearance.  At  the  same 
time,  the  yellowish-green  blotches  con- 
tinue to  appear  on  successively  lower 
portions  of  the  leaf  in  advance  of  the 
changes  in  color.  The  affected  portions 
of  the  leaf  often  die  rapidly. 

In  addition,  a  rather  characteristic  in- 
ward curling  of  affected  leaves  frequently 
occurs.  Symptoms  generally  appear  on 
the  oldest  leaves  first  and  then  succes- 
sively involve  the  younger  leaves.  Oc- 
casionally the  youngest  leaves  will  show 
a  longitudinal  striping  resulting  from  a 
yellow-green  color  in  the  interveinal 
areas  and  a  darker  green  in  the  tissue 
over  the  veins.  The  root  system  is  as 
severely  stunted  as  the  tops  of  the 
plants. 

Blasting  of  the  florets  is  the  most  seri- 
ous aspect  of  the  disease.  It  may  vary 
from  only  a  few  blasted  florets  to  com- 
plete failure  of  the  plant  to  head.  A 
shriveling  and  lower  test  weight  of  ker- 
nels also  may  occur.  The  severity  of 
the  disease  depends  on  the  variety  of 
oat  infected,  the  age  of  the  plants  at 
the  time  they  become  infected^  and  the 
strain  of  virus  involved. 

Winged  aphids  moving  into  small  grain 
fields  in  the  spring  from  various  grasses 
are  believed  to  be  responsible  for  the 
initial  spread.  Each  adult  aphid  is  cap- 
able of  producing  daily  from  10  to  20 
young,  which  upon  maturity  (one  to  two 


weeks)  also  begin  to  produce.  These 
later  aphids  are  usually  vingless  and 
move  about  by  crawling  from  plant  to 
plant.  When  food  conditions  become  un- 
favorable, winged  forms  develop  which 
fly  to  other  fields  of  small  grain  and 
grasses. 

In  order  to  transmit  the  virus  to  healthy 
plants,  the  aphid  first  must  acquire  it 
by  feeding  on  diseased  plants.  However, 
once  the  aphid  has  acquired  the  virus,  it 
apparently  is  able  to  transmit  it  for 
the  rest  of  its  life. 

Virus -free  aphids --less  than  a  hundred 
per  plant --cause  very  little  damage  to 
small  grain.  The  greenbug  is  an  excep- 
tion, since  it  secretes  a  toxin.  A  sin- 
gle viruliferous  apple -grain  aphid  is 
able  to  transmit  the  virus  to  a  healthy 
oat  plant  in  as  short  a  time  as  four 
hours. 


For  an  aphid-transmitted  virus  to  cause 
serious  loss  in  an  annual  crop  raised 
from  seed,  the  virus  must  spread  rapidly. 
Rapid  spreading  can  occur  only  if  the 
crop  is  easily  infected,  the  source  of 
the  virus  is  readily  available,  and  the 
vector  is  very  numerous  and  active.  For- 
tunately, all  of  these  conditions  do  not 
usually  occur  at  the  same  time,  and  losses 
therefore  vary  greatly  from  year  to  year 
and  from  locality  to  locality. 

No  oat  variety  tested  has  been  found  to 
possess  satisfactory  resistance  to  red 
leaf  disease.  Therefore,  an  intensive 
effort  is  being  made  to  locate  sources 
of  resistance  in  oats. 

Early  planting  is  the  only  practice  that 
can  be  recommended  at  present.  This  rec- 
ommendation is  based  on  the  fact  that 
large  plants  are  better  able  to  "toler- 
ate" the  disease  than  smaller  ones. 


R.  M.  Takeshita 
5-li^-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


C-7 


CORN  HYBRIDS  FOR  SPECIALIZED  FAR/V^  AND  MARKET  USES 


Corn  is  an  extremely  versatile  crop. 
Consequently,  breeders  are  able  to  se- 
lect types  for  particular  uses.  They 
may  work  with  dent,  sweet,  pop,  flint, 
floury,  or  waxy  corn.  These  types,  how- 
ever, may  be  modified  greatly  by  breed- 
ing and  selection. 

Livestock  feed.  From  75  to  90  percent 
of  the  corn  crop  in  the  United  States  is 
fed  to  livestock.  In  contrast,  most  of 
the  corn  crop  in  many  other  areas  of  the 
world  is  used  for  human  food.  Most  live- 
stock feeders  in  the  United  States  pre- 
fer a  dent  grain  that  is  yellow,  soft, 
and  high  in  quality  and  quantity  of  pro- 
tein. Feeders  in  many  other  covintries 
prefer  a  white  flint  corn. 

Corn  has  certain  limitations  for  feed- 
ing. It  is  low  in  quality  and  quantity 
of  protein  and  is  relatively  low  in 
vitamins.  Seme  feeders  also  ccmplain  of 
poor  palatability  and  reduced  gains  from 
certain  hybrids.  Many  feeders  grind  the 
harder  types. 

Corn  breeders  need  to  develop  special 
hybrids  with  high  tonnage  and  better 
quality  of  silage  and  green  feed. 
Multiple -eared,  heavy- tillering  strains 
may  be  useful  for  this  purpose.  Consid- 
eration must  be  given  to  yield  and  per- 
centage of  dry  matter,  proportion  of 
ears  to  stalks  and  leaves,  and  percent- 
age 1  of  crude  fiber  and  protein.  These 
studies  should  be  supported  by  digesti- 
bility experiments  and  by  feeding  trials. 

Milling  industry.  Wet  millers  desire 
strains  that  are  high  in  starch,  oil, 
and  protein.  Since  corn  contains  about 
70  percent  starch  (dry  basis),  a  varia- 
tion of  one  or  two  percent  is  important 
in  large-scale  operation.  The  industry 
claims  that  flinty  types  do  not  steep 
and  process  so  well  as  softer  types. 

Most  dry  millers  prefer  a  kernel  that  is 
semihard  and  vitreous  and  that  does  not 


have  too  much  soft  starch  on  either  the 
tip  or  the  dent  end.  They  want  neither 
the  shoe -peg  type  nor  small,  roiond 
kernels.  The  dent  must  not  be  too  deep 
or  the  hull  too  rough.  Kernels  of  this 
type  make  chaffy  or  chalky  products 
which  are  fit  only  to  put  into  feed. 
The  cob  color  is  of  little  consequence. 

An  adequate  supply  of  white  corn  is 
another  requirement  of  dry  millers.  Con- 
s\jmers  claim  a  distinct  preference  for 
the  flavor  and  taste  of  meal  made  from 
white  corn.  The  finished-product  demand 
is  for  either  pure  white  or  pure  yellow. 

Protein  content  and  quality.  Protein  is 
an  expensive  but  necessary  constituent 
of  food  and  feed.  The  University  of 
Illinois  gave  the  first  evidence  that 
protein  and  oil  content  in  corn  could  be 
greatly  increased  or  lowered  by  breed- 
ing. After  50  generations  of  selection, 
the  average  protein  content  was  19.5 
percent  for  Illinois  High  Protein  and 
4.9  percent  for  Illinois  Lev  Protein. 
These  open-pollinated  strains  yield  only 
about  50  percent  as  much  grain  as  adapted 
hybrids.  Fortunately,  the  high  pro- 
tein trait  can  be  transferred  to  stand- 
ard inbred  lines  by  breeding  procedvires. 

Quality  of  protein  is  fully  as  inrportant 
as  quantity  of  protein.  The  corn  kernel 
contains  two  main  types  of  protein. 
That  found  in  the  endosperm  is  primarily 
zein.  Zein  is  deficient  in  tryptophane 
and  lysine,  which  are  essential  for  ani- 
mal nutrition.  The  other  type  of  pro- 
tein, fo\ind  in  both  endosperm  and  germ, 
contains  both  tryptophane  and  lysine  and 
is  biologically  balanced.  The  corn 
breeder  would  like  to  increase  the  per- 
centage of  these  amino  acids  in  the  en- 
dosperm protein.  The  alternative  is  to 
add  them  to  the  diet  from  other  sources. 

Oil  for  industry  and  high-energy  feed. 
Corn  oil,  a  valuable  by-product  of  the 
starch  industry,  is  high  in  energy  value 


for  livestock  feeding.  Most  of  ■'the  oil 
is  in  the  germ  of  the  kernel.  Germ  pro- 
tein contains  tryptophane  and  lysine, 
is  biologically  balanced,  and  is  prob- 
ably more  valuable  for  livestock  feeding 
than  endosperm  protein.  High- oil  hy- 
brids having  a  high  proportion  of  germ 
to  endosperm  should  therefore  benefit 
both  the  starch  industry  and  livestock 
feeders. 

After  50  generations  of  selection  at  the 
University  of  Illinois,  the  average  oil 
content  of  Illinois  High  Oil  vas  15.^ 
percent  compared  with  1.0  percent  for 
Illinois  Lov  Oil.  Unfortunately,  these 
open-pollinated  high-oil  strains  are  low 
yielding.  High  oil,  however,  was  trans- 
ferred to  standard  inbred  lines  at  the 
Illinois  ' station  by  crossing,  followed 
by  back-crossing,  selection,  and  self- 
fertilization.  Selection  for  high  oil 
was  accomplished  by  selecting  ears  bear- 
ing kernels  with  large  germs. 

Breeding  programs  have  been  inaugurated 
by  several  Com  Belt  agricultural  exper- 
iment stations  and  private  hybrid  seed 
corn  companies  to  develop  hybrids  with 
high -oil  or  high -protein  content.  Seme 
of  these  hybrids  appear  to  be  very  prom- 
ising. For  example.  111.  6063  produced 
lij-,0  percent  more  protein,  32.8  percent 
more  oil,  and  was  8.5  percent  superior 
in  grain  yield  to  U.  S.  I3,  a  standard 
hybrid.  However,  these  Illinois  experi- 
mental combinations  are  not  yet  in  com- 
mercial use. 

Zein  for  special  fabrics.  Protein  con- 
tent of  corn  grain  may  be  increased  by 
breeding  and  by  high  applications  of 
nitrogen  fertilizers.  Most  of  the  in- 
crease of  endosperm  protein  is  zein, 
whith  is  not  high  in  nutritive  value  be- 
cause it  is  poorly  balanced  among  its 
constituent  amino  acids. 

Zein  is  obtained  from  the  gluten  in  the 
corn  wet-milling  process.  The  Northern 
Utilization  Research  Branch  of  the  U.  S. 
Department  of  Agriculture,  Peoria,  Illi- 
nois, studied  dispersion  of  zein  in 
strong  alkali,   "spinning"  it  into  a  fi- 


ber- and  stretching  and  curing  to  give 
the  fiber  added  strength. 

This  fiber,  which  is  available  on  the 
market  under  the  trade  name  "Vicarai'!  is 
used  mostly  in  blends  with  wool  for  such 
garments  as  socks,  swimming  suits,  and 
sweaters.  Possible  increased  use  of 
zein  for  special  fabrics  has  created 
seme  interest  in  breeding  comfbr-higlier 
zein  content, 

Amylose  for  plastics,  cellophane,  and 
films,  Amylose  is  a  linear-type  molecule 
which  can  be  made  into  thin,  transparent 
films  resembling  cellophane.  Acceptable 
films  require  amylose  of  80  percent 
purity.  Ordinary  com  starch  contains 
about  27  percent  amylose.  Samples,  how- 
ever, have  been  found  in  which  the  starch 
was  62  percent  amylose.  Consequently, 
it  appears  that  it  may  be  possible 
eventually  to  obtain  dent  corn  with  a 
high  enough  amylose  content  for  the  prac- 
tical production  of  plastics,  cellophane, 
and  films. 

Vitamin  A  (B-darotene),  An  association 
has  been  foijnd  between  the  yellow  pig- 
ment and  vitamin  A  in  corn.  There  is  a 
direct  quantitative  relation  between 
vltemln  A  and  the  number  of  genes  for 
yellow  pigment  in  the  endosperm.  In 
fact,  the  yellow  endosperm  genes  act  in 
an  arithmetic,  cimiulative  manner,  each 
gene  adding  2,5  units  of  vitamin  A  per 
gram  of  grain.  Feeding  tests  have  dem- 
onstrated that  yellow  corn  is  better 
than  white  corn  for  hogs  on  drylot  feed- 
ing. 

Niacin  (nicotinic  acid).  Fortunately, 
wide  differences  in  niacin  concentra- 
tions have  been  found  among  various 
strains  of  corn.  Hybrids  tend  to  rank 
between  their  parents,  and  the  seed  par- 
ent generally  exercises  more  influence 
than  the  pollen  parent.  Dent  kernels 
are  lowest  in  niacin  content,  waxy  ker- 
nels intermediate,  and  sugary  "  kernels 
highest.  Adequate  niacin  in  the  diet 
eliminates  certain  malnutritional  dis- 
turbances. 

R.  W,  Jugenheimer 
9-5-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


C-8 


TOMORROW'S  HYBRID  CORN 


It  is  becoming  more  and  more  difficult 
to  develop  hybrids  that  are  definitely- 
superior  in  all  characteristics  to  the 
better  ones  nov  available  in  the  Corn 
Belt.  For  this  reason,  the  Corn  Belt 
hybrids  of  I965  may  not  be  radically 
different  from  those  of  today.  However, 
it  should  be  possible  to  greatly  im- 
prove the  hybrids  that  are  adapted  to 
other  areas  of  the  United  States  and  many 
other  sections  of  the  world. 

Hybrids  for  special  purposes  and  uses 
should  soon  be  available.  Producers  and 
industry  \d.ll  be  able  to  choose  between 
better  dent,  flint,  sweet,  pop,  waxy  or 
possibly  floury  types. 

Livestock  feeders  in  the  United  States 
prefer  a  yellow  grain  that  is  soft  and 
high  in  quality  and  quantity  of  protein. 
Multiple -eared,  heavy  -tillering  strains 
will  be  useful  for  silage  and  green 
feed. 

Industry  will  eventually  be  able  to  ob- 
tain more  suitable  types  of  corn.  Dry 
millers  prefer  white  kernels  with  smooth 
dent.  Wet  millers  and  livestock  feeders 
will  welcome  high- oil  hybrids.  Waxy 
corn  is  available  for  food  and  glue. 
High-zein  corn  can  be  used  for  special 
fabrics,  and  a  high-amylose  corn  would  hybrids  are  better  husk  cover,  better 
be  valuable 
and  films. 


Hybrids  differ  greatly  in  drouth  re- 
sistance. The  leaves  of  some  strains 
remain  green,  while  others  are  badly  in- 
jured by  heat.  Some  hybrids  set  seed 
satisfactorily  under  conditions  of  high 
temperature  and  low  humidity,  while 
others  shed  little  pollen  for  only  short 
periods. 

Excellent  standability  has  contributed 
greatly  to  the  popvilarity  of  hybrids  in 
the  Corn  Belt,  This  desirable  trait 
needs  more  emphasis  in.  many  other  places. 
Lodging  lowers  quality  and  yield  and 
makes  harvesting  more  difficult.  Varia- 
tions in  standability  between  hybrids 
are  caused  by  differences  in  stalk  struc- 
ture, root  system,  ear  height,  soil 
fertility,  plant  population,  and  resist- 
ance to  insects  and  diseases. 

For  hand  harvesting,  farmers  want  single- 
eared  strains  with  the  ear  borne  at  a 
convenient  height.  It  may  be  possible  to 
harvest  future  hybrids  with  a  mechanical 
picker  more  easily  and  satisfactorily 
than  the  present  types  can  be  harvested. 
Hybrids  with  shorter  plants  may  also  be 
better  adapted  for  field  shelling  and 
ccm.bine  harvesting. 

Other  traits  that  may  be  added  to  future 


for  plastics,  cellophane,    grain  quality,  higher  shelling  percent- 
age, and  resistance  to  chemical  weed 


Yields  of  grain,  silage,  and  fodder  will 
gradually  edge  upward  because  hybrids 
will  be  better  able  to  resist  hazards. 
Effective  disease  inoculation  and  insect 
infestation  techniques  will  result  in 
hybrids  that  have  greater  resistance  to 
diseases  and  insects.  In  general,  flint 
corn  germinates  better  and  the  seedings 
grew  more  vigorously  than  dent  in  the 
cooler  climates. 


sprays , 

By  1965  the  use  of  male  sterility  and 
pollen  restorers  will  probably  eliminate 
much  of  the  detasseling  now  required  in 
producing  hybrid  seed.  This  development 
should  lower  production  costs  and  result 
in  a  better  product, 

R,  ¥,  Jugenheimer 
10-10-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


TEMPERATURE  AND  OTHER  INTERRELATED  FACTORS  IN 
DROUGHT  DAMAGE  TO  THE  CORN  PLANT 


C-9 


The  question,  "Is  it  high  temperature  or 
lack  of  moisture  that  is  damaging  the 
corn  plant?"  commonly  asked  in  a  hot,  dry 
year  is  exceedingly  hard  to  answer.  The 
reason  for  this  is  that  the  two  variahles 
are  so  intimately  interrelated  that  it 
is  impossihle  to  separate  them  under 
normal  field  conditions. 

Some  of  the  factors  involved  in  "drought 
damage"  of  the  corn  plant  under  field 
conditions  in  addition  to  temperature 
are  listed  below  and  show  the  complexity 
of  the  problem. 

1.  Metabolic  status  of  the  plant 

2.  Soil  moisture 

3.  Atmospheric  moisture  or   relative 
humidity 

h.  Physiological  moisture 

5.  Variety  of  the  plant 

6.  State  of  development  of  the  plant 

7.  Part  of  the  plant 

Since  under  field  conditions  all  of 
these  factors  may  be  in  operation  at  the 
same  time,  it  is  extremely  hard  to  dis- 
cuss the  problem  in  general.  This  arti- 
cle will  therefore  emphasize  temperature 
and  try  to  relate  the  other  factors  to  it . 

The  temperature  factor.  The  following 
method  is  commonly  used  to  determine  the 
temperature  that  is  required  to  kill 
plant  tissue  and  cells:  A  leaf,  branch, 
or  section  of  tissue  is  cut  off  and  im- 
mersed in  water  maintained  at  a  constant 
temperattire .  The  material  is  removed 
after  an  appropriate  time  interval,  and 
staining  techniques  are  used  to  deter- 
mine whether  the  cells  have  been  killed. 
By  varying  the  temperature  and  the  time 
of  Immersion,  and  determining  the  per- 
centage of  cells  killed,  it  is  possible 
to  determine  the  "thermal  death  point." 
This  term  which  is  used  to  express  the 
results  is  based  on  three  components: 
tim£,  temperature,  and  percentage  of 
cells  killed. 


The  main  advantage  of  this  method  is 
that  it  separates  temperature  effects 
from  many  of  the  environmental  factors. 
As  an  illustration,  it  was  found  that 
100  percent  of  the  cells  of  range  grass 
roots  were  killed  when  immersed  in  water 
at  162  F.  In  contrast  where  the  roots 
were  placed  in  water  which  was  slowly 
warmed  over  a  150-minute  period,  the 
lethal  temperature  was  126  F.  This 
method,  or  modifications  of  it,  has  been 
used  by  many  investigators  to  establish 
a  critical  temperature  range  that  varies 
from  113  to  l40  F.  for  many  different 
plant  species.  The  literature  shows 
that  the  corn  plant  falls  within  this 
temperature  range. 

In  visualising  hew  high  temperatures 
kill  a  plant  cell,  it  should  be  kept  in 
mind  that  all  the  vital  metabolic  pro- 
cesses are  carried  out  by  proteinaceous 
compounds  called  enzymes.  Heat,  or  de- 
hydration by  heat,  can  inactivate  the  en- 
zymes by  coagulation  in  much  the  same 
mamier  as  egg  protein  is  coagulated  by 
frying  or  boiling. 

Leaves  in  general,  and  corn  leaves  are 
no  exception,  tend  to  maintain  them- 
selves at  the  same  temperature  as  the 
air  surrounding  them.  Using  over  a  thou- 
sand separate  measurementF,  experimenters 
at  the  Kansas  Experiment  Station  found 
the  average  temperature  of  tiirgid  leaves 
to  be  87.2  F.  compared  to  an  average  of 
87  F.  for  air  temperature.  Wilted  corn 
leaves  measured  from  3  to  8  F.  higher. 
This  indicates  that  transpiration  does 
not  have  a  major  role  in  regulating  leaf 
temperature.  The  leaf  then  must  maintain 
its  temperature  by  a)  reflecting  a  por- 
tion of  the  light  and  b)  radiating  heat. 
The  latter  is  accomplished  in  mu'h  the 
same  way  as  the  "leaf -like"  finned  por- 
tion of  an  air-cooled  motor  dissipates 
heat. 

Temperature  and  metabolism.  Plants  have 
two  major  metabolic  systems  that  are 
"geared  together,"  a)  photosynthesis 
which   synthesizes  the   carbohydrates 


vhich  are  \ised  for  "building  blocks"  and 
for  energy  and  b)  respiration  which  oxi- 
dizes (burns )  carbohydrates  to  provide 
energy  for  maintenance  and  growth^  and 
to  supply  "building  blocks"  of  different 
types  needed  in  plant  growth .  At  a  tem- 
perature of  68  F.  the  photosynthetic 
process  exceeds  the  respiratory  process 
by  a  considerable  margin.  This  supplies 
an  adequate  amoiont  of  carbohydrates  for 
the  respiratory  process  and  also  pro- 
vides the  "building  blocks"  needed  for 
grovth.  As  temperatui-e  is  increased,  a 
compensation  point  is  reached  where  in- 
put of  carbohydrates  just  balances  the 
consumption  by  respiration,  while  at 
higher  temperatures  (96  F. )  the  respir- 
atory utilization  exceeds  that  provided 
by  the  photosynthetic  process.  Prolonged 
exposiu:e  of  the  plant  to  high  temper- 
atures would  therefore  markedly  curtail 
plant  growth. 

It  has  been  observed  that  a  wilted  leaf 
absorbs  but  one-third  the  amount  of  CO2 
taken  up  by  a  turgid  leaf.  Naturally, 
this  would  reduce  the  photosynthetic  pro- 
duction of  carbohydrates  by  the  same 
amount.  This  emphasizes  the  interrela- 
tion of  moisture  and  temperature. 

Although  the  information  is  meager, 
there  seems  to  be  seme  relationship  be- 
tween the  levels  of  carbohydrates,  pro- 
teins, and  colloids  in  the  plant  cells 
and  their  resistance  to  dehydration.  It 
has  been  pointed  out  that  dehydration  of 
the  proteinaceous  material  of  cells  can 
result  in  their  death.  These  levels  of 
cellular  constituents  are  controlled  by 
the  metabolism  of  the  plant. 

Temperature  and  moisture.  Three  major 
factors  involved  in  maintaining  an  ade- 
quate physiological  moisture  level  in 
the  plant  are:  soil  moisture,  water- 
conducting  system  of  the  plant,  and  rate 
of  transpiration  of  water  loss  from  the 
plant.  Soil  moisture  is  the  major  reserve 
of  water  supply  and  must  be  adequate  to 
meet  the  demands  made  by  the  plant  for 
maintaining  its  physiological  moisture 
level  and  transpirational  losses.  Since 
water  is  conducted  frcm  the  soil  by  the 
xylem  system  of  the  plant,  this  "piping 
system"  must  develop  rapidly  enough  and 
be  large  enough  to  supply  the  demands  of 
all  parts  of  the  plant.   It  has  long  been 


known  that  certain  varieties  of  corn  are 
more  susceptible  to  top  leaf  blasting 
than  others.  Recently  it  has  been  shcwnl/ 
that  the  susceptible  varieties  were  much 
slower  in  developing  xylem  vessels  in  the 
leaves  than  the  non-blasting  varieties. 
Consequently,  in  high  transpirational 
periods  (hot,  dry  windy  weather)  the 
leaves  of  the  plant  with  inadequately 
developed  "piping  systems"  were  severely 
desiccated  and  subsequently  died.  This 
desiccation  could  occur  even  with  ade- 
quate soil  moisture  since  the  failure  is 
in  the  water  trajisport  system. 

The  rate  of  transpiration  from  leaves 
depends  largely  on  temperature,  relative 
humidity,  and  air  movement  (wind  cur- 
rents). The  relationship  between  tem- 
perat-ure  and  rela.tive  humidity  is  siio-rfn 
by  the  fcllov^ing:  air  at  50  ,  68  ,  and 
100  F.  must  contain,  respectively;  0.3^ 
0.6,  and  3»5  oimces  of  water  per  cubic 
yard  to  achieve  100  percent  relative  hu- 
midity at  each  temperature.  Air  at 
50  F.  and  a  relative  humidity  of  80  per- 
cent if  heated  to  68  F.  would  drop  to 
40  percent  relative  hvunidity  and  at 
100  F,  would  be  only  0.6  percent  satu- 
rated. The  loss  of  water  from  leaves  is 
controlled  by  the  gradient  between  the 
relative  humidity  of  the  stcmata  of  the 
leaves  (assuming  100  percent  R.H.)  and 
that  of  the  air.  Rapid  air  movement 
tends  to  keep  this  gradient  at  amaximum. 

Temperature  and  part  of  the  plant.  Some 
parts  of  the  plant  are  more  susceptible 
to  heat  and  desiccation  damage  than 
other  parts.  For  example,  pollen  and 
silk  seem  to  be  most  sensitive.  In 
field  trials2/  representing  some  7^000 
pollinations,  a  good  correlation  was  ob- 
tained between  high  temperatures  and 
failure  to  set  seed.  At  75  F«  'the  per- 
centage of  ovules  setting  seed  was  65, 
while  at  IO5-IIO  F,  only  eight  percent 
seed  set  was  obtained.  Desiccation  of 
pollen  and  silks  rather  than  lethal  tem- 
perature effects  was  considered  the  pri- 
mary cause  of  the  damage. 


1/  Private  communication  from  Dr.  L.  A. 

Tatum,  Kansas  State  College,  Manhattan, 

Kansas. 

2/  lonnquist,  J.  A.  and  Jugenheimer,  R.W. 

Jour.  Amer.  Soc.  Agron.  35:923.  19^3* 

R.  H.  Hageman 
2-6-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


C-10 


HOW  TO  ESTIMATE  HAIL  LOSSES  TO  CORN 


Hail  insurance  on  growing  crops  in  this 
country  increased  gradually  from  87 
million  dollars  in  193^  "bo  over  1  3/^ 
"billion  in  1953^  or  20  fold.  Payments 
to  farmers  for  losses  ranged  from  a  low 
of  1.5  percent  of  the  insured  value  to 
a  high  of  3-1  percent,  with  an  average 
of  2.3  percent  over  the  20-year  period. 

The  amount  of  damage  inflicted  by  hail 
is  hard  to  estimate.  The  stage  of  the 
crop  when  the  storm  strikes  and  the  se- 
verity of  the  injury  are  the  two  main 
factors  that  need  to  be  considered  in 
appraising  losses.  Without  data  from 
experiments,  an  estimate  of  the  loss  re- 
sulting from  a  hailstorm  might  be  no 
better  than  a  wild  guess.  Fortunately, 
field  trials  have  been  conducted  by 
agricultural  experiment  stations  in 
Illinois  (6  years),  Iowa  (7  years), 
Nebraska  (9  years).  South  Dakota  (2 
years),  and  West  Virginia  (l  year),  in 
addition  to  some  extensive  tests  by  in- 
surance companies.  The  results  of  these 
experiments  agree  closely  and  make  it 
possible  to  assess  the  damaging  effect 
of  a  hailstorm  on  a  crop  of  corn  rather 
accurately. 


this  stage,  the  plant  will  therefore 
produce  no  grain.  Removing  all  exposed 
blades  when  the  plants  are  younger  does 
little  harm  because  defoliation  at  that 
time  takes  off  only  a  little  leaf  surface 
and  the  plant  produces  new  leaves  as  the 
stem  pushes  upwards  inside  the  whorl. 
The  later  the  blades  are  removed,  the 
greater  the  percentage  of  leaf  surface 
destroyed.  Thus,  grain  yield  goes  down 
as  blade  removal  is  delayed,  and  this 
continues  until  the  tasseling  stage. 
After  tasseling,  however,  grain  yield 
goes  up  as  blade  removal  is  delayed. 
This  relation  between  grain  yield  and 
stage  of  plant  development  at  the  time 
blades  were  removed  was  borne  out  in  t"ne 
experiments  in  all  the  states.  So  if  a 
hailstorm  occurs,  carefully  note  the 
stage  of  development  your  crop  is  in  when 
the  hail  strikes  it. 

Degree  of  injury  is  also  important  in  es- 
timating damage  from  hail.  Any  injury 
to  the  corn  plant  will  usually  decrease 
grain  yield,  because  Nature  does  not  pro- 
vide the  corn  plant  with  enough  leaf  sur- 
face to  permit  part  of  it  to  be  sacrificed 
without  affecting  the  yield. 


Sometimes  farmers  are  not  fully  satis- 
fied with  the  appraisal  of  injury  to 
their  hail-damaged  crops.  They  ask  how 
the  losses  are  estimated.  This  brief 
discussion  is  presented  to  explain  the 
factors  that  need  to  be  considered  in 
arriving  at  an  estim.ate. 

Stage  of  crop  development  has  an  im- 
portant bearing  on  the  losses  from  hail 
injury.  Corn  plants  in  the  tassel  and 
ear-shoot-emerging  stage  are  most  sub- 
ject to  injury  so  far  as  grain  pro- 
duction is  concerned.  No  grain  has  been 
produced  before  the  injury,  and  no  new 
blades  can  be  produced  afterwards.  If 
all  the  blades  are  removed  by  hail  at 


Experimental  results  show  that  grain 
yields  are  reduced  in  direct  proportion 
to  the  amount  of  leaf  area  that  is  re- 
moved. There  is  a  tendency,  however,  es- 
pecially when  only  small  percentages  of 
leaves  are  removed,  for  the  yield  reduc- 
tion to  be  somewhat  less  than  the  amoimt 
of  leaf  surface  that  is  lost.  This  sug- 
gests that  the  efficiency  of  the  uninjured 
leaf  surface  is  stepped  up  after  some  of 
the  leaves  have  been  removed,  possibly 
because  the  remaining  leaves  get  more 
light. 

As  soon  as  possible  after  the  storm  sub- 
sides, get  as  careful  an  estimate  as  you 
can  of  the  amount  of  blade  surface  re- 
moved from  the  plants  by  the  hailstorm. 


Blade  shredding,  midrib  breaking,  and 
stalk  and  ear  bruising  are  other  forms 
of  injury  caused  by  hail.  Tests  show  that 
as  long  as  any  part  of  the  blade  rem.ains 
attached  to  the  plant  it  is  capable  of 
contributing  to  grain  yield.  In  lowa^ 
when  all  the  blades  were  severely  shredded, 
yield  of  grain  was  37  percent  of  normal 
even  when  the  shredding  was  done  at  the 
beginning  of  tasseling.  Severe  shredding 
earlier  and  later  caused  progressively 
less  damage. 

Midrib  breaking  did  not  do  much  harm. 
With  every  midrib  broken  at  the  most 
critical  time,  namely,  tasseling  time, 
yield  was  80  percent  of  normal. 

Stalk  bruising  decreased  yields  about  10 
percent  beyond  that  caused  by  blade 


shredding.  Ear  bruising  did  little  harm 
to  yield,  but  when  it  occurred  at  the 
milk  stage  the  market  quality  of  the 
grain  was  reduced  somewhat  because  of 
the  damage  to  kernels . 

Believe  it  or  not,  under  some  conditions 
hail  injury  may  actually  increase  grain 
yields.  This  happened  in  Iowa  during 
the  dry  year  of  1930-  Cutting  out  blades 
reduced  transpiration,  and  the  moisture 
thus  conserved  was  more  beneficial  to  the 
plant  than  the  leaf  removal  was  harmful. 

Experimental  data  have  taken  much  of  the 
"guess"  out  of  estimating  losses  to  corn 
from  hail  injury.  Yet  it  is  still  neces- 
sary to  weigh  the  significance  of  the 
many  factors  that  have  a  bearing  on  the 
outc  ome . 


George  H.  Dungan 
5-28-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


IDENTIFYING  COMMON  LEGUME  SEEDLINGS 


F-17 


It  is  often  necessary  to  identify  cer- 
tain legumes  before  they  have  flowered 
or  after  they  have  been  closely  grazed. 
Many  times  it  is  necessary  to  identify 

Cot yle denary  leaves  -  the  seed  leaves  of 
the  embryo  -which  act  as  storage  organs 
in  seeds  of  plants. 

Leaflet  -  one  of  the  divisions  of  a  com- 
pound leaf;  e.g.,  the  red  clover  leaf 
has  three  leaflets. 

Petiole  -  the  stalk  of  a  leaf. 

Pubescent  -  having  fine,  soft  hairs. 


In  the  following  key  to  identifying 
legume  seedlings,  the  cotyledonary  leaves 
are  considered  to  be  the  first  and  second 
leaves.  Most  of  the  common  legvmes 
exhibit  epigean  emergence;  i.e.,  the 
cotyledons  emerge  aboveground.  The  pea 
and  vetch,  notable  exceptions,  exhibit 
hypogean  emergence;  i.e.,  the  cotyledons 
remain  imderground  during  germination 
and  emergence. 


leg\minous  plants  in  the  seedling  stage. 
The  follo-vrLng  definitions  and  distin- 
guishing featiires  should  be  helpful  in 
identifying  some  ccmnon  legume  seedlings. 

Serrate  -  having  sharp  teeth. 

Trifoliolate  -  having  three  leaflets. 

Unifoliolate  -  having  one  leaflet. 

Variegation  -  the  barring  (water  marks) 
on  leaves,  seen  in  nearly  all  American 
strains  of  red  clover. 

Vein  (nerve,  rib)  -  nerve  or  rib  in 
leaves,  bracts,  scales,  sepals,  etc. 

This  key  is  greatly  simplified.  It 
should  be  remembered  that  many  weed  seed- 
lings have  characteristics  similar  to 
those  of  legume  seedlings.  Further, 
there  are  many  variations  within  the 
different  species  presented  in  the  key; 
e.g.,  most  European  strains  of  red  clover 
are  not  pubescent.  However,  for  practi- 
cal field  use,  the  key  will  help  to 
identify  some  common  legume  species  in 
the  seedling  stage. 


Key  to  the  Seedlings  of  Some  Common  Legume  Species 

-la.  Third  leaf  imifoliolate  (fourth  leaf  trif oliolate ) 
_  2a,  Petiolar  branches  of  vmequal  length 

3a •  Leaflets  one -third  serrate  -  alfalfa 

yo.     Leaflets  completely  serrate  -  sveet  clover 


-213.  Petiolar  "branches  of  equal  length 
_3a.  Vegetative  parts  pubescent 


Ua.  Variegation  present  -  red  clover 

4b,  No  variegation  present  -  crimson  clover 

3b.  Vegetative  parts  not  pubescent 

ka.     No  variegation  present  -  alsike  clover 

I hh.     Variegation  present 

. 5a- •  Giant  form  -  Ladino  clover 

I 5^3,  Snail  form  -  common  vhite  clover 

lb.  Third  leaf  trif oliolate  or  both  third  and  fourth  leaves 

unif oliolate 
_2a.  Third  leaf  trif oliolate,  veins  not  prominent  -  birdsfoot 

trefoil 
_2b.  Both  third  and  fovirth  leaves  unif  oliolate,  veins 

prominent  -  common,  Korean,  and  sericean  lespedeza 


A,  W,  Burger 
10-31-55 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SELECTING  ALFALFA  VARIETIES 


F-18 


The  main  point  to  consider  in  selecting 
an  alfalfa  variety  is  the  time  you  ex- 
pect the  alfalfa  to  stand  before  plowing 
it  down.  If  you  plan  to  use  the  stand 
several  years  for  hay^  plant  seed  of  a 
winter-hardjj  wilt-resistant  variety  like 
Ranger  or  Buffalo.  If  you  plan  to  use 
it  only  one  or  two  years  for  hay^  you 
can  use  a  winter-hardy^  wilt-susceptible 
variety  like  Atlantic  or  Du  Puits.  In 
either  case,  use  certified  seed. 

Bacterial  wilt  does  not  reduce  alfalfa 
yield  until  about  the  third  year.  Be- 
cause certain  wilt -susceptible  vari- 
eties, such  as  Atlantic  and  Du  Puits,  are 
as  productive  as  Ranger  and  Buffalo  dur- 
ing the  first  year  or  two,  there  is  no 
advantage  in  usinga  wilt-resistant  vari- 
ety in  short  rotations. 

Several  varieties  of  alfalfa  have  been 
developed  in  the  United  States.  There 
is  a  good  seed  supply  of  most  varieties. 
Following  are  descriptions  of  several 
varieties  and  status  of  seed  supplies. 

Ranger,  which  is  resistant  to  bacterial 
wilt,  was  developed  at  the  Nebraska  Ex- 
periment Station  by  intercrossing  se- 
lected strains  of  Cossack,  Ladak,  and 
Turkistan.  Ranger  is  a  good  forage  pro- 
ducer and  is  as  winter-hardy  as  the 
hardy  common  alfalfas.  The  flower  color 
is  variegated.  Ranger  is  recommended 
for  the  northern  two-thirds  of  Illinois. 
Seed  supply  is  adequate. 

Buffalo,  also  resistant  to  bacterial 
wilt,  was  developed  by  the  Kansas  Experi- 
ment Station  out  of  Kansas  Common.  It 
is  a  good  forage  producer  and  is  only 
slightly  less  winter-hardy  than  Ranger. 
Flower  color  is  purple.  Buffalo  is  rec- 
ommended in  the  southern  two-thirds  of 
Illinois.  Seed  supply  is  adequate. 

Atlantic,  a  high-yielding  variety  devel- 
oped by  the  New  Jersey  Experiment  Sta- 
tion,  is  not  resistant  to  bacterial 


wilt.  It  was  developed  especially  for 
the  eastern  states,  where  bacterial  wilt 
is  not  serious.  It  is  about  as  winter- 
hardy  as  Buffalo.  Flower  color  is  varie- 
gated. Atlantic  is  recommended  throughout 
Illinois  for  short  rotations.  Seed  sup- 
ply is  adequate. 

Du  Puits  is  a  variety  developed  in  France 
that  has  yielded  exceptionally  well  in 
tests  in  Illinois  and  several  other 
states.  Lu  Puits  is  not  wilt-resistant. 
It  is  about  as  winter-hardy  as  Buffalo. 
Du  Puits  is  recommended  for  the  southern 
two-thirds  of  Illinois  in  short  rota- 
tions.  Seed  supply  is  limited. 

Vernal  is  a  variegated  variety  developed 
at  the  Wisconsin  E^cperiment  Station.  It 
is  very  cold-resistant  and  highly  resist- 
ant to  bacterial  wilt.  It  is  not  so 
susceptible  to  leaf  and  stem  diseases  as 
Ranger.  This  variety  has  not  been 
tested  in  Illinois  long  enough  to  deter- 
mine its  value  in  relation  to  the  recom- 
mended varieties.  It  is  not  reccmmended 
in  Illinois  at  the  present  time.  Seed 
supply  is  limited. 

Narragansett,  a  high-yielding  variety 
developed  by  the  Rhode  Island  Experiment 
Station,  is  not  resistant  to  bacterial 
wilt.  It  was  developed  for  use  in  the 
eastern  United  States  north  of  the  area 
where  Atlantic  is  adapted.  Flower  color 
is  variegated.  Atlantic  is  preferred  to 
Narragansett  in  Illinois  at  the  present 
time.  Seed  supply  is  limited,  but  it 
should  be  adequate  to  meet  the  demand. 

Nomad  has  a  high  proportion  of  creeping 
plants  that  will  root  at  stem  nodes.  It 
is  from  an  old  field  in  Oregon  found  to 
have  this  type  of  plant.  Nomad  is  sus- 
ceptible to  bacterial  wilt,  and  it  has 
not  been  tested  long  enough  to  determine 
its  adaptability.  In  most  tests  it  has 
not  appeared  to  be  so  vigorous  as  other 
varieties.  Because  of  its  creeping  habit 
of  growth,  it  may  be  useful  in  pastures. 


It  is  not  recommended  in  Illinois  at  the 
present  time.  A  limited  amount  of  seed 
is  available  ccmmercially. 

Rhizcma  is  a  broad-crowned  type  of  al- 
falfa developed  at  the  British  Columbia 
Experiment  Sta.tion.  It  does  not  root  at 
the  nodes  and  thus  is  not  a  true  creeping 
alfalfa.  Rhizoma  is  a  variegated^  very 
winter -hardy  variety  that  is  not  resist- 
ant to  bacterial  wilt.  It  beccmes  dor- 
mant very  early  in  the  fall  and  begins 
growth  very  late  in  the  spring.  For  this 
reason  it  is  not  recommended  in  Illinois. 

Certified  seed  is  available  for  all  the 
varieties  recommended  for  use  in  Illi- 
nois^ and  it  should  be  used  in  preference 
to  uncertified  seed. 

Certified  seed  may  be  produced  outside 
the  region  of  adaptation,  principally  in 


California.  For  seed  to  be  certified 
under  such  conditions,  the  seed  fields 
must  be  established  from  seed  produced 
in  the  region  of  adaptation. 

Seed  fields  can  remain  down  only  six 
years;  therefore  certified  seed  of 
winter-hardy  varieties  that  is  produced 
in  California  is  only  one  generation  re- 
moved from  plants  that  grew  in  the  re- 
gion of  adaptation.  Also,  in  fields 
growing  certified  seed,  precautions  must 
be  taken  to  prevent  the  growth  of  volun- 
teer seedlings.  Winter-hardiness  studies 
have  shown  that,  when  these  precautions 
are  taken,  there  is  only  slight  loss  of 
winter-hardiness.  It  is  only  when  these 
varieties  are  grown  for  two  or  more 
generations  outside  the  region  of  adap- 
tation that  there  is  serious  loss  of 
winter-hardiness . 


J.  A.  Jackobs 
12-26-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-19 


HOW  HYBRID  SORGHUMS  WERE  DEVELOPED  AND  ARE  BEING  PRODUCED 


Varieties  of  grain  sorghums  like  Martin, 
Midland,  Westland,  RedlDine  60,  and  Com- 
"bine  Kafir  60  and  varieties  of  forage 
sorghums  like  Atlas,  Leoti  Red,  and  Kan- 
sas Orange  are  pure  lines- -just  as  are 
varieties  of  soybeans  or  oats.  Hybrids 
of  sorghums  are  first-generation  single 
or  three-way  crosses  between  certain  of 
these  pure  lines. 

It  has  been  known  for  a  long  time  that. 
Just  as  in  corn,  hybrid  vigor  will  result 
from  crossing  certain  varieties  of  sor- 
ghum. However,  in  the  past,  controlling 
pollination  has  been  a  major  problem. 
Since  the  anthers,  or  the  pollen- shedding 
organs,  of  the  sorghums  are  located  in 
the  same  floral  envelope  as  the  female 
parts,  it  is  impossible  to  use  the  prin- 
ciple of  detasseling  to  control  pollina- 
tion, as  is  done  with  corn. 

Work  to  devise  methods  for  producing  hy- 
brid sorghum  seed  in  quantity  has  been 
under  way  at  the  Texas  Agricultural  Ex- 
periment Station,  in  cooperation  with 
the  United.  States  Department  of  Agricul- 


ture, for  more  than  20  years 


In  1929 


J.  C.  Stephens  of  the  Texas  Station  dis- 
covered an  antherless  character  in  Sudan- 
grass,  and  in  1935  he  discovered  a 
better  male -sterile  in  Texas  Blackhull 


Kafir.  In  19^13  Glen  H  Kuykendall  dis- 
covered a  still  better  male-sterile  in  a 
field  of  the  Day  Milo  variety  on  his 
father's  farm  in  Cookeville,  Tennessee, 
and  in  I95O  J.  C.  Stephens  and  H.  F. 
Holland  foixnd  cytoplasmic  male-sterility 
in  progeny  of  crosses  between  Milo  and 
Kafir.  The  cytoplasmic  type  of  male- 
sterility  is  utilized  in  single  crosses 
and  has  advantages  over  the  tln-ee-way 
cross  which  is  used  with  the  Day  l^'ge  of 
male -sterility. 

Sorghum  plants  with  male -sterility  do 
not  shed  pollen,  and  the  flowers  are 
readily  fertilized  by  pollen  carried  by 
the  wind  from  nonnal  plants .  With  this 
type  of  sterility,  it  is  a  simple  proc- 
ess to  produce  and  maintain  both  sterile 
and  fertilized  plants  in  crossing  fields 
for  producing  hybrid  seed  at  a  reason- 
able cost.  To  make  it  clear  how  hybrid 
seed  is  and  will  be  produced,  it  might 
be  well  to  follow  the  method  of  produc- 
tion tlirough  all  the  steps  from  mainte- 
nance of  parental  stocks  to  production 
in  farmers'  fields.  The  necessary  steps 
for  maintaining  stock  and  producing  hy- 
brid seed  are  shown  in  the  following 
diagrams,  originally  prepared  by  J.  C. 
Stephens . 


Diagrams  Showing  the  Method  of  Maintaining  Seed  of  a  Cytoplasmic  Male-Sx.erile 
Seed  Parent  and  of  Producing  Hybrid  Sorghum  Seed 


I.  The  maintenance  and  increase  of  a 
male-sterile  line  is  illustrated. 
Male -sterile  strain  A  and  normal 
strain  A  are  identical  except 
that  the  male -sterile  strain  does 
not  have  anthers  that  shed  pol- 
len. The  chromosome  complement 
of  both  strains  is  the  same,  since 
the  male-sterile  strain  is  main- 
tained by  backcrossing  to  the 
normal  A  strain. 


I       MAINTENANCE  AND  INCREASE  OF 
MALE-STERILE  STRAIN 


MALE-STERILE  A 
COUNTERPART 


NORMAL  STRAIN  A 

MALE-STERILE 

PRODUCING 


/^ 


WIND-BLOWN 


/r\ 
^ 
^ 


POLLEN 


X 


ISOLATED  FIELD 


II.  Hybrid  sorghum  seed  will  be  pro- 
duced in  a  second  crossing  block 
in  which  the  seed  parent  rows 
will  be  male-sterile  strain  A 
ard  the  pollen  parent  will  be 
normal  strain  B.  Lines  chosen 
as  male  parents  must  restore 
normal  fertility  in  the  succeed- 
ing crop,  give  a  good  hybrid  of 
combine  height,  and  be  good  pol- 
len producers.  The  hybrid  seed 
from  the  male-sterile  female 
rows  is  harvested  and  used  for 
commercial  production. 


I[      SEED-GROWER   CROSSING  BLOCK 


MALE-STERILE 
STRAIN  A 


\ 


NORMAL  STRAIN    B 
MALE-FERTILE 
RESTORING 


WIND-BLOWN 


POLLEN 


X 


ISOLATED  FIELD 
TO  PRODUCE 


III.  The  seed  produced  in  the  second 
crossing  block  will  be  planted 
by  sorghum  growers  for  commer- 
cial production.  This  is  the 
single-cross  A  x  B  sorghum.  All 
plants  are  completely  male  and 
female  fertile.  With  these  hy- 
brids it  is  necessary  to  pur- 
chase new  seed  each  year,  just 
as  is  true  of  hybrid  corn. 


m  SINGLE  CROSS  (A  X  B)  HYBRID  SORGHUM 

NORMAL  CROP  ON  FARM 


At  present  work  in  the  main 
sorghum  states  is  devoted  to 
crossing  many  lines  and  testing 
to  find  the  most  suitable  hy- 
brid combinations.  It  will  prob- 
ably be  several  years  before  seed 
stocks  can  be  increased,  the 
various  hybrids  can  be  tested  for 
adaptability,  and  seed  of  "proved" 
hybrids  is  made  available  for 
commercial  production  to  any  ex- 
tent. 


It  should  be  emphasized  that  not  all  sor- 
ghum hybrids  can  be  expected  to  be  supe- 
rior, but  yield  increases  of  30  to  50 
percent  above  those  of  present  commercial 
varieties  have  been  reported  in  states 
where  these  hybrids  have  been  evaluated. 
Testing  is  needed  and  is  being  carried 
out  in  Illinois  to  determine  the  per- 
formance of  hybrid  sorghums  at  various 
locations  in  the  state. 

C.  N.  Hittle 
i+-23-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SUDANGRASS  IN  ILLINOIS 


Sudangrass  is  ideal  for  use  as  a  summer 
supplemental  pasture  in  Illinois.  It 
may  also  be  harvested  for  hay  or  silage. 
This  forage  grass,  which  is  a  sorghum 
and  an  annual,  is  very  leafy,  tillers 
profusely,  and  has  great  capacity  for 
regrowth  after  cutting  or  grazing.  It 
becomes  somewhat  dormant  under  condi- 
tions of  severe  drought,  but  resumes 
growth  when  rains  come  during  mid-  or 
late  summer. 

Sudangrass  for  Pasture 

Sudangrass  should  not  be  pastured  until 
the  crop  is  l8  to  2h  inches  tall.  At 
this  stage  the  plants  will  contain 
roughly  from  10  to  13  percent  protein, 
and  both  common  and  sweet  types  will  be 
readily  eaten.  The  possibility  of  poi- 
soning from  hydrocyanic  (prussic)  acid 
is  increased  if  Sudan  is  pastured  at 
shorter  heights.  The  grazing  management 
should  consist  of  rotational  grazing 
with  heavy  stocking  so  that  the  growth 
may  be  grazed  down  rather  quickly.  The 
crop  should  then  be  allowed  to  grow 
until  there  is  time  for  l8  to  2^+  inches 
of  regrowth  before  it  is  grazed  again. 
The  place  of  Sudan  in  a  balanced  pasture 
program  is  for  late  summer  grazing  in 
conjunction  with  cool-season  perennial 
pasture  crops  for  spring  and  fall  usage. 

When  Sudangrass  is  to  be  used  for  pas- 
ture, it  may  be  planted  with  soybeans. 
This  combination  furnishes  considerably 
more  roughage  than  either  crop  alone  and 
is  ready  for  use  in  midsummer  when  other 
pasturage  is  short.  Soybeans  also  pro- 
vide added  protein  to  the  forage  and, 
since  they  are  not  injured  by  chinch 
bugs,  they  aid  in  reducing  the  chinch 
bug  damage  on  the  Sudangrass. 

Other  Uses 

Although  Sudangrass  is  difficult  to  cure, 
it  may  be  harvested  for  hay.  The  best 
quality  hay  is  obtained  if  cut  and  prop- 
erly cured  when  the  very  first  heads 
begin  to  appear.  Yields  of  up  to  three 
tons  of  good-quality  hay  may  be  expected 


from  the  finer-stemmed  varieties.  The 
coarseness  of  some  of  the  new  varieties 
makes  them  unsuitable  for  hay. 

Sudan  may  also  be  ensiled  and,  when 
properly  stored,  makes  good-quality  si- 
lage. The  yield  for  silage  would  be  the 
best  when  the  crop  is  heading  to  soft 
dough  in  stage.  For  use  as  hay  or  si- 
lage, it  should  be  harvested  before  leaf 
drying  occurs. 

Frussic  Acid  Poisoning 

Sudangrass  contains  a  glucoside  called 
dhurrin,  which  releases  hydrocyanic  acid 
when  hydrolyzed  in  the  ruminants.  This 
may  cause  HOW  (or  prussic  acid)  poison- 
ing. Quantities  of  prussic  acid  large 
enough  to  cause  sickness  are  usually 
fatal,  and  a  poisoned  animal  may  die  in 
a  matter  of  minutes .  However,  a  remedy 
that  has  sometimes  proved  effective  is 
the  intravenous  injection  of  sodium 
thiosulfate.  Symptoms  of  poisoning  are 
depression,  paralysis,  stupor,  and  dif- 
ficult breathing. 

Shortly  after  animals  are  first  turned 
in  to  a  Sudan  field,  they  should  be  ob- 
served closely  for  symptoms  of  prussic 
acid  poisoning.  Sudangrass  whose  growth 
has  been  slowed  by  drought  or  partially 
killed  by  frost  may  be  dangerous  to 
graze,  since  the  cattle  will  graze  the 
young,  tender  shoots  that  are  much  high- 
er in  dhurrin.  Grain  and  silage  sorghioms 
are  usually  much  higher  in  the  glucoside 
than  is  Sudangrass,  and  if  they  are  al- 
lowed to  cross  with  Sudan  the  resulting 
hybrids  will  usually  be  higher  in  poten- 
tial HON  producers  than  Sudan. 

The  danger  of  prussic  acid  poisoning  can 
be  largely  eliminated  by: 

1.  Using  only  certified  seed  or  seed 
that  is  known  to  be  pure  Sudan. 

2.  Letting  the  crop  grow  at  least  l8 
inches  before  grazing. 

3-  Not  feeding  excessively  hungry 
cattle. 

h.  Not  grazing  frosted  or  drought- 
stunted  crops. 


Diseases 

Probably  the  most  severe  disease  of 
Sudangrass  in  Illinois  is  leaf  blight, 
caused  by  the  fungus  Helminthosporium 
turcictim.  Leaf  blight  lesions  appear 
first  as  water-soaked  areas.  Drying  out 
occurs  as  the  lesions  spread  to  elon- 
gated, irregular  areas.  Entire  leaf 
blades  may  be  and  frequently  are  killed. 
Bacterial  leaf  diseases  may  also  cause 
considerable  damage.  Best  control  of 
the  leaf  diseases  may  be  obtained  by  the 
use  of  resistant  varieties.  Such  vari- 
eties as  Piper,  Greenleaf ,  and  _  Lahoma 
showed  a  relatively  high  degree  of  dis- 
ease resistance  in  Illinois  in  195^  and 
1955. 

Insects 

The  chinch  bug  is  more  harmful  to  Sudan 
than  any  other  insect;  and  in  years  when 
chinch  bug  infestations  are  severe, 
stands  of  Sudan  may  be  practically  elim- 
inated. None  of  the  varieties  are  com- 
pletely resistant  to  this  pest,  but  the 
sweet  types  possess  more  resistance  than 
do  the  common  varieties. 

Varieties 

There  are  two  main  classes  of  Sudan- 
grass:  those  which  have  sweet  and  juicy 
stalks  and  those  which  are  non-sweet  or 
relatively  dry-stalked.  The  mid-rib  of 
the  leaf  of  sweet  types  is  cloudy  ap- 
pearing, and  the  pith  in  the  stalk  is 
almost  completely  juicy.  The  palata- 
bility  of  the  sweet  types  is  high,  even 
at  later  stages  of  growth,  and  they  are 
generally  eaten  more  readily  when  pas- 
tured than  the  non-sweet  types.  The 
dry-stalked  varieties  cure  more  readily 
when  cut  for  hay  and  are  usually  higher 
in  yield  than  the  sweet  types. 

Sweet  Sudangrass  was  developed  in  Texas 
from  a  cross  of  Sudangrass  and  Leoti 
sorghum.  Its  performance  in  Illinois 
has  been  good,  and  excellent  quality 
certified  seed  has  been  available  from 
Oklahoma,  Texas  and  California.  _The 
damage  caused  by  leaf  diseases  on  Sweet 


varies  considerably,  depending  upon  the 
location  and  the  year.  Sweet  is  a  juicy- 
stalked  variety,  quite  early  in  maturity, 
and  has  reddish-brown  colored  seed. 

Piper  was  developed  by  the  Wisconsin 
Experiment  Station  and  released  in  1950' 
It  is  generally  more  vigorous  in  the 
northern  states  than  other  varieties,  is 
mostly  dry-stalked,  has  a  lower  level  of 
hydrocyanic  acid  potential  and  increased 
resistance  to  leaf  blight  and  anthrac- 
nose.  The  strain  is  not  homozygous,  be- 
ing somewhat  variable  in  seed  and  foli- 
age color.  In  variety  trials  conducted 
in  Illinois  during  the  past  two  years. 
Piper  has  consistently  outyielded  all 
other  varieties  and  has  been  damaged 
only  slightly  by  leaf  diseases. 

Common,  a  dry-stalked  type,  was  devel- 
oped from  many  of  the  early  introduc- 
tions. In  Illinois  Common  yields  well, 
but  because  of  its  susceptibility  to 
leaf  diseases  and  extreme  early  maturity, 
it  is  not  recommended  when  seed  of  other 
varieties  can  be  obtained. 

Greenleaf  is  a  new  juicy-stalked  variety 
of  Sudangrass  released  by  the  Kansas 
Experiment  Station  in  1953-  It  has  a 
low  HCW  potential,  and  the  seed  is  loni- 
formly  mahogany-colored.  Preliminary 
results  in  Illinois  show  that  it  is 
exceptional  in  resistance  to  leaf  dis- 
eases and  degree  of  leafiness,  but  is 
somewhat  lower  yielding  than  many  other 
varieties .  Further  testing  of  Greenleaf 
is  necessary  before  its  adaptability  in 
Illinois  can  be  determined. 

Lahoma  is  a  sweet  Sudan  and  in  tests  in 
Oklahoma,  where  it  was  developed,  it  has 
shown  uniformity,  good  leafiness,  palata- 
bility,  and  greater  resistance  to  leaf 
diseases  and  later  maturity  than  other 
sweet  Sudans.  It  is  rather  tolerant  to 
chinch  bug  attack.  At  Urbana  and  Browns- 
town,  Illinois, the  yields  of  Lahoma  have 
been  relatively  low,  but  at  Carbondale 
it  has  performed  very  well.  Lahoma  also 
needs  further  evaluation  in  this  state 
before  its  performance  can  be  deter- 
mined. 

Carl  W.  Hittle 
5-7-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-21 


ORCHARDGRASS  AND  ITS  MANAGEMENT 


Orchardgrass  is  a  long-lived  perennial 
and  a  distinctly  bunch-type  grass  with 
folded  leaf  hlades  and  compressed 
sheaths.  Because  it  does  not  produce 
stolons  or  linderground  rhizomes^  it  forms 
an  open  sod.  This  characteristic  makes 
it  a  good  companion  crop  for  pasture  and 
hay  when  seeded  with  such  legumes  as  al- 
falfa^  Ladino  clover,  red  clover,  and 
lespedeza. 

Orchardgrass  owes  its  common  name  to  its 
shade  tolerance  and  its  consequent  use 
in  orchards  and  other  shaded  areas.  In 
many  other  English-speaking  countries, 
it  is  commonly  known  as  cocksfoot,  a 
name  that  aptly  describes  its  distinctive 
stiffs  finger-like  panicles  upon  which 
spikelets  are  "borne  in  dense  clusters  or 
glomule  s . 


Characteristics.  Although  less  i-7inter 
hardy  than  some  of  the  other  pasture - 
type  grasses,  orchardgrass  starts  to 
grow  early  in  the  spring  and  grows  very 
rapidly.  It  matures  for  hay  or  seed  about 
two  weeks  earlier  than  smooth  bromegrass 
and  about  three  weeks  earlier  than  tim- 
othy. It  recovers  rapidly  after  mowing 
or  grazing  and  produces  large  quantities 
of  leafy  pasturage  or  aftermath.  It  may 
produce  less  first-crop  hay  or  silage 
than  some  of  the  other  pasture -type 
grasses,  but  because  it  continues  to  grow 
during  the  summer,  its  total  production 
of  hay  is  equal  to  or  higher  than  that 
of  many  other  grasses.  Because  it  will 
grow  during  the  drier,  warmer  part  of 
the  summer  and  recovers  rapidly  follow- 
ing defoliation,  its  seasonal  yield  is 
also  more  uniformly  distributed. 


Regions  of  adaptation.  Orchardgrass  is 
grown  most  extensively  and  is  most  im- 
portant in  the  southern  half  of  the  so- 
called  timothy-bluegrass  belt,  extending 
from  southern  New  York  to  southern  Vir- 
ginia and  westward  through  Kentucky,  Ten- 
nessee, southern  Ohio,  southern  Indiana, 
southern  Illinois,  Missouri,  and  eastern 
Kansas.  However,  it  can  be  grown  to 
advantage  in  the  northern  part  of  Indiana 
and  Illinois  as  well. 

Orchardgrass  is  better  adapted  to  and 
more  productive  in  the  southern  range  of 
the  timothy  growing  belt  than  smooth 
bromegrass  or  timothy  because  it  will 
tolerate  more  heat  and  drought.  It  will 
survive  and  grow  better  on  thinner  and 
less  fertile  soils  than  timothy  and 
especially  smooth  bromegrass.  However, 
orchardgrass  is  not  well  adapted  to  tight, 
poorly  drained  soils,  especially  if  they 
tend  to  be  cold.  It  responds  well  to 
high  levels  of  soil  treatment,  particu- 
larly nitrogen  supplied  either  from  a 
chemical  source  or  by  a  legume  seeded  in 
a  grass -legume  mixture. 


Uses  of  orchardgrass.  Orchardgrass  is 
used  primarily  for  pasture, but  it  can  be 
used  for  hay  and  silage  as  well.  It  is 
recommended  for  use  in  permanent  pasture 
mixtures  along  with  annual  lespedeza, 
white  and  Ladino  clover,  and  other 
grasses.  It  is  frequently  substituted 
for  timothy  in  mixtures  with  red  clover 
or  alfalfa  for  hay;  however,  it  may  ma- 
ture somewhat  earlier  than  the  legume^ 
and  the  legume  may  have  to  be  harvested 
sooner  than  normally  to  prevent  the 
orchardgrass  from  becoming  too  mature. 

Because  of  its  vigor  and  productiveness, 
orchardgrass  lends  itself  well  to  use  in 
pasture  renovation  where  short-term  pas- 
tures are  fitted  into  a  forage  program. 
Seedling  stands  are  easily  established,and 
excellent  yields  of  forage  can  be  ob- 
tained the  first  crop  year. 

Management .  Although  generally  con- 
sidered to  be  tolerant  to  grazing,  orchard- 
grass  does  not  persist  \inder  continuous 
close  grazing.   To  best  utilize  the 


forage^  it  is  therefore  necessary  to  fol- 
low a  program  of  rotational  grazing. 

To  maintain  a  high-quality  orchardgrass 
pasture;,  remove  the  early  spring  gro\vrth 
by  grazing  or  clipping  before  it  reaches 
the  full  head  stage.  Then  rotationally 
graze  the  regroirth  so  that  an  area  vill 
be  grazed  for  about  one  week  and  allowed 
to  rest  from  three  to  four  weeks.  To 
control  weeds  and  permit  uniform  re- 
groirth;  clip  the  grazed  area  to  a  height 
of  about  four  inches  with  a  field  mower 
following  removal  of  cattle.  Undergraz- 
ing  or  delaying  grazing  not  only  reduces 
palatability  and  feeding  value ^  but  may 
also  weaken  the  legume  stand  in  a  mixture 
as  a  result  of  excessive  competition  from 
the  grass. 

Orchardgrass  makes  excellent  hayandpro- 
duces  high  yields  if  cut  in  the  earlier 
stages  of  maturity,  preferably  at  the 
early  head  stage.  After  this  stage  it 
m.atures  rapidly  and  becomes  woody  and 
unpalatable.  This  early  maturity  is  of- 
ten a  disadvantage  at  the  first  cutting 
when  orchardgrass  is  seeded  in  a  mixture 
with  alfalfa. 

Orchardgrass  makes  excellent  silage.  If 
it  matures  before  it  can  be  grazed^,  it 
can  therefore  be  ensiled.  The  silage 
can  be  used  to  supplement  late  summer 
pasture  or  as  winter  roughage.  Often 
the  entire  first  crop  is  removed  for 
silage.  Orchardgrass  should  be  ensiled 
at  about  the  early  head  stage  to  insure 
high  yields  of  good-quality  silage. 


Seedling  establishment.  The  best  time 
to  seed  orchardgrass  is  usually  in  the 
early  spring ,  although  late  summer  or 
fall  seedings  are  successful  if  made 
early  enough  to  allow  the  seedlings  to 
become  established  before  mnter.  Or- 
chardgrass seedlings  are  less  winter 
hardy  than  many  of  the  common  pasture 
grasses,  and  fall  seedings  are  more  sub- 
ject to  winterkilling,  particularly  in 
the  northern  part  of  the  state.  Spring 
seedings  should  be  made  early  enough  to 
permit  the  seedlings  to  become  estab- 
lished before  weeds  become  a  problem. 

In  general,  good  stands  of  orchardgrass 
can  be  obtained  in  mixtures  seeded  at 
four  to  eight  pounds  per  acre.  In  pure 
grass  stands,  the  rate  should  be  in- 
creased to  10  or  12  pounds  or  more,  de- 
pending on  the  germination  percentage  of 
the  seed.  Either  broadcast  or  band 
seeding  m.ethods  can  be  used,  but  band 
seeding  requires  less  seed.  For  best 
results,  soil  fertility  should  be  kept 
as  high  as  possible.  Orchardgrass  is 
not  seriously  troubled  with  insect  pests, 
but  such  diseases  as  anthracnose,  leaf 
stripe,  leaf  rust,  and  scald  do  reduce 
the  quality  of  the  forage  and  may  reduce 
the  vigor  of  the  stand. 

Varieties  of  orchardgrass.  Recently 
Potomac ,  a  new  variety,  has  been  released 
for  certified  seed  increase.  It  has  some 
resistance  to  leaf  rust  and  shows  some 
superiority  over  the  common  strains  in 
seedling  vigor  and  leafiness. 


Earl  C. 


Spurrier 
6-U-56 


JNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


G-13 


WINTER  BARLEY  IN  ILLINCIS 


Winter  barley  is  not  a  new  crop  in  Illi- 
nois, but  there  is  a  demand  at  present 
for  a  small  grain  crop  to  be  planted  on 
areas  taken  out  of  wheat  production  by- 
acreage  allotments.  Winter  barley  might 
well  substitute  for  wheat  on  these  areas 
in  the  southern  half  of  Illinois. 


Winter  barley  has  several  advantages 
over  spring -planted  barley.  \Tiien  '  it 
survives  the  -vrinter  it  yields  more  and 
its  quality  is  better  than  the  yield  and 
quality  of  the  spring  types.  Winter 
types  normally  mature  earlier  and  thus 
escape  the  higher  temperatures  and  some 
diseases  that  are  serious  hazards  to  the 
spring  crop. 

Winter  barley  makes  excellent  fall  pas- 
ture and  is  a  good  companion  crop  for 
legumes  and  grasses.  The  grain  makes  ex- 
cellent livestock  feed  and  is  considered 
nearly  equal  to  corn  in  feeding  value 
when  fed  to  poultry  and  certain  types  of 
livestock. 

U.  S.  Route  3*5,  or  a  line  from  Hannibal, 
Missouri,  through  Decatur,  Illinois,  is 
usually  considered  about  the  northern 
limit  for  winter  barley.  But  the  right 
variety,  planted  early  under  favorable 
conditions,  has  a  good  chance  to  sur- 
vive somewhat  farther  north.  \-Jhile  it 
is  scme\^hat  hazardous  to  grow  imiter 
barley  north  of  U.  S.  Route  36,  if  it 
winterkills  you  can  still  plant  a  spring 
crop  •VTith  little  extra  seedbed  prepara- 
tion. Your  only  loss  would  be  the  cost 
of  seed  plus  planting  charges. 

Cultural  practices.  Winter  barley  is 
not  so  winter  hardy  as  winter  wheat  or 
winter  rye,  but  it  is  hardier  than  win- 
ter oats.  Early  seeding  is  recommended 
to  give  the  crop  a  chance  to  become  es- 
tablished before  cold  weather  prevents 
further  growth. 


Seed  in  time  to  insure  a  good  root 
growth  and  at  least  four  inches  of  top 
growth  before  the  crop  becomes  winter 
dormant.   The  right  date  is  about  10 
days  to  two  weeks  ahead  of  normal  wheat 
seeding,  that  is,  from  September  15 to 
October  15,  depending  on  how  far  south 
you  are.  Seed  with  a  grain  drill  at  the 
rate  of  eight  pecks  an  acre  on  a  well- 
prepared  seedbed. 

Barley  responds  well  to  fertilizers,  and 
fertile  soils  mean  good  root  growth  and 
more  winter  hardiness.  A  high  nitrogen 
content  in  soils  may  cause  barley  to 
lodge.  The  straw  of  all  barleys  will 
break  rather  quickly  once  they  are  ma- 
txore.  For  this  reason  it  is  important 
not  to  delay  harvesting. 

Varieties.  Besides  yield,  winter  hardi- 
ness and  straw  strength  are  the  most  im- 
portant characteristics  to  consider  in 
choosing  a  variety  of  barley.  At  pres- 
ent the  fo.iJLowing  varieties  are  being 
recommended:  Kearney,  Reno,  and  Ken- 
tucky #1  for  the  area  between  U.  S.  Route 
36  and  U.  S.  Route  50  (which  is  frcm  St. 
Louis  east  to  Vincennes,  Indiana)  and 
these  three  plus  Kenbar  and  Mo,  B-UOO 
for  the  axea  south  of  U,  S,  Route  50* 

Kearney  is  one  of  the  most  winter  hardy 
varieties,  is  medium  early,  and  has  a 
medium  stiff  straw.  Reno  has  a  slightly 
stiffer  straw  than  Kearney  but  is  not 
so  winter  hardy.  Kentucky  #1^  is  vlliter- 
hardy,  has  a  rather  weak  straw,  and  is 
later  than  either  Kearney  or  Reno. 

Kenbar  is  the  earliest  and  the  shortest 
of  the  varieties  recommended.  It  is  not 
quite  so  hardy  as  Reno  but  it  has  a  much 
better  straw.  It  is  more  resistant  to 
smut,  mildew,  and  scald  than  Reno, 
Kearney,  or  Kentucl^y  /)-l. 


Mo.  B-UOO  is  a  high-yielding  variety  early  as  Kenbar  nor  does  it  have  so  good 
that  is  resistant  to  loose  smut,  mildew,  a  straw, 
and  splot  blotch.  Because  it  grows  rap- 
idly and  vigorously  in  the  fall  it  makes  The  1955  yields  of  the  recommended  vari- 
excellent  fall  pastxire.   It  is  not  so  eties  are  shown  in  the  following  table: 


Per  acre 

yield 

Variety 

Urbana 

Brownstown 

Dahl gren 

Carbondale 

Average 

bu. 

bu. 

bu. 

bu. 

bu. 

Kearney 

55.7 

39.9 

24,3 

25.2 

36.3 

Reno 

68.6 

52,0 

26.0 

32.9 

it4.9 

Kentucky  #1 

5^.0 

39.8 

19.6 

30.7 

36.0 

Kenbar 

2k,  Q* 

60,9 

26,9 

18,8^^ 

32.8 

Mo,  B-1+00 

62.4 

•  •  •  • 

, , , , 

31.1 

U6,7 

*Poor  fall  stands  due  to  low  germination  reduced  yields  at  these  locations. 


R,  0.  Weibel 
9-12-55 


AGRONOMY  FACTS 


G-14 


WINTER  WHEAT 


Winter  wheat  ranks  third  as  a  cash  grain 
crop  in  Illinois.  The  agricult-ure  of 
southern  Illinois  is  strongly  supported 
hy  this  crop.  The  climate  and  soils  of 
this  area  are  veil  suited  to  the  produc- 
tion of  high-quality  soft  red  winter 
wheat.  On  the  other  hand,  hard  red  win- 
ter wheats  produced  in  Illinois,  espe- 
cially in  the  southern  half  of  the  state, 
are  usually  too  low  in  protein  to  produce 
a  satisfactory  bread  flour.  And  because 
of  the  characteristic  of  the  protein, 
the  flour  is  not  suitable  for  cakes  or 
pastry. 


Reccmmended  Varieties 


Soft 

Saline 

Knox 

Seneca 


Hard 

Pawnee 

We star 
Pone  a 


Acceptable  Varieties 


Soft 

Royal 

Vigo 

Butler 


Hard 


Triumph 


Growing  both  soft  and  hard  wheats  in  the 
same  area  has  caused  a  considerable 
amount  of  concern.  Because  local  eleva- 
tor personnel  cannot  always  distinguish 
between  them,  they  are  often  mixed  in 
handling  or  in  shipment.  Thus  they  are 
graded  mixed  wheat  when  they  reach  the 
inspection  points.  Mixed  wheat  is  below 
the  straight  grades  on  the  market.  To 
protect  himself,  the  local  buyer,  if  in 
doubt,  must  class  the  wheat  mixed. 

This  problem  will  continue  as  long  as 
there  is  a  price  differential  in  favor 
of  hard  wheat  and  as  long  as  we  have  no 
quick  way  to  determine  protein  at  the 
local  buying  points.  We  can  help  con- 
siderably by  recommending  that  growers 
know  the  variety  they  are  growing.  All 
persons  selling  seed  should  stress  the 
name  of  the  variety  and  sell  only  those 
that  are  reccmmended. 

Variety  Descriptions.  All  of  the  varie- 
ties listed  below  have  produced  good 
yields  in  Illinois.  All  have  acceptable 
grain  quality  for  their  class. 


Mew  Varieties  Being  Increased 

Soft 

Dual 
Vermillion 

Of  the  recommended  soft  varieties.  Saline 
is  the  tallest  and  also  the  latest. 
Knox  has  the  shortest  straw  and  is  the 
earliest,  Seneca  is  intermediate.  Pawnee 
and  Ponca,  hard  wheats,  are  very  similar 
in  maturity  and  straw  strength.  Both 
are  a  few  inches  shorter,  a  little  ear- 
lier, and  have  slightly  stiffer  straw 
than  We star. 

The  grain  of  Ponca  will  not  bleach  out 
in  the  field  so  readily  as  Pawnee,  and 
hence  its  milling  quality  is  better. 
Westar  is  more  resistant  to  mosaic  than 
Pawnee  or  Ponca,  but  all  three  may  be- 
come heavily  infested  when  conditions 
are  favorable. 

Other  characteristics  of  the  reccmmended 
varieties  are  given  in  the  tables  on 
the  back. 


Table  1. --Characteristics  of  Varieties  of  VJheat  Reccmmended  for  Illinois 


Area  of 

Lodg- 

Winter 

"■"Rela- 

CI. 

state  vhere  Test 

ing 

hardi- 

tive 

Head 

Grain 

Variety 

Ko, 

adapted*  weight 

res. 

ness 

height 

type 

texture 

Saline 
Knox 

1267^^ 
12798 

All 
C  & 

S 

Med. 
Med. 

Excel. 
Excel. 

Excel. 
I-med. 

Tall 
Short 

Bearded 
Smooth 

Soft 
Soft 

Seneca 
Royal 

12529 
12558 

S 
C  & 

S 

Low 
High 

Excel. 

Med. 

Fair 
Excel. 

Med, 
Tall 

Smooth 
Bearded 

Soft 
Soft 

Vigo 
Butler 

12220 
12527 

c  & 

s 

S 

Med. 
Med. 

Med. 
Excel. 

I-med. 
I-med. 

Tall 
Tall 

Smooth 
Bearded 

Soft 
Soft 

Dual 
Vermillion 

13083 
I27I+8 

c  & 
All 

S 

Lew 

Med. 

Excel. 

Excel. 

Excel. 
Excel. 

Med. 

Med. 

Smooth 
Smooth 

Soft 
Soft 

Pavnee 
Ponca 

11669 
12128 

N  & 
W  & 

c 
c 

Med. 
Med. 

Med. 

Med. 

Excel. 
I-med, 

Short 
Short 

Bearded 
Bearded 

Hard 
Hard 

We star 
Triumph 

12110 
12132 

N  & 

c 
c 

Med. 
Med. 

Med. 
Med. 

Excel. 
I-med, 

Med, 
Short 

Bearded 
Bearded 

Hard 
Hard 

*  W  =  North; 

C  =  Central;  S  = 

South. 

1 


Tahle  2. --Reaction  of  Wheat  Varieties  to  Diseases  Common  in  Illinois 


Leaf 

Stem 

Loose 

Covered 

Sep- 

Hessian 

Variety 

Mosaic 

rust 

rust 

smut 

smut 

Mildew 

toria 

Scab 

fly 

Saline 

R 

I 

I 

S 

S 

S 

S 

S 

s 

Knox 

R 

R 

S 

S 

S 

S 

S 

S 

s 

Seneca 

R 

S 

S 

I 

S 

S 

s 

S 

s 

Royal 

R 

S 

I 

S 

S 

S 

s 

S 

s 

Vigo 

R 

I 

S 

I 

S 

S 

s 

S 

s 

Butler 

R 

S 

s 

I 

I 

&' 

s 

S 

s 

Dual 

R 

R 

S 

S 

S 

I 

s 

S 

R 

Vermillion 

R 

R 

s 

s 

S 

S 

s 

S 

s 

Pawnee 

S 

I 

R 

R 

R 

S 

s 

s 

S 

Ponca 

S 

I 

R 

R 

R 

s 

s 

S 

R 

Westar 

I 

I 

S 

I 

S 

S 

s 

s 

s 

Tri\iQiph 

S 

S 

S 

I 

S 

s 

s 

s 

s 

R  =  Resistant;  S  =  Susceptible;  I  =  Intermediate, 


R.  0.  Weibel 
9-19-55 


AijRONOMY  rMciS 


"BLAST"  IN  OATS 


G-15 


"Blast"  is  a  term  that  is  applied  to  a 
type  of  sterility  in  oats.  It  is  evi- 
denced by  white,  empty  glumes  in  the 
lower  branches  at  the  base  of  the  pani- 
cle about  the  time  the  oats  are  in  full 
head.  The  condition  is  also  called 
blight,  blindness,  and  white  ear. 

Blast  is  not  a  disease;  it  results  from 
inability  of  some  of  the  spikelets  to 
develop  completely.  Anything  that  in- 
terferes with  the  physiological  processes 
during  development  of  the  plant,  partic- 
ularly the  panicle,  may  cause  blast. 
Late  seeding,  lack  of  moisture,  nutrient 
deficiencies,  insect  attacks,  and  dis- 
ease, either  singly  or  in  combination, 
will  increase  the  condition.  Tillers 
are  affected  more  than  main  stems. 

The  base  of  the  panicle  is  where  blast 
is  most  prevalent.  The  sequence  of  de- 
velopment in  the  oat  panicle  makes  it 
easy  to  imderstand  why.  An  oat  panicle 
is  composed  of  many  branches,  each  of 
which  ends  in  a  many-flowered  spikelet 
in  which  usually  only  two  flowers  pro- 
duce seed.  The  main  axis  of  the  panicle 
terminates  in  a  spikelet.  Beneath  the 
tip  spikelet,  and  placed  alternately  on 
the  main  stem  of  the  panicle,  are  five  to 
six  groups  of  spikelet -bearing  branches. 
The  number  of  spikelet -bearing  branches 
increases  from  the  tip  of  the  panicle 
downi-ra-rd. 

The  first  structure  ■  that  develops  from 
the  main  axis  of  the  panicle  is  a  branch 
primordium  (a  branch  of  the  first  order), 
which  is  the  beginning  of  the  group  of 
branches  at  each  node  of  the  panicle. 


From  the  first -order  branches,  branches 
of  the  second  order  are  formed;  from  the 
second  order,  the  third  order;  and  so  on. 
At  the  nodes,  especially  the  basal  group, 
branches  of  the  fifth  and  sixth  orders 
may  be  found. 

The  oat  panicle  starts  to  develop  from 
the  tip  spikelet  and  proceeds  to  the 
base.  At  any  node,  development  begins 
with  the  first -order  branch,  followed  in 
sequence  by  the  second,  third,  etc.  Con- 
sequently the  panicle  is  oldest  at  the 
tip  and  yo\ingest  at  the  base,  and  at  any 
node  the  first -order  branches  are  oldest 
and  the  fifth-  or  sixth-order  branches 
are  youngest. 

It  takes  some  time  for  a  panicle  to  de- 
velop. At  Urbana  a  panicle  of  Clinton 
requires  15  to  18  days,  or  from  about 
May  10  to  25  or  28,  to  develop  fully. 
Heading  occurs  about  15  days  later. 

Adverse  changes  during  panicle  develop- 
ment, especially  the  first  half,  will 
affect  the  youngest  parts  more  than  the 
oldest.  The  youngest  parts  are  more 
susceptible  because  they  are  farthest 
from  producing  seed.  We  can  thus  expect 
to  find  more  blast  in  the  basal  groups 
of  branches  because  that  is  where  the 
largest  number  of  high-order  branches 
are  found. 

Varieties  differ'  in  amount  of  blast  even 
though  their  environment  and  maturity 
are  similar.  This  fact  would  indicate 
that  plant  breeders  can  produce  varie- 
ties that  have  a  low  percentage  of  blast 
and  hence  higher  yields. 


0.  T.  Bonnett 
9-26-55 


AGRONOMY 


G-16 


WINTER  RYE  IN  ILLINOIS 


The  acreage  of  -winter  rye  has  climbed 
steadily  since  1951/  according  to  the 
Illinois  Crop  Reporting  Service,  The 
crop  harvested  in  1955  vas  the  largest 
since  1919 .  Perhaps  we  should  take  a 
closer  look  at  this  age-old  crop  that  is 
making  a  ccmetack  in  Illinois.  Why  the 
increased  interest  in  rye? 

1,  Wheat  and  corn  acreage  allotments 
have  resulted  in  extra  land. 

2,  More  rye  is  being  used  for  pasture 
and  forage. 

3,  Rye  is  being  inter seeded  as  a  winter 
cover  and  as  a  green  maniire  crop  in 
corn  and  soybean  fields  both  before 
and  after  harvest. 

Characteristics .  Winter  rye  is  the  har- 
diest of  the  cereals — "the  roughest, 
toughest  of  them  all."  It  will  grow  on 
poorer  soil,  in  drier  soil, and  in  colder 
weather  than  our  other  grain  crops.  It 
will  produce  in  soil  that  is  sandy  or  low 
in  fertility  where  other  cereals  will  do 
little  or  nothing.  On  good  soils  rye  is 
capable  of  making  high  yields,  although 
not  so  high  as  wheat. 

Two-year  comparisons  of  average  acre 
yields  from  several  rye  varieties  with 
average  yields  frcm  wheat  varieties  grown 
in  the  same  field  showed  the  following 
res\ilts:  Urbana,  central  Illinois  -  wheat 
k8  bu.  and  rye  39  bu.  DeKalb,  northern 
Illinois  -  wheat  3^  bu.  and  rye  30  bu. 

Although  a  little  spring  rye  is  grown  in 
the  western  United  States,  the  Illinois 
rye  crop  is  all  of  the  winter  type  and 
therefore  is  fall  seeded.  Rye  differs 
from  the  other  common  small  grains  in 
being  almost  completely  cross  ferti- 
lized. That  is, the  flowers  on  one  plant 
are  fertilized  not  by  their  own  pollen, 
but  by  pollen  from  other  rye  plants. 


Culture .  Rye  ^d-ll  respond  to  good  cul- 
tural practices  and  to  fertilizers,  but 
the  return  for  fertilization  is  generally 
greater  on  wheat  and  other  grains.  A 
seeding  rate  of  5  "to  6  pecks  per  acre 
is  thought  best  for  Illinois.  The  crop 
can  be  sown  frcm  August  to  Kovember,  Al- 
though a  good  seed  bed  is  desirable,  rye 
has  the  ability  to  germinate  and  grow 
under  poor  seeding  conditions. 

Uses.  Rye  may  be  used  as  a  cash  grain, 
as  a  grain  feed,  as  pasture,  or  as  a 
green  manure  crop. 

As  a  cash  grain  the  crop  generally  goes 
into  the  following  trade  channels:  dis- 
tilling, dry  milling,  feed,  export,  and 
seed.  The  distilling  industry  uses  rye 
for  whiskey  and  alcohol.  The  dry  millers 
make  rye  flour,  which  is  generally  blended 
with  wheat  flour  to  make  the  kind  of  rye 
bread  Americans  prefer.  The  feed  indus- 
try also  blends  rye  with  other  grains. 

Although  rye  may  be  used  as  a  feed  crop 
on  the  farm,  it  is  less  valuable  than 
corn,  wheat,  or  barley.  Alone,  it  is 
somewhat  unpalatable  and  is  considered 
heavy  and  sticky.  For  best  results,  it 
should  be  mixed  with  other  grains. 

Rye  makes  excellent  fall  and  spring  pas- 
ture. It  is  superior  to  other  small 
grains  in  Illinois  because  it  will  grow 
later  in  the  fall  and  start  growth  ear- 
lier and  more  rapidly  in  the  spring. 

The  protein  content  of  young  rye  plants 
may  run  30  percent  or  higher  in  the 
spring  on  fertile  soils. 

Use  of  rye  as  a  green  manure  is  rela- 
tively new  in  the  Corn  Belt.  At  present 
the  agriciiltural  experiment  stations  are 
doing  a  great  deal  of  research  on  the 
various  aspects  of  this  potentially  im- 
portant cultural  practice.   In  addition 


to  supplying  organic  matter^  rye  serves 
as  a  winter  cover  or  guard  against  ero- 
sion and  it  may  also  be  pastured.  If 
corn  is  to  follow  rye,  the  land  should 
be  plowed  in  late  April  or  early  May, 
and  nitrogen  should  be  added. 


The  success  of  rye  as  a  green  manure  will 
depend  to  a  great  extent  en  soil  mois- 
ture. In  late,  wet  springs,  the  crop 
will  mature  before  it  can  be  plowed,  and 
in  dry  springs  it  will  remove  large 
amotints  of  water  from  the  soil  profile 
before  corn  is  planted. 


Results  from  Winter  Rye  Variety  Trials  at  Urbana  and  DeKalb,  Illinois, 

195^  and  1955 


Adams 

Balbo 

Caribou 

Emerald 

Imperial 

Pierre 

Tetra 
Petkus 


Yield 

Test 
weight 

Height 

Plant 
erect- 
ness 

Head- 

Urbana          DeKalb 

ing 

Variety 

195^  1955  Av.    195'J-  1955  Av. 

date 

bu,   bu,  bu, 
in. 7  ^3.8  i^2.8 
37.9  ^^.9    ^1.^ 


bu.   bu,  bu, 
22,0  3^.5  28.3 
29. i^  30.6  30.0 


37.3  38.1^  37.9 

29,1  i+1,9  35.5 

3>h,S  Uo.8  37.7 

37.0  36.9  37.0 


I  •  •  •    •  •  •  • 


33.2  3G.k  34.8 
3i^.3  36.6  35.5 
30,7  32.8  31.8 


lbs. 

in. 

perct. 

51.7 

57 

^5 

May  9 

51.5 

55 

57 

"  3 

51.2 

50  • 

•  • 

"  13 

51.0 

56 

hi 

"  9 

51.0 

57 

55 

"  10 

51.8 

5^ 

51 

"  8 

•  •  •  • 


13.i+ 


•  •  •  t 


50.1 


53 


75 


16 


Balbo  is  believed  to  be  the  first  choice 
for  pasture  because  it  will  grow  earlier 
in  the  spring.  In  extreme  northern  Illi- 
nois, however,  it  may  siiffer  from  winter- 


killing and  Pierre  or  Emerald  might  be 
better.  Tetra  Petkus  has  larger  kernels 
and  wider  leaves,  but  it  has  not  out- 
yielded  Balbo  in  either  grain  or  forage. 


J.  W. 


Pendleton 
10-3-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


m 


S-5 


ROOT  AND  STEM  ROT  OF  SOYBEANS 


Root  rots  occur  on  soybeans  in  Illinois 
from  time  to  time^,  depending  largely  on 
weather  conditions.  They  are  likely  to 
he  noticeable  in  wet  seasons^  especially 
in  low  spots  in  fields  where  drainage  is 
poor.  One  of  these  root  rots  is  caused 
hy  Rhizoctonia,  a  fungus  that  is  present 
in  most  soils  where  crop  plants  are 
grown.  The  fungus  usually  attacks  young 
plants  when  the  soil  is  abnormally  wet^ 
causing  a  reddish-brown  decay  of  the 
outer  layer  of  the  main  root  and  basal 
stem.  Much  of  the  secondary  root  system 
is  destroyed^  and  the  plants  wilt  and 
die.  Dead  plants  occtu:  typically  in 
areas  four  to  10  feet  in  diameter,  usually 
distributed  irregularly  over  a  field. 
In  most  seasons  Rhizoctonia  root  rot  is 
of  little  economic  importance. 

During  the  1955  season,  xa.  root  and 
stem  rot  new  to  Illinois  was  discovered 
in  five  or  six  fields  in  northern  and 
central  Illinois.  This  disease  affects 
plants  of  all  ages.  Seedlings  that  have 
just  emerged  may  shrivel  and  die,  leaving 
gaps  ranging  from  a  few  inches  to  several 
feet  in  the  rows.  Older  plants  wilt  and 
ic"y  'U-P,  or  they  may  be  severely  stunted 
and  perhaps  wilt  only  slightly  at  midday. 
When  such  plants  are  dug  or  pulled,  they 
show  a  badly  decayed  root  system.  The 
disease  is,  however,  not  confined  to  the 
roots;  often  the  brown  decay  is  noted  on 
the  stem  several  inches  above  the  soil 
line. 

Although  this  root  and  stem  rot  is  espe- 
cially damaging  in  poorly  drained  areas 
of  the  field,  it  sometimes  occurs  on 


higher  ground.  The  disease  is  not  wide- 
spread or  serious  in  Illinois  at  present, 
but  it  should  be  watched  closely  because 
of  its  potential  threat  to  soybean  pro- 
duction. 

This  same  root  rot  has  "been  present  in 
northwestern  Ohio  since  1951«  It  has  be- 
come prevalent  and  destructive  in  the 
clay  soils  of  the  old  lakebed  region. 
The  disease  is  caused  by  a  fungus,  iden- 
tified by  Ohio  Experiment  Station  pathol- 
ogists as  a  Phytophthora.  Sometimes 
it  is  impossible  to  differentiate  the 
Phytophthora  root  rot  from  the  one 
caused  by  Rhizoctonia.  However,  the  Rhi- 
zoctonia root  rot  lesion  usually  has  a 
reddish  brown  color,  while  that  of  the 
Phytophthora  root  rot  is  brown.  Also, 
the  Phytophthora  root  rot  seems  to  per- 
sist throughout  most  of  the  growing  sea- 
son, while  the  Rhizoctonia  root  rot 
usually  disappears  before  mid-July. 

Work  at  the  Ohio  Station  indicates  that 
the  varieties  Illini,  Monroe,  and  Black- 
hawk  are  resistant  to  Phytophthora, 
while  Hawkeye,  Lincoln,  and  Harosoy  are 
susceptible.  Seed  treatment  has  no 
value  in  preventing  seedling  blight.  It 
is  recommended  that  rotation  mth  other 
crops  be  practiced  on  land  where  the 
root  rot  has  appeared. 

Investigations  on  Phytophthora  root  and 
stem  rot  are  under  way  at  the  Illinois 
Experiment  Station,  and  more  information 
on  this  disease  will  be  made  available 
as  controls  are  developed  or  resistant 
varieties  are  released. 


U.  S. 


D.  W.  Chamberlain 

Plant  Pathologist 

Dept.  of  Agriculture 

5-21-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


S-6 


ESTIMATED  HAIL  LOSSES  TO  SOYBEANS 


Because  soybeans  grow  throughout  the 
cropping  season,  they  are  subject  to  in- 
jury by  hailstorms.  Fully  two-thirds  of 
the  hailstorms  that  occur  in  the  Corn 
Belt  come  between  May  and  September, 
when  soybeans  are  in  the  field. 

Insurance  to  protect  the  farmer  against 
loss  of  his  crop  by  hail  is  becoming  more 
common  each  year.  Insurance  companies 
have  conducted  and  are  conducting  experi- 
ments designed  to  get  information  on  how 
to  evaluate  losses  to  soybeans  from  hail 
injury.  Experiment  stations,  too,  have 
studied  the  problem,  and  the  insurance 
companies  have  supported  some  of  this 
work.  Illinois  has  been  conducting  such 
tests  for  six  years,  Iowa  for  six  years, 
and  North  Carolina  for  one  year. 


Results  at  the  Iowa  Station  showed  that 
when  all  leaves  were  removed  at  the  blos- 
soming stage  the  yield  of  beans  was  l8 
percent  of  norm.al,  and  when  the  stems 
were  broken  in  addition  to  100  percent 
leaf  removal  the  yield  was  l6  percent  of 
normal  (see  Stage  7  in  diagram).  Leaf 
removal  earlier  and  later  than  this 
critical  period  caused  progressively 
less  reduction  in  yield. 

Recoverability  is  highest  when  plants 
are  about  three  weeks  old  and  after 
three  or  four  trifoliate  leaves  have  un- 
rolled. Although  leaf  removal  at  this 
stage  causes  some  reduction  in  yield, 
the  drop-off  in  production  is  less  than 
before  or  after  this  stage.  In  the  dia- 
gram this  stage  is  shown  as  2. 


Effect  of  stage  of  development  on  recov- 
ery  from  injury.  The  soybean  plant  pos- 
sesses great  ability  to  recover  from 
injury,  particularly  at  certain  stages 
of  development.  Knowing  the  stage  at 
which  the  damage  occurred  is  therefore 
just  as  important  in  estimating  losses 
as  knowing  the  extent  of  the  injury. 

Unless  the  plants  are  broken  off  at  the 
ground  or  are  otherwise  destroyed  by 
beating  of  the  hail,  they  will  yield 
some  grain.  That  is  to  say,  there  is  no 
stage  when  injury  will  completely  elimi- 
nate all  yield. 

The  stage  of  lowest  recoverability  is 
just  at  the  end  of  blossoming.  At  this 
time  the  pods  on  the  lower  branches  are 
nearly  full  length  and  beans  are  devel- 
oping in  them.  Tlie  pods  on  these  branches 
are  far  enough  along  to  yield  some  grain, 
but  pods  in  the  top  part  of  the  plant 
are  just  starting  to  form.  No  new  blos- 
soms or  leaves  form  afterward,  and  removal 
of  the  leaves  robs  the  plants  of  the 
photosynthetic  area  when  it  is  needed 
most. 


Extent  of  injury.  In  general,  yield  is 
reduced  in  direct  proportion  to  the  per- 
centage of  leaf  surface  rem.oved.  Bruis- 
ing of  the  stem  also  affects  yield. 
Tests  at  Iowa  showed  that  breaking  of 
stems  lowered  yield  below  that  caused  by 
leaf  removal.  This  decrease  amounted  to 
only  15  percent  at  the  first-bloom  (2) 
stage,  but  increased  to  over  50  percent 
at  the  critical  (7)  stage. 

A  severe  storm  that  kills  plants  out- 
right will  reduce  the  stand  and  conse- 
quently the  yield,  but  the  reduction  v;ill 
vary  with  stage  of  growth.  If  it  occurs 
during  the  early  (l  to  3)  stages,  as 
many  as  50  percent  of  the  plants  can  be 
destroyed  without  any  great  reduction  in 
yield.  But  at  Stage  6  or  later,  a  re- 
duction in  stand  will  mean  a  marked  de- 
crease in  yield.  By  the  end  of  the 
blooming  period,  the  plants  have  lost 
their  capacity  to  spread  out  and  take  up 
the  extra  space. 


Other  effects 


Loss  of  leaw 


the  critical  (7)  stage  delays  matui' 
the  plants,   but  such  injury  aft^. 


stage  seems  to  hasten  maturity.  Actu- 
ally, however,  maturity  only  appears  to 
be  speeded  up.  The  crop  comes  only  from 
the  most  advanced  pods  because  the  leaf 
area  is  not  sufficient  to  provide  reserves 
for  the  later  formed  pods. 

large  leaf  losses  reduce  seed  size  and 
also  decrease  the  oil  content  of  the 
seed  if  the  loss  occurs  while  the  grain 
is  filling. 

Estimating  losses.  It  is  hard  to  deter- 
mine the  percentage  of  leaves  removed  by 
a  hailstorm.  It  is  possible  to  tell  the 
stage  of  plant  development  by  carefully 
observing  the  plants  immediately  after  a 
storm.  But  figuring  out  how  many  leaves 
remain  in  relation  to  the  number  before 
the  storm  is  like  probing  in  the  dark. 

Because  of  this  difficulty,  Dr.  James  C. 
Weill,  who  did  his  Ph.  D.  thesis  on  the 
effects  of  artificial  hail  on  soybeans 
at  the  University  of  Illinois,  suggested 
the  possibility  of  determining  the  de- 
gree of  injury  by  counting  the  terminal 
buds  that  had  been  knocked  off.  In  two- 
year  tests  (1950-51)  Weill  blew  cracked 
ice  through  a  three-inch  rubber  tube  onto 


soybean  plants  at  various  stages  of  de- 
velopment. In  this  way  he  inflicted  in- 
juries similar  to  those  caused  by  natural 
hail,  removing  different  percentages  of 
leaves  and  at  the  same  time  damaging 
stems  and  removing  terminal  buds . 

Weill  counted  the  leaves  before  treat- 
ment and  then  counted  those  left  on  the 
plants  after  treatment.  He  also  coimted 
the  plants  from  which  the  topmost  or 
terminal  bud  had  been  removed.  In  both 
years  in  which  he  made  these  tests  he 
found  a  very  high  correlation  between 
the  percentage  of  leaves  lost  and  the 
percentage  of  terminal  buds  lost. 

Because  in  these  tests  the  correlation 
between  loss  of  leaves  and  loss  of  ter- 
minal buds  was  so  close  and  because  the 
percentage  of  terminal  buds  that  are 
lost  can  be  easily  and  accurately  deter- 
mined after  a  hailstorm,  Weill  suggests 
that  the  severity  of  injury  be  estimated 
by  counting  the  number  of  plants  in  a 
himdred  from  which  the  terminal  buds  have 
been  rem^oved. 


G.   H.   Dungan 
6-18-56 


100 


+3 

a 

Q) 

CO 

C) 

-P 

U 

C 

(U 

^^ 

PnrH 

yu 

C 

-H 

Ti 

(i) 

Ti 

u 

M 

:3 

fl) 

"-n 

•H 

r, 

>^ 

•H 

a 

i^ 

D 

•H 

01 

<+-l 

!h 

C) 

0 

20 


lOC;^  leaf  remova-l 
^.      +   stem  breakrage 


3  ^  567 

Stages   in  plant  development 


10 


Diagram  of  grain  yield  reduction  as  a  result  of  f-:  .  _  . 
hail  damage  at  10  stages  of  soybean  plant  development. 


"erities  of 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND              -^^Z 
TESTING       -^^ 

■■■' S 

SF-37 


CHEMISTRY  OF  ORGANIC  NITROGEN  IN  SOILS 


Nitrogen  is  different  frcm  the  other  nu- 
trient elements  in  the  soil  because  it 
occurs  almost  entirely  in  organic  ccm- 
"bination.  Only  a  very  small  fraction  of 
the  nitrogen- -usually  frcm  1  to  3  per- 
cent --is  in  the  inorganic  forms  at  any 
one  time. 

During  the  year  nitrogen  is  released 
slowly  from  the  organic  matter  to  the 
mineral  forms ^  which  are  the  available 
forms  of  nitrogen  in  soils  (see  SF-4). 
The  amount  that  is  released  depends  on 
the  kind  and  amount  of  nitrogen  in  the 
organic  matter^  on  climatic  conditions;, 
and  on  the  physical  condition  of  the 
soil. 

Several  methods  are  used  to  estimate  the 
quantity  of  nitrogen  converted  to  the 
available  forms  during  the  growing  sea- 
son, but  all  of  these  methods  have  cer- 
tain limitations  (see  SF-I7).  If  we 
knew  more  about  the  nature  of  organic 
nitrogen  in  soils,  we  could  overcome 
seme  of  the  uncertainties  involved  in 
estimating  nitrogen  availability  and  in 
making  fertilizer  recommendations. 

Unfortunately,  we  know  very  little  about 
the  nature  of  soil  organic  nitrogen  or 
about  how  soils  differ  in  their  contents 
of  organic  nitrogen  compounds.  Do  fer- 
tile soils  contain  nitrogen  compounds 
that  are  not  found  in  infertile  soils? 
Are  some  nitrogen  compounds  in  humus 
easily  mineralized  while  others  resist 
attack  by  soil  microbes?  Are  well- 
fertilized  and  manured  soils  different 
from  infertile  soils  in  their  contents  of 
certain  kinds  of  organic  nitrogen  com- 
pounds? 

To  answer  these  questions  the  Department 
of  Agronomy  has  a  research  project  under 
way  that  is  concerned  with  the  chemistry 
of  humus  nitrogen.  As  indicated  above, 
the  purpose  of  this  study  is  to  find  out 
what  forms  of  organic  nitrogen  the  soils 


contain  and  to  determine  how  cropping 
and  management  practices  affect  these 
forms. 

Recently  a  study  was  made  of  the  protein 
nature  of  soil  humus.  The  building 
units  of  the  proteins--the  amino  acids-- 
were  isolated  frcm  several  soils  and 
their  amounts  were  determined.  Briefly, 
the  results  showed  that  soils  differed 
in  the  quantity  and  quality  of  their  pro- 
teins. In  seme  soils  as  much  as  half  of 
the  nitrogen  was  in  the  form  of  pro- 
teins; in  others  less  than  a  third  of 
the  nitrogen  was  proteinaceous.  Also, 
the  amino  acid  composition  of  the  pro- 
tein material  in  one  soil  was  quite 
different  frcm  that  in  another.  This 
difference  suggests  that  the  ability  of 
humus  to  supply  nitrogen  to  the  plant 
may  depend  considerably  upon  the  nature 
of  its  proteins. 

The  famous  Morrow  Plots  at  the  Univer- 
sity of  Illinois  were  used  to  determine 
the  effects  of  some  long-time  rotations 
on  the  distribution  of  amino  acids  in 
soils.  The  results  of  this  study  were 
very  interesting.  It  was  foimd  that  the 
proteins  in  the  soils  from  the  untreated 
plots  (such  as  the  i^ntreated  continuous- 
corn  plot)  were  low  in  the  kinds  of  ami- 
no acids  that  would  be  expected  to  be 
ready  sources  of  nitrogen--for  example, 
mono -amino  acids  like  glycine,  alanine, 
valine,  and  leucine,  and  the  amino  acid 
amides,  asparagine  and  glutamine.  The 
proteins  in  the  soil  frcm  the  corn-oats- 
clover  rotation  plot  that  had  been 
manured,  limed,  and  supplied  with  phos- 
phate were  high  in  these  amino  acids. 

These  results  show  that  when  soils  are 
heavily  cropped  they  lose  heavily  in  cer- 
tain kinds  of  amino  acids.  Hence,  not 
only  does  an  intensive  system  of  farming 
deplete  the  soil  of  proteins,  but  the 
protein  material  that  remains  is  of  low 
quality. 


Needless  to  say,  more  research  needs  to 
be  dene  before  the  full  practical  signif- 
icance of  these  findings  can  be  deter- 
mined. But  the  results  obtained  thus 
far  have  served  to  emphasize  the  desir- 
ability of  using  management  practices 
that  will  furnish  a  continuous  supply  of 
actively  decomposing  organic  matter  to 
the  soil.  The  soil  organisms  use  plant 
residues  and  manures  as  sources  of  food. 
During  growth  and  reproduction  they  syn- 


thesize body  proteins.  It  is  these  pro- 
teins that  later  become  good  sources  of 
mineralizable  nitrogen. 

Research  work  on  the  chemistry  of  organ- 
ic nitrogen  in  soils  is  continuing.  In 
the  future  we  can  look  forward  to  unrav- 
eling seme  of  the  mysteries  surrounding 
the  availability  of  hiimus  nitrogen  in 
soils. 

F.  J,  Stevenson 


10/31/55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AND 
TESTING 


AGRONOMY  FACTS 


SF-38 


1955  WHEAT  YIELDS  -  ILLINOIS  SOIL  EXPERIMENT  FIELDS 

Cropping  123^56789 

Location      system 0    M   ML   MLF   0    R   RL   RIP  RIPK 

Dark-colored  soils 

bu.   bu.   bu.   bu.   bu.   bu.   bu.   bu.   bu. 

Mercer  C-C-O-W       kk  h2.  39  ^0  U6 

Macoupin  C-B-W-H  26       "^h       39       38  31  32  37  ^0  ij-5 

Hancock  C-B-W-H  28       36       !+3       i+3  29  2h  28  32  39 

Adams  C-B-O-W                 I8  29  30  33  37 

Lee  C-O-H-W  lj-2       1+8       5I        50  4l  hG  hh  52  1+9 

Logan  C-C-O-H                1+1  1+7  1+1  1+3  39 

Will  C-B-C-0-W-H        20        26        29        3!+  I7  I5  20  3I+  36 

Henry  C-O-W-H                31  36  hh  51  1+9 

St.    Clair  C-B-W-H  11       25        33        36  I3  12  28  35  37 

Putnam  C-C-O-W                17  37  38  1+3 

Woodford  C-C-O-W               37  39  37  39  ^2 

Ogle  C-O-W-H  j_L.ij.iZ.        ♦•  18213137  37 

25      36      39      5o  28  32  35  1+0  5l 


Field 


Ale  do 

Carlinville 
Carthage 
Clayton 
Dixon 
Hartsburg 
Joliet 
Kevanee 
Lebanon 
McWabb 
Minonk 
Mt.  Morris 
Average 


Lip;ht- colored  soils 


Brownstown 

Fayette 

C-B-W-H 

•  • 

•  • 

•  • 

•  • 

•  • 

1 

33 

^5 

51 

Enfield 

White 

C-O-W-H 

1+ 

11 

26 

30 

1+ 

1+ 

15 

20 

33 

Eving 

Franklin 

C-B-W-H 

0 

1+ 

23 

31 

2 

1+ 

17 

20 

27 

Oblong 

Crawford 

C-B-W-H 

13 

27 

36 

1+1 

0 

9 

26 

1+0 

ho 

Raleigh 

Saline 

C-O-H-W 

6 

13 

27 

26 

15 

12 

17 

25 

32 

Toledo 

Cumberland 

C-B-W-H 

9 

22 

52 

56 

10 

11 

21+ 

36 

39 

Average 

6 

15 

33 

37 

7 

7 

22 

31 

37 

Cropping  System  Symbols: 


Soil  Treatment  Symbols: 


C  =  Corn,  B  =  Soybeans,  W  =  Wheat,  0  =  Oats,  H  =  Hay 
(legumes  and  mixed  grasses). 

0  =  Untreated  land,  M  =  Manure  returned  equal  to  crops 
removed,R  =  Crop  residues,  L  =  Limestone,  P  =  Rock  phos- 
phate, K  =  Muriate  potash. 


(Continued  en  back) 


Average  whea.t  yields  in  Illinois  for 
1955  were  the  highest  on  record,  31»5 
"bushels.  Nevertheless  yields  varied 
widely  from  location  to  location  and 
with  different  soil  productivity  and 
management  pi-actices.  Yields  from  the 
Illinois  experiment  fields  (see  tahle) 
illustrate  those  variations,  as  they  rep- 
resent a  cross  section  of  the  produc- 
tive capacity  of  Illinois  soils. 

On  untreated  dark-colored  soils  yields 
ranged  from  I3  to  kh  bushels  an  acre. 
On  fully  treated  land  the  range  was  32 
to  52  bushels.  The  response  to  treat- 
ment varied  from  none  to  26  bushels. 
Similar  variations  occurred  on  the  light - 
colored  soils  of  the  state. 

This  kind  of  information  should  alert 
agricultural  workers  and  farmers  to  the 
danger  of  making  prodictions  regarding 
the  response  that  can  be  expected  from 
a  given  fertilizer  or  management  prac- 
tice in  any  one  year.  The  data  also 
show  the  advantages  of  keeping  a  soil 
adequately  supplied  with  plant  food  and 
ready  for  any  favoi'able  growing  condi- 
tions that  come  along,  such  as  those  of 
1955. 


The  yields  given  in  the  table  were  ob- 
tained after  bulk  application  of  such 
fertilizing  materials  as  manure,  crop 
residues,  limestone,  rock  phosphate,  and 
muriate  of  potash  (on  individual  plots) 
and  under  the  cropping  system  described. 
In  these  experiments  no  attempt  is  m.ade 
to  fertilize  the  individual  crop.  Mate- 
rials have  been  applied  in  quantities 
adequate  to  determine  the  needs  of  the 
various  soils  and  to  supply  all  crops  in 
the  system  under  a  wide  range  of  seasonal 
conditions. 

On  many  of  the  fields  additional  tests 
have  been  made  with  complete  mixed  ferti- 
lizer, various  phosphate  carriers,  nitro- 
gen, and  potash.  In  seme  cases  yields 
have  been  increased  by  annual  direct  ap- 
plications, and  in  other  cases  they  have 
not. 

A  detailed  explanation  of  the  treatments, 
cropping  systems,  and  soil  types  is  given 
in  Illinois  Bulletin  516,  "Effect  of 
Soil  Treatment  on  Soil  Productivity. " 
This  publication  is  supplemented  by  a 
mimeograph  pamphlet  that  brings  data  on 
each  field  up  to  date  for  each  year. 
These  publications  are  available  from 
the  Agronomy  Department,  University  of 
Illinois,  Urbana. 

A.  L.  Lang 
ll-li|-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-39 


EARTHWORMS 


In  1777  Gilbert  White  published  a  paper 
in  which  he  said:  "Worms  seem  to  be  the 
great  promoters  of  vegetation^  which 
would  proceed  but  lamely  without  them, 
by  boring,  perforating,  and  loosening 
the  soil,  and  rendering  it  pervious  to 
rains  and  the  fibers  of  plants,  by  draw- 
ing straws  and  stalks  of  leaves  and 
twigs  into  it;  and,  most  of  all,  by 
throwing  up  such  infinite  numbers  of 
lumps  of  earth  called  worm-casts,  which, 
being  their  excrement,  is  a  fine  manure 
for  grain  and  grass.  .  .the  earth  with- 
out worms  would  become  cold,  hard  bound, 
and  void  of  fermentation,  and  conse- 
quently sterile." 

Since  1777  much  information  concerning 
the  relation  between  the  earthworm 
population  and  soil  conditions  has  been 
collected.  In  spite  of  this  knowledge 
concerning  the  activities  of  earthworms 
and  the  conditions  under  which  they  flour- 
ish, it  still  is  not  clear  whether  they 
affect  the  productivity  of  soils  materi- 
ally. 

Certain  facts  are,  however,  recognized 
and  a  few  of  them  are  worth  enumerating: 

1.  Earthworms  occur  in  fairly  large  num- 
bers in  many  farm  soils.  Observa- 
tions in  the  United  States  and  in 
other  countries  indicate  that  under 
favorable  conditions  the  number  may 
exceed  a  million  an  acre,  with  a  to- 
tal live  weight  of  more  than  l/h 
ton. 

2.  The  worms  are  most  abundant  in  soils 
that  are  high  in  organic  matter. 
Consequently  they  may  be  found  most 
extensively  in  forest,  pasture,  and 
heavily  manured  soils. 

3.  Cultivated  soils  are  less  favorable 
for  earthworm  survival  than  are 
areas  that  are  covered  with  sod 


crops.  This  difference  is  explained 
in  part  by  their  sensitivity  to  sud- 
den changes  in  the  soil  temperature 
when  the  late-fall  freezes  occur. 
They  apparently  need  the  insulating 
protection  that  vegetation  cover 
gives  the  soil. 

k.  Earthworms  appear  to  need  a  contin- 
uous supply  of  calcium,  which  they 
excrete  from  their  digestive  tract. 
Their  numbers  therefore  decrease  as 
the  pH  of  the  soil  goes  down.  Dif- 
ferent species  also  differ  in  their 
tolerance  to  soil  acidity. 

5.  In  virgin  soils  and  in  pastures  the 
worms  drag  into  their  burrows  leaves 
and  other  dead  surface  litter.  Mi- 
croorganisms then  attack  the  litter 
and  convert  it  into  the  so-called 
humus  fraction  of  xhe   soil. 

6.  It  is  believed  that  earthworm  activ- 
ity improves  soil  aeration.  The 
channels  the  earthworms  make  help  to 
improve  air  and  water  movement. 
These  channels  may  also  serve  as 
passageways  for  plant  roots.  Since 
the  worms  that  burrow  deeply  in  the 
soil  may  carry  lime  and  plant  nutri- 
ent elements  into  their  channels  in 
the  subsoil,  the  occurrence  of  roots 
in  subsoils,  which  ordinarily  would 
be  unfavorable  for  them,  may  be  due 
to  earthworm  activity. 

Correspondence  wwith  farmers  indicates 
concern  in  seme  areas  about  the  effect 
of  use  of  anhydrous  ammonia  on  the  earth- 
worm population.  Although  no  experi- 
mental data  are  available  on  this  subject, 
the  lack  of  proof  of  the  value  of  earth- 
worms in  soil  productivity  suggests  that 
arguments  for  and  against  the  use  of 
anhydrous  ammonia  should  be  based  on  fac- 
tors other  than  its  effect  on  the  earth- 
worm population. 

0.  H.  Sears 
11-21-55 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-40 


BAND  APPLICATION  OF  FERTILIZERS  IN  ILLINOIS  -  PART  I 


Banded  fertilizer  may  "be  defined  as  any 
fertilizer  that  is  banded  or  drilled 
with  seed.  Banding  or  drilling  ferti- 
lizer has  been  a  standard  practice  in 
the  East  and  South  for  many  years.  In- 
terestingly enough,  fertilizer  so  applied 
is  generally  called  starter  fertilizer 
in  the  Midwest.  An  eastern  or  southern 
farmer  merely  says  that  he  is  fertilizing 
his  crop. 


other  good  management  practices  are  fol- 
lowed. 

On  the  other  hand,  there  are  alternative 
management  and  fertilization  practices 
through  which  high  yields  can  be  secured 
without  the  use  of  banded  fertilizers. 
The  farmer's  choice  of  the  alternatives 
is  not  solely  an  agronomic  problem--it 
is  a  joint  agronomic -economic  problem. 


Banded  fertilizers  may  serve  a  number  of 
useful  functions.  It  is  perhaps  lonfor- 
tunate,  therefore,  that  the  term  starter 
fertilizer  was  coined.  Under  certain 
conditions,  banded  fertilizers  promote 
rapid,  early  plant  growth  and  vigor. 
The  seedlings,  therefore,  are  better 
able  to  overcome  such  early  hazards  as 
grape  colaspis,  a  root-feeding  insect, 
and  adverse  weather.  Also,  by  promoting 
early,  liniform,  vigorous  growth  in  row 
crops,  banding  makes  it  possible  to  do  a 
more  thorough  job  of  weed  control. 
These  functions  help  to  get  the  better 
stands  that  are  essential  for  top  yields. 

On  moderately  phosphorus-  and  potassium- 
deficient  soils,  banded  fertilizers  may 
promote  deeper  and  more  extensive  root- 
ing. In  wheat,  this  reduces  winter  heav- 
ing and  assures  better  winter  survival. 
Banding  may  also  lead  to  more  complete 
fertility  exploitation  by  all  crops. 
Critics  of  banded  or  starter  fertilizers 
often  cite  this  argument  to  discredit 
band  or  row  applications,  saying  that 
banded  fertilizers  make  it  possible  to 
more  thoroughly  mine  or  deplete  soils. 
This  may  be  true  where  small  amounts  of 
low-analysis  fertilizer  are  applied,  but 
it  is  not  true  where  adequate  amounts  of 
high-analysis  fertilizer  are  applied  for 
each  crop.  In  fact,  it  is  possible  not 
only  to  maintain  the  mineral  fertility 
of  productive  soils,  but  also  to  main- 
tain very  satisfactory  yields  on  infer- 
tile soils  by  applying  adequate  amounts 
of  high  analysis  fertilizer   provided 


In  Illinois  the  fields  are  frequently 
large  and  the  rows  long.  Application  of 
banded  fertilizers,  particularly  in  ade- 
quate amounts,  requires  frequent  filling 
of  hoppers,  adds  to  the  labor  and  re- 
duces the  acreages  planted  per  day  as 
much  as  25  percent.  Many  farmers  are 
sold  on  the  value  of  banded  fertilizers, 
others  question  their  need,  and  occasion- 
ally seme  even  say  that  yields  have  been 
reduced.  Virtually  all  complain  of  the 
added  labor  and  weight-lifting. 

In  most  cases  starter  effects  induced  by 
banding  fertilizer  are  primarily  a  re- 
flection of  seedling  response  to  highly 
available  soluble  phosphorus.  So  let  us 
examine  the  chemical  aspects  of  applying 
soluble  phosphates  to  soils.  This  will 
help  to  clarify  the  reasoning  that  gave 
rise  to  the  practice  of  banding  or  drill- 
ing phosphatic  fertilizers  or  mixed  fer- 
tilizers containing  available  phosphorus. 

When  soluble  phosphorus  is  applied  to 
strongly  acidic  soils  or  soils  that  con- 
tain excess  lime,  phosphorus  fixation 
takes  place.  Soil  chemists  at  first  be- 
lieved that  phosphorus  fixed  by  strongly 
acidic  soils  was  permanently  converted 
into  unavailable  forms.  The  original 
thinking  behind  placement  of  phosphorus - 
containing  fertilizers,  therefore,  was 
to  minimize  soil-fertilizer  contact. 
Concentrating  the  fertilizer  close  to 
the  seed  made  it  possible  for  the  plants 
to  take  up  most  of  the  phosphorus  they 
needed  before  fixation  occurred.   The 


-2- 


economic  loss  of  phosphorus  through  fix- 
ation was  believed  to  be  reduced. 

A  "better  understanding  of  the  chemistry 
of  soil  phosphorus  has  developed  in  re- 
cent years.  Soil  chemists  have  found 
that  the  phosphorus  fixed  by  acidic  soils 
is  not  permanently  lost.  The  fixed  phos- 
phorus is  now  merely  considered  "diffi- 
cultly available"  to  plants.  It  has  been 
learned  that  the  use  of  sufficient  lime 
makes  it  possible  for  plants  to  use  the 
phosphorus  that  acidity  had  made  physio- 
logically unavailable.  Strongly  acidic 
soils  already  containing  large  amounts 
of  difficultly  available  phosphorus  will 
not  respond  to  phosphorus  for  several 
years  when  first  limed  to  neutrality. 
This  does  not  mean  that  lime  can  be  sub- 
stituted permanently  for  phosphorus  on 
such  soils.  It  means  that  lime  makes  it 
possible  to  reclaim  much  of  the  phos- 
phorus previously  unavailable  to  the 
plant . 

The  fixation  of  phosphorus  to  difficultly 
available  forms  in  calcareous  (shelly) 
soils  is  a  more  serious  matter.  It  is 
sometimes  claimed  that  rock  phosphate  is 
produced.  Chemically  this  is  an  untenable 
hypothesis.  On  calcareous  soils  the 
fixation  to  difficultly  available  forms 
is  caused  by  excess  lime.  There  is  no 
practical  way  to  remove  the  lime.  For- 
tunately the  reversion  to  difficultly 
available  forms  is  slow,  usually  taking 
a  full  growing  season.  Annual  applica- 
tions of  phosphate-containing  fertilizers 
are  preferable  on  calcareous  soils. 


lizer  is  applied  just  ahead  of  seeding. 
Top-dressing  of  permanent  meadows  in  the 
spring  is  preferable.  Banding  or  drill- 
ing is  best,  however,  and  leads  to  the 
most  efficient  use  of  soluble  phosphates, 
particularly  where  small  applications 
are  made. 


A  second  problem  in  the  use  of  mixed  fer- 
tilizers containing  phosphorus  is  posed 
by  the  immobile  nature  of  soil  phospho- 
rus. For  all  practical  purposes  plant 
roots  must  forage  for  phosphorus.  The 
degree  to  which  seedlings  are  stimulated 
into  faster  growth  depends,  therefore, 
on  the  extent  of  the  soil  phosphorus  de- 
ficiency. An  estimate  of  the  early 
growth  stimulation  of  various  crops  is 
illustrated  in  Figure  1.  It  is  evident 
that  on  very  phosphorus-deficient  soils 
the  starter  effects  can  be  quite  large. 
Early  plant  stimulation  may  or  may  not 
be  reflected  in  final  yields.  On  moder- 
ately acid  soils  testing  medium  to  high 
in  available  phosphorus,  the  growth  stim- 
ulation effects,  except  for  wheat  and 
clovers,  are  apt  to  be  small  or  even  ab- 
sent. 

Potassium  is  likewise  an  immobile  nutri- 
ent for  which  plant  roots  must  forage. 
The  stimulating  effects  of  potash  in 
mixed  fertilizers  will  vary  with  the 
level  of  soil  potassium  availability, 
much  as  is  the  case  for  phosphorus.  On 
most  soils,  however,  early  growth  stimu- 
lation is  essentially  a  phosphorus  ef- 
fect because  the  phosphorus  requirements 
of  seedlings  are  usually  very  high. 


To  avoid  excessive  fixation,  the  ferti- 
lizer may  be  banded  or  drilled  with  the 
seed.  Broadcasting  is  also  satisfactory 
if  excessive  mixing  (disking)  is  avoided 
and  if  the  phosphate-containiDg  ferti- 


The  production  of  radioactive  phosphorus 
by  the  Atomic  Energy  Commission  at  Oak 
Ridge,  Tennessee,  has  made  it  possible, 
through  the  use  of  tagged  radioactive 
phosphorus,  to  trace  the  proportion  of 


Table  1. --Percent  of  Phosphorus  in  Corn  Secured  From  Banded 
Fertilizer  During  the  Growing  Season 


Available  phosphorus 

Percent 

of 

phosphorus 

m 

plant  from  fertilizer 

in  soil 

30  days 

60  days 

90  days 

110  days 

Low 
High 

58 
26 

36 
21 

28 
17 

23 
15 

-3- 


the  phosphorus  absorhed  hy  plants  from 
fertilizers  throughout  the  growing  sea- 
son. Results  of  such  an  experiment  con- 
ducted with  corn  in  North  Carolina  are 
given  in  Table  1. 

These  data  indicate  that  during  the 
first  30  days  of  growth  corn  absorbed 
slightly  more  than  twice  as  much  phospho- 
rus from  band  applications  on  soils  that 
were  low  or  deficient  in  available  phos- 
phorus as  from  the  same  applications  on 
soils  that  were  high  in  available  phos- 
phorus. In  other  words,  the  phosphorus 
in  banded  fertilizers  can  be  expected  to 
be  more  effective  in  promoting  rapid, 
early  growth  with  increasing  soil  phos- 
phorus deficiencies. 


The  data  also  show  that,  regardless  of 
the  level  of  available  soil  phosphorus, 
less  and  less  phosphorus  is  derived  from 
the  fertilizer  as  growth  progresses  and 
the  root  system  develops.  After  110 
days,  on  soils  that  were  high  and  low  in 
available  phosphorus,  only  23  and  15  per- 
cent, respectively,  of  the  phosphorus 
needs  of  the  crop  came  from  the  applied 
fertilizer.  The  remainder  of  the  phos- 
phorus that  was  absorbed--some  77  sjid  85 
percent--came  from  the  soil.  This  ex- 
plains why,  on  moderately  fertile  soils, 
early  growth  stimulation  of  corn  by 
banded  fertilizers  often  is  not  reflected 
in  the  final  yield.  This  being  the  case, 
benefits  other  than  yield  increases  must 
be  assigned  to  banded  fertilizers  for 
some  soils. 


Fig.  1. — Estimated  Relative  Early  Growth  Stimulation  Induced 
by  Soluble  Phosphorus  Applied  in  Bands  to  Soils  of 
Different  Soil  Phosphorus  Test  Values 


a 
o 

•H 

-p 
H 
I 

•H 
-P 
CO 


o 
u 
o 

a 

(U 
0) 
CD 

i) 
> 
•H 

1^ 
H 
(U 

Ti 

V 

-p 


-P 
to 


\^^^^M  wheat  and  Clovers 
Corn 


Soybeans  and  Oats 


i 


b^ 


t^ 


^ 


i:^ 


El 


Low     Slight     Medium     High 
Illinois  Soil  Phosphorus  Test  Values 


E.  H.  Tyner 
12-5-55 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


^oiL  PERTitmr 

AND  ,^ 

TESTING  ,  - 


AGRONOMY  FACTS 


SF-41 


BAND  APPLICATION  OF  FERTILIZERS  IN  ILLINOIS  -  PART  2 


The  preceding  Fact  Sheet  was  devoted  pri- 
marily to  some  of  the  fundamental  aspects 
of  hand  fertilization.  This  sheet  will 
deal  with  the  more  practical  aspects  of 
the  problem- -amounts^  fertilizer  ratios 
in  relation  to  soil  test  values^  etc. 

Except  on  calcareous  (shelly)  soils ^ 
banding  fertilizers  with  each  row  crop 
is  not  urgent  on  soils  testing  at  least 
M-  in  available  phosphorus  or  above  170 
pounds  in  available  potassiiim.  On  such 
soils  the  primary  benefits  from  banded 
fertilizers,  if  any,  are  likely  to  be 
secured  only  with  wheat  and  legumes  (see 
Fig.  1,  Fact  Sheet  SF-ij-O). 

Under  these  conditions  applying  mainte- 
nance amounts  of  phosphorus  and  potassium 
once  in  the  rotation  will  maintain  enough 
mineral  fertility  for  high  crop  yields, 
assuming  adequate  nitrogen  fertility. 
Moreover,  these  amounts  can  be  applied 
with  bulk  distribution  equipment  during 
slack  periods.  One  exception  might  be 
where  grape  colaspis  must  be  controlled, 
but  it  can  also  be  controlled  with  pes- 
ticide sprays.  Farmers  who  have  serious 
grass  weed  problems  or  who  are  shooting 
for  extraordinary  yields  may  still  prefer 
to  apply  seme  banded  fertilizer  in  order 
to  insure  better  stands. 

Banded  fertilizers  applied  to  each  crop, 
however,  have  a  definite  place  where  de- 
pleted farms  are  operated  by  tenants  with 
uncertain  tenure,  or  where  capital  is 
not  sufficient  for  build-up  applications 
or  where  it  is  needed  more  in  other 
phases  of  the  farm  business  than  for 
rapid  build-\ip  of  basic  soil  fertility. 

In  general,  on  very  deficient  soils  one 
cannot  apply  enough  fertilizer  to  get 
maximum  yields  by  hill-dropping  or  band- 
ing in  the  row.  Even  so,  it  is  possible 
to  get  good  yield  increases  with  mixed 
fertilizers  alone,  provided  the  analysis 
supplies  reasonable  amounts  of  the  most 
needed  nutrients  and  provided  nitrogen 


fertility  is  adequate.  Table  1  lists 
first-year  phosphorus  and  potassivmi  re- 
quirements for  moderately  high  yields  at 
various  soil  test  values. 

Table  1. --Phosphorus  and  Potassium  Re- 
quired the  First  Year  at  Vari- 
ous Soil  Test  Values 


Phosphorus 

Potassium 

Test  value 

(P2O5) 

(K2O) 

lb. /A 

lb. /A 

L- 

60 

L 

5^ 

L+ 

kQ 

S- 

k2 

S 

36 

s+ 

30 

Uo 

•  • 

120 

80 

•  • 

70 

120 

•  • 

1|0 

170-200 

•  • 

30 

The  above  requirements  are  stated  in 
terms  of  phosphorus  (P2O5)  and  potassium 
(K2O)  needed  per  acre.  How  can  we  use 
such  information  in  determining  the  prop- 
er fertilizer  analysis  to  buy:  Let  us 
assume  that  the  soil  test  indicates 
phosphorus  availability  as  L-  and  potas- 
sium availability  as  120  pounds.  On  the 
basis  of  this  information,  we  would  need 
to  apply  60  poimds  of  P2O5  and  ^0  poionds 
of  K2O  per  acre.  The  P205:K20  ratio  needed 
in  a  mixed  fertilizer  would  therefore 
be  1.5  to  1.0.  It  would  be  difficult 
to  find  a  mixed  commercial  fertilizer 
with  this  ratio.  Therefore,  we  will 
choose  a  fertilizer  with  a  2  to  1 
phosphorus-potassiijm  ratio,  such  as  0-20- 
10.  If  we  were  to  apply  3OO  pounds  of 
this  analysis  per  acre,  it  would  supply 
the  60  poimds  of  P2O5,  but  only  30  pounds 
rather  than  to  pounds  of  K2O.  Even  so,  we 
could  still  obtain  satisfactory  yields. 

Can  this  amount  of  fertilizer  be  hill- 
dropped  or  banded  for  row  crops?  Large 
amounts  of  fertilizer  close  to  the  seed 
can  delay  or  even  prevent  germination. 
The  reason  is  that  the  "salt  action"  in- 
hibits moisture  uptake  by  the  seed  or  the 


roots  just  emerging  frcm  the  seed.  In 
general  practice,  it  is  only  the  nitrogen 
and  potassium  in  mixed  fertilizers  that 
are  "hot"  and  that  interfere  with  germi- 
nation. 

A  good  rule-of -thumb  is  not  to  hill-drop 
or  band  more  than  30  pounds  of  "hot" 
solubles  (nitrogen  (n)  plus  potassium. 
(K20))per  acre.  It  is  apparent  that  the 
safe  amount  will  vary  with  the  analysis, 
e.g.,  3-12-12  (200  pounds),  10-10-10 
(150  pounds),  3-9-27  (100  pounds).  The 
30-pound  rule  is  for  dry  to  average  sea- 
sons. In  wet  seasons  higher  rates  may 
not  be  injurious.  According  to  this 
rule,  the  3C0-pound  application  of  0-20- 
10  could  be  made  provided  the  fertilizer 
attachment  would  deliver  this  amount. 
If  not,  100  pounds  could  be  banded  and 
the  rest  broadcast  and  either  plowed 
Tinder  or  disked  in. 

This  explanation  shows  why  it  is  diffi- 
cult to  prescribe  certain  fertilizer  ra- 
tios for  use  on  crops  grown  on  soils 
that  may  vary  considerably  in  basic  fer- 
tility. Moreover,  a  certain  analysis 
may  be  satisfactory  to  apply  for  a  few 
years,  but  carry-over  effects  may  cause 
the  ratio  and  the  amount  to  change.  Pe- 
riodic soil  testing  will  help  to  deter- 
mine the  most  practical  and  profitable 
ratios  and  rates. 

How  necessary  is  nitrogen  in  mixed  banded 
fertilizers?  This  is  a  question  on  which 
agronomists  do  not  agree.  Experimental 
evidence  indicates  that  nitrogen  in- 
creases the  uptake  of  phosphorus.  It 
may  therefore  be  argued  that  nitrogen  in 
banded  fertilizers  serves  a  very  useful 
purpose.  This  may  be  true  on  soils  that 
are  highly  deficient  in  available  phos- 
phorus, but  it  is  not  so  important  on 
soils  that  are  moderately  supplied  with 
available  phosphorus.  More  will  be  said 
on  this  point  later. 

In  general,  where  experience  indicates  a 
substantial  response  to  nitrogen,  large 
amounts  of  nitrogen  must  be  applied.  It 
is  usually  best  to  apply  a  nitrogen  ma- 
terial, e.g.,  20-0-0,  33-0-0,  82-0-0. 
This  does  not  mean  that  12-12-12,  etc., 
are  not  satisfactory  sotirces  of  nitrogen. 


Such  analyses,  if  used  in  amounts  ade- 
quate to  supply  the  required  nitrogen, 
often  supply  more  phosphorus  and  potas- 
sium than  can  be  used  efficiently.  But 
the  excess  phosphorus  and  potassium  are 
not  lost  through  leaching  and  can  be  used 
later. 

Applying  nitrogen  in  large  amounts  in 
mixed  fertilizers  can,  therefore,  lead 
to  inefficient  use  of  phosphorus  or  po- 
tassium if  the  soil  already  tests  moder- 
ately high  in  these  elements.  Where  high 
nitrogen  mixed  fertilizers  are  used,  the 
carry-over  effects  of  excess  phosphorus 
and  potassium  should  be  carefully  ana- 
lyzed before  subsequent  fertilizer  appli- 
cations are  made. 

In  general,  conditions  preceding  planting 
and  level  of  available  soil  phosphorus 
should  determine  the  advisability  of  ap- 
plying amounts  of  nitrogen  in  mixed  fer- 
tilizers, such  as  3-12-12,  Normally  the 
decay  of  soil  organic  matter  will  take 
care  of  the  small  nitrogen  requirements 
of  seedlings.  If  the  weather  is  abnor- 
mally cool  with  frequent  rains  before 
corn  is  planted,  it  might  be  advisable  to 
use  a  mixed  fertilizer  containing  seme 
nitrogen,  particularly  on  phosphorus  defi- 
cient soils.  On  the  other  hand,  if  tem- 
peratures are  normal  and  moisture  is 
average,  it  is  questionable  whether  ni- 
trogen will  be  needed  in  starter  ferti- 
lizers even  to  increase  phosphorus 
uptake.  Nitrogen  in  mixed  fertilizers 
may,  however,  be  beneficial  in  most  sea- 
sons on  weedy  fields  where  a  considerable 
amount  of  trash,  particularly  straw,  has 
been  plowed  under. 

Is  nitrogen  necessary  for  establishing 
stands  of  winter  wheat.  If  wheat  follows 
soybeans  and  is  seeded  just  after  the 
fly-free  date,  the  value  of  applying  ni- 
trogen in  mixed  fertilizer  to  stimulate 
fall  growth  is  questionable.  On  the  other 
hand,  if  seeding  is  delayed  because  of 
wet  weather,  seme  nitrogen- -perhaps  not 
more  than  3  to  5  pounds  per  acre --might 
be  desirable.  Applying  nitrogen  in  the 
fall  on  clay-pan  soils  to  avoid  the  need 
for  spring  applications  is  a  different 
matter.   See  Fact  Sheet  SF-28. 

E.  H.  Tyner 
12-12-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-42 


PROGRESS  REPORT  ON  A  GREEN-MANURING  PROJECT 


In  1953  3.n  experiment  was  started  to  de- 
termine the  value  of  northern  and  south- 
ern alfalfa  varieties,  red  clover,  ladino 
clover,  sweet  clover  and  lespedeza  as 
green-manure  crops.  A  comparison  of  the 
green-manure  crops  with  chemical  nitro- 
gen was  also  included. 

The  Series  1102  plots  on  the  Agronomy 
South  Farm,  where  the  various  green-manure 
crops  were  seeded  in  oats  in  1953^  had 
the  following  crop  history: 

19^8  Corn  followed  hy  an  application  of 
1^  tons  of  manure  an  acre. 

1949  Corn 

1950  Soybeans  harvested  for  seed 

1951  Oats  in  which  clover  was  seeded  but 
failed 

1952  l-Jheat  (straw  left  on  land) 

1953  Before  oats  were  seeded,  three  tons 
of  200-mesh  limestone,  5OO  pounds 
of  0-20-0,  and  110  pounds  of  O-O-5O 
were  applied 

The  Series  W-6C0  plots  had  been  in  a 
rotation  of  corn,  corn,  oats,  and  clover 
for  50  years.  The  clover  failed  in  1953 
and  oats  were  seeded  again  in  195^  as  a 
companion  crop  for  the  green-manure 
crops . 

In  each  series  the  green-manure  crops 
were  plowed  under  about  a  yea^  after 
seeding.  To  some  plots  where  a  green 
manure  had  not  been  seeded  (NHi^)2S0i^.  was 
applied  in  195^  ^nd  plowed  under  at  once. 
KHPIO3  was  used  in  the  same  way  on  certain 
plots  in  1955.  Corn  was  planted  by  hand 
at  the  rate  of  four  kernels  per  hill.  A 
nearly  perfect  stand  was  sec\ired  in  each 
year. 


The  yields  of  No.  2  corn  on  these  plots 
for  the  years  195^  snd  1955  are  given 
below. 

CORK  YIELDS  FOLLOWING  GREEN-MANURE  CROPS 
AND  WITH  NITROGEN  FERTILIZERS 


Acre 

yields 

Green-man\ire  crops 

195^ 

1955 

bu. 

bu. 

Alfalfa 

African 

119 

102 

Chilean 

120 

111 

Indian 

123 

103 

New  Mexico 

120 

108 

Northern  Common 

^\?^ 

109 

Ranger 

119 

110 

Clover 

Ladino 

119 

103 

Medium  red 

124 

103 

Lespedeza  (Korean) 

122 

103 

Sweet  clover 

White  blossom 

117 

109 

Yellow  blossom 

116 

109 

AVERAGE 

120 

103 

None 

119 

103 

None  plus  nitrogen 

60  poiinds/acre 

m 

97 

None  plus  nitrogen 

120  pounds/acre 

— 

99 

In  each  year  a  randomized  block  design 
■vriLth  four  replications  was  used.  Conse- 
quently it  was  possible  to  make  a  sta- 
tistical analysis  of  the  data. 

Although  seme  differences  in  corn  yields 
were  associated  with  the  previous  green- 
manure  crops  and  with  nitrogen  fertilizer 
these  differences  were  not  statistically 
significant.   On  the   basis  of  this 


Information,  it  cante  concluded  only  that 
neither  nitrogen  fertilizer  nor  legumi- 
nous green-manure  crops  had  a  measiirahle 
effect  on  yields  of  corn  in  these  plots 
in  195^  and  1955*  This  information 
should  not  be  interpreted  to  mean  that  in 
other  years  or  on  other  soils  in  the  same 
years  the  use  of  leguminous  green-manure 
crops  or  nitrogen  fertilizers  would  not 
or  did  not  affect  corn  yields  favorably. 

The  question  then  arises  why  increased 
corn  yields  did  not  occur.  While  it  is 
not  possible  to  say  with  authority  why 
these  results  were  obtained,  some  possi- 
ble ejcplanations  can  be  presented:  Obvi- 
ously these  soils  were  furnishing  a 
larger  amount  of  available  nitrogen  than 
is  usually  the  case.  Again  the  question 
why  arises  naturally. 

In  the  years  1953,  195^  and  1955;,  there 
were  no  periods  of  excessive  rainfall. 
In  fact,  a  moisture  deficiency  occurred 
for  several  extended  periods  in  each  of 
these  years.  As  a  result,  it  seems  rea- 
sonable to  postulate  that  the  soils,  even 


without  green  m.anure,  fiirnished  suffi- 
cient available  nitrogen  for  maximum 
yields  under  the  seasonal  conditions 
that  prevailed.  This  large  amoiuit  of 
available  nitrogen  was  the  result  of: 

1.  Moisture  and  temperature  favorable 
for  nitrate  formation. 

2.  IJot  enough  soil  moisture  to  cause 
leaching  losses  of  nitrate  nitrogen 
or  denitrification. 

In  other  areas  on  the  Agronomy  Farm  there 
was  evidence  that  the  availability  of 
soil  forms  of  nitrogen  was  high  in  195^ 
and  1955*  Consequently  the  response  to 
added  nitrogen  was  less  than  many  people 
expected. 

These  data  should  not  be  construed  to 
mean  that  leguminous  green-manixre  crops 
and  chemical  nitrogen  are  not  important 
in  the  nitrogen  economy  of  the  land. 
Rather,  they  indicate  that  seasonal  con- 
ditions must  be  considered  in  evaluating 
the  worth  of  any  soil-improving  practice 
in  a  particular  year. 


J,  A.  Jackobs 


0.  H,  Sears 
1-9-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-43 


COMPOSTS 


Composts  have  iDeen  used  in  agricultiire 
for  centuries.  Roman  farmers  prepared 
composts  from  the  strav  and  chaff  of 
grain  crops  and  from  the  leaves  of  for- 
est trees.  Although  the  farmers  of  an- 
cient times  did  not  understand  all  of 
the  principles  involved, they  were  famil- 
iar vith  the  kinds  of  ingredients  needed 
for  successful  composting. 

One  kind  of  composting,  knovn  as  sheet 
composting,  has  been  used  in  Illinois 
for  more  than  half  a  century.  It  con- 
sists of  plowing  under  such  materials  as 
straw,  manure,  and  green  manure  crops 
grown  for  soil  improvement  purposes. 

Composts  have  "been  used  extensively  in 
the  United  States  for  mulching  shrubbery 
where  it  is  not  desirable  to  incorporate 
the  organic  residues  in  the  soil.  They 
have  also  been  used  to  some  extent  in 
vegetable  crops  and  flower  gardens  to 
conserve  moisture  and  to  prevent  the 
soil  structure  from  being  destroyed  by 
beating  rains. 


be  used,  but  grease  and  meat  scraps  will 
develop  offensive  odors  and  attract  rats 
and  flies. 

During  composting  a  considerable  part  of 
the  materials  decay  and  part  of  them  go 
into  the  air  as  gases.  The  remainder 
is  similar  to  well -rotted  stable  manure. 
A  good  manure  from  composts  must  go 
through  this  decomposition  process. 

Bacteria  and  molds  are  largely  responsi- 
ble for  decomposition.  Although  they  de- 
rive energy  from  the  refuse  which  they 
decompose,  they  also  need  other  sub- 
stances for  growth.  One  of  the  most  es- 
sential is  nitrogen.  Because  most  of 
the  substances  which  go  into  a  compost 
heap  are  low  in  this  element,  it  is  nec- 
essary to  furnish  additional  nitrogen  if 
a  rapid  rate  of  decay  is  to  be  obtained. 

In  the  process  of  decomposition,  acids 
are  produced.  Some  nitrogen  fertilizers 
also  form  acids.  Consequently,  it  is  ad- 
vantageous to  add  limestone. 


One  advantage  of  decomposing  organic  ma,t- 
ter  is  lost  when  composts  are  prepared 
in  a  compost  heap.  One  reason  for  in- 
corporating organic  m.atter  in  the  soil 
is  to  improve  soil  structure  or  tilth. 
As  the  organic  materials  decompose,  the 
microbes  produce  substances  that  in- 
crease the  aggregation  or  crumb  struc- 
ture of  the  soil.  Although  soil  tilth 
is  not  improved  solely  by  microbial 
activity,  it  is  recognized  generally 
that  microbes  have  an  important  function 
in  keeping  soils  in  good  physical  condi- 
tion. 

Many  materials  can  be  used  in  the  com- 
post heap,  including  leaves  from  trees 
and  shrubs,  weeds,  la^-m  clippings,  and 
garden  residues.   Even  table  scraps  can 


A  satisfactory  compost  may 
by  using  the  following: 


be  prepared 


Organic  residues  (dry  weight)  100  pounds 

Ammonium  sulfate 5  pounds 

Limestone 5  pounds 

Five  hundred  pounds  of  green  plant  resi- 
dues will  contain  about  100  pounds  of 
dry  material.  A  bushel  of  leaves  weighs 
about  5  to  8  pounds,  depending  upon  con- 
dition and  packing. 

To  build  a  compost  heap,  place  about  1/5 
to  1/6  of  the  leaves,  grass  clippings, 
or  garden  residues  in  a  layer  10  to  12 
inches  thick.  Moisten  this  layer  and 
spread  I/5  to  1/6  of  the  mineral  mixture 
over  it.  Alternate  the  layers  of  residues 


and  minerals  until  the  stack  is  complete. 
Make  the  top  of  the  stack  concave  to 
catch  and  hold  rain.  If  the  material  is 
kept  moist,  rotting  will  proceed  rapidly. 
One  ton  of  dry  material  will  produce 
about  2  1/2  tons  of  moist  artificial  ma- 
nure. 

If  the  heap  is  made  in  early  or  even 
late  summer,  the  compost  will  "be  avail- 
able for  early  spring  use.  However,  if 
the  materials  are  not  composted  until 
late  fall,  when  the  temperatures  are  low, 
decay  will  be  slow,  and  a  sufficient  de- 
gree c£  decomposition  may  not  be  obtained 
by  early  spring. 

Although  it  is  not  necessary  to  add  phos- 
phates to  decompose  the  residues,  2 
pounds  of  superphosphate  added  to  the 


mineral  mixture  will  increase  the  value 
of  the  manure,  particularly  if  it  is  to 
be  used  on  soils  that  are  low  in  avail- 
able phosphorus. 

Even  though  artificial  manure  in  the 
stack  does  not  have  a  noticeable  odor 
during  decomposition,  when  spread  it  has 
an  odor  resembling  that  of  natural  ma- 
nures. 

Prepared  mineral  niixtures  are  available 
in  some  localities.  More  recently  a  num- 
ber of  commercial  products  which  are 
said  to  contain  the  microbes  needed  for 
decomposition  have  been  sold.  Investi- 
gations in  California  and  Florida  indi- 
cate that  there  is  little  need  to  apply 
microbial  concoctions.  The  same  results 
may  be  secured  by  adding  small  amovmts 
of  fertile  soil  to  the  coiirpost. 


0.  H.  Sears 
i<-2-56 


.^IIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND 
TESTING 

m 

> 
■ 

SF-44 


THE  NATURE  OF  EXCHANGEABLE  CALCIUM  AND  MAGNESIUM  AND 
THEIR  RELATION  TO  SOIL  ACIDITY  AND  LIME  REQUIREMENT 


In  moist  soils  calcium  and  magnesium  are 
present  mainly  in  exchangeable  form. 
This  form  is  attached  by  valence  bonds 
to  the  surfaces  of  the  soil  clay  and  or- 
ganic matter  particles.  Exchangeable 
potassium  also  occurs  on  these  siirfaces, 
although  usually  only  in  small  amounts 
in  relation  to  calcium  and  magnesium. 

The  exchangeable  form  is  usually  the 
principal  available  form  of  each  of  these 
soil  nutrients --the  form  the  plant  de- 
pends on  for  grovth.  ^^ 

However^  calcium  and  magnesium  play  an- 
other role  in  soil  fertility.  They 
control  the  acidity  or  pH  of  the  soil. 
If  the  clay  and  organic  matter  particles 
are  covered  mostly  with  calcium  and  mag- 
nesium;, the  soil  will  be  nearly  neutral 
or  "sweet."  But  whenever  a  cation  like 
the  calcium  or  magnesium  ion  is  lost  by 
leaching  or  removed  by  plant  roots,  hy- 
drogen,  the  "acid"  ion  takes  its  place 
and  the  soil  becomes  more  acid.  Liming 
is  merely  the  process  of  replacing  the 
exchangeable  calcium  and  magnesium  lost 
by  leaching  in  order  to  bring  the  soil 
back  to  a  pH  favorable  for  plant  growth. 

In  the  claypan  soils  of  southern  Illi- 
nois, the  native  soil  is  usually  highly 
acid.  The  calcium  and  sometimes  the  mag- 
nesiiim  are  so  low  that  liming  is  needed 
for  two  purposes:  First,  liming  adds 
calcium  and  magnesi'um  and  thus  overcomes 
deficiencies  to  the  extent  that  these 
nutrients  are  supplied  in  available  form. 
Second,  proper  liming  corrects  the  acid- 
ity sufficiently  to  make  the  soil  reac- 
tion (pH)  favorable  for  plant  growth. 

In  one  sense  the  two  fimctions  of  liming 
are  completely  independent  of  each  other. 
In  fact,   except  in  southern  Illinois  , 
most  of  the   soils  in  the  state  already 
contain  so  much  exchangeable  calcium  and 


magnesi'um  that  they  provide  plenty  of 
nutrient  for  plant  growth,  yet  they  are 
often  so  low  in  these  elements  in  rela- 
tion to  the  acid  ion  that  the  soil  can 
be  harmfully  acid  to  some  crops.  Except 
in  these  claypan  soils,  therefore,  the 
chief  purpose  of  liming  is  usually  to 
change  the  soil  reaction. 

One  effect  of  changing  the  pH  upward  is 
that  it  makes  it  possible  for  plants  to 
feed  more  efficiently  on  the  available 
phosphorus  in  the  soil.  Another  is  that 
many  legumes  nodulate  only  at  the  higher 
pH  levels.  (A  low  pH  means  a  more  acid 
reaction. )  Organic  matter  appears  to 
decompose  more  readily  at  the  higher  pH 
levels. 

Except  in  soils  that  are  very  low  in 
clay  and  organic  matter,  a  favorable  pH 
level  is  practically  a  sure  sign  that 
calcium  will  not  be  deficient.  In  such 
soils  a  high  pH  could  theoretically  be 
due  mostly  to  potassium  and  magnesium. 
But  such  situations  have  never  been  found 
in  Illinois. 

The  pH  of  a  soil  is  not  determined  by 
how  much  or  how  little  exchangeable  cal- 
cium and  magnesium  it  contains,  but 
rather  by  the  proportion  of  these  basic 
ions  to  the  acid  hydrogen  ions.  The  to- 
tal amount  of  exchangeable  cations  Ca++, 
iy[g++^  and  H+  held  on  the  clay  surfaces 
is  called  the  base  exchange  capacity  and 
is  measured  in  terms  of  milligram- 
equivalents  per  100  grams  of  soil  (m.e. 
per  100  grams). 

One  m.e.  per  100  grams  is  about  the 
amount  of  calcium  and  magnesium  contained 
in  1,000  pounds  of  high-grade  lime- 
stone. If  a  soil  contains  on  its  clay 
and  organic  matter  surfaces  8  m.e.  of 
bases  and  2  m.e.  of  acid  ion,  or  a  total 
of  10  m.e.,   it  will  be  in  the  sweet 


range  because  it  is  80  percent  saturated 
with  exchangeable  bases  and  only  20  per- 
cent saturated  with  the  acid  ion.  If  it 
contains  l6  m.e.  of  bases  and  ^4-  m.  e.  of 
acid^  it  will  have  a  total  of  20  m.e., 
but  the  percent  of  saturation  and  also 
the  pH  will  be  the  same  as  before.  So 
the  degree  of  acidity  or  pH  depends  not 
on  the  actual  amount  of  acid  that  is 
present;  but  rather  on  the  proportion  of 
acid  to  base. 

Lime  requirement  is  another  matter.  Sup- 
pose the  first  soil  has  5  m.e.  of  bases 
and  5  m.e.  of  acid,  for  a  total  of  10 
m.e.  It  is  then  50  percent  saturated 
with  bases  and  is  in  the  unfavorable 
range  of  acidity.  A  more  favorable  range 
is  80  to  90  percent  saturation  with 
bases.  This  means  that  from  3  "to  ^  m.e. 
of  hydrogen  must  be  neutralized.  This  is 
equal  to  3^000  to  ^,000  pounds  of  pure 
limestone.  Hence  the  tentative  lime  re- 
quirement is  3^000  to  ^,000  pounds. 

Wow  suppose  a  20  m.e.  soil  is  also  only 
50  percent  saturated  and  it  is  desirable 
to  increase  the  saturation  to  around  80 
to  90  percent.  Fifty  percent  of  20  m.e. 
is  10  m.e.  of  the  bases  present.  Eighty 
to  90  percent  saturation  is  16  to  I8 
m.e.  of  bases  needed.  If  10  m.e.  are 
present  and  I6  to  I8  are  needed,  then  6 
to  8  m.e.  or  6,000  to  8,000  pounds  of 
limestone  is  the  tentative  lime  require- 
ment. 

Silt  loam  and  clay  soils  have  higher 
base  requirements  for  the  same  pH  value 
than  do  the  lighter  soils.  Sands  gener- 
ally have  the  lowest. 

Theoretically,  in  order  to  estimate  a 
practical  lime  requirement,  one  should 
first  know  the  magnitude  of  the  base- 
exchange  capacity  and  the  sum  of  the  mil- 
liequivalents  of  the  bases  present.  This 
would  require  a  quantitative  estimate  of 
the  exchangeable  calcium,  magnesium,  and 
hydrogen  (acid  ion). 


But  that  is  not  all  one  would  have  to 
know.  Knowing  that,  theoretically,  it 
would  take  6,000  pounds  of  pure  lime- 
stone to  sufficiently  neutralize  the 
soil  is  only  one  item.  Next  one  must 
consider  the  neutralizing  value  of  the 
limestone.  If  it  is  only  90  percent  C.C.E. 
(calcium  carbonate  equivalent ),  the  orig- 
inal 6,000-pound  calculation  must  be 
increased  to  compensate  for  the  10  per- 
cent impurities.  This  increases  the 
requirement  to  6^666   pounds. 

However,   this  is  still  not  the  answer. 

The  fineness  of  the  limestone  must  be 
rated  according  to  its  rate  of  neutrali- 
zation, i.e.,  how  much  acid  it  can  neu- 
tralize within  a  relatively  short  time. 
For  years,  until  a  government  agency  took 
over  limestone  inspection,  such  ratings 
were  made  on  all  Illinois  limestones  and 
an  effectiveness  score  was  given  to  the 
stone.  If  the  effectiveness  score  is  low, 
more  limestone  is  needed.  Wow  suppose 
the  limestone  has  a  score  of  85  percent 
effectiveness  over  the  first  three  years. 
This  was  about  the  average  score  for  Il- 
linois quarries  at  the  time  effectiveness 
inspection  was  discontinued.  Applying  this 
correction  to  the  above  6,666  pounds  gives 
7,840  pounds  as  the  corrected  requirement. 

But  again  this  is  not  the  whole  story. 
Many,  if  not  most,  soils  have  acid  sub- 
soils. But  the  acidity  of  the  subsur- 
face varies;  in  the  claypan  soils  it  is 
higher  than  in  the  dark-colored  silt 
loams.  With  deeper  plowing  this  acid 
soil  gets  mixed  with  the  top  soil,  in- 
creasing the  acidity.  Also  the  transfer 
of  bases  downward  increases  when  sub- 
soils are  more  acid.  These  things  would 
all  affect  the  need  for  limestone  over  a 
period  of  years. 

And,  last,  there  is  the  matter  of  quick- 
ness of  leaching.  A  sandy  soil  with  a 
sufficiently  low  exchange  capacity  can 
become  acid  through  the  loss  of  only  one 


-3- 


milliequivalent  of  calcium.  And  more 
water  moving  through  such  a  soil  hastens 
leaching.  But  heavy  soils  change  in  pH 
much  more  slowly  because  their  capacity 
is  higher  and  less  water  goes  out  the 
tile.  The  limestone  reconmiendation  must 
include  recognition  of  this  point. 

So  estimating  a  practical  lime  require- 
ment is  not  merely  a  matter  of  knowing 
the  amounts  of  exchangeable  bases  and  acid 
present^  although  this  is  the  soundest 
starting  point  for  estimating  the  theoret- 
ical requirement.  Other  considerations 
are  the  effectiveness  of  the  limestone 
(fineness)^  purity  of  the  limestone, 
acidity  of  the  subsurface,  and  rate  of 
leaching  of  the  exchangeable  bases.  When 
all  of  these  things  are  considered,  the 
final  recommendation  may  appear  to  have 
little  relation  to  the  theoretical  re- 
quirement . 

For  example,  some  sands  in  Illinois  have 
a  base -exchange  capacity  of  3  milli- 
equivalents  per  100  grams.  This  means 
that  they  can  hold  calcium  and  magnesium 
equivalent  to  not  much  over  2.,  500  pounds 
of  a  fine  100  percent  C.C.E.  stone.  Yet 
when  they  are  acid,  3  "to  4  tons  of  ordi- 
nary limestone  are  commonly  added  after 
considering  screen  score,  C.C.E. ,  and 
especially  the  high  rate  of  leaching  on 
sandy  soils.  On  the  other  hand,  a  soil 
like  Muscatine  silt  loam  with  a  base- 
exchange  capacity  of  20  m.e.  per  100  grams 
will,  at  the  same  pH,  have  a  much  higher 
theoretical  requirement,  but  the  practical 
requirement  may  be  little  higher  than  the 
practical  requirement  for  the  sand  when 
all  the  other  factors  are  considered. 

It  is  therefore  not  "fool  proof"  to  base 
the  lime  requirement  on  measurement  of 
the  exchangeable  bases  and  the  exchange- 
able hydrogen  (acid)  alone. 

The  lime  requirement  recommendations 
based  on  pH  or  thiocyanate  readings  have 
resulted  from  practical  experience  over 
a  period  of  30  or  more  years.  VJhile  a 
thorough  study  of  Illinois   soil  types 


and  of  their  base-exchange  capacities  and 
pH — degree  of  saturation  relationships 
was  made  a  couple  of  decades  ago,  it  has 
not  yet  appeared  practical  to  apply  this 
knowledge  to  refining  the  lime  require- 
ment recommendations  made  in  our  county 
laboratories. 

The  Missouri  "Lime  Meter"  method  repre- 
sents one  approach  to  this  problem,  but 
when  corrected  for  these  other  factors 
it  correlates  too  closely  with  our  recom- 
mendations based  on  pH  or  thiocyanate  to 
make  it  practical  to  use. 

The  pH  and  thiocyanate  methods,  while 
they  do  not  involve  a  determination  of 
the  bases  and  acid,  do  give  a  measure  of 
degree  of  saturation  with  bases  and  can 
be  Interpreted  in  terms  of  lime  require - 
m.ent  when  the  base -exchange  capacities 
of  the  soil  types  are  known. 

In  general,  the  high-capacity  soils  occur 
in  the  northern  two-thirds  of  Illinois, 
and  their  capacities  and  pH  vs.  degree 
of  saturation  relationships  have  been 
thoroughly  studied  and  found  sufficiently 
similar  to  make  it  practical  to  use  pH  or 
thiocyanate  as  a  measure  of  the  lime 
requirement. 

On  the  other  hand,  the  soils  of  southern 
Illinois,  while  lower  in  base-exchange 
capacity^  have  much  more  acid  subsoils, 
which  would  tend  to  increase  the  rate  at 
which  a  limed  soil  becomes  acid  and  thus 
require  more  than  the  theoretical  amount 
of  lime. 

Measuring  the  theoretical  amount  is  there- 
fore not  the  whole  answer.  The  higher 
cost  of  the  required  tests  leads  to  a 
tendency  to  run  only  one  or  two  samples, 
whereas  in  the  Illinois  plan  11  samples 
in  a  UO-acre  field  are  analyzed.  Given 
a  choice, the  11  samples  run  by  the  pH  or 
thiocyanate  test  are  generally  preferable 
and  may  be  more  accurate  than  a  single 
composite  of  a  whole  field  run  by  a  the- 
oretically better  method.  In  fact,  some 
results  reported  to  us  of  interpretations 


-1^- 


based  on  theoretically  better  determina- 
tions indicate  that  the  interpretations 
must  have  oeen  made  "by  persons  mth  so 
little  knovledge  of  soil  chenistry  that 
the  recommendations  -were  unsoimd  and 
vorthless. 

Years  ago  this  station  put  out  a  very 
siniple  titration-indicator  method  that 
involved  using  several  samples  of  the 
same  soil  and  shaking  each  one  •'.■ri.th  a 


salt  containing  a  different  amount  of  a 
base.  This  procedixre  measured  the  theo- 
retical lime  requirement  directly^  re- 
gardless of  variations  in  base-exchange 
capacity,  and  is  easier  to  run  than 
methods  involving  the  total  of  each  ion 
involved. 


Roger  H.  Bray 
6-11-56 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEM 
CONSERVATIO. 


SM-12 


OBJECTIVES  OF  CROP  ROTATIONS  -  INTRODUCTION  AND  EROSION  CONTROL 


This  is  the  first  in  a  series  of  five 
Agroncmy  Fact  sheets  devoted  to  the  "Ob- 
jectives of  Crop  Rotations."  This  one 
is  concerned  with  control  of  soil  ero- 
sion. The  second  one  ■will  discuss  the 
effects  of  crop  rotations  on  soil  physi- 
cal properties^  such  as  absorption  of 
rainfall;,  internal  drainage^  and  compac- 
tion. Nvunber  3  will  explain  how  crop 
rotations  may  help  to  control  insect 
pests  and  crop  diseases.  Number  h  -vrill 
take  up  the  problem  of  plant  nutrients 
with  particular  emphasis  on  nitrogen. 
The  fifth  and  last  of  this  series  will 
discuss  the  economic  factors  to  be  con- 
sidered in  deciding  what  crop  rotation 
to  follow. 

Crop  Rotations  and  Erosion  Control 

The  effectiveness  of  a  crop  rotation  in 
controlling  soil  erosion  depends  upon 
the  type  of  growth^  the  amount  of  growth 
and  the  time  of  growth  of  the  crops  in- 
cluded in  the  rotation  and  the  propor- 
tion of  the  time  that  the  crops  with 
different  characteristics  are  on  the 
land. 

Type  of  Growth 

Grasses  and  legumes  are  erosion  resist- 
ing crops.  If  a  good  stand  of  such 
crops  occupies  the  land^  erosion  losses 
are  negligible  even  on  relatively  steep 
slopes.  At  the  other  extreme  is  bare 
soil  which  is  subject  to  serious  erosion 
even  on  gentle  slopes.  Inter-tilled 
crops,  like  corn  and  soybeans,  furnish 
some  protection  against  erosion  and  are 
therefore  better  for  the  soil  than  no 
crop.  Small  grains  are  intermediate  be- 
tween grasses  and  legumes  and  inter- 
tilled crops  in  holding  down  erosion. 

Amount  of  Growth 

In  the  case  of  any  crop  the  amount  of 
top  growth  determines  to  a  considerable 
extent  its  effectiveness  in  controlling 
erosion.  The  more  completely  the  soil 
is  covered  by  a  crop  the  less  it  is 


exposed  to  the  beating  action  of  rain- 
drops which  break  up  the  soil  crumbs  or 
graniiles.  The  character  and  extent  of 
the  root  system  of  a  crop  are  also  impor- 
tant. For  example,  in  August  a  crop  of 
soybeans  ma,y  cover  the  ground  as  com- 
pletely as  a  crop  of  alfalfa  and  still 
the  soil  may  be  subject  to  much  greater 
erosion  losses .  This  is  due  to  the  fact 
that  the  bean  ground  is  in  a  looser  con- 
dition than  the  alfalfa  ground.  The 
bean  roots  are  also  less  extensive  and 
are  usually  localized  in  rows. 

Abundant  root  growth  of  crops  improves 
the  physical  condition  of  soils  so  that 
water  is  more  readily  absorbed  and  the 
soil  is  less  damaged  by  the  beating 
action  of  raindrops.  A  soil  full  of 
roots  also  resists  the  cutting  action  of 
water  concentrated  into  small  streams. 

Time  of  Growth 

The  amount  of  erosion  that  m.ay  be  attri- 
buted to  a  particular  crop  depends 
largely  on  the  time  of  its  groirth.  In 
Illinois  much  of  the  corn  is  planted  in 
May,  when  the  amount  and  intensity  of 
rainfall  is  relatively  high.  Since  the 
soil  is  loose  from  tillage  and  the  soil 
gets  no  protection  from,  the  crop^  erosion 
losses  are  usually  high.  In  June  the 
corn  is  in  the  active  growing  stage,  the 
soil  is  cultivated  and  the  amount  and 
the  intensity  of  rainfall  are  relatively 
high.  In  this  month  also  erosion  losses 
are  high.  From  kO  to  60  percent  of  the 
annual  soil  losses  from  corn  land  on  the 
Agronomy  South  Farm  occurred  in  June. 

Expected  Soil  Losses 

From  available  data  it  is  possible  ^-  -r- 
timate  the  soil  loss  by  erosio:.  -,  u 
will  occur  on  different  slopes,  from 
different  kinds  of  soils  under a  particu- 
lar rotation.  If  the  sril  loss  is 
greater  than  the  estir.  ermissable 
loss,  then  more  sc;^  .;--  be  included 
in  the  rotation.         .'  in  Illinois 


-2- 


farmers  are  interested  in  growing  corn 
and  soybeans.  To  figure  out  a  crop  rota- 
tion that  will  satisfactorily  contx'ol 
erosion  just  enough  sod  crops  are  included 
to  keep  the  soil  loss  dovn  to  a  per- 
missahle  amount.  Permissable  loss  is 
the  amount  in  tons  per  acre  which  it  is 
estimated  can  "be  lost  annually  from  a 
particular  soil  and  still  maintain  the 
land  in  continued  productivity.  (The 
table  appearing  at  the  end  of  this  re- 
port shows  how  this  works . ) 

Supporting  Practices 

By  using  supporting  practices  a  rotation 
may  he  followed  that  would  permit  too 


high  soil  loss  without  the  supporting 
practices.  It  works  like  thisl  A 
farmier  selects  the  crops  he  wants  to 
grow  and  the  amount  of  a  particular  crop^ 
like  corn,  he  wants  to  include  in  the  ro- 
tation. This  is  checked  for  the  condi- 
tion of  his  land,  the  percent  .of  slope, 
the  length  of  slope,  the  kind  of  soil 
and  its  condition,  particularly  with 
reference  to  past  erosion  damage.  If 
the  erosion  losses  are  higher  than  per- 
mis sable  under  the  conditions,  the  use 
of  supporting  practices,  such  as  contour- 
ing, strip  cropping,  and  terracing  may 
reduce  the  soil  loss  enough  so  the  de- 
sired rotation  can  be  followed. 


Expected  Soil  Losses  from  Selected  Rotations  on  Four 
Soil  Types  on  a  200-foot  Contoured  Slope  in  Illinois 


a 


:/ 


Rota.tion— ' 


CCCG* 

CCCGM 

CCGM 

CGM 

CGMM 

CGMMI#I 
Permis sable 
Loss 


Flanagan 
2i  Slope 

Siv-ygert 

5i 

Clinton 

epjo 

Grant sbur 
5fo 

Tons /A 

Tons/A 
6.2 

Tons/A 
14.6 

Tons/A 

1.9 

7.8 

1.2 

4.2 

9.8 

5.3 

1.0 

3.4 
2.0 

7.8 
4.5 

4.2 

.6 

2.4 

.k 

1.2 

2.8 

1.5 

.2 

0.8 

1.8 

1.0 

4.5 


1.5 


3.0 


2.5 


(Losses  below  heavy  line  are  small  enough  to  permit  use  of 

rotation  indicated. ) 

a/  Calculations  are  based  on  expected  losses  on  soils  with  8  or 
more  inches  of  siirface  soil  remaining.  Average  management  is 
assumed  in  preparing  the  table.  With  poor  management  the  losses 
should  be  multiplied  by  1.3.  For  high-level  management  of  crops 
and  soil  multiply  by  0.7. 
b/  C  -  corn;  G  -  small  grain;  M  -  meadow.   *G  -  small  grain  with 
catch  crop  to  plow  down. 


C.  A.  Van  Doren  &  R.  S.  Stauffer 

1-30-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


EFFECT  OF  CROP  ROTATIONS  ON  SOIL  PHYSICAL  CONDITION 


SM-13 


The  physical  condition  of  soils  is  de- 
termined largely  by  their  texture^  state 
of  compaction,  and  degree  of  aggregation. 
Cultural  practices  have  little  effect  on 
soil  texture,  hut  such  management  vari- 
ables as  organic  matter  management,  sur- 
face cover,  and  tillage  will  change  soil 
compaction  and  aggregation  and  thus  help 
to  determine  physical  condition. 

Organic  matter  management .  The  degree 
of  aggregation  is  closely  related  to  the 
amount  of  readily  decomposable  organic 
matter  in  the  soil.  For  this  reason, 
cropping  systems  that  add  large  amounts 
of  readily  decomposable  organic  matter 
to  soils  are  the  systems  that  promote 
good  aggregation  and  thus  improve  physi- 
cal condition.  The  effectiveness  of 
residues  in  increasing  organic  matter  in 
the  soil,  and  thus  improving  soil  aggre- 
gation, depends  on  the  amount  of  resi- 
dues, their  ability  to  decompose,  and 
the  thoroughness  with  which  they  are 
mixed  with  the  soil. 

If  other  conditions  are  constant,  crop 
rotations  that  add  the  greatest  amount 
of  readily  decomposable  crop  residues  to 
the  soil  will  be  most  effective  in  cre- 
ating good  physical  condition. 

Surface  cover.  The  amount  of  protection 
provided  by  the  crops  grown  in  the 


rotation  also  affects  soil  physical  con- 
dition. Cropping  systems  that  provide 
a  protective  vegetative  cover,  either 
living  or  dead,  for  the  soil  during  the 
greatest  part  of  the  year  help  to  lessen 
the  impact  of  raindrops.  Heavy  rains 
destroy  aggregation  in  the  surface  soil 
and  often  cause  serious  crusting.  Air 
and  water  cannot  then  move  freely  into 
the  soil,  and  seedlings  may  not  be  able 
to  emerge. 

Tillage .  Tilling  tends  to  cause  soil 
physical  condition  to  deteriorate,  par- 
ticularly when  the  soil  is  wet.  Crop 
rotations  differ  greatly  in  the  amount 
of  tillage  they  require.  Intertilled 
crops  have  a  greater  structure -depleting 
effect  than  others. 


Sod  crops  provide  readily  decomposable 
organic  matter  and  vegetative  cover  and 
require  fewer  tillage  operations  than 
intertilled  crops.  It  is  thus  easy  to 
understand  how  the  sod  crops  help  to  im- 
prove soil  structure.  Possibly  some  of 
the  new  techniques  now  being  used  to 
produce  intertilled  crops  may  eventually 
reduce  their  structure -depleting  effect 
enough  to  make  it  necessary  to  reevaluate 
their  usefulness  in  crop  rotations  for 
improving  soil  physical  structure . 

M.  B.  Russell 
2-13-56 


JNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-14 


CROP  ROTATIONS  AND  INSECTS 


Cultural  practices  are  essential  in  com- 
bating attacks  of  many  species  of  in- 
sects. Crop  rotations  are  a  cultural 
practice  that  reduces  the  number  of  in- 
sects farmers  have  to  combat  and  thus 
cuts  down  the  amount  of  insecticide  they 
have  to  use.  Insecticides  are  only  a 
supplementary  means  of  controlling  in- 
sects. If  populations  were  not  reduced 
by  rotations  and  other  cultural  prac- 
tices^ as  well  as  by  the  weather,  the 
insecticide  bill  on  each  farm  would  be 
astounding. 

Northern  corn  rootworm  is  a  good  example 
of  how  insects  can  be  controlled  by  cor- 
rect crop  rotation.  This  pest,  which 
has  a  life  cycle  of  one  year,  presents  a 
serious  problem  where  corn  is  grown  in 
the  same  field  for  more  than  two  years 
in  succession.  The  rootworm  overwinters 
in  the  egg  stage,  and  the  small  larvae 
hatch  in  the  spring  and  stay  in  the  soil 
waiting  to  feed  on  the  corn  roots.  The 
damage  they  do  may  cause  the  corn  to 
lodge  seriously. 

Correct  rotations  will  adequately  con- 
trol this  pest.  Growing  other  crops  in 
the  rotation  for  two  years  after  corn 
reduces  the  niitnber  of  larvae  and  emerg- 
ing adults,  providing  adequate  control 
without  use  of  an  insecticide.  A  two- 
year  break  is  necessary,  however,  be- 
cause rootworms  will  survive  for  one 
year  on  some  crops  besides  corn.  ^-Jheat 
jointworms  can  also  be  partly  controlled 
by  rotating  crops. 


White  grubs  are  another  pest  that  can  be 
controlled  by  rotations,  but  not  so  eas- 
ily as  the  northern  corn  rootworm.  Be- 
cause grubs  have  a  three -year  life  cycle, 
rotation  plans  must  be  made  two  years 
before  the  damage  is  expected.  In  the 
first  year  of  the  cycle,  June  beetles, 
the  adults  of  white  grubs,  lay  their  eggs 
in  the  spring.  The  grubs  hatch,  feed, 
and  overwinter.  The  next  summer,  during 
the  second  year  of  the  cycle,  they  feed 
heavily,  severely  damaging  the  crop 
roots.  During  the  third  year,  they  feed 
during  May,  pupate,  and  remain  in  the 
soil  as  adults  the  following  winter, 
emerging  in  the  spring  to  lay  eggs. 

To  avoid  damage  from  grubs  during  the 
year  of  heavy  feeding,  it  is  necessary 
to  have  had  some  crop  on  the  land  that 
was  not  suitable  to  the  adults  for  lay- 
ing eggs  during  the  previous  season  (the 
first  year  of  the  cycle).  Such  crops 
are  clover,  alfalfa,  and  corn.  At  one 
time  soybeans  were  included  in  the  list 
of  resistant  crops,  but  there  is  now  one 
species  of  grub  that  will  lay  eggs  in 
this  crop. 


A  carefully  planned  rotation  will  also 
reduce  some  species  of  wireworms  and 
cutworms.  If  length  of  life  cycle  and 
other  facts  about  the  insect  are  known, 
then  a  crop  rotation  can  be  planned  that 
should  reduce  its  attacks  on  the  crop. 


H,  B.  Petty 
2-20-56 


(Over ) 


SM-14 


CROP  ROTATIONS  AND  DISEASE 


It  is  obvious  that  continuous  cropping 
perpetuates  and  increases  the  pathogenic 
organisms  in  the  soil.  Good  examples  of 
this  process  in  Illinois  are  the  in- 
crease in  the  amount  of  take-all  and  of 
bunt  through  soil  infestation  in  fields 
where  wheat  has  followed  wheat  for  two 
successive  years.  Under  such  situations 
rotating  crops  would  constitute  a  good 
method  of  control.  Crop  rotation  may^ 
however,  be  recommended  as  a  means  of 
controlling  disease  without  considering 
whether  the  pathogen  or  pathogens  would 
be  effectively  reduced. 

The  first  question  to  consider  in  rec- 
ommending crop  rotation  as  a  means  of 
controlling  a  specific  disease  is  to  de- 
termine whether  the  pathogen  that  is  re- 
sponsible for  the  disease  is  a  true  soil 
inhabitant  or  whether  it  is  a  soil  in- 
vader of  short  duration.  Some  organisms 
are  capable  of  living  in  the  soil  for  10 
to  20  years  without  coming  into  contact 
with  their  natural  host.  Some  examples 
are  species  of  Fusaria  and  damping-off 
and  root-rotting  fungi  like  Pythium. 
Crop  rotation  could  obviously  be  of  lit- 
tle value  in  controlling  diseases  caused 
by  this  group  because  it  would  take  too 
long  to  eliminate  them. 


may  be  at  least  partly  eliminated  by  ro- 
tating crops.  Most  of  these  fungi,  how- 
ever, are  parasites  of  vegetable  crops. 
Some  of  the  more  common  ones  are  the  or- 
ganisms causing  bean  anthracnose,  black- 
leg of  cabbage,  and  bacterial  blight  of 
common  beans. 

Some  work  done  in  Illinois  to  determine 
the  persistence  of  the  soil-borne  wheat 
mosaic  virus  showed  that  growing  nonsus- 
ceptible  crops  for  at  least  four  years 
reduced  the  amount  of  virus  but  did  not 
eliminate  it.  Therefore  crop  rotation 
cannot  be  recommended  as  an  adequate  con- 
trol for  this  disease,  in  which  the  virus 
is  known  to  persist  in  the  soil  for  a 
long  time. 

In  most  cases  rotation  is  of  little  value 
as  the  sole  means  of  controlling  soil- 
borne  diseases  in  agronomic  crops.  On 
the  other  hand,  crop  rotation  together 
with  other  types  of  control  could  be 
very  effective.  Often  the  two  combined 
will  keep  the  disease-producing  organisms 
from  building  up  or  hold  them  to  a  mini- 
mum so  that  they  will  cause  little  loss 
in  yield.  If  they  accomplished  no  other 
purpose,  this  result  alone  would  make 
crop  rotation  worth  while. 


On  the  other  hand,  those  fungi  that  can 
live  for  no  more  than  two  to  four  years 
in  the  soil  without  their  natural  host 


Wayne  M.  Bever 
Department  of  Plant  Pathology 

2-20-56 


( Over ) 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-15 
AN  ANALYSIS  OF  THE  NITROGEN  STATUS  OF  THE  AGRONOMY  SOUTH  FARM  ROTATIONS 


Numerous  experiments  ha"ve  shoi-m  that  sat- 
isfactory^ although  not  necessarily  maxi- 
mum, grain  yields  can  be  maintained  by 
using  rotations  where  the  legume -grain 
crop  ratio  is  1  to  3  or  1  to  ^4-.  The 
marked  improvement  in  soil  physical  con- 
dition (tilth)  caused  by  the  legume  mead- 
ow and  the  noticeable  deterioration  in 
physical  condition  after  several  years 
of  tillage  have  tended,  however,  to  ob- 
scure the  primary  fiinction  of  legumes  in 
rotations,  namely,  to  restore  and  main- 
tain nitrogen.  It  is  only  when  nitrogen 
is  applied  to  grain  crops  several  years 
removed  from  the  legume  that  it  becomes 
evident  that  the  decline  in  crop  yields 
which  necessitates  a  return  to  legumes 
is  primarily  a  reflection  of  lower  ni- 
trogen fertility  rather  than  of  tilth 
deterioration. 

The  transitory  nature  of  nitrogen  fer- 
tility in  rotations  where  legumes  are  the 
primary  source  of  nitrogen  is  illustrated 
in  Figure  1.  The  corn,  corn,  oat,  wheat 
rotation  was  planned  to  determine  the 
effects  of  catch-legxanes  sown  in  small 
grains  en  subsequent  grain  yields .  There 
were  check  plots  where  legumes  were  not 
seeded  and  plots  where  legumes  were 
seeded.  Thus  it  is  possible  to  evaluate 
the  yield  effects  of  seeding  the  catch 
legumes. 

Figure  1  shows  that  the  catch  legume  in- 
creased yields  of  all  grains.  The  yield 
effect  of  the  legume,  however,  expressed 
as  percent  of  increase  in  yield, was  al- 
ways greatest  the  first  year.  A  rather 
sharp  break  in  the  residual  yield  effect 
of  the  legume  is  evident  in  the  second 
year.  The  yield  effect  of  the  legume 
continues  to  decline  thereafter,  but  at 
a  lesser  rate. 

The  data  in  Figure  1  for  the  yield  ef- 
fects of  commercial  nitrogen  indicate 
that  commercial  nitrogen  is  equally  as 


50 


0) 

o 

c 


0) 


30" 

so- 
lo 


-^ 


For 
nitrogen 


^ 


For  catih  legume 


Corn 


Corn 


Oats 


Wheat 


Fig,  1,  Percent  of  Increase  In  grain  yields 
for  planting  a  catch  legume  and  using  nitrogen 
only  where  yields  of  plots  receiving  no  nitro- 
gen or  legume  seedlngs  are  the  standard  for 
comparison.  For  nitrogen  graph  line  only: 
first  corn,  100  lb.  N;  second  corn, no  N;  oats, 
20  lb, N;  wheat,  20  lb.  N.  (Data  from  Illinois 
Agronomy  South  Farm) 


satisfactory  as  legume  nitrogen  in  so  far 
as  first-year  corn  yields  are  concerned. 

The  residual  effects  of  commercial  nitro- 
gen applied  to  first-year  corn  on  second- 
year  corn  yields  were  insignificant.  In 
this  respect  legume  nitrogen  was  superior 
to  commercial  nitrogen.  It  is  quite  ap- 
parent, however,  that  the  leg-ume  system 
did  not  supply  enough  available  nitrogen 
for  maximum  small  grain  yields,  because 
oat  and  wheat  yields  were  higher  when 
nitrogen  was  applied. 

The  preceding  discussion  presented 
evidence  of  the  transitory  nature  of 
nitrogen  fertility.  Figure  2  gives  a 
generalized  concept  of  the  nitrogen  fer- 
tility pattern  one  might  expect  in  rota- 
tions where  the  ratio  of  non-legume  to 
legume  crops  is  3  to  1.  The  pattern  is 
carried  through  nine  years,  or  two  full 
rotation  periods,  to  show  the  saw-toothed 
cyclic  nature  of  nitrogen  fertility  in- 
duced into  rotations  by  periodic  legume 
growth. 


-2- 


4J 

\ 

\ 

/ 

■H 
H 

-p 

\ 

\l 

/ 

0) 

c 

\ 

\ 

/ 

bO 
O 
U 

■\^ 

X 

/ 

B 

Years 
1234567  89 

Non-legume   crops        Non-leguKe   crops 

Legume  meadow  Legume  meadow 

Fig,  2,  A  generalized  nitrogen  fertility  pat- 
tern for  rotations  where  the  grain  to  legume 
ratio   Is  3   to   1. 

Two  areas  in  the  nitrogen  fertility  pat- 
tern are  of  interest :  the  peak  and  the 
floor.  In  terms  of  minimum  rotational 
nitrogen  availability^  the  floor  can  be 
expected  to  vary  with  the  organic  matter 
content  of  soils ^  the  activity  of  decay 
of  this  organic  matter,  and  the  residual 
legume  nitrogen.  If  the  legume  is  not 
sown  or  if  it  fails,  there  can  be  no 
peak.  The  floor  of  minimal  nitrogen 
availability  would  then  appearto  broaden 
and  gradually  sink,  since  nitrogen  avail- 
ability at  this  point  depends  primarily 
on  the  decay  rate  of  an  ever-decreasing 
soil  organic  matter  supply. 

If  the  stand  is  pure,  the  height  to  which 
nitrogen  availability  or  fertility  rises 
following  a  legume  would  appear  to  be 
determined  primarily  by  the  amount  of 
nitrogen  the  legume  contributes.  Lower 
peaks,  and  frequently  double  peaks,  with 
the  higher  of  the  two  peaks  in  the  second 
year,  are  possible  where  mixed  legume - 
grass  sods  or  legumes  mixed  with  a  con- 
siderable amount  of  straw  are  turned 
under. 

Figure  3  shows  examples  of  multiple  ni- 
trogen availability  peaks  of  this  nature. 
Thus  the  generalized  nitrogen  fertility 
pattern  illustrated  in  Figure  2  can  vary 
with  different  rotations.  Moreover,  the 
peak  nitrogen  fertility     associated  with 


a  specific  rotation  may  not  represent 
the  optimum  nitrogen  fertility  needed 
for  maximxim  grain  yields. 


3_.0  _    Critical   leaf   nitrogen 

„     "content    {2.3fa  N) 
2.8 


2.6 

2.4 
2.2 
2.0 
1.8 
1.6 


n 


2345 

Rotation  No. 


6       7       8       9       10 
[See    Table    1) 


Fig,  3.  Nitrogen  adequacy  peak  measure  by  leaf 
analysis  for  various  rotations,  Illinois  Agron- 
omy South  Farm. 

Leaf  analysis  studies  with  corn  have  in- 
dicated that  a  leaf  nitrogen  content  of 
2.9  percent  gives  maximimi  corn  yields. 
This  is  the  critical  leaf  nitrogen  per- 
centage for  corn.  By  means  of  leaf  analy- 
sis it  has  been  possible,  in  terms  of 
leaf  nitrogen  contents,  to  define  the  ni- 
trogen fertility  peaks  associated  with 
various  rotations  at  the  Agronomy  South 
Farm,  Ten  rotations  and  associated  corn 
leaf  nitrogen  contents  are  listed  in 
Table  1.  The  results  are  presented 
graphically  in  Figure  3« 


Table  1.  Rotations  and  associated  corn  leaf 
nitrogen  contents  at  the  University  of  Illinois 
Agronomy  South  Farm* 


Rotation 
number  Rotation 

1  Corn,  soybeans 

2  Corn,  oats 

3  Corn,  oats** 

4  Corn,  oats,  wheat** 

5  Corn,  corn,  wheat** 

6  Corn,  oats,  wheat,  timothy 

7  Corn,  oats,  wheat,  alfalfa 

8  Corn,  corn,  oats**,  wheat** 

9  Corn, corn,  soybeans,  wheat** 
10  Corn,  soybeans,  oats,  wheat** 


Percent 
leaf  nitrogen 

2.42 

2.17 

2.67 

2.67 

1.80  &  1.70 

2.14 

2.85 

1.82  & 


2.07 


1.94  &  2.07 
2.05 

*A11  plots  Included  In  rotation  experiment 
have  been  limed  and  phosphated.  Soil  test 
Indicates  adequate  potash, 
**Catch  legumes  seeded. 


-3- 


Rotation  7?  which  is  a  corn,  oat,  wheat, 
alfalfa  sequence,  was  the  only  rotation 
in  which  soil  nitrogen  fertility,  as  in- 
dicated by  leaf  analysis,  approached 
that  considered  optjjnum  for  first-year 
corn.  Rotations  2,  h.  5^  6,  8,  9,  and 
10,  judged  by  the  same  standard,  gave 
soil  nitrogen  fertility  peaks  that  were 
substantially  suboptimum  for  maximum 
corn  yields. 

The  leaf  nitrogen  content  observed  for 
rotation  1,  a  corn-soybean  sequence,  is 
of  considerable  interest.  Most  workers 
do  not  consider  that  harvested  soybean 
residues  contribute  m.uch  nitrogen  to  the 
soil.  Yet,  except  in  rotations  3  and  J, 
the  leaf  nitrogen  content  of  corn  fol- 
lowing soybeans  exceeds  that  for  other 
rotations. 

The  microbial  demands  for  nitrogen  set 
up  by  corn  residues  probably  have  no  ef- 
fect on  yields  of  nodulated  soybeans. 
Thus  soil  nitrogen  perhaps  contributes 
toward  the  decay  of  most  of  the  corn 
residues  diiring  the  season  in  which  soy- 
beans occupy  the  land.  '  Corn  following 
soybeans  would  then  appear  to  grow  in  a 
soil  environment  that  is  virtually  free 
of  microbial  competition  for  nitrogen. 
Thus  the  greater  part  of  the  available 
nitrogen  is  released  from  soil  organic 
matter.  This  nitrogen  plus  that  re- 
leased from  partly  decayed  corn  and  de- 
caying soybean  residues  probably  makes 
the  soil  nitrogen  fertility  status  higher 
than  one  might  expect.  It  should  be  ob- 
vious, however,  that  this  practice  can 
not  assure  above-average  corn  yields  in- 
definitely because  under  this  highly 
nitrogen-deficient  rotation  the  soil  or- 
ganic matter  will  eventually  be  drastic- 
ally reduced,  leading  to  progressively 
lower  corn  yields. 

The  effect  of  the  kind  of  residues  that 
precede  corn  on  net  soil  nitrogen  avail- 
ability can  be  evaluated  by  comparing 
rotations  1  and  2.  Where  soybeans  pre- 
cede corn,  microbial  nitrogen  demands 


are  probably  at  a  minimum  for  the  rea- 
sons previously  given.  Where  corn 
follows  oats  (rotation  2),  microbial  com- 
petition for  available  nitrogen  appar- 
ently persists  during  most  of  the  growing 
season.  This  is  reflected  in  lower  leaf 
nitrogen  contents  and  lower  corn  yields 
for  the  corn-oat  sequence.  Planting  a 
catch  legume  in  the  oats  (rotation  3 ) 
appears  to  greatly  increase  the  net  ni- 
trogen availability,  and  this  increase 
is  reflected  in  a  higher  leaf  nitrogen 
content. 

Multiple  nitrogen  fertility  peaks,  with 
maximiim  nitrogen  fertility  in  the  second 
year,  are  not  uncommon  for  some  rota- 
tions. This  is  true  for  rotations  8  and 
9.  It  would  appear  that  the  nitrogen 
contributed  by  the  catch  legume  that 
preceded  corn  was  not  sufficient  to  over- 
come all  of  the  microbial  nitrogen  de- 
mands occasioned  by  the  decay  of  the 
wheat  straw.  Thus  first-year  corn  is 
produced  in  a  less  favorable  soil  nitro- 
gen availability  environment. 

The  initial  decay  processes  that  reduce 
first -year  nitrogen  availability,  how- 
ever, appear  to  be  more  or  less  complete 
prior  to  August  of  the  second  year.  The 
subsequent  release  of  available  nitrogen 
previously  withheld  during  decay  then 
gives  a  higher  second-year  nitrogen  fer- 
tility pattern,  as  the  data  for  corn 
leaf  composition  show. 

The  nitrogen  fertility  pattern  illus- 
trated in  Figure  2  might  be  considered 
to  represent  a  normal  nitrogen  fertility 
pattern.  The  data  in  Figure  3^  however, 
indicate  that  rotations  can  alter  the 
normal  pattern,  i.e.,  multiple  nitrogen 
peaks.  Moreover,  it  is  apparent  that 
the  nitrogen  fertility  peaks  achieved 
by  some  rotations  do  not  constitute  ni- 
trogen adequacy  in  so  far  as  maxim'um 
yields  are  concerned.  Supplementary 
nitrogen  fertilization  throughout  such 
rotations  is  needed  to  obtain  maximum 
grain  yields. 

Edward  H,  Tyner 
2-27-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


MANAGEMENT  & 
CONSERVATION 


AGRONOMY  FACTS 


SM-16 


ECONOMIC  OBJECTIVES  OF  CROP  ROTATIONS 


Four  previous  Agronomy  Fact  sheets  have 
discussed  the  various  agronomic  objec- 
tives of  crop  rotations:  controlling 
erosion;,  maintaining  desirahle  soil 
physical  properties^  controlling  insects 
and  diseases,  and  supplying  plant  nutri- 
ents to  crops.  Attaining  any  one  of 
these  four  objectives  to  the  fullest  ex- 
tent is  likely  to  mean  sacrificing  the 
complete  fulfillment  of  one  or  more  of 
the  others.  They  must  therefore  he  bal- 
anced when  a  rotation  is  selected  and 
put  into  effect  in  the  farm  business. 

An  economic  analysis  of  this  problem 
should  consider  the  "best"  use  of  labor 
and  capital,  as  well  as  the  "best"  use 
of  the  land.  In  short,  the  economic  ob- 
jective of  crop  rotations  should  be  to 
select  the  rotation  that  will  give  the 
maximum  profit  for  the  total  farm  busi- 
ness over  a  period  of  years. 


Economic  Principle  Involved.  One  crop 
can  be  substituted  for  another  to  vary- 
ing degrees  in  rotations.  For  example, 
going  from  a  C-C-0  (clover  catch  crop) 
rotation  to  a  C-C-O-M  rotation  means 
that  meadow  is  being  substituted  for 
part  of  the  corn  and  oats.  In  terms  of 
total  production  of  each  crop  (per  acre 
yield  times  number  of  acres),  the  result 
of  substituting  one  crop  for  another  in 
a  rotation  is  not  always  the  same.  For 
example,  the  number  of  bushels  of  corn 
sacrificed  for  each  ton  of  legume  hay 
gained  is  likely  to  be  less  in  shifting 
from,  say,  a  C-C-O-M  to  a  C-C-0-M-M  ro- 
tation than  in  shifting  from  a  C-O-M-M 
to  a  C-0-M-M-M.  This  difference  is  due 
to  the  different  effects  of  crop  se- 
quences on  yields  as  the  proportion  of 
land  in  each  crop  changes. 

The  economic  principle  involved  in  se- 
lecting a  rotation  is  that,  in  order  to 
maximize  profits,  one  crop  (for  example, 
meadow)  is  substituted  for  another  (for 


example,  corn)  until  the  returns  sacri- 
ficed by  decreasing  corn  production  are 
exactly  balanced  by  the  gain  in  returns 
from  increasing  meadow. 

Rotation  experiments  frequently  show  a 
"complementary"  effect  on  corn  when  leg- 
\imes  are  added  to  the  rotation  in  small 
amoionts.  That  is,  total  corn  production 
(per  acre  yield  times  number  of  acres ) 
increases,  up  to  a  point,  as  legumes  oc- 
cupy a  larger  percent  of  the  rotation. 
If  legumes  and  corn  are  complementary, 
adding  legumes  to  the  rotation  will  be 
profitable  even  if  the  roughage  that  is 
produced  is  not  sold  or  used  by  live- 
stock. In  m.any  commercial  fertilizer 
programs,  however,  this  complementary  re- 
lationship disappears,  and  corn  and  leg- 
umes compete  throughout  a  wider  range 
of  rotations.  This  means  that  the  farmer 
has  a  larger  ntmiber  of  choices,  and 
thus  his  decisions  regarding  cropping 
systems  become  more  difficult, 

Basic  Data  Needed  for  Choosing  Rotation. 
The  economic  principle  can  be  applied 
by  using  expected  yields  from  each  alter- 
native rotation.  The  expected  yields 
summarize,  in  a  sense,  the  combined  ef- 
fect of  the  relationships  described  in 
the  four  previous  Agronomy  Fact  sheets 
on  rotation  objectives.  Since  the  prob- 
lem of  selecting  a  rotation  cannot  be 
divorced  from  that  of  applying  fertilizer 
to  individual  crops  within  the  rotation, 
alternative  fertilizer  programs  and 
their  expected  effects  on  yield  must  be 
considered  in  combination  with  each  ro- 
tation. 

Except  where  a  cash-grain  system  is  to 
be  followed,  the  livestock  system  must 
also  be  considered.  Roughage -consimiing 
livestock  may  be  desirable  to  use  labor 
during  slack  seasons.  Livestock  may  in 
turn  require  a  higher  percent  of  leg- 
umes in  the  rotation  than  would  be  dic- 
tated by  a  simple  cost-returns  analysis 
of  the  cropping  system  by  itself. 


For  example,  a  cost-returns  analysis  of 
the  cropping  system  made  independently 
of  the  livestock  system  might  show  a 
catch-crop  rotation  to  "be  more  profit- 
atile  than  a  stand-over  rotation.  If, 
however,  the  farm  is  small  and  the  farmer 
wishes  to  increase  his  vol'ume  of  busi- 
ness by  using  roughage-consuming  live- 
stock, the  stand-over  rotation  will  be 
more  appropriate. 

The  place  of  manure  and  its  effect  on 
yields  also  needs  to  be  taken  into  ac- 
count. And  the  effect  of  substituting 
supporting  practices  for  meadow  to  sat- 
isfy soil  conservation  objectives  must 
be  estimated. 

Comparing  Relative  Profits  of  Rotations. 
Using  the  basic  data  outlined  above,  the 
farmer  can  make  a  "budget"  of  estimated 
costs  and  returns  for  each  alternative 
rotation,  including  other  parts  of  the 
farm  business  that  are  related  to  the 
rotation.  This  comparison  of  costs  and 
returns  can  be  simplified  by  considering 
only  those  costs  that  differ  among  the 
alternative  plans.  For  example,  "such 
fixed  costs  as  taxes,  interest  on  land, 
overhead  on  machinery,  etc . ,  can  be 
omitted  because  they  stay  the  same  re- 
gardless of  rotation.  Operator  and  fam- 
ily labor  can  also  sometimes  be  omitted. 
Since  all  costs  are  not  included,  the 
resulting  figures  should  not  be  confused 
with  "profits . "  This  budget  is  simply  a 
tool  to  help  compare  the  effects  of  dif- 
ferent rotations;  it  is  not  a  measure  of 
profitability  of  the  farm  business. 

Legume  Nitrogen  vs.  Commercial  Nitrogen. 
An  added  advantage  in  selecting  a  rota- 
tion as  part  of  the  total  farm  business 
is  that  there  is  less  need  for  "internal" 
accounting.  We  need  not,  for  example, 
attempt  to  calculate  a  cost  for  produc- 
ing nitrogen  from  legumes.  So  long  as 
the  yield  estimates  for  each  rotation 
adequately  reflect  the  effect  of  the 
crop  sequence,  and  varying  levels  of  ni- 
trogen are  considered  in  combination 
with  the  rotations,  the  value  of  the  leg- 
ume will  show  up  in  subsequent  yield 


increases  and,  in  a  livestock  system,  in 
increased  livestock  production.  In- 
terest should  focus  on  the  comparative 
returns  from  the  alternative  total  farm 
plans  and  not  on  the  value  of  " goods- in - 
process. " 

Computing  Met  Returns  for  a  Period  of 
Years.  Adoption  of  a  rotation  implies 
that  the  farm  operator  expects  to  re- 
ceive income  and  to  inctir  expenses  over 
a  period  of  years.  Alternative  cropping 
systems  may  give  him  a  choice  in  the  way 
his  income  and  expenses  are  spread  over 
this  period.  For  example,  some  cropping 
systems  may  require  heavy  initial  ex- 
penses for  fertilizer,  while  others  may 
require  smaller  initial  expense  but 
cover  a  longer  time.  The  time  at  which 
the  crop  sequence  will  affect  yields  also 
differs  among  rotations.  The  farmer  must 
consider  these  differences  in  developing 
a  budget  that  is  designed  to  help  him 
pick  a  rotation. 

Budgets  of  returns  and  expenses  over  a 
period  of  years  can  be  compared  more  ac- 
curately by  using  a  discounting  proce- 
dure. This  will  give  the  net  returns 
over  a  period  of  time  from  each  plan  in 
terms  of  its  present  value.  For  in- 
stance, using  an  annual  discount  rate  of 
5  percent,  we  find  that  an  income  of 
$100  three  years  from  now  is  worth  only 
$86  today.  The  same  procedure  must  be 
applied  to  costs.  Discounting  is  espe- 
cially important  in  comparing  alterna- 
tive plans  that  have  widely  different 
timing  of  expenses  of  income. 

Comparative  Risks.  Some  farmers  prefer 
a  lower,  more  stable  income  to  one  that 
is  higher  but  varies  more  from  year  to 
year.  Since  weather  and  price  fluctua- 
tions do  not  affect  all  crops  in  the  same 
way,  rotations  differ  in  variability  of 
returns  as  well  as  in  average  level  of 
returns.  In  the  final  selection  of  a 
rotation,  these  differences  in  risks 
need  to  be  balanced  against  the  compara- 
tive returns  from  the  alternative  rota- 
tions. 

Earl  R.  Swans on 
3-5-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


CONTINUOUS  CORN 


SM-17 


How  often  should  corn  be  grown  on  (pro- 
ductive) corn-belt  soil?  This  much- 
discussed  question  has  been  studied 
experimentally  for  80  years  on  the  Morrow 
plots  on  the  campus  of  the  University  of 
Illinois.  Many  other  tests  have  been 
made  on  experiment  fields  and  on  farmers' 
fields  throughout  the  state. 

At  the  Momence  soil  experiment  field  in 
Kankakee  county;,  corn  was  grown  continu- 
ously for  1^  years,  beginning  in  1902. 
Average  yields  were  6.5  bushels  an  acre 
on  untreated  land;  4ij-.3  bushels  with 
limestone,  phosphate,  and  potash  (LPK); 
and  50«6  bushels  with  limestone,  phos- 
phate, potash,  and  nitrogen  (lIPKW). 

Fertilizers  were  applied  at  the  following 
acre  rates  each  year:  phosphorus  as 
bone  meal,  200  pounds;  potassium  as  mu- 
riate of  potash,  150  poimds;  and  nitro- 
gen as  dried  blood  (l2foNO),  8OO  pounds. 
The  soil  was  peaty  loam. 

On  the  Davenport  plots  at  Urbana,  a  con- 
tinuous corn  experiment  was  operated  for 
13  years,  beginning  in  I9OI.  Fertilizers 
were  used  in  the  same  amounts  as  described 
above  in  the  tests  at  Momence.  Average 
yields  were  as  follows:  LPK,  50.1; 
and  LPKN,  6l.h.  During  these  same  years 
(1901,  1913) J  a,  rotation  of  corn,  oats, 
clover,  and  wheat  catch  crop  was  also 
used  on  the  Davenport  plots.  Average 
yields  were  57«9  bushels  with  no  soil 
treatment  and  78.7  bushels  with  LPK.  No 
nitrogen  fertilizer  was  used  on  the  rota- 
tion plots.  The  soil  on  this  area  was 
Flanagan  silt  loam. 

A  continuous  corn  culture  study  was 
started  on  the  Dixon  soil  experiment 
field  in  1932.  To  maintain  a  high  test 
level,  soil  treatments  have  included 
lime,  superphosphate,  and  potash.  Since 
19^2,  600  pounds  of  ammonium  sulphate  an 
acre  have  been  plowed  under  each  year, 
and  130  pounds  of  3-12-12  have  been  used 


as  a  starter.  Rye  has  been  seeded  in 
the  fall  as  a  cover  crop  since  1951- 

Twelve-year  average  corn  yields  0-9^^-55) 
for  these  plots  and  for  corn  under 
rotation  at  Dixon  and  at  the  Morrow 
plots  are  reported  in  Table  1.  Growing 
costs  are  indicated  in  terms  of  bushels 
of  corn  (calculated  at  $1.25  a  bushel). 
These  costs  were  subtracted  from  yield 
to  give  "take-home"  corn  per  acre  . 

During  recent  years  hybrid  corn,  cheaper 
nitrogen  fertilizers,  and  corn  price  sup- 
ports have  caused  renewed  interest  in 
continuous  corn.  At  the  Lebanon  experi- 
ment field  on  Jarvis-LeClaire  silt  loam 
and  at  the  Newton  experiment  field  on 
Cisne  silt  loam,  tests  with  continuous 
corn  were  established  in  1951  on  land 
that  had  been  in  rotation  with  soil 
treatment  for  many  years.  Treatments 
with  continuous  corn  include  the  use  of 
non-legume  cover  crops  and  nitrogen  at 
the  rate  of  1^0  pounds  each  year.  Yields 
were  low  as  a  result  of  severe  drought 
in  195^  and  moderate  drought  in  1955 • 
Table  2  gives  average  corn  yields  for 
the  four  years  1952-1955  with  continuous 
corn  and  with  corn  in  a  corn,  beans, 
wheat,  hay  rotation. 

At  the  Urbana  Mumford  (M-9)  plots  an 
area  of  land  has  been  in  continuous  corn 
culture  since  1935*  Average  yield  on 
the  untreated  areas  of  these  plots  from 
19^0  to  1952  was  6h  bushels  an  acre. 
Table  3  lists  treatments  and  yields  for 
the  past  three  years  (1953-1955 )•  This 
soil  is  a  Drummer  clay  loam  that  has 
been  adequately  limed  and  phosphated. 

A.  L.  Lang 

L.  B.  Miller 

C.  H.  Farnham 

P.  E.  Johnson 

D.  L.  Mulvaney 

3-26-56 


Table  1.   Continuous  Corn  Versus  Rotation  Corn  at  Dixon  and  at  Morro-w  Plots 

12-yr.  Averages^  19ij-i4-1955 


Costs  in 

bushels 

Ratio-/  of 

of  corn  per  acre 

"Take- 

Soil 

Acre 

Soil 

Total  / 
costs- 

home" 

yield  to 

Rotation 

treatment 

yield 

treatment 

corn 

"Take -home" 

Dixon  Soil 

Experiment  Field  -  Tama 

Silt  Loam 

bu. 

bu. 

bu. 

bu. 

Continuous  corn 

LPKN 

3-12- 

12 

75.9 

18.0 

58.2 

17.7 

4.29 

Continuous  corn 

L 

^9.2 

1.0 

38.6 

10.6 

4.64 

C-O-Cl-W 

LPK 

95.1 

5.0 

i^7.0 

48.1 

1.98 

C-O-Cl-W 

0 

58.5 

- 

38.5 

20.0 

2.92 

C-0-W( legume) 

LPK 

80.2 

6.0 

k6.6 

33.6 

2.39 

C-O-W 

LPK 

^6.0 

k.o 

i^l.3 

4.7 

9.79 

Morrow 

Plots  -  Flanagan  Silt 

Loam 

Continuous  cox-n 

0 

22.0 

M 

39.0 

-17.0 

X 

Continuous  corn 

MIP 

64.0 

5.0 

41^.0 

20.0 

3.20 

C-O-Cl 

0 

68.0 

39.4 

28.6 

2.38 

C-O-Cl 

I/ELP 

108.0 

5.0 

48.2 

59.8 

1.81 

1/  Includes  fertilizer  costs,  harvesting,  and  marketing  @  125z!/bu.  plus  all  other 
costs,  based  on  Detailed  Cost  Report  for  Central  Illinois.    (A.  E.  Mimeo  2969) 

2/  This  ratio  indicates  how  many  bushels  of  corn  must  be  harvested  for  each  bushel 
of  net  or  profit.  It  also  shows  hov  many  bushels  must  go  to  market  or  be  added 
to  surplus  for  the  producer  to  maice  the  same  net  profit. 


Table  2.   Continuous  Corn  vs.  Rotation  Corn  at  Newton  and 
Lebanon,  1952-1955 


Soil 

Average  corn  yields 

Cropping 

treatment 

Neirton 

Lebanon 

bu. 

bu. 

Corn  continuous 

LPK 

35.7 

61.0 

Corn  continuous  and  cover  crop 

LPK 

30.1 

54.3 

Corn  continuous 

LPKN 

35.1 

63.0 

Corn  continuous  and  cover  crop 

LPKN 

37.9 

64.3 

Corn,  beans,  wheat,  hay 

LPK 

45.9 

83.4 

Table  3*   Continuous  Corn  With  and 

Without  Rye, 

Mumford  Plots, 

M-9,  Urbana 

Year        K  Rye      K 

K  Rye  nV 

10 

-lo-ioV 

Nl/ 

lo-io-ioi/ 

'17 

bu.       bu. 

bu. 

bu. 

bu. 

1953  57      66 

1954  58      65 

69 
69 

79 
72 

74 
68 

1955         59      71 

87 
75 

88 

90 

Average       58       67 

79 

77 

1/  Treatment  5OO  lb. /A  10-10-10,  N  -  100  lb.  N  alone  or  50  lb. 
with  10-10-10. 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SP-9 


THE  PRODUCTIVITY  OF  SOME  IMPORTANT  SOUTHERN  ILLINOIS  SOILS 


In  the  last  few  years  a  considerable 
amo-unt  of  interest  has  centered  on  in- 
creasing the  yield  possibilities  of  seme 
of  the  southern  Illinois  soils.  This 
interest  has  arisen  as  a  result  of  the 
relatively  higher  prices  received  for 
central  and  northern  Illinois  soils  and 
some  rather  favorable  responses  to  soil 
management  on  experimental  fields  in  the 
southern  area. 

Productivity  is  the  ability  of  a  soil  to 
produce  crops  or  other  plants  under  vari- 
ous management  practices  and  weather  con- 
ditions. Productivity  may  be  measured 
in  per  acre  yields  of  certain  crops  or 
in  terms  of  an  index  of  combined  yields 
of  grain  crops_,  forage^  or  timber  (see 
AG-141+3 ) . 


The  soils  included  in  this  report  occur 
generally  south  of  a  line  from  Calhoion 
county,  Illinois,  on  the  vest  to  Clark 
county  on  the  east.  On  the  soil  associ- 
ation map  (see  AG-l4^3)  they  occur  in 
Areas  M,  N,  0,  and  P.  These  soils  have 
generally  developed  in  less  than  five 
feet  of  loess  lying  on  a  weathered  gla- 
cial till  of  Illinoian  age  (SP-l).  In 
most  cases  they  are  leached  of  free  car- 
bonates, and  their  degree  of  base  satu- 
ration is  low  (SM-7). 

Soils  in  Areas  M,  N,  and  P  were  gener- 
ally developed  under  a  native  prairie 
grass  vegetation  and  are  somewhat  better 
supplied  with  organic  matter  and  with 
the  desirable  base  nutrients  (Ca,  Mg,  K) 
than  are  the  soils  of  Area  0.   The  soils 


Table  1. --Average  Per  Acre  Yields  of  Hybrid  Corn,  Soybeans, 
and  VJheat  Obtained  by  Farmers  on  Southern  Illinois  Soils 
Under  Medium  and  Moderately  High  Management  Levels* 


Hybrid 

corn, 

Soyb 

2ans, 

.Jheat, 

Soil 

Soil  type 

management** 

manag 

iiaent** 

management** 

assn. 

or 

Mod. 

Mod. 

Mod. 

area 

associated  types 

Med. 

high 

Med. 

hiph 

Med. 

high 

bu. 

bu. 

bu. 

bu. 

bu. 

bu. 

M 

Herrick  silt  loam  and 

Virden  silty  clay  loam 

61 

68 

# 

# 

# 

M- 

tr 

M 

Herrick  silt  loam 

5h 

59 

25 

28 

30 

32 

N 

Ccwden  silt  loam  and 

Oconee  silt  loam 

1+8 

62 

JL 

.J. 

25 

27 

N 

Cowden  silt  loam 

hi 

56 

# 

7r 

2k 

26 

P 

Cisne  silt  loam 

^5 

53 

22 

30 

21 

21+ 

0 

Bluford  silt  loam  and 

Ava  silt  loam 

1+6 

57 

ir 

# 

19 

20 

*About  95  percent  of  data  represent  the  I9I+O-5O  decade. 
**The  standard  error  of  estimate  of  these  figures,  when  considered  as  10-year 
average  yields,  is  calculated  to  be  about  +  5  percent. 


//Insufficient  data  reported. 


-2- 


of  Area  0  were  generally  developed  under 
forest  vegetation  and  are  usually  quite 
acid  (pH  5»0)  iJ^  their  untreated  state. 

The  yields  presented  in  Table  1  are 
hased  on  data  reported  by  farmers  who 
have  been  cooperating  with  the  Agronomy 
Department  in  a  state-wide  project  aimed 
at  evaluating  the  productivity  of  some 
major  Illinois  soils.  The  calculated 
yields^  based  on  farm-reported  data^  are 
tiiven  for  two  levels  of  management.  For 
convenience,  these  management  levels  are 
referred  to  as  medium  and  moderately 
high  and  are  expressed  in  terms  of  pounds 
of  nitrogen,  phosphate,  and  potash  used 
and  the  interval  of  time  between  legumes 
and  the  crop  under  study. 

For  hybrid  corn  and  soybeans,  yields 
were  calculated  by  assuming  6.5  inches 
of  total  rainfall  and  an  average  maximum 
temperature  of  90  for  the  months  of 
July  and  August.  These  figures  are  aver- 
ages for  the  period  I925-5O  reported  by 
the  weather  stations  in  the  area. 


A  medium  level  of  management  for  esti- 
mating hybrid  corn  yields  consisted  of 
50  pounds  of  N  per  acre  in  the  current 
and  the  previous  year,  contributed  from 
both  legume  and  nonlegume  sources;  20 
pounds  each  of  equivalent  PpOc  and  K„0 
per  acre,  applied  or  estimated  as  resid- 
ual from  previous  applications  (30  pounds 
for  Bluford-Ava  soils);  and  a  legume  or 
legume -grass  mijcture  two  years  before 
the  corn  crop. 

Comparable  figures  for  a  moderately  high 
level  of  management  were  100  pounds  of  W 
per  acre,  ^l-O  pounds  of  PpO^  (60  pounds 
for  Bluford-Ava  soils),  60  pounds  of  K  0 
{kO  pounds  for  Herrick  soils),  and  the 
equivalent  of  an  alfalfa — red  clover  mix- 


ture immediately  preceding  the  corn 
crop. 

For  soybeans  and  wheat  the  comparable 
figures  for  medium  and  moderately  high 
management  are  approximately  one -half  of 
those  given  for  corn. 

Table  2  lists  yields  from  similar  crops 
gro-ji/n  on  University  of  Illinois  soil  ex- 
periment fields  having  the  same  soils  as 
those  included  in  Table  1  or  closely 
associated  soils.  Huey  silt  loam  listed 
in  Table  2  includes  many  of  the  so- 
called  slick  spots  in  southern  Illinois 
(AG-li|i4-3  and  SM-8). 

The  check-plot  yields  show  the  productiv- 
ity of  these  soils  in  an  untreated  condi- 
tion, and  particularly  the  influence  of 
so-called  slick  spot  soils.  The  combina- 
tion of  slick  spots  and  low  organic  mat- 
ter content  in  the  soil  surface  may  be 
partly  responsible  for  the  low  soybean 
yields  at  the  Sparta  field.  Good  germi- 
nation and  early  growth  are  frequently 
poor  because  of  "crusting"  after  rain. 

The  yields  on  the  plots  having  full 
treatment  show  how  these  soils  respond 
to  adequate  fertilization  and  appropri- 
ate rotations.  These  yields  are  higher 
than  those  reported  for a  moderately  high 
management  level  in  Table  1.  Farmers 
whose  long-time  yields  are  similar  to 
those  given  in  Table  1  may  wisely  examine 
their  crop  production  practices  not  only 
with  regard  to  soil  management,  but  also 
weed  and  disease  control,  choice  of  hy- 
brids or  varieties,  planting  rates,  and 
harvesting  procedures.  The  adoption  of 
appropriate  improved  management  prac- 
tices should  bring  their  soil  up  to  such 
a  level  that  they  could,  within  a  reason- 
able time,  expect  to  obtain  yields  similar 
to  those  shown  in  Table  2. 


-3- 

Table  2. --Average  Per  Acre  Yields  of  Hybrid  Corri;,  Soybeans,  and 
Wheat  Obtained  on  University  Soil  Experiment  Fields, 
19i|0-195^-^ 


Soil 

Soil  type 

Hy. 

corn. 

Soyb 

eans, 

Wheat, 

assn. 

or 

treatment 

treatment 

treatment 

Experiment 

area 

associated  types 

None 

Full** 

None 

Full** 

None 

Full-J«^ 

fields*** 

bu. 

bu. 

bu. 

bu. 

bu. 

bu. 

Clayton 

M 

Dominantly  Herrick 

Carlinville 

silt  loam 

h9 

90 

23 

32 

1? 

32 

Lebanon 

P 

Cisne  silt  loam 

23 

73 

11 

21 

5 

27 

Oblong 

P 

Cisne  silt  loam  and 

Hoyleton  silt  loam 

18 

62 

8 

21 

2 

25 

Ewing 

P 

Cisne  silt  loam  and 

Huey  silt  loam 

9 

58 

9 

21 

1 

22 

Nevton 

0 

Wynoose  silt  loam 

and  Huey  silt  loam 

6 

52 

2 

12 

3 

26 

Sparta 

*See  111.  Bui.  516,  Effect  of  Soil  Treatment  on  Soil  Productivity,  for  history  of 
fields  and  yields  prior  to  19^2. 
**Full  treatment  represents  an  average  of  yields  obtained  on  plots  treated  with 
manure,  limestone,  and  phosphate  (MIP)  and  with  residues,  limestone,  phosphate, 
and  potash  (RIPK). 
***See  SF-21  for  rotations  used.  A  rotation  of  corn-soybeans-wheat-hay  is  used  on 
most  of  the  fields. 


R.  H.  Rust 
11-28-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SP-10 


CORN  ROOT  DISTRIBUTION  IN  FERTILIZED  AND  UNFERTILIZED 
FLANAGAN  SILT  LOAM 


Comparison  of  corn  root  development  in 
fertilized  and  unfertilized  Flanagan 
silt  loam  at  Urbanaj  Illinois^  during 
the  moderately  dry  season  of  195^  shoved 
greater  root  penetration  and  root  growth 
and  also  higher  corn  yield  on  the  ferti- 
lized than  on  the  unfertilized  plot. 

Over  a  long  period^  the  fertilized  plot 
had  received  residue  (stover^  straw,  leg- 
umes), lime,  and  rock  phosphate,  whereas 
the  unfertilized  plot  had  received  only 
crop  residues. 

Soil  tests  indicated  that,  except  for  ni- 
trogen, the  greatest  difference  in  fer- 
tility was  in  the  sizrface  soil,  where 
the  available  phosphorus  was  high  on  the 
fertilized  plot  and  low  on  the  unferti- 
lized plot.  There  was  very  little  dif- 
ference in  available  phosphorus  below 
the  surface  soil,  and  practically  no  dif- 
ference in  acidity  or  in  available  po- 
tassium throughout  the  soil  profiles 
from  the  two  plots. 

Although  Flanagan  is  a  dark-colored,  per- 
meable, naturally  fertile  soil,  crop 
yields  invariably  decrease  with  con- 
tinued farming  unless  a  good  soil  manage- 
ment program  is  followed. 

Corn  yield  was  79  bushels  an  acre  on  the 
fertilized  plot  and  66  bushels  on  the 
unfertilized  plot.  Total  root  weight  on 
the  unfertilized  (r)  plot  was  1,398 
pounds  an  acre,  and  the  roots  penetrated 
to  about  hQ     inches  (see  illustration  on 


back).  To  this  depth  this  soil  is  capa- 
ble of  storing  about  10.5  acre-inches  of 
available  water. 

On  the  fertilized  (RIP)  plot,  total  root 
weight  was  1,  &^6  poiinds  an  acre,  and  the 
roots  penetrated  to  about  60  inches. 
VJith  this  larger  rooting  volume,  the 
soil  had  a  greater  available  soil  mois- 
ture storage  capacity  (l2.8  acre-inches) 
and  a  greater  supply  of  nutrients  for  the 
crop  to  draw  upon. 

Calculated  acre  weights  of  corn  roots  by 
soil  horizons  are  given  in  the  table  on 
page  2.  Soil  horizons  are  marked  on  the 
left  of  the  photographs  on  page  3' 

Roots  were  sampled  with  a  soil-core  sam- 
pling machine  that  took  four-inch  diam- 
eter cores  to  a  depth  of  72  inches. 
Core  samples  were  taken  in  five  concen- 
tric rings  each  four  inches  wide  aroiind 
corn  hills.  In  this  way 
were  obtained  up  to 
corn  hill,  or  halfway 
since  the  corn  was 
inches.  Each  of  the  five  vertical  sec- 
tions of  roots  in  the  photographs  is 
from  one  four-inch  diameter  core  72 
inches  long  at  distances  from  the  corn 
hill  specified  at  the  top  of  the  root 
panels . 

For  comparison  of  corn  root  development 
in  fertilized  and  unfertilized  Cisne 
silt  loam  during  the  moderately  dry  sea- 
son of  1952,  see  Agronomy  Facts  SM-5. 

J,  B,  Fehrenbacher 
12-19-55 


root  samples 

20  inches  from  the 

to  the  next  hill, 

checked  i^-0  by  kO 


-2- 


Calculated 

Calculated 

Percent 

Soil 

root  weights 

root  weights 

of  total 

horizon 

Depth 

per  acre 

per  acre-inch 

roots 

in. 

lb. 

lb. 

perct. 

R  Plot 

^1 

0-li+ 

kkk 

32 

31.8 

^ 

11^-18 

11.5 

36 

10.1+ 

\ 

18-23 

168 

3i^ 

12.0 

\ 

23-39 

1^58 

29 

32.7 

^ 

39-i^3 

85 

21 

6.1 

^1 

^3-5^^ 

77 

7 

5.5 

\ 

5U-72 

21 

1 

1.5 

Total 

1,398 

-- 

100.0 

RIP  Plot 

h 

0-16 

769 

1^8 

1+1.7 

s 

16-20 

li^3 

36 

7.7 

\ 

20-2I4- 

142 

36 

7.7 

\ 

2^4-^0 

435 

27 

23.6 

^3 

ko-k6 

165 

27 

8.9 

^1 

h6-^l 

138 

13 

7.5 

^1 

57-72 

3h 

k 

2.9 

Total 

l,eh6 

-- 

100.0 

CORN  ROOTS  IN   FLANAGAN   SILT  LOAM-R  PLOT 


CORN    ROOTS  IN  FLANAGAN  SILT  LOAM-RLP  PLOT 


INCHES   FROM    HILL 
0  4  9  12  16       20 


SURFACE       Ai 

SliBSURFACE_    Aj^ 
Bi 


SUBSOIL       Ba  JV' 
|te4 


2>: 


SUBSTRATA  b:>  . 


SURFACE  A I 


SUBSURFACE 


SUBSOIL 


B3 


SUBSTRATA 


INCHES    FROM   HILL 
0  4  B  12         16       20 

if 


I  FT 


2  FT 


3  FT 


4  FT 


5  FT 


6  FT 


Corn  roots  in  Flanagan  silt  loam  from  a  fertilized  (RLP)  plot  on  the  left  and 
an  unfertilized  (r)  plot  on  the  right.  In  both  photographs  each  of  the  five 
vertical  sections  of  the  root  panels  is  from  one  soil  core  k  inches  in  diameter 
and  72  inches  long.  Distance  of  each  vertical  section  from  the  corn  hill  is 
indicated  at  the  top  of  the  root  panel. 


jNIVERSin  >-yr  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


I 




SP-11 


THE  PRODUCTIVITY  OF  DARK,  TILL-DERIVED  SOILS  IN  NORTHEASTERN  ILLINOIS 


Soils  in  the  northeastern  one -fifth  of 
Illinois  are  derived  primarily  from  cal- 
careous glacial  till  of  Wisconsin  age. 
Although  most  of  these  soils  are  dark 
colored  and  appear  similar  to  the  casual 
observer^  they  differ  widely  in  produc- 
tivity (Table  l). 

These  differences  in  productivity  of  the 
various  soils  are  related  to  the  texture 
of  the  subsoil  and  underlying  glacial 
till  (SP-7).  The  underlying  parent  ma- 
terial of  Clarence -Rove  soils  contains 
so  much  clay  that  moisture  movement  (data 
in  Soil  Sci.  Soc.  Am.  Proc.^  Vol.  l^i: 
p.  51-55^  1950^  and  Agricultural  Engi- 
neering^ Vol.  30:  p.  38if-386;,  19k9)   and 


root  penetration (unpublished  data  of  J.  B. 
Fehrenbacher )  are  restricted  and  crop 
yields  are  rather  low^  even  under  a 
moderately  high  level  of  management. 
In  contrast^  such  soils  as  Saybrook^ Lis- 
bon^ and  Drummer^  which  are  derived  from 
permeable  loam  till^  produce  consider- 
ably higher  crop  yields  under  comparable 
management.  Such  management  problems  as 
drainage  and  erosion  are  also  much  more 
difficult  on  Clarence-Rowe  soils  than  on 
Saybrook,  Lisbon,  and  Drummer.  The  phys- 
ical properties,  productivity,  and  man- 
agement problems  of  Swygert-Bryce  and 
Elliott -Ashkum  soils  are  intermediate 
between  those  of  the  preceding  two  soil 
associations. 


Table  1. --Average  per  acre  yields*  of  corn,  soybeans,  and  oats  obtained 
by  farmers  on  certain  northeastern  Illinois  soils  under  medium 
and  moderately  high  levels  of  management 


Soil 

Texture  of 
underlying 

Corn 

Soybe 

Me- 

2 ans 

Mod. 

Oat 

s 

associ- 

Me- 

Mod. 

Me- 

Mod. 

ation 

glacial 

dium 

high 

dium 

high 

dium 

high 

area** 

till 

Soil  series** 

mgt. 

mgt. 

mgt. 

mgt. 

mgt. 
bu. 

mgt. 

bu. 

bu. 

bu. 

bu. 

bu. 

C 

Loam 

Saybrook,  Lisbon, 

and  Drummer 

70 

79 

28 

33 

56 

65 

E 

Silty  clay 

loam 

Elliott  and  Ashkum 

62 

66 

27 

30 

50 

53 

G 

Silty  clay 

Swygert  and  Bryce 

56 

6k 

25 

26 

kk 

51 

G 

Clay 

Clarence  and  Rowe 

53 

61 

21 

27 

36 

k9 

*About  95  percent  of  the  yield  data  represent  the  decade  from  19^0  to  1950.  The 
standard  error  of  estimate  of  these  figures,  when  considered  as  10-year  average 
yields,  is  calculated  to  be  approximately  +  5  percent. 
**Described  in  Illinois  Agricultural  Experiment  Station  publication  AG-1^^3^  en- 
titled "Illinois  Soil  Type  Descriptions." 


The  crop  yields  in  Table  1,  which  are 
based  upon  detailed  records  kept  by 
farmers,  are  given  for  two  levels  of 
management.  These  two  management  levels, 
designated 'inedium" and  "moderately  high," 
are  defined  in  terms  of  pounds  of  nitrogen. 


phosphate,  and  potash  used  and  the  in- 
terval of  time  between  legumes  and  the 
crop  under  study. 

For  corn  and  soybeans,  yields  were  cal- 
culated by  assiffiiing  6.1  inches  of  total 


rainfall  and  an  average  maximum  tempera- 
ture of  86  F,  for  the  months  of  July  and 
August.  These  figures  are  averages  for 
the  period  1925-50  reported  "by  the 
weather  stations  in  the  area. 

A  medium  level  of  management  for  estimat- 
ing corn  yields  consisted  of  50  pounds 
of  N  per  acre  in  the  current  and  previ- 
ous year^  contributed  from  both  legume 
and  nonlegiime  sources;  20  pounds  each  of 
equivalent  P2O5  and  K2O  per  acrO;,  applied 
or  estimated  as  residual  from  previous 
applications;  and  a  legume  or  legume - 
grass  mixture  two  years  before  the  corn 
crop. 

Comparable  figures  for  a  moderately  high 
level  of  management  were  100  pounds  of  K 
per  acre_,  kO  pounds  each  of  equivalent 
P2O5  and  KgO  per  acre^  and  the  equiva- 
lent of  a  legume  mixture^  such  as  alfalfa- 
red  clover^  immediately  preceding  the 
corn  crop. 


For  soybeans  and  oats  the  corresponding 
requirements  for  medium  and  moderately 
high  management  were  approximately  70 
percent  (ranging  from  ^+0  to  100  percent) 
of  those  given  for  corn. 

Crop  yields  on  the  Joliet  experiment 
field,  which  is  located  on  Elliott  silt 
loam  and  Ashkum  silty  clay  loam,  are 
given  in  Table  2.  These  data  indicate 
that  both  limestone  and  phosphate  are 
needed  on  these  soils  if  near -maximum 
crop  yields  are  desired.  Comparison  of 
yields  obtained  with  RIPK  treatment  on 
the  Joliet  experiment  field  (Table  2) 
with  the  yields  in  Table  1  for  Elliott 
and  Ashkum  soils  indicates  that  farm 
yields  under  the  moderately  high  level  of 
management  are  approximately  80  to  90 
percent  of  the  yields  with  RLPK  treat- 
ment. These  results  indicate  that  with 
improved  management  practices  farmers 
may  obtain  higher  crop  yields  on  Elliott - 
Ashkum  and  probably  other  till-derived 
soils  in  northeastern  Illinois. 


Table  2. --Average  per  acre  yields  of  corn,  soybeans,  and  oats  obtained 
with  various  soil  treatments*  on  Elliott  silt  loam  and  Ashkum 
silty  clay  loam  at  the  Joliet  Experiment  Field,  19^^-1955 


Yields  with  various  treatments* 


Crop 


** 


RL 


RIP 


RLPK 


First- year  corn  (after  alfalfa — red  clover) 
Second- year  corn  (after  soybeans) 
Soybeans 
Oats 


bu. 

ko 

32 
23 
51 


bu. 
53 

hi 

25 

52 


bu. 
77 

60 

29 
62 


bu. 

8lf 

72 
32 
58 


^Symbols  for  the  various  soil  treatments  are:   0  =  no  treatment;  R  =  crop  residues; 
L  —   limestone;  P  =  rock  phosphate;  K  =  muriate  of  potash.   Refer  to  Illinois  Agri- 
cultural Experiment  Station  Bulletin  5I6  for  information  on  soil  treatment  and 
cropping  prior  to  19^2. 
**The  cropping  system  followed  is  corn,  soybeans,  corn,  oats  (legume  catch  crop), 
wheat,  alfalfa — red  clover. 

R.  T.  Odell 
1-2-1956 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SP-12 


BOTTOMLAND  SOILS  OF  ILLINOIS 


Because  interest  in  the  management  of 
bottomland  soils  has  heen  increasing, 
the  following  brief  discussion  and  the 
key  on  the  opposite  page  are  given  to 
help  identify  such  soils  and  group  them 
J  according  to  their  management  needs  and 
adaptation. 

'  All  of  the  soils  in  the  very  poorly 
drained  column  in  the  key  need  drainage. 
Bonnie_,  Jacob,  Fordyce,  Karnak,  Darwin, 
Turtle  Creek,  Muskrat,  and  Wabash  are  so 
slowly  permeable  to  water  that  drainage 
by  tile  is  usually  not  practical.  In 
such  soils  open  ditches  are  recommended 
and  are  usually  used.  Jacob  is  so  diffi- 
cult to  drain  that  it  is  best  used  for 
timber  or  pasture.  Some  of  the  others, 
like  Karnak,  Darwin,  Muskrat,  and  VJabash, 
sometimes  occur  in  sloughs  where  very 
poor  outlets  make  drainage  impractical. 
Such  areas  are  best  used  for  production 
of  water-loving  species  of  trees  or  for 
wildlife. 


Most  large  areas  of  any  of  the  very 
poorly  to  poorly  drained  soils  except 
Romeo  need  some  dredging  to  get  proper 
outlets  for  either  tile  or  open-ditch 
drainage  systems.  Some  of  the  soils 
having  sandy  substrata,  like  Wewart, 
Riley,  Gorham,  and  Ambraw,  may  present 
difficult  problems  of  ditch-bank  main- 
tenance if  ditches  must  be  cut  through 
them  into  the  sandy,  underlying  mate- 
rials. 

The  soils  in  the  moderately  well  to  well 
drained  column  do  not  need  drainage. 
Some  of  the  soils  in  the  imperfectly 
drained  column,  like  Belknap,  Dupo,  VJake- 
land,  Coffeen,  Tice,  and  Gorham,  need 
drainage  for  best  crop  growth.  Of  this 
group,  Bellaiap  is  least  responsive  to 
tile  drainage,  and  in  it  open  ditches 
are  usually  recommended.  The  others  usu- 
ally have  low  enough  water  tables  and 
are  permeable  enough  to  keep  drainage 
from  becoming  much  of  a  problem. 


Surface  soil  texture  and  also  organic 
matter  content,  of  which  color  is  a 
fairly  good  indicator,  determine  work- 
ability to  a  large  extent.  So  far  as 
possible  in  the  key,  surface  texture  is 
arranged  within  pH  groups,  with  the 
coarser  textures  at  the  top  and  the 
finer  textures  at  the  bottom.  On  the 
fine-textured  soils  (silty  clay  lo.am  or 
finer),  plowing  in  the  fall  and  working 
only  when  moisture  conditions  are  favor- 
able will  help  to  prevent  compaction  and 
cloddiness. 

Assuming  adequate  drainage,  the  light - 
colored  soils  have  the  highest  nitrogen 
needs,  and  the  dark-colored  soils  the 
lowest  nitrogen  needs  for  satisfactory 
crop  growth.  The  strongly  to  moderately 
acid  (pH<5.8)  light-colored  soils  have 
the  highest  limestone,  phosphate,  and 
potash  needs.  Superphosphate  and  mixed 
fertilizers  should  be  used  for  specific 
crops  on  those  soils  that  are  alkaline 
(pH>7.5)»  Limestone  should  not  be  used 
on  the  soils  that  have  high  pH  values. 

Most  of  the  soils  having  pH  values  with- 
in the  range  of  5«8  to  7*5  are  mediiun 
to  high  in  available  phosphorus  and 
available  potassium.  However,  the  soils 
in  this  group  having  pH  values  near  ^.Q 
will  need  some  limestone,  phosphorus, 
and  potassium  to  produce  high  yields  of 
most  crops,  particularly  legimies. 

Two  of  these  bottomland  soils,  Burnside 
and  Romeo,  are  not  well  suited  for  gen- 
eral crops  because  they  have  only  shal- 
low soil  profiles  over  bedrock.  Pasture, 
or  in  some  cases  timber,  is  the  best  use 
for  these  two  soils.  Perks,  because  of 
its  very  sandy  texture,  is  usually 
drouthy  and  not  well  suited  for  simmer 
crops  like  corn  and  soybeans. 

Lack  of  space  makes  it  possible  to  show 
only  the  major  characteristics  that  are 
useful  in  identifying  and  classifying 
the  bottomland  soils  in  the  key. 


, A 

KEY  TO  BOTTOMIAND  SOILS  OF  ILLINOIS 

/ 

( 

Colorft/ 

sur- 
face 
soil 

of 
pro- 
file 

Inches 
of 
sur- 
face 

Texture 

Soil  seriesii/  grouped  according 
to  natural  drainage;^/  of  profile 

Surface  soil 

Below  surface 

Very  poor 
to  Door 

Imperfect 

ModerateOj 
well  to  well 

Light 

<5.8 

12-36 

silt  loam 

sandstone 

Burns ide 

Btirnside 

>8e/ 

silt  loam 

silt  loam 

BeUcnap 

Sharon 

<8 

silt  loam 

silt  loam 

Bonnie 

silty  clay  loam 

silty  clay  loam 

Piopolis 

silty  clay  to  clay 

silty  clay  to  clay 

Jacob 

5.8 
to  7.5 

12-36 

fine  sandy  loam 

sand 

Landes   1 

15-ij-o 

silt  loam 

silty  clay  loam 

to  silty  clay 

Dupo 

Dupo 

Arenzville 

>8 

silt  loam 

silt  loam 

Wake land 

Haymond 

1 

<8 

silt  loam 

silt  loam 

Birds 

silty  clay to  clay 

For dye e 

silty  clay  loam 

silty  clay  loam 

Petroli^ 

silty  clay  to  clay 

silty  clay  to  clay 

KarnakL/ 

>7.5 

>8 

sand 

sand 

Perks 

silt  loam 

silty  loam  to 
siltv  clay  loam 

Jules 

Jules 

Moder- 
ately 
dark 

5.8 
to  7.5 

30-ito 

silt  loam 

sand 

Newart 

clay  loam  to 
silty  clay  loam 

sand 

Newart 

8-30 

silty  clay  loam 

sand 

Riley 

>8 

silt  loam 

silt  loam 

Coffeeni/ 

Coffeeni/ 

Kempers/ 

silty  clay  loam 

silty  clay  loam 

Beaucoup 

Tice 

Allison 

gravelly  clay  loam. 

gravelly  clay  loam 

Beaucoup 

,  / 

clay  loam  to 
silty  clay  loam 

clay  loam  to 
silty  clay  loam 

Ambraw^/ 

GorhamS/ 

silty  clay  to  clay 

silty  clay 
to  clay 

Darwin 
Turtle  Creek 

1 

Dark 

5.8 
to  7.5 

12-30 

silt  loam 

silty  clay  loam 

Radford 

>8 

loam 

sandy  clay 

Muskrat 

sandy  loam  to 
clay  loam 

Otter 

Huntsville 

silt  loam 

silt  loam 

Huntsville 

gravelly  clay  loam 

gravel 

Huntsville 

silty  clay  loam 

silty  clay  loam 

Sawmill 

clay  loam 

silty  clay  loam 

Sawmill 

silxy  clay  to  clay 

silty  clay  to  clay 

VJabash 

>7.5 

>8 

loam  to  silt  loam 

loam  to  silt  loam 

Millington 

DuPage 

DuPage 

2-10 

silt  loam 

limestone 

Romeo 

Romeo 

i 

a/  Light  colors  have  values  of  k   or  more  on  Munsel  soil  color  charts  (dark  gray  to  hrovn  or; 

lighter).  Moderately  dark  color  values  are  usually  3  (very  dark  gray  to  dark  hrown). 

Dark  color  values  are  usually  2  ("black  to  very  dark  "brcvn). 
h/  pH  refers  to  reaction:   pH  <  5.8  is  strongly  to  moderately  acid;  pH  5.8  to  7.5  is 

slightly  acid  to  neutral;  pH  >7.5  is  plkaline  (usually  calcareous), 
c/  Soil  series  name  plus  surface  soil  texture  equals  soil  type  name, 
d/  For  an  explanation  of  natural  soil  drainage  classes,  see  Agronomy  Facts  SP-3. 
e/  The  symbol  >  8  means  more  than  8.  The  symbol  <C  8  means  less  that  8. 
f/  The  pH  of  Karnak  may  be  as  low  as  5«0« 
g/  Tentative  series  (not  yet  correlated), 
h/  Ambrav  and  Gorham  are  sandy  below  Uo  inches. 

J.  B.  Fehrenbacher 
1-23-5^ 

UNIVERSITY  OF  ILLINOIS 


AGRONOMY  FACTS 


.-.ULTURE 


ORGANIC  SOILS  IN  ILLINOIS 


SP-13 


Organic  soils  are  soils  that  contain 
more  than  ahout  25  to  30  percent  of  or- 
ganic matter.  They  occur  in  moist  to 
wet  locations  where  organic  materia.1-- 
primarily  plant  remains --accimiulated 
faster  than  hirnius  decomposed  or  decayed. 


to  the  botanical  composition  of  the  plant 
remains  and  to  the  nature  of  accumula- 
tion. These  in  turn  are  responsible  for 
differences  in  texture ^  color ^  shrinkage, 
etc.;  and  determine  the  uses  to  which 
the  peat  m.aterials  may  be  put. 


Organic  soils  are  of  two  kinds :  peat 
soils  are  those  in  which  the  plant  re- 
mains are  sufficiently  well  preserved  to 
permit  the  plant  forms  to  be  identified. 
Muck  soils  are  those  in  which  the  plant 
remains  are  so  thoroughly  decayed  that 
the  plant  parts  cannot  be  recognized. 

In  most  areas  peat  probably  formed  be- 
fore muck.  Some  muck  may  possibly  have 
formed  without  first  going  through  the 
long  period  of  thick  peat  accumulation. 
The  development  of  muck  in  this  way,  how- 
ever,  would  have  required  short  but  reg- 
ular wet  periods  for  organic  matter  to 
acciomulate,  alternating  with  drier  peri- 
ods for  it  to  decompose.  This  alternat- 
ing wet  and  dry  cycle  would  have  had  to 
continue  throughout  the  entire  period  of 
muck  development. 

About  one-foiirth  to  one -third  of  the 
total  area  of  organic  soils  in  Illinois 
is  peat,  and  the  remainder  is  muck. 
Little  or  no  true  woody  peat  exists,  al- 
though shrubs  and  trees  contributed  part 
of  the  plant  rem.ains  in  som^e  areas,  such 
as  the  area  at  Manito  in  Mason  county. 
Also,  there  is  very  little  true  Sphagnum 
moss  peat  in  this  state.  This  is  the 
strongly  acid  type  of  peat  so  well  kno'i-m 
in  Canada  and  northern  United  States. 
Only  two  small  areas,  located  in  Lake 
coiinty,  are  known  in  Illinois. 

Peat  materials  in  Illinois  are  chiefly 
of  two  kinds:  fibrous  (reed-sedge  vari- 
ety) and  sedimentary  or  colloidal.  Dif- 
ferences between  these  two  peats  are  due 


Fibrous  peat  is  the  most  commonly  kno'^-m 
peat  in  Illinois.  It  is  formed  in  shal- 
low water  from  marsh  plants  like  sedges, 
reeds,  certain  grasses,  and  rushes.  These 
are  upright -growing  plants  that  live 
where  the  watertable  remains  permanently 
at  or  near  the  surface.  A  few  of  the 
more  common  mosses,  particularly  some 
s  ■  :lytrichum  and  Hypnum,  also 
hc_kCL.  ^o  i^iiii  the  fibrous  peat,  but  not 
to  the  same  extent  as  the  m.arsh  plants. 

Fibrous  peat  in  Illinois  is  .  .  ji  or 
felted,  stringy  mass  that  resembles 
firmly  compressed,  half-rc"^""-  -traw.  It 
is  usually  bro^^m  in  color  _-_  .  .ut  neu- 
tral in  rea.ction  it  .3 
large  amounts  of  snaj._L  .^nells  oi-  c-ne_l 
fragments.  The  shells  and  shell  frag- 
ments scm.etimes  give  a  grayish  cast  to 
the  : --"'  '  mass  and  also  provide  an  ex- 
cess 1  /:iount  of  calcium,  carbonate. 
Freshly  exposed  fibrous  peat  usually 
gives  off  hydrogen  sulfide  gas,  which 
has  a  very  distinctive  odor. 

Fibrous  peat  is  low  in  ash,  usuaJ.j.y  con- 
taining: less  than  about  8  to  10  percent. 
It  i  in  organic  matter,  averaging 
f  •  art  between  60  and  70  per- 

-atively  high  in  nitrogen, 
:  ween  2  and  k   percent.    It 

has  about  as  much  total  phosphorus  as 
the  surface  .l;:vr:v  of  an  average  brovm 
silt  loam  pra '  il,  such  as  Saybrook 
or  Elliott.  It  contains  less  total  po- 
tassium and  somewhat  less  total  magnesivim 
than  the  surface  of  Saybrook  or  Elliott. 
It  is-  lered  high  in  cellulose,  hemi- 

cell^^^.^^,.  and  lignin. 


Sedimentary  peat  is  foi-med  in  small 
lakes  where  the  water  is  at  least  a  foot 
or  two  deep.  It  is  composed  primarily 
of  the  remains  of  aquatic  plants^  such 
as  water  lilies,  pondweeds,  and  stone - 
worts,  and  free-floating  plants,  such  as 
algae,  duckweeds,  and  diatoms.  The  re- 
mains of  such  plants  tend  to  disinte- 
grate rather  thoroughly- -except  diatoms, 
which  are  already  very  small --and  upon 
settling  to  the  lake  bottom  form  a  finely 
divided,  incoherent,  structureless  ooze. 

The  sedimentary  type  of  peat  is  mostly 
gray  in  color  and  calcareous--i.e. ,  high 
in  lime--and  will  effervesce  with  dilute 
hydrochloric  acid.  Compared  with  fi- 
brous peat,  it  is  high  in  ash,  averaging 
between  kO  and  50  percent.  It  contains 
less  organic  matter  than  fibrous  peat 
(about  30  percent)  and  considerably  less 
nitrogen  (between  1  and  2  percent ) .  It 
is  also  relatively  low  in  cellulose,  hemi- 
cellulose,  and  lignin. 

Sedimentary  peat  is  soft  and  smooth  when 
wet,  shrinks  greatly  upon  drying,  and 
dries  to  a  fine,  powdery  dust.  This 
dust  is  easily  stirred  up  by  tillage  and 
by  wind,  and  the  diatoms,  which  have  si- 
licified  cell  walls,  cause  itching  when 
the  soil  contacts  the  skin. 

In  Illinois  most  sedimentary  peats  are 
covered  by  a  layer  of  fibrous  peat. 
After  drainage  and  cultivation,  however, 
this  layer  of  fibrous  peat  decays  rapidly 
and  soon  becomes  muck.  Most  mucks  are 
black  and  usually  contain  some  added 
mineral  matter.  Although  muck  soils  are 
harder  to  form  than  the  mineral  soils, 
they  are  more  stable  than  the  peats  and 
usually  need  less  specialized  fertilizer 
treatment  and  management. 

More  than  90  percent  of  the  organic 
soils  in  Illinois  are  in  the  northeast- 
ern one -fifth  of  the  state  or  in  the  re- 
gion lying  north,  northeast,  and  east  of 


McLean  county.  The  few  remaining  im- 
portant areas  are  in  V/hiteside,  Henry, 
Bureau,  and  Mason  counties,  although 
other  small  spots  occur  in  various  other 
parts  of  the  state. 

Individual  areas  of  organic  soils  vary 
in  size  from  small  spots  of  less  than 
one  acre  up  to  more  than  1,000  acres. 
The  combined  area  of  such  soils  in  Illi- 
nois totals  about  25O  square  miles.  Al- 
though this  area  is  small  compared  with 
the  total  area  of  the  state  (about  l/2 
percent),  the  organic  soils  are  extremely 
important  on  the  individual  farms  where 
they  occur.  They  often  differ  radi- 
cally from  the  mineral  soils  with  which 
they  are  associated  in  drainage  and  fer- 
tilizer requirements,  workability,  and 
adaptation  to  crops. 

Three  series  of  organic  soils --Houghton, 
Lena,  and  Edwards - -have  been  established 
in  Illinois  to  date.  Houghton  peat  (No. 
97 )  is  fibrous  peat  that  is  about  neu- 
tral in  reaction,  and  Houghton  muck  (No. 
103)  is  muck  that  is  approximately  neu- 
tral in  reaction  and  that  decomposed  pri- 
marily from  fibrous  peat.  Lena  peat 
(No.  32^)  is  primarily  calcareous  fi- 
brous peat  or  fibrous  peat  that  is  highly 
charged  with  snail  shell  fragments,  and 
Lena  muck  (No.  210 )  is  calcareous  muck 
formed  from  both  calcareous  or  shelly 
fibrous  peat  and  calcareous  sedimentary 
peat.  Edwards  muck  (No.  312)  is  neutral 
to  calcareous  muck  between  12  and  36  inches 
thick  on  marl.  It  is  decomposed  from 
either  fibrous  or  sedimentary  peat.  No 
areas  of  sedimentary  peat  that  are  -cov- 
ered by  fibrous  peat  have  been  mapped. 
A  few  areas  of  peat  and  muck  consisting 
of  shallow  to  mineral  material  of  sand, 
silt,  and  clay  textures  are  known,  but 
to  date  they  have  not  been  described  and 
designated  as  separate  soil  series. 

H.  L.  Wascher 
3-12-56 


UNIVERSirt 


AGRONOMY  FACTS 


SP-14 


FRAGIPANS  IN  ILLINOIS  SOILS 


The  term  fragipan  was  formed  by  combin- 
ing paxt  of  the  Latin  word  fragilis 
(fragi ),  meaning  brittle,  with  the  word 
pan  which,  in  reference  to  soils,  means 
a  horizon  or  layer  that  is  strongly  com- 
pacted and  dense,  indurated,  or  very 
high  in  clay. 

Fragipans  differ  from  claypans  in  usually 
being  relatively  low  in  clay,  but  having 
a  high  silt  and/ or  sand  content.  Fragi- 
pans that  are  high  in  silt  have  often 
been  called  "siltpans."  These  veiy  slowly 
permeable,  dense  horizons  that  are  ex- 
tremely hard  when  dry  usually  occur  in 
soils  in  the  lower  part  of  the  subsoil. 

In  Illinois  fragipans  are  most  common  in 
seme  of  the  upland  soils  in  the  southern 


part  of  the  state.  In  this  area  upland 
soils  that  developed  from  moderately 
thick  and  thin  loess  usually  nave  "pan" 
horizons.  On  the  flats,  claypans  are 
found;  and  on  the  moderately  rolling, 
but  not  steep,  better  drained  areas, 
soils  with  fragipans  are  common.  The 
Grantsburg,  Hosmer,  and  Ava  soils  of 
southern  Illinois  all  have  fragipan  hori- 
zons of  varying  degrees  of  development 
in  the  lower  part  of  their  subsoils.  In 
the  tlilck  loess  areas  bordering  the  Mis- 
sissippi and  Wabash  river  valleys, 
weathering  or  soil  development  has  not 
progressed  far  enough  for  fragipans  to 
have  formed.  However,  there  is  little 
doubt  but  that  soil  development  in  these 
thick  loess  areas  is  in  the  direction  of 
fragipan  formation. 


A|     -Dark    grayish -brown  silt  loam,  crumb     structure. 


A2    -Brownish -yellow    s:  I  t    loom,    ploty     structure. 


Yellowish-brown    silty    clay    loam,     granulor     to 


'         fine     subongulor     blocky     structure. 

Bj    -Yellowish-brown    silty    day   loom,  subongulor    blocky    structure. 

_  Yellowish- brown   silty   clay  loam,     subongulor     blocky 
5roy   '-°i'"' "nodyigj      heovily     cooted     with    gray     silt. 

B   _  Yellowish-brown    silty    cloy   loom    mottled  with    groy, 
priimotlc    Structure     breoking   to    blocky     oggregotes. 


Yellowish-brown     silt    ipom      mottled    with    groy ,  extremely 
Frogipon  —    lorge     prismatic   polygonal     aggregates     or    mony     sided 

blocks     surrounded     by    very     gray     streaks  of    cloy  and  silt. 


The  usual  morphology  of  southern  Illi- 
nois soils  with  fragipan  horizons  is 
shown  in  the  diagram  on  the  opposite 
page.  The  major  type  of  structure  in 
each  horizon  is  shown  in  the  diagram  and 
is  also  indicated  along  with  color  and 
texture  in  the  description  at  the  right. 

The  upper  part  of  the  profile  above  the 
gray  layer  has  uniform  colors  of  a  well 
drained  soil}  hut  because  of  the  mottled 
colors  in  and  below  the  gray  layer,  the 
entire  profile  is  considered  to  be  only 
moderately  well  drained.  Fragipan  hori- 
zons are  mixed  yellowish  brown  and  gray. 
\Then  dry  they  are  very  hard  and  brittle, 
but  upon  thorough  wetting  they  slake 
down  to  a  noncohesive  or  only  slightly 
plastic  mass.  They  seem,  therefore,  to 
be  reversibly  cemented  by  some  agent. 
\lhether  the  cementing  agent  is  chemical 
or  whether  it  is  small  amounts  of  cohe- 
sive clay  between  closely  packed  silt 
particles  is  still  a  question. 


such  as  Grantsburg  and  Hosmer,  water 
moves  readily  through  the  upper  part  of 
the  profile  above  the  gray  layer.  Be- 
cause of  the  very  slow  permeability  of 
the  fragipan,  the  water  often  moves  lat- 
erally in  the  gray  layer  above  the  pan. 
During  late  winter  and  early  spring  the 
upper  part  of  the  profile  often  is  satu- 
rated with  water,  whereas  the  fragipan 
may  be  only  moist.  The  moisture  stor- 
age capacity  of  the  fragipans  of  south- 
ern Illinois,  in  the  range  available  to 
plants,  is  reasonably  good,  but  the  in- 
ability of  roots  to  penetrate  the  pan 
means  that  plants  are  usually  deprived 
of  most  of  this  water. 

In  Illinois  soils  fragipans  occur  at -vari- 
ous depths,  depending  on  soil  type, 
slope,  and  amovmt  of  erosion.  In  most 
uneroded  areas  the  top  of  the  pan  is  be- 
low 2^  or  3  feet.  The  lower  boundary  is 
often  indefinite,  but  the  pan  is  commonly 
2  to  3  feet  thick. 


Fragipan  horizons  are  not  entirely  lack- 
ing in  structure,  although  the  structural 
aggregates  are  usually  very  large,  as 
shown  in  the  diagram  on  the  opposite 
page.  The  large  aggregates  are  separated 
by  gray  or  almost  white  streaks  that  are 
composed  largely  of  clay.  The  sides  of 
the  large  aggregates  next  to  the  gray 
streaks  are  often  covered  with  a  black 
substance.  The  vertical  dimensions  of 
these  large  aggregates,  bounded  by  the 
gray  streaks,  are  usually  greater  than 
the  horizontal  widths  so  that  in  excava- 
tions with  big  machinery,  such  as  is 
used  in  road  construction  or  strip  min- 
ing, the  aggregates  break  out  as  large 
prisms. 

Fragipans  are  very  slowly  permeable  to 
water  and  restrict  root  penetrations 
largely  to  the  gray  streaks.    In  soils 


At  present  there  is  no  proved  and  prac- 
tical means  of  correcting  the  adverse 
conditions  in  fragipans.  Deep  tillage 
or  mechanical  breaking  up  of  the  pan  re- 
quires tremendous  power,  and  the  benefi- 
cial effects  of  such  treatment,  if  any, 
are  unknown.  Chemical  treatment  has  not 
been  tried  to  any  great  extent  to  date. 
Fragipans  usually  have  low  pH  values, 
ranging  from  k.'^  to  about  5»5»  Base 
saturation  and  available  phosphorus  are 
low,  but  available  potassium  is  generally 
moderate  to  high.  The  poor  chemical  prop- 
erties appear  to  be  easier  to  correct 
than  the  adverse  physical  properties. 

Controlling  erosion  on  soils  with  fragi- 
pan horizons  is  doubly  important.  Ero- 
sion not  only  removes  valuable  topsoil, 
but  also  reduces  the  depth  to  the  fragi- 
pan and  thus  reduces  the  rooting  depth 
of  plants. 


J.  B.  Fehrenbacher 
lf-9-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICl  '" 


AGRONOMY  FACTS 


LAllii. 


SP-15 


BASIS  FOR  SEPARATING  AND  CLASSIFYING  SOILS 


Soils  are  characterized  and  classified 
primarily  for  two  reasons:  (a)  to  under- 
stand hov  they  differ  and  why  they  differ 
and  (h)  to  develop^  as  a  result  of  laho- 
ratory,  greenhouse  and  field  research^ 
systems  of  management  suitable  for  dif- 
ferent kinds  of  soils. 

The  identification  and  separation  of 
soil  types  are  hased  upon  the  important 
characteristics  of  the  profile  (see  SP-2)^ 
especially  the  following: 

1.  Color  of  the  various  soil  horizons 

2.  Wumher,  thickness^  and  arrangement 
of  the  horizons 

3.  Texture  of  the  horizons 
k.      Structure  of  the  horizons 

5.  Chemical  characteristics  of  the  ho- 
rizons^ such  as  total  cation  exchange 
capacity,  kind  and  amount  of  ex- 
changeable ions,  percentage  of  base 
saturation,  pH^etc. 

6.  Mineralogical  composition  of  the  ho- 
rizons, with  special  emphasis  on  the 
clay  mineral  fraction. 

Color  is  one  of  the  most  easily  observed 
soil  characteristics.  In  Illinois,  as 
elsewhere,  color  tends  to  indicate  two 
entirely  different  properties:  (a)  or- 
ganic carbon  accumulation  and  (b)  degree 
of  oxidation  and  diffusion  of  iron  and 
manganese  compounds. 

Organic  carbon  is  black  and  its  accumula- 
tion is  responsible  for  the  very  dark 
gray  to  dark  brown  to  black  soil  colors, 
particularly  of  the  upper  or  surface  ho- 
rizons. The  acc^umulation  of  organic 
carbon  (organic  matter)  tends  to  be 
greater  under  grass  vegetation  than 
under  forest,  other  things  being  equal 
(see  SP-1  and  2),  and  greater  under 


anaerobic  (wet)  conditions  than  londer 
aerobic  (dry).  Thus  the  greatest  accumu- 
lation of  organic  carbon  and  resulting 
blackness  of  the  surface  or  "A"  horizon 
occurs  under  grass  vegetation  in  wet 
places.  Oxides  of  manganese  are  also 
dark  brown  to  black,  particularly  in  the 
hydrated  state,  but  in  Illinois  they  are 
never  present  in  sufficient  quantity  to 
produce  more  than  a  few  dark  concretions 
or  dark  splotches  on  some  of  the  soil 
aggregates. 

Oxides  of  iron,  primarily  in  the  ferric 
state,  vary  from  yellowish  brown  to  red- 
dish brown.  Under  aerobic  (well  drained) 
conditions  these  compounds  are  diffused 
throughout  the  soil  mass  (see  SP-3). 
They  coat  so  many  of  the  individual  soil 
particles  that  the  color  is  uniform 
where  it  is  not  obscured  by  organic 
matter.  Under  anaerobic  (poorly  drained) 
conditions  the  iron  compounds  are  in  the 
reduced  state  and  are  more  generally 
concentrated  into  concretions.  It  is 
believed  that,  as  some  soils  age,  mole- 
cules of  water  are  lost  from  the  iron 
compoiHids  and  the  color  gradually  changes 
from  yellowish  brown  to  reddish  brown. 

The  number,  thickness,  and  arrangement 
of  soil  horizons,  discussed  at  some 
length  in  SF-2,  are  also  rather  easily 
observed  characteristics  that  are  used 
in  identifying  soil  units.  Unweathered 
parent  material  is  thought  of  as  having 
one  soil  horizon,  i.e.,  a  "C"  horizon. 
As  weathering  progresses,  horizons  de- 
velop one  by  one.  In  some  areas  in 
Illinois  as  many  as  six  horizons  have  de- 
veloped, each  having  features  that  tend 
to  distinguish  it  from  adjacent  horizons. 
The  soils  known  to  be  most  productive 
for  agricultural  purposes  under  the  cli- 
matic conditions  prevailing  in  Illinois 
are  those  having  a  few  mediijun-textiired 
(loam,  silt  loam,  silty  clay  loam)  hori- 
zons and  a  thick,  dark  surface. 


Texture  is  another  rather  easily  ob- 
served soil  characteristic.  It  often 
varies  markedly  from  one  horizon  to  an- 
other. In  the  field  it  is  determined  "by 
rubbing  some  soil  between  the  thumb  and 
fingers  (see  111.  Cir.  758)^  ^^"t  experi- 
ence is  needed  in  texturing  standard 
samples  before  close  correlations  can  be 
made.  Laboratory  analyses  are  sometimes 
needed  for  final  comparison. 

Textiore  is  a  function  of  relative  parti- 
cle size  and  therefore  is  an  indicator 
of  permeability.  Coarse  materials^  such 
as  gravels  and  sands,  have  large  pores 
through  which  water  moves  freely.  As 
the  particles  become  smaller  and  smaller, 
a  point  is  eventually  reached  in  very 
fine  clay  where  the  pores  are  so  small 
that  moisture  and  air  movement  are  often 
seriously  restricted. 

The  kind  and  arrangement  of  structiiral 
aggregates  in  the  various  soil  horizons 
are  also  useful  in  characterizing  soils. 
The  size,  shape,  and  arrangement  of 
structural  aggregates  give  some  indica- 
tion of  the  moisture -absorptive  capacity 
of  a  horizon,  as  well  as  some  indication 
of  its  permeability.  Loosely  packed 
granular  to  rounded  aggregates  absorb 
water  more  readily  and  permit  easier  air 
and  water  movement  than  tightly  packed 
angular  to  square  or  platy  aggregates. 
But  any  form  of  aggregation  tends  to  pro- 
duce cleavage  planes  or  channels  that 
permit  freer  water  movement  and  root 
penetration  than  would  otherwise  be  pos- 
sible. 

Soil  acidity,  including  the  presence  or 
absence  of  highly  calcareous  material, 
is  used  as  a  criterion  in  separating 
certain  soil  types.  Tests  with  dilute 
hydrccMcric  acid  are  used  to  detect  areas 


of  high-lime  (calcareous)  soils.  pH 
tests  indicate  the  relative  acidity  or 
alkalinity  of  a  soil,  its  probable  re- 
sponse to  liming  materials,  and  its  ap- 
proximate base  saturation.  A  soil  or 
any  one  of  its  horizons  having  a  pH  of 
5.0  or  less  is  considered  strongly  acid. 
It  is  also  likely  to  be  relatively  low 
in  exchangeable  bases,  such  as  calcium, 
magnesiiom,  and  potassium.  Soils  having 
a  pH  of  about  6.0  are  considered  slightly 
acid,  and  many  of  them  will  be  about  70 
to  80  percent  saturated  with  bases. 
Neutral  soils  with  a  pH  of  7-0  are  in 
general  90  to  100  percent  saturated  with 
bases,  whereas  soils  of  pH  8.0  usually 
contain  free  basic  salts,  primarily 
calcium  carbonate  and,  less  frequently, 
salts  of  magnesium  and  sodium. 

The  kind  and  amount  of  clay  minerals  are 
important  in  classification  as  well  as 
in  the  use  and  management  of  many  soils 
(see  SP-8).  Clays  impart  sticky  or 
plastic  properties  to  soils,  and  any  in- 
crease in  clay  above  a  certain  point 
increases  tillage  and  drainage  difficul- 
ties. On  the  other  hand,  any  decrease 
in  clay  content  below  a  certain  point, 
especially  of  montmorillonitic  clay,  re- 
duces the  ability  of  a  soil  to  hold 
nutrients  in  a  readily  available  form 
and  release  them  to  plants. 

The  accurate  characterization  of  soil 
units  consolidates  past  experience  with 
those  units  and  indicates  the  probable 
future  behavior  of  the  soils  under  similar 
conditions.  Classifying  soils  through 
accurately  defined  characteristics  is  not 
only  an  attempt  to  better  understand  and 
interpret  nature,  but  a  means  of  preserv- 
ing in  an  orderly  manner  the  facts  known 
about  the  soils  that  produce  our  food. 


H.  L.  Wascher  and  R.  T.  Odell 

1^-16-56 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


CONTROLLING  WILD  GARLIC  AND  WILD  ONION 


W-6 


It  has  been  estimated  that  wild  garlic 
and  wild  onion  cost  Illinois  farmers 
well  over  a  half -million  dollars  yearly. 
This  loss  is  mainly  through  dockage  in 
wheat  and  does  not  include  loss  of  milk 
and  meat  products  due  to  undesirable 
flavor  caused  by  these  weeds. 


Wild  garlic  (Allium  vineale)  is  much 
more  common  than  wild  onion.  VJild  onion 
(Allium  canadense )  is  found  in  the  same 
areas  as  wild  garlic  but  usually  pre- 
sents a  small  problem  compared  with  its 
neighbor. 


How  to  Tell  the  Plants  Apart 


Wild  garlic 


Wild  onion 


leaves 


Form 
Base 

Cylindrical 
Sometimes  above- 
ground  on  stems 

Bulbs  (undergrovind) 
Number         Clusters  at  base 

of  each  plant 
Covering       Fibrous 
Kind          Hard- shelled  (brown) 

and  soft-shelled 

Flavor  and  odor 

Strong 

Both  of  these  weeds  begin  to  grow  in  the 
fall  from  the  old  plants  as  well  as  from 
the  bulblets.  Fall  growth  starts  any 
time  from  September  to  November,  depend- 
ing on  fall  rains.  Both  weeds  seemingly 
"grow  under  the  snow"  during  the  winter. 
Wild  garlic  begins  to  form  undergro\and 
bulblets  in  March.  In  May  the  aerial 
bulblets  begin  to  form  on  both  wild  gar- 
lic and  wild  onion. 


Both  plants  have  matured  by  small  grain 
harvest,  and  the  aerial  biolblets  are 
harvested  with  the  small  grain.  By  mid- 
July  they  become  dormant,  and  plowing 
or  disking  during  the  summer  has  little 
effect  on  them.  The  old  plants  and  the 
new  bulblets  are  ready  to  start  their 
life  cycle  again  with  the  fall  rains  of 
September  and  October, 

Both  wild  garlic  and  wild  onion  can  be 
controlled  and  eliminated  by  growing 
crops  that  can  be  plowed  in  either  late 
fall  or  early  spring.  If  such  crops  can 
be  combined  with  one  that  can  be  culti- 
vated during  the  growing  season,  such 


Flat 

At  ground  level,  rising 
out  of  the  bulb 


One  at  base  of  each 

plant 
Ketlike 
All  soft-shelled 


Moderate 

as  corn  or  soybeans,  both  weeds  can  be 
eliminated  in  three  to  four  years. 

Plowing  in  late  fall  or  early  spring 
is  particularly  effective  because  it 
smothers  the  plants  that  have  germinated 
and  fall  plowing  usually  prevents  the 
underground  garlic  bulblets  from  form- 
ing. The  cultivated  crop  then  destroys 
any  seedlings  that  may  appear  with  rains 
during  the  growing  season.  Three  or 
four  years  of  this  program  will  practi- 
cally exhaust  all  seeds  or  bulblets  that 
are  in  the  soil, 

2,^-D  is  also  effective  in  destroying 
wild  garlic.  Experiments  conducted  from 
19^8  to  1950  by  the  Agronomy  Department 
showed  that  1  l/2  to  2  pounds  of  2,U-D 
ester  in  late  fall  destroyed  both  the  old 
plants  and  the  newly  germinated  seed- 
lings. The  same  rates  in  early  April 
were  only  slightly  less  effective  than 
the  late  fall  spraying. 

Unfortunately,  winter  wheat  will  not 
tolerate  these  rates  of  2,i|— D.  Only 
pastures  or  stubblefields  can  be  sprayed 
with  these  amounts. 


The  folloving  table  on  wheat  yields  in- 
dicates that  winter  wheat  will  not 
tolerate  a  rate  of  2,k-'D  that  will  effec- 


tively control  aerial  bulblets  without 
seriously  reducing  yields. 


Percent 

Rate  of 

Yield  of 

control  of 

2,l^-D  ester/A 

wheat       aerial  bulhlets 

Fall  Applica 

ticn,  November  22,  1948 

Check 

32.0 

0 

1/8 

28.0 

20 

lA 

31.1 

40 

1/2 

25.3 

65 

1 

23.5 

100 

1  1/2 

20.9 

ICO 

Spring  Appli 

cation,  April, 5^ 

1949 

Check 

21.4 

0 

1/k 

18.8 

25 

1/2 

19.1 

50 

1 

16.4 

70 

2 

lo.o 

eo 

Spring  Application,  April  29, 

,  1949 

Check 

16.8 

0 

l/,3 

16.3 

0 

2/3 

14.4 

10 

11/3 

12.0 

30 

2  2/3 

13.0 

40 

Applications  made  about  the  first  week 
in  April  at  I/2  pound  of  2,4-D  ester  per 
acre  have  had  very  little  effect  on 
wheat  yields  but  have  reduced  aerial 
bulblet  formation  an  average  of  50  per- 
cent. In  addition,  the  remaining  plants 
have  been  so  deformed  that  the  combine 
has  picked  up  very  few  of  them.  Appli- 
cations in  late  April  have  not  been  ef- 
fective in  controlling  garlic  in  winter 
wheat . 

The  best  way  to  control  both  wild  garlic 
and  wild  onion  is  to  change  the  cropping 


sequence  so  that  ctiltivated  crops  are 
grown  continuously  for  three  to  four 
years.  If  this  program  cannot  be  car- 
ried out,  then  applications  of  l/2  pc\and 
of  2,4-D  ester  applied  to  winter  wheat 
about  the  first  week  in  April  will  ma- 
terially reduce  aerial  biilblet  formation 
and  will  gradually  thin  out  stands  of 
wild  garlic.  One  and  a  half  to  2  pounds 
of  2,4-D  acid  in  the  ester  form  is  high- 
ly effective  in  eliminating  garlic  either 
in  pastures  without  legumes  or  in  stub- 
blefields.  The  application  can  be  made 
either  in  late  fall  or  in  early  spring. 


F.  W.  Slife 
10-24-55 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


W-7 


REACTION  OF  VARIOUS  V/EEDS  AND  BRUSH  TO  2,4-D  AND  2,4,5-T 


Many  veeds  and  woody  plants  are  not 
killed  when  sprayed  with  2^i4--D  and 
2,k,'^-T,      while  others  are  easily  con- 


trolled. Following  is  a  listing  of 
various  weeds  and  woody  plants  and  their 
reactions  to  2,U-Dand  2,h,^-1!   herbicides. 


Annuals 


Weeds  and  Their  Reaction  to  2,4-E 
Susceptible  Perennials  &  Biennials  -  Susceptible  (Cont.) 


Beggar-ticks 

Bitter  wintercress 

Black  medic 

Carpet  weed 

Cocklebur 

False  flax 

Flower-of -the -hour 

Hemp 

Hemp -nettle 

Henbit 

Jewelweed 

Kochia 

Lambsquarters 

Marsh  elder 


Morning  glory,  annual 

Mustards 

Peppergrasses 

Pigweeds 

Plantain,  annual 

Prostrate  verbain 

Radish,  wild 

Ragweeds 

Rape,  annual 

Rough  cinquefoil 

Sow  thistle,  annual 

Stinkweed 

Sunflower 

Vetch 

Yellow  star  thistle 


Annuals  -  less  Susceptible 
(plants  may  recover  under  seme  conditions, 


Bedstraw 

Buckwheat,  wild 

Chickweed 

Dodder 

Dog-fennel 

Fleabane 

Goosefoot 

Jimsonweed 


Khotweed 
Lettuce,  wild 
Mallow,  roundleaved 
Purslane 
Russian  thistle 
Shepherd's  purse 
Smartweeds 
Speedwells 
Velvet  weed 


Annuals  -  Not  Susceptible 


Annual  grasses 
Black  nightshade 
Buffalo  bur 
Catchfly 


Corn  cockle 
Cow  cockle 
Wild  cucumber 
Wood  sorrel 


Perennials  and  Biennials  -  Susceptible 
(Frequently  killed  by  one  application) 


Artichoke 
Broadleaf  plantain 
Buckhorn 


Bull  thistle 

Burdock 

Catnip 


Chicory 

Cinquefoils 

Coneflowers 

Creeping  charley 

Dandelion 

Dragonhead 

Evening  primrose 

False  ragweed 

Figwort 

Four-o-clock 

Gummweed 

Heal-all 

Hedge  bindweed 


Hedge  nettle 
Hoary  alyssum 
Horsetail 
Licorice,  wild 
Moonseed 
Kettle,  stinging 
Poppy,  mallow 
Roadside  thistle 
Rosin  weed 
Skelton  weed 
Slender  rush 
Verbains 
Water  hemlock 
VJild  parsnip 


Perennials  &  Biennials  -  Less  Susceptible 
(Tops  are  killed  but  regrowth  may  occur) 


Bouncing  Bett 

Buttercups 

Canda  thistle 

Carrot,  wild 

Docks 

Dogbane 

Field  bindweed 


Goatsbeard 
Goldenrod 
Lettuce,  blue 
Poke weed 
Poverty  weed 
Sorrel,  red 
Teasel 
Yarrow 


Perennials  &  Biennials  -  Wot  Susceptible 


Asters 

Bittersweet 

Bracken 

Catchfly 

Cattail 

Chickweed,  mouse-ear 

Climbing  milkweed 

Ferns 

Foxglove 

Goatweed 

Ground  cherry 

Hoary  verbain 

Milkweeds 


Mullen,  ccmmon 
Nettles,  horse 
Ox-eye  daisy 
Russian  knapweed 
Smartweed,  swamp 
Sorrel,  yellow 
Spurges 

Strawberry,  wild 
Tansy  rag\rort 
Tick-trefoils 
Toadflax 
Violets 
White  cockle 


Woody  Plants 


Woody  Plants  -  Susceptible  (Cont. 


A  mixture  of  2,U-D  and  2,k,'^-1  or 
straight  2.,h,^-']l  is  more  effective  than 
2,4-D  alone  on  most  of  these  plants. 

Vfoody  Plants  -  Susceptible 
(Current  growth  killed  but  retreatment 
may  be  required. ) 


Alder 

Apple ^  crab 
Aspen 
Barberry 
Birch^  black 
Blackberry 
Boxelder 
Buckbrush 


Cherry,  wild 

Cottonwood 

Currant 

Dogwood 

Elderberry 

Elm 

Gooseberry 

Grape,  wild 


Hackberry 
Hazelnut 
Honeysuckle 
Locust,  black 
Mulberry 
Osage  orange 
Persimmon 
Plum,  wild 


Poison  ivy 
Sassafras 
Sumac 
Tamarisk 
Trumpet  vine 
Virginia  creeper 
Walnut,  black 
Willows 


Woody  Plants  -  Not  Susceptible 


Ash 

Basswood 
Bittersweet 
Lead  plant 
Locust,  honey 


Oak 

Raspberries 
Red  cedar 
Rose,  wild 


Earl  C.  Spurrier 
U-30-56 


8/4/2010 

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