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University  of 

Illinois  Library 

at  Urbana-Chajipaign 

ACES 


V.Vt. 
''1 


ACES  l!f?^ARY 
AUb  1  2  2010 

UNtvERsmr  cr  Illinois 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://www.archive.org/details/agronomyfacts01univ 


f/ir-z    iar/i\  TABLE  OF  CONTEITOS 


Miscellaneous 


Some  New  Materials  Being  Sold  as  Soil  Conditioners  and  Fertilizers M-1 

Suitability  of  Illinois  Soil  Areas  for  Ponds M-2 

Hay  and  Grain  Preservatives M-3 

Use  of  Asphalt  in  Establishing  Grass  Seedings  M-^ 

Okaw  Broomcorn M-5 


Corn 


Producing  Hybrid  Corn  Without  Detasseling  C-1 

Rate  of  Planting  Corn C-2 

Stewart's  Disease,  Leaf  Blight  and  Northern  Leaf  Blight  of  Field  Corn  .  .  .  C-3 
Drying  Corn  Grain  at  High  Temperature  Lowers  its  Value  for  Processing  .  .  .  C-ij- 

Cornstalk  Rot  Diseases C-5 

Effect  of  Time  of  Planting  on  Yield  of  Corn C-6 


Forage  Crops 


Selecting  Alfalfa  Varieties  F-1 

Nonhardy  Alfalfas  F-2 

Birdsfoot  Trefoil  F-3 

Strains  of  Bromegrass F-k 

Effect  of  Seed  Treatment  on  Small-Seeded  Legumes F-5 

Red  Clover  Diseases F-6 

Red  Clover  Seed  Supplies  and  Variety  Recommendations  for  Illinois  F-7 

Use  and  Management  of  Grass-Legiome  Mixture  in  Pastures F-8 

Tall  Fescue  vs.  Smooth  Bromegrass  F-9 

Ladino  Clover  F-10 

Common  Alfalfa  Diseases  F-11 


Small  Grains 


Oat  Varieties  for  Illinois G-1 

195^  Oat  Varieties  for  Illinois G-1  revised 

Crown  Rust  of  Oats  (puccinia  coronata  avenae) G-2 

Grey  Spot  of  Oats G-3 

Row  Spacing  for  Small  Grains G~k 

Sow  Spring  Grains  Early  G-5 

Nitrogen  for  Illinois  Wheat G-6 

Drilling  vs.  Broadcasting  of  Oats G-7 

Loose  Smut  of  Wheat G-8 

Stinking  Smut  (Bunt)  of  Wheat G-9 

Seed  Treatments  for  Small  Grains G-IO 


Soybeans 


Soybean  Varieties    S-1 

Soybean  Varieties    S-1  revised 

Soybean  Disease  and  the  Weather S-2 

When  to  Seed  Soybeans S-3 

Effective  Methods  and  Rates  of  Seeding  Soybeans    .  -  -    -        .    .   S-^ 

ACES  LIBRARY 

UNIVERSITY  OF  ILLINOIS 

1101  S  GOODWIN  AVE 

URBANA,  IL  61801 


-2- 
Soil  Management  and  Conservation 

Loss  of  Plant  Nutrients  by  Leaching  From  Three  Illinois  Soils SM-1 

Krilium  and  Other  Soil  Conditioners  , SM-2 

Fundamentals  of  Maintaining  Soil  Tilth SM-3 

Published  Information  of  the  Characteristics  and  Distribution  of  Different 

Kinds  of  Soils  in  Illinois SM-4 

Effect  of  Soil  Treatment  on  Corn  Roots SM-5 

Mulch  Cover  Saves  Aggregates  in  the  Surface  Soil SM-6 

Importance  of  Soil  Clays  in  Plant  Growth SM-7 

Slick  Spots SM-8 

How  Much  Water  and  Plant  Nutrients  are  Lost  by  Runoff  and  Erosion  From 

Gently  Sloping,  Permeable,  Dark-Colored  Soils  in  Illinois? SM-9 

Management  Practices  and  Crops  Adapted  to  Sandy  Soils SM-10 

What  Do  We  Know  About  Deep  Tillage? SM-11 

Soil  Fertility  and  Testing 

The  Nature  of  Soil  Acidity SF-1 

The  Nature  of  Available  Potassium  in  Soils SF-2 

The  Nature  of  Available  Phosphorus  in  Soils SF-3 

The  Nature  of  Available  Nitrogen  in  Soils SF-i^ 

Principles  of  Fertilizer  Use  Based  on  Soil  Reactions 

1.  Phosphates SF-5A 

2.  Potassium,  Sulfur,  and  Boron SF-5B 

3.  Nitrogen  and  Mixed  Fertilizers SF-5C 

Kinds  of  Nitrogen  Fertilizer SF-6 

The  Illinois  Soil  Testing  Program SF-7 

Legumes  as  Nitrogen  Fixers SF-8 

Foliar  Spray  Application  of  Fertilizer  Materials SF-9 

Illinois  Soil  Experiment  Fields SF-10 

Nitrogen  and  Soil  Organic  Matter SF-11 

Using  Borax  Fertilizer  on  Illinois  Soils SF-12 

Fall  vs.  Spring  Plowing SF-13 

Soil  Tests:  Their  Changes  With  Fertilizer  Applications SF-lU 

Soil  Fertility  Maintenance SF-15 

Principles  of  Testing  for  Available  Soil  Phosphorus SF-I6 

Methods  for  Determining  Nitrogen  Requirements SF-l? 

Rotations SF-I8 

The  Nature  of  Reserve  and  Active  Soil  Acidity SF-19 

The  Minor  Element  Problem  in  Illinois  Soils SF-20 

Corn  Yields  -  Illinois  Soil  Experiment  Fields SF-21 

Wide-Row  Spacing  of  Corn SF-22 

Nitrogen  Is  the  Key  to  Good  Organic  Matter  Use SF-23 

Soil  Reaction  Preferences  of  Crops SF-2U 

Corn  as  a  Soil  Builder SF-25 

Organic  Matter  Replenishment SF-26 

Evaluation  of  Catch  Crops SF-27 

Weed  Control 

Giant  Foxtail  (Setaria  faberii)  W-1 

Controlling  Weeds  in  Soybeans  W-2 

Brush  Control W-3 

WOS:mw 
2-18-55 


UNIVERSITY  OF  ILLINOIS      COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M-1 


SOME  NEW  MATERIALS  BEING  SOLD  AS  SOIL 
CONDITIONE.R5  AND  FERTILIZERS 


WHAT  IS  "CALFIDE"? 

A  material  knovn  as  "Calfide"  is  being 
sold  as  a  soil  conditioner  in  certain 
counties  of  Illinois.  Because  it  is 
sold  as  a  soil  conditioner,  and  not  as  a 
fertilizer,  the  company  is  not  required, 
under  Illinois  fertilizer  law,  to  show 
any  analysis. 

We  wrote  two  letters  to  the  Calcium  Com- 
pany of  Salida,  Colorado,  producer  of 
this  material,  asking  for  information 
regarding  its  identity  and  value,  but 
received  no  answer. 

We  then  wrote  to  various  agencies  in  Col- 
orado and  to  the  Kansas  Experiment  Sta- 
tion, where  it  was  tried  out  in  plot  and 
greenhouse  experiments  last  year.  Fol- 
lowing are  excerpts  from  the  replies  we 
received: 

Agronomy  Department,  Colorado  A.  &  M. 
College,  Fort  Collins,  Colorado 

"I  have  no  complete  analyses  of  this 
product  and  we  have  not  used  it  in  any 
experiments;  however,  I  am  informed  by 
the  State  Department  of  Agriculture  of 
Colorado  that  it  contains  22  percent 
calcium,  15.5  percent  sulfur, and  is  evi- 
dently composed  primarily  of  gypsum.  We 
would  consider  the  product  of  some  value 
in  treating  high  alkaline  soils  with  a 
high  sodium  percentage,  but  it  is  of  no 
other  particular  value." 

Colorado  Department  of  Agriculture,  Den- 
ver, Colorado 

"Calfide  is  recognized  in  the  state  of 
,  Colorado  as  a  gypsum  product  containing 
approximately  20  percent  calcium, 15  per- 
cent sulfur,  and  iron,  copper,  lead, 
zinc,  magnesium,  cobalt,  phosphorus  and 
potash. 


"Our  law  allows  this  to  be  registered  as 
a  soil  amendment  not  sold  as  a  fertili- 
zer, and  the  only  use  we  can  permit  them 
to  advertise  in  our  state  is  for  a  cor- 
rective with  alkaline  soils." 

Kansas  Agricultural  Experiment  Station, 
Garden  City  Branch  Station,  Garden  City, 
Kansas. 

"So  far  as  we  can  determine  this  materi- 
al is  gypsum.  It  was  originally  sold  by 
the  Arkansas  Valley  Gypsum  Company  of 
Salida,  Colorado,  as  gypsum.  We  have 
made  a  number  of  tests  with  this  materi- 
al in  the  field  and  in  the  greenhouse 
and  have  had  absolutely  no  response.  It 
is  our  opinion  that  this  material  will 
do  only  a  small  part  of  the  claim  made 
for  it.  Where  gypsum  can  be  used  to  ad- 
vantage, this  material  might  be  substi- 
tuted." 


A  news  release 
states: 


from  Purdue  University 


"A  material  known  as  'Calfide'  is  being 
sold  in  certain  counties  in  Indiana  as  a 
soil  conditioner  at  prices  up  to  $7'+-50 
a  ton.  The  office  of  the  state  chemist 
at  Purdue  University  reports  that  this 
material  is  not  a  fertilizer,  but  that 
it  appears  to  be  from  a  deposit  which 
contains  limestone  and  gypsum." 

It  has  been  reported  that  salesmen  claim 
this  material  to  be  radioactive.  The 
value  of  radioactive  material  in  crop 
production  has  been  thoroughly  studied 
by  this  and  other  experiment  stations 
and  by  the  U.  S.  Department  of  Agricul- 
ture. In  none  of  these  experiments  have 
radioactive  materials  shown  any  benefit. 

Under  certain  conditions,  gypsum  might 
be  of  some  benefit  as  a  soil  conditioner 
and  as  a  supplier  of  calcium.  The  gyp- 
sum itself  does  not  correct  acidity;  the 


value  would  te  in  any  limestone  that 
might  be  mixed  with  the  gypsum.  In  the 
amounts  recommended,  however,  the  amount 
of  limestone  would  be  so  small  as  to 
have  no  practical  value  for  correcting 
acidity.  The  ordinary  Illinois  lime- 
stone will  do  the  job  better  and  many 
times  cheaper. 


occurs  very  slowly.  Granite  dust  con- 
tains about  ^  or  5  percent  total  potash 
that  would  become  available  so  slowly 
and  in  such  small  amounts  as  to  make  it 
of  no  practical  value  as  a  potash  ferti- 
lizer. 

WHAT  IS  GREEWSAWD  MARL? 


As  two  of  the  previously  quoted  letters 
point  out, calcium  sulfate  is  used  effec- 
tively in  the  West  in  helping  to  get  rid 
of  the  sodiiim  in  black  alkali  soil.  But 
black  alkali  is  altogether  different 
from  the  common  alkali   soils  of  Illinois. 

WHAT  IS  GRANITE  DUST? 

Granite  dust  is  being  sold  under  the 
trade  name  of  "Hybro-Tite"  as  a  source 
of  potash  and  various  trace  minerals. 

An  important  mineral  in  granite  rock  is 
felspar.  A  large  part  of  the  potassium 
in  soils  occurs  in  the  form  of  felspar 
potassium.  The  potassium  in  this  miner- 
al is  not  available  to  plants  until  the 
mineral  breaks  down,   and  this  breakdown 


Greensand  marl, also  known  as  glauconite, 
is  being  sold  under  the  trade  name  of 
"Kaylorite"  for  use  as  a  potash  ferti- 
lizer. This  material  is  found  in  large 
deposits  in  New  Jersey  and  other  eastern 
states.  The  advertisements  claim  that 
it  contains  8  percent  total  potash  but 
only  about  1  l/2  percent  available  pot- 
ash. 

Probably  the  best  way  to  answer  inquir- 
ies about  greensand  marl  is  to  compare 
the  1  1/2  percent  available  potash  it 
contains  with  the  50  or  60  percent 
available  in  muriate  of  potash.  The 
trace  elements  it  is  also  claimed  to 
contain  would  have  no  practical  value 
for  Illinois  soils. 


C.  M. 


Linsley 
1/12/53 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M-2 


SUITABILITY  OF  ILLINOIS  SOIL  AREAS  FOR  PONDS 


Because  water  storage  is  the  main  func- 
tion of  farm  ponds, V  it  is  important 
that  there  he  no  appreciable  loss  hy 
seepage.  Gravel,  sand,  coarse  silt,  and 
fissured  rock  do  not  hold  water  satis- 
factorily. On  the  other  hand,  clay  is 
generally  impenneable  or  only  very 
slowly  permeable.  For  this  reason  areas 
that  have  clay  subsoils  or  substrata 
usually  provide  good  sites  for  farm 
ponds . 

In  Illinois  the  permeability  of  the 
soils  and  underlying  materials  varies 
tremendously  from  one  area  to  another. 
These  differences  are  important  in  de- 
termining whether  an  area  is  suitable 
for  pond  sites.  On  the  basis  of  permea- 
bility of  the  subsoil  and  substrata,  Il- 
linois soils  have  been  divided  into  five 
main  groups  (Figure  1  and  Table  l)  ac- 
cording to  their  suitability  for  farm 
ponds.  The  characteristics  of  these 
groups  are  described  below: 


SUITABILITY      OF 

DIFFERENT     SOIL 

AREAS    IN    ILLINOIS 

FOR   POND    SITES 


LEGEND 

1  I  ^  VERY  GOOD 

2  ns    GOOD 

3  C:J    FAIR 

4  rZl  POOR 

5  ;_J  VERY  POOR 


NIVERSITT     Of     II.LIMOIS     UniCULTURAL    EXPEOiyENT    STATION 


Fi";ure  1 


Group  1.  There  are  many  excellent  pond 
sites  in  soil  association  areas  M,  N,  0, 
P,  and  w2/  in  southern  and  southwestern 
Illinois,  where  the  soils  developed  from 
thin  to  moderately  thick  loess  on  weath- 
ered drift.  Here  the  subsoils  are  fine 
textured  and  so  slowly  permeable  to 
water  that  little  or  no  seepage  will  oc- 
cur if  the  pond  is  properly  constructed. 

The  underlying  Illinoian  drift  is  also 
slowly  permeable  except  on  a  few  coarse- 
textured,  isolated  morainal  ridges,  no- 
tably those  that  extend  from  Pana  south- 
west to  Greenville.  It  is  fortunate 
that  surface  water  supplies  may  be  ob- 
tained easily  in  Group  1  because  ground- 
water is  often  deficient. 

Good  ponds  may  be  easily  constructed  in 
the  silty  clay  and  clay  till  areas  (area 
G)  of  northeastern  Illinois  because  the 
soils  and  underlying  calcareous  till  are 
nearly  impermeable.  However,  the  need 
for  ponds  is  not  great  because  good 
groiindwater  supplies  are  available  from 
the  drift  and  bedrock. 

Group  2.  It  is  rather  easy  to  construct 
good  ponds  in  northeastern  Illinois 
where  the  predominant  underlying  materi- 
al is  a  silty  clay  loam  glacial  till  (a- 
reas  E,  F,  and  V) .  But  here  again  the 
need  is  not  great  because  groundwater 
supplies  are  generally  adequate. 

In  the  hilly,  unglaciated  section  of  ex- 
treme southern  Illinois  (area  X), ground- 
water is  deficient  and  ponds  are  needed 
to  store  surface  runoff.  The  loess- 
derived  soils  are  sufficiently  impermea- 
ble to  make  it  possible  to  construct 
good  ponds.  Where  the  loess  is  thin, 
however,  it  is  advisable  not  to  choose  a 
site  where  there  is  fissured  rock.  In 
the  part  of  area  0  farthest  from  the 
bluff,  permeability  is  slov;  enough  to 
prevent  seepage . 


Tatle  1, --Suitability  of  Predominant  Illinois  Soils  for  Pond  Sites 


Group 
No. 


Permeability 


Suitability 


Subsoil 


Substrata 


Groundwater 

supply 


Very  good  (M,  K,  0,  P,  W)  Very  slow  to  slow  Very  slow  to  slow 

Very  good  (G)  Very  slow  to  slow  Very  slow  to  slow 

Good  (E,  F,  V)  Slow  to  mod.  slow  Slow  to  mod.  slow 

Good  (Q  away  from  bluff, X)  Slow  Generally  slow 


3   Fair  (Q  near  bluff,  Z) 


Fair  (K,  L) 

Fair  (C,  D,  H,  l) 

k 

Poor  (J,  T,  U) 

5 

Very  poor  (R,  Y) 
Very  poor  (a,  B,  S) 

Slow 


Slow  to  moderate 


Mod.  slow  to  mod.   Slow  to  moderate 
Moderate  Moderate 


Deficient 
Adequate 

Adequate 
Deficient 

"Deficient  (Q) 
.Adequate  (z) 

Adequate 

Adequate 


Moderate 


Mod.  to  mod.  rapid  Adequate 


Moderate  Moderate  to  rapid  Adequate 

Mod.  rapid  to  rap.  Mod.  rapid  to  rap.  Adequate 


Group  3 •  In  the  parts  of  area  Q  nearest 
the  bluff,  ponds  are  frequently  needed, 
but  sites  must  be  carefully  chosen.  In 
general  the  subsoils  are  slowly  permea- 
ble, but  the  underlying  deep  loess  is 
often  permeable  enough  to  permit  exces- 
sive seepage. 

In  the  gray  terrace  and  bottomland  soils 
of  southern  Illinois  (area  Z),  the  sub- 
soils are  fine  textured  and  slowly  per- 
meable enough  to  be  adapted  to  pond  con- 
struction, but  the  underlying  material 
is  variable  and  requires  careful  inves- 
tigation. Ponds  are  generally  not  needed 
because  groundwater  supplies  are  avail- 
able. 

Many  good  ponds  have  been  constructed  in 
areas  K  and  L,  but  several  factors  need 
to  be  considered  in  selecting  sites. 
The  soils  are  developed  from  thick  to 
moderately  thick  loess  over  weathered 
Illinoian  glacial  till  or  calcareous 
Wisconsin  till.  Where  only  moderately 
underlain  by  weathered 
as  in  west-central  Illi- 
nois, there  is  less  danger  of  seepage 
than  where  the  loess  is  deeper  near  the 
bluff  or  where  it  is  underlain  by  calcar- 
eous Wisconsin  till,  as  in  north-central 
Illinois. 


thick  loess  is 
Illinoian  till. 


Care  must  also  be  taken  in  selecting 
sites  for  ponds  in  areas  C,  D,  H,  and  I, 
because  the  subsoils  and  underlying  cal- 
careous loam  till  are  moderately  perme- 
able to  water,  and  seepage  will  occur  on 
all  except  the  better  sites.  Fortunate- 
ly, ponds  are  generally  not  needed  in 
these  areas  because  good  groundwater 
supplies  are  available  from  drift  or  bed- 
rock. 

Group  k .  In  area  J  the  deep  permeable 
loess  makes  it  difficult  to  find  sites 
for  ponds  where  excessive  seepage  will 
not  occur.  Satisfactory  sites  are  also 
scarce  in  areas  T  and  U,  because  the 
loess -derived  soils  are  permeable  and 
are  generally  underlain  by  bedrock  that 
may  be  fissured. 

Group  3 .  The  medium-textured,  dark- 
colored  bottomland,  terrace,  and  outwash 
soil  areas  (R  and  Y)  contain  very  few 
satisfactory  pond  sites.  The  subsoils 
are  moderately  permeable  and  the  under- 
lying stratified  materials  are  variable 
but  sufficiently  permeable  to  allow 
water  to  move  freely  both  horizontally 
and  vertically.  Because  groundwater  is 
plentiful,  ponds  are  rarely  needed,  how- 
ever. 


Soils  developed  from  coarse-textured 
till  or  sandy  material  in  areas  A,  B, 
and  S  make  poor  pond  sites.  The  sub- 
soils and  underlying  materials  are  gen- 
erally so  permeable  that  water  moves 
readily  downward  to  the  watertable.  How- 
ever^ adequate  groundwater  makes  it  un- 
necessary to  rely  on  ponds  for  water  in 
these  areas. 

Not  all  of  the  soils  and  soil  conditions 
in  Group  1  are  particularly  well  adapted 
to  pond  sites,  and  not  all  of  those  in 
Group  5  are  poorly  adapted.  The  rfeason 
is  that  there  are  local  soil  variations 
that  could  not  be  shown  in  Figure  1. 
Even  a  detailed  soil  map  does  not  pro- 
vide enough  information  to  make  it  pos- 
sible to  choose  a  pond  site  without  fur- 
ther investigation. 

The  best  way  to  select  a  location  is  to 
bore  holes  in  a  number  of  places  to  find 
out  whether  the  soil  is  sufficiently  im- 
pervious to  water.  Even  in  impervious 
areas  there  may  be  permeable  wash  in  the 
bottom  of  natural  watercourses.  This 
permeable  wash  material  should  be  re- 
moved or  avoided  if  possible.  It  should 
not  be  used  in  the  earth  fill,  except 
possibly  on  the  dry  side  of  the  dam. 

If  it  is  necessary  to  construct  a  pond 
on  moderately  permeable  soils,  con- 
trolled siltingl/  may  help  to  make  it 
watertight.  Puddling  the  soil  in  the 
bottom  may  also  be  helpful. 


In  extreme  cases  a  layer  of  clay  may  be 
placed  over  permeable  soils  to  reduce 
seepage;  or  a  swelling  type  of  clay  min- 
eral, such  as  sodium  bentonite  (mont- 
morillonite) ,  may  be  used  to  seal  pores 
in  open  soil  material.  Sodium  bentonite 
absorbs  nearly  five  times  its  weight  in 
water  and  occupies  about  five  times  as 
much  space  when  fully  saturated  as  when 
dry.  The  bentonite  may  be  used  in  any 
one  of  these  three  ways: 

1.  Spread  evenly  over  the  surface  at 
the  lace  of  about  1  pound  of  bentonite 
per  square  foot  of  soil,  and  then  mix 
with  the  top  three  or  four  inches  of 
soil  by  harrowing  or  hand  raking. 

2.  Spread  a  layer  of  bentonite  carefully 
over  the  surface,  and  cover  with  a  layer 
of  soil  or  sand  two  to  four  inches  thick. 

3.  Sprinkle  coarse  particles  {k  to  20 
mesh)  of  bentonite  on  the  surface  of  the 
water  in  an  undrained  pond.  They  will 
sink  to  the  bottom,  swell,  and  form  a 
water-repellent  gel. 

In  constructing  a  pond,  first  remove  the 
topsoll  from  the  entire  area.  Then  use 
the  least  permeable  material,  such  as 
the  subsoil,  in  the  core  or  center  of 
the  dam,  the  next  best  on  the  wet  side, 
and  the  most  permeable  on  the  dry  side. 
The  topsoll  maybe  pushed  back  on  the  dry 
sides  of  the  dam  after  the  fill  is  com- 
pleted. 


1/  Although  ponds  are  sometimes  used  for  gully  control,   this  purpose  is  not  in- 
cluded here. 
2/  For  soil  association  areas,  see  111.  Agr.  Exp.  Sta.  Pub.  AGlUl+3,  entitled  "Illi- 
nois Soil  Type  Descriptions." 
3/  Excessive  silting,  such  as  may  occur  if  ponds  are  located  in  deep,   active  gul- 
lies or  downstream  from  cultivated  land,  is  undesirable  and  should  be  avoided. 

R,  T.  Odell 
2/23/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M"3 


HAY  AND  GRAIN  PRESERVATIVES 


Chemical  compounds  are  being  offered  for 
sale  that,  if  applied  at  the  rate  of  5 
to  10  pounds  per  ton  of  crop,  supposedly 
prevent  moist  hay  or  grain  from  spoiling. 
Because  large  volumes  can  be  treated  rap- 
idly, the  use  of  such  chemicals  would 
appear  to  be  an  excellent  emergency  meas- 
ure for  preserving  crops  when  bad  weath- 
er prevents  proper  curing. 

Farmers'  interest  has  resulted  in  large 
sales  and  use  of  these  compounds.  Both 
success  and  failure  have  been  reported 
from  their  use .  Research  at  experiment 
stations,  however,  has  not  shown  these 
materials  to  be  effective. 

Why  these  contradictory  results?  Much 
of  the  moisture  in  crops, especially  hay, 
that  are  considered  unsafe  for  storage 
is  border  line.  Whether  they  are  treated 
or  not,  some  of  them  will  undergo  a  pro- 
longed "sweating"  period  that  involves 
mild  heating  and  some  condensation  of 
moisture  near  the  surface.  Although  the 
heating  causes  considerable  loss  of  dry 
matter,  the  farmer  is  not  aware  of  the 
loss  if  the  end  product  has  good  color 
and  is  free  from  visible  mold.  For  this 
reason  farmers  who  use  compounds  to  pre- 
serve hay  or  grain  that  appears  to  be 
too  moist  for  safe  storage  are  convinced 
that  the  chemical  is  beneficial  if  the 
crop  does  not  mold.  Some  of  them  will 
even  write  testimonials  to  that  effect. 

Manufacturers  of  hay  and  grain  preserva- 
tives have  a  strong  advantage  in  promot- 
ing their  use  because  most  of  the  time 
crops  thought  to  be  unsafe  for 
are  not  severely  damaged, 
hay  or  grain  is  definitely 
store,  the  treated  crop 
musty  or  moldy  and  there  will  be  more 
heating,   possibly  to  the  point  where 


storage 

But   if  the 

too  wet  to 

will  become 


charring  and  spontaneous  combustion  oc- 
cur. Because  of  the  possibility  of  com- 
bustion, it  is  dangerous  to  rely  on  in- 
effective compounds  to  preserve  moist 
hay  and  grain.  Then  crop  and  building, 
as  well  as  animals  and  stored  machinery, 
may  be  lost . 

Research  indicates  that  preventing  mold 
growth  in  moist  hay  or  grain  will  elimi- 
nate most  of  the  problem  of  heating  and 
deterioration.  Certain  preservatives 
are  claimed  to  be  effective  because  they 
release  carbon  dioxide,  which  inhibits 
mold  growth. 

Molds  will  not  grow  in  an  atmosphere  of 
pure  carbon  dioxide,  but  they  will  grow 
in  high  concentrations  of  carbon  dioxide 
if  some  oxygen  is  present.  It  is  impos- 
sible to  exclude  oxygen  from  the  average 
hay  stack  or  grain  bin.  Also,  if  carbon 
dioxide  would  prevent  mold  growth  in 
stored  crops,  then  moist  hay  or  grain 
would  preserve  itself,  because  one  ton 
of  the  moist  crop  releases  100  times  as 
much  carbon  dioxide  as  5  to  10  pounds  of 
sodium  bicarbonate  (baking  soda) ,  which 
is  the  principal  active  ingredient  of 
many  so-called  hay  and  grain  "preserva- 
tives." 

Drying  compounds  have  also  been  suggested 
for  treating  moist  hay  and  grain.  The 
object  is  to  reduce  moisture  content  to 
a  level  where  molds  can't  grow.  To  re- 
duce one  ton  of  hay  with  35  percent  mois- 
ture down  to  25  percent,  265  pounds  of 
water  must  be  quickly  removed  or  the  hay 
will  mold.  This  would  require  about  60O 
pounds  of  silica  gel,  one  of  the  most 
effective  drying  substances. 

It  is  not  feasible  to  use  the  quantity 
of  chemical  necessary  to  dry  moist  hay. 


Incidentally,  mold  will  grow  in  hay  if 
the  moisture  content  is  above  15  percent, 
but  it  usually  does  not  cause  excessive 
damage  if  the  hay  contains  only  25  per- 
cent moisture  or  less  when  stored. 
Sweating  reduces  the  moisture  content  to 
about  15  percent,  but  at  the  same  time 
about  a  5  percent  loss  of  dry  matter  oc- 
curs. 

Can  moist  hay  and  grain  be  preserved  by 
treating  with  certain  chemicals?  Yes, 
but  there  are  no  compounds  on  the  market 
that  are  known  to  be  effective.  Certain 
organic  fungicides  will  definitely  pre- 
vent mold  growth  on  moist  hay  and  grain, 
and  they  do  not  appear  to  be  toxic  to 
animals  eating  the  treated  crops.  But  at 
present  these  materials  are  not  being 
sold  because  of  cost  or  problems  in  han- 
dling. 

A  compound  is  not  satisfactory  as  a  hay 
or  grain  preservative  unless  it  is  a 
strong  fungicide.   If  it  is  a  strong 


fungicide,  it  must  be  carefully  tested 
to  be  sure  it  is  not  toxic  to  humans 
handling  it  and  to  animals  eating  the 
treated  crop. 

Before  a  chemical  is  used,  tests  must  be 
made  to  determine  whether  it  appears  as 
a  residue  in  the  animal  product,  milk, 
or  meat.  Not  only  must  it  leave  no  res- 
idue, but  it  must  be  inexpensive.  It 
costs  $5  a  ton  to  treat  moist  hay  with 
the  cheapest  fungicide  that  has  shown 
promise  as  a  hay  and  grain  preservative. 
This  compound  has  other  limitations  that 
prevent  it  from  being  recommended. 

Although  it  is  possible  to  preserve 
moist  hay  and  grain  with  chemicals,  at 
present  it  is  not  feasible.  Furthermore, 
it  is  dangerous  to  rely  on  ineffective 
compounds  to  preserve  these  crops  when 
spontaneous  combustion  may  occur  and 
cause  large  losses.  Drying  or  in  some 
cases  ensiling  is  now  the  only  reliable 
method  for  handling  either  moist  hay  or 
moist  grain. 

Keith  Kennedy 
3/30/53 


f 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


;y\-4 


USE  OF  ASPHALT  IN  ESTABLISHING  GRASS  SEEDINGS 


Asphalt  has  been  used  in  various  forms 
for  centuries  as  a  road  "building  mate- 
rial. It  has  been  hard  enough  to  with- 
stand traffic  and  at  the  same  time  pre- 
vent vegetation  from  growing  through  the 
roadway.  Now,  with  certain  chemical  and 
physical  changes  in  the  preparation  of 
the  asphaltic  material,  it  will  remain 
soft  enough  for  plants  to  grow  through 
it  and  at  the  same  time  be  nontoxic  to 
vegetation.  It  can  therefore  be  used  as 
a  means  of  stabilizing  the  soil  against 
erosion  during  the  time  grass  stands  are 
being  established. 


The  length  of  the  normal  seeding  season 
can  be  extended  somewhat  by  using  as- 
phalt. Tests  show  that  temperatures  are 
from  3°  F-  to  l8°  F.  warmer  in  the  as- 
phalt treated  plots  than  in  the  check 
plots.  Evaporation  is  also  cut  down, 
providing  a  better  moisture  relation  for 
the  young  plants. 

Tests  have  also  been  made  on  terrace  out- 
lets in  cooperation  with  the  Soil  Conser- 
vation Service  and  the  Illinois  Highway 
Department.  Results  of  these  field  tests 
have  been  very  good. 


Asphalt  occurs  in  native  deposits  as  rock 
asphalt  and  as  a  residue  of  the  petroleiim 
industry  known  as  asphalt  cement.  When 
reduced  with  oil, it  is  known  as  cutback. 
When  reduced  with  water  and  an  emulsifi- 
er,  it  is  known  as  emulsion.  Its  hard- 
ness and  elasticity  can  be  controlled  in 
the  manufacturing  process. 

Asphaltic  materials  have  been  tested  by 
the  Agronomy  Department  of  the  Univer- 
sity of  Illinois  during  the  past  three 
years.  The  first  tests  were  made  in  the 
greenhouse,  where  different  types  of  as- 
phalts were  tried  on  varying  soil  mate- 
rials, such  as  clay,  silt,  sand,  and 
gravel.  Different  kinds  of  grasses  were 
also  tried.  The  ordinary  road  asphalts 
were  not  satisfactory  because  they  were 
too  hard  for  the  grass  to  come  through 
and  they  contained  toxic  oils. 

Special  cutback  asphalt  from  the  Lion  Oil 
Company  and  special  emulsion  from  Shell 
Oil  Company  were  found  to  be  satisfac- 
tory during  these  preliminary  tests. 
After  the  greenhouse  experiment,  tests 
were  made  at  the  Agronomy  South  Farm, 
where  seedings  were  made  each  week  dur- 
ing the  summer.  These  seedings  were  all 
satisfactory  with  the  exception  of  those 
made  during  July  and  August, 


The  first  step  in  the  use  of  asphalt  as 
a  mulch  is  to  prepare  the  seedbed.  It 
should  be  prepared  in  the  usual  way  and 
worked  down  until  it  is  firm  and  compact. 
On  almost  all  lawns,  waterways,  highway 
shoulders,  etc.,  complete  fertilizer 
should  be  applied.  A  minimum  of  6o 
pounds  of  nitrogen  per  acre  should  be 
used.  This  means  that  with  a  10-10-10 
fertilizer  at  least  600  pounds  per  acre 
should  be  applied.  Sterile  areas  of 
subsoil  may  need  as  much  as  1,000  pounds 
of  10-10-10  per  acre.  The  fertilizer 
should  be  well  worked  into  the  soil. 

Bromegrass  may  be  used  on  waterways  and 
outlets,  highway  shoulders,  etc.,  in  the 
northern  one-third  of  Illinois.  Tall 
fescue  (Kentucky  31  or  Alta)  is  recom- 
mended for  the  southern  two  thirds  of 
the  state.  Either  the  bromegrass  or  the 
tall  fescue  should  be  seeded  at  the  rate 
of  25  pounds  per  acre.  The  tall  fescue 
is  better  adapted  to  the  poorer  soils. 

Legumes  are  not  generally  recommended  on 
areas  of  this  type.  They  do  not  form  a 
tough,  dense  sod  as  do  the  grasses;  and 
with  the  heavy  fertilization  that  is 
recommended,  the  grasses  will  crowd  them 
out  after  the  first  year.  The  seed 
should  be  covered  lightly  by  harrowing. 


\ 


The  same  rates  of  fertilization  are  rec- 
oimnended  for  establishing  lawns.  A 
straight  seeding  of  10  pounds  of  Ken- 
tucky bluegrass  per  acre  is  perhaps  the 
quickest  and  most  economical  way  to  es- 
tablish a  lawn.  In  shady  areas,  how- 
ever, Chewings  fescue  at  the  rate  of  10 
pounds  per  acre  will  be  more  apt  to 
catch,  as  it  is  tolerant  to  shade. 


In  the  tests  the  asphalt  emulsion  was 
applied  with  a  three-gallon  knapsack  or 
orchard-type  sprayer.  The  nozzle  must 
be  reamed  out  with  a  drill  because  the 
hole  in  the  nozzle  that  comes  with  the 
sprayer  is  too  small  to  handle  this 
heavy  material.  This  method  of  applica- 
tion is  generally  not  recommended  on 
areas  more  than  a  few  yards  square. 


After  the  seedbed  has  been  prepared  and 
the  seed  and  fertilizer  applied,  the 
area  is  ready  to  apply  the  asphalt.  When 
the  soil  moisture  is  near  normal,  the 
asphalt  may  be  applied  directly.  In 
periods  when  the  surface  is  dry,  the 
area  should  first  be  wet  with  water  to  a 
depth  of  at  least  one  inch.  The  asphalt 
may  be  applied  as  soon  as  the  water  has 
disappeared  from  the  soil  surface. 

The  recommended  rate  of  applying  asphalt 
is  .2  to  .h  gallon  per  square  yard.  On 
level  to  gently  sloping  areas,  .2  gallon 
may  be  ample,  while  on  steeper  slopes  .k 
gallon  may  be  needed  to  provide  adequate 
protection  from  erosion.  If  a  rate 
heavier  than  .6  gallon  per  square  yard 
is  applied,  the  material  will  run.  As 
good  growth  and  stands,  or  better,  have 
been  obtained  with  the  heavy  applications 
as  with  lighter  applications;  and  they 
have  also  equaled  those  on  the  check 
plots,  where  no  asphalt  was  applied. 

The  asphalt  must  be  applied  in  the  form 
of  a  spray.  Sprinkling  has  been  tried, 
but  it  is  not  satisfactory  because  a  thin 
even  coat  cannot  be  applied.  The  asphalt 
emulsion  can  be  applied  at  the  prevailing 
air  temperature.  The  cutback  asphalt 
must  be  heated  before  application.  It 
should,  however,  never  be  heated  above 
190°  F.,as  the  heat  may  injure  the  seed. 

A  temperature  of  170°  F.  seems  ample. 
The  University  of  Illinois  Physical  Plant 
recently  applied  some  cutback  at  lUo°  F. 
with  good  results. 


There  are  numerous  sprayers  designed  to 
handle  asphalt.  They  apply  the  material 
in  the  shape  of  a  fan  and  do  a  good  job 
of  application.  The  University  of  Illi- 
nois Physical  Plant  has  a  small  two- 
wheeled  trailer-type  sprayer  that  holds 
about  two  barrels.  It  will  handle 
either  the  emulsion  or  cutback.  It  was 
purchased  from  the  Aeroil  Products  Co. 
of  Chicago,  Illinois.  Division  highway 
garages  often  use  similar  equipment  in 
patching  roadways.  In  two  cases  we  have 
applied  emulsion  with  a  garden  hose.  The 
hose  was  attached  to  a  small  compressor 
mounted  directly  on  the  tractor  power 
takeoff.  The  barrel  was  mounted  on  the 
tractor  and  an  intake  hose  was  run  di- 
rectly from  the  compressor  into  the  bar- 
rel. With  some  improvements  this  method 
may  be  practical. 

At  present,  55-ga-llon  drums  are  the  smal- 
lest containers  in  which  asphalt  can  be 
purchased.  The  cost  is  about  22  cents 
per  gallon  in  drums  and  about  12  cents 
per  gallon  in  tank  cars.  On  a  square- 
yard  basis  the  cost  would  be  approxi- 
mately 5  to  8  cents.  This  price  com- 
pares favorably  with  a  straw  mulch  and 
overcomes  such  disadvantages  as  fire, 
blowing,  and  spreading  weed  seeds. 


The  emulsion  used  in  experimental  work 
was  supplied  by  Shell  Oil  Company,  Blum 
Building,  Chicago,  Illinois.  The  cut- 
back was  supplied  by  the  Lion  Oil  Com- 
pany, El  Dorado,  Arkansas. 

Harold  M.  Smith 

Soil  Conservation  Service 

5-25-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


MISCELLANEOUS 


AGRONOMY  FACTS 


M-5 


OKAW  BROOMCORN 


Origin  and  development.  Okaw  broomcorn 
originated  from  a  cross  between  Black 
Spanish  broomcorn  and  Leoti  Red  sorgo. 
It  was  developed  by  the  Illinois  Agricul- 
tural Experiment  Station.  The  original 
cross  was  made  about  20  years  ago  by  Dr. 
John  Martin,  senior  agronomist  in  charge 
of  sorghum  and  broomcorn  investigations, 
U.  S.  Department  of  Agricult\are . 

The  parents  differed  in  many  characters, 
and  consequently  there  was  extreme  seg- 
regation in  the  second -hybrid  generation. 
Selection  thereafter  was  made  for  good 
brush,  tan  plant  color,  and  resistance 
to  lodging.  later,  under  conditions  of 
natural  infection,  it  was  observed  that 
some  of  the  progenies  had  marked  resist- 
ance to  anthracnose  stalk  rot,  and  se- 
lection was  then  directed  toward  inten- 
sifying this  character.  Tan  plant  color 
and  anthracnose  resistance  came  from  the 
Leoti  parent . 

Description  and  performance.  Okaw  is  a 
standard  type.  It  resembles  Black  Span- 
ish in  height  and  seed  color,  but  dif- 
fers from  it  in  having  tan  instead  of 
red  plant  color  and  in  being  resistant 
instead  of  susceptible  to  anthracnose. 
Because  it  has  the  tan  color  factor  and 
is  disease  resistant,  it  holds  its  green 
color  longer  than  other  varieties  do. 
The  brush  will  not  turn  red  in  the  field 
or  shed,  and  the  seed  brush  compares 
very  favorably  with  the  green  brush  in 
color  and  quality. 

These  factors  should  be  of  great  help  to 
growers,  especially  in  western  states, 
since  Okaw  will  produce  a  good  colored 
brush  even  if  harvested  late  or  under 
adverse  weather  conditions. 

Okaw  compares  very  favorably  with  other 
varieties  in  brush  length  and  quality. 


According  to  results  obtained  in  1952,  the 
brush  runs  from  self -working  to  strong 
self -working.  Like  other  standard  vari- 
eties, Okaw  will  produce  short  brush  and 
some  center  stem  if  planted  too  thick. 
Some  growers  who  had  plantings  in  1952 
thought  it  tended  to  bear  seed  too  far 
down  on  the  brush.  Its  yields  of  both 
brush  and  seed  seem  to  compare  favorably 
with  those  of  other  varieties. 

Okaw  mati:ires  at  about  the  same  time  as 
Black  Spanish  or  perhaps  a  few  days 
later.  It  stands  well  \xnder  most  condi- 
tions, and  when  anthracnose  stalk  rot  is 
present  it  stands  much  better  than  other 
standard  varieties. 


Seed  increase  and  distribution. 


Before 


increase  of  seed,  small  isolated  plots 
of  this  variety  were  planted.  The  head- 
row  system  was  used.  The  rows  were  care- 
fully examined  before  the  pollen  shed- 
ding stage,  and  any  red  plants  were  re- 
moved. When  the  seed  was  ripe,  the  heads 
were  sorted,  and  those  with  acceptable 
length  of  fiber  and  quality  were  saved. 
The  strain  was  designated  111.  No.  1  be- 
fore the  name  Okaw  was  given  to  it. 

In  1951  an  isolated  increase  plot  of  .8 
acre  was  grown  on  the  Agronomy  South 
Farm.  This  plot  was  inspected  by  the  Il- 
linois Crop  Improvement  Association,  and 
the  seed  that  was  produced  was  later  cer- 
tified. In  the  spring  of  1952,  this  seed 
was  distributed  for  further  increase  to 
seven  growers  in  the  Arcola-Humboldt- 
Charleston  area,  who  planted  it  on  a  total 
of  104  acres  and  in  turn  had  the  result- 
ing seed  crop  certified.  These  Illinois 
growers,  with  their  addresses,  are  as 
follows:  Wm.  E.  Abell,  Humboldt;  Wm.  M. 
Grant,  R.  2,  Charleston;  Chas.  W.  Hood, 
R.  h,  Areola;  Geo.  Pfeifer,  Areola;  W.  E. 
Rennels,  R.  2,  Charleston;  C.  E.  Shawver, 
R.  3>   Charleston;  and  Henry  Vogel,  Areola. 

C.  M.  Woodworth 
Benjamin  Koehler 
1-11-53 


UNIVERSITY  OF  ILLINOIS      C 


)F  AGRICULTURE 


AGRONOMY  FACTS 


PRODUCING  HYBRID  CORN  WITHOUT  DETASSELING 


C-1 


The  use  of  cytoplasmic  male  sterility 
may  eliminate  the  need  for  manually  de- 
tasseling  some  500,000  acres  of  hybrid 
seed  corn  production  fields  and  save 
seven  to  eight  million  dollars  yearly. 
In  ^jdition,  the  need  for  large  numbers 
of  temporary  workers  will  be  decreased, 
and  the  hazards  of  unfavorable  weather 
during  detasseling  will  be  largely  elim- 
inated. 

To  understand  the  use  of  cytoplasmic 
male  sterility  for  this  purpose  requires 
a  knowledge  of  several  basic  facts. 
This  sterility  represents  a  rjire  and  pe- 
culiar type  of  inheritance  that  is  dis- 
tinguished by  the  following  points: 

(1)  The  plants  produce  a  normal  appear- 
ing tassel,   but  it  sheds  no  pollen;  and 

(2)  sterility  results  from  some  property 
in  the  cell  cytoplasm  that  differs  from 
the  ordinary  characteristics  (kernel  col- 
or, etc.)  that  are  determined  by  chromo- 
somes in  the  nucleus  and  inherited  from 
both  parents. 

For  an  analogy  one  might  think  of  the 
"yolk"  of  a  hen's  egg  as  the  nucleus  and 
the  "white"  as  the  cytoplasm.  Since  on- 
ly the  ear  parent  (female)  transmits  cy- 
toplasm to  the  offspring,  sterility  can 
be  inherited  only  from  the  ear  parent. 

Even  though  sterility  results  from  some 
property  in  the  cytoplasm,  there  are 
genes  located  on  the  chromosomes  which 
still  control  the  expression  or  degree 
of  sterility.  For  example,  two  plants 
may  both  have  sterile  cytoplasm,  but  one 
is  male  sterile  and  the  other  is  male 
fertile  because  it  carries  genes  which 
prevent  the  expression  of  sterility. 

Male  sterility  does  not  normally  occur 
in  standard  inbreds,  such  as  WF9,  and  so 
the  sterile  cytoplasm  must  be  introduced. 


This  is  accomplished  by 
with  the  sterile  strain 
this  progeny  back  to  WF9 
times . 


crossing  W9 
and  crossing 
at  least  five 


In  the  crossing  back  to  WF9,  only  ster- 
ile plants  with  characteristics  of  WF9 
are  used.  The  resulting  male-sterile 
WF9  is  maintained  and/or  increased  for 
use  in  seed  production  by  crossing  it 
with  the  normal  WF9,  using  the  male- 
sterile  version  as  the  ear  parent.  The 
sterile  and  normal  WF9  differ  only  in 
that  the  former  is  male  sterile. 

Fortunately,  of  the  four  inbreds  used  to 
produce  a  hybrid,  only  one  inbred  must 
possess  male  sterility  (see  Figure  l) . 
A  large  percentage  of  the  hybrids  grown 
in  the  Corn  Belt  have  WF9  as  a  common 
parent.  Hence  no  detasseling  would  be 
required  in  producing  these  hybrids  with 
male-sterile  WF9  as  one  line  of  the  ear 
parent  single  cross. 

The  production  of  hybrid  111.  I57O  with- 
out detasseling  is  shown  in  Figure  1: 


Figure  1.  Production  of  111. 
Without  Detasseling 


1570 


Ear  parent 

Inbred  WF9 
(Male  sterile) 


X 


Pollen  parent 

Inbred  38-II 
(Normal) 


WF9  X  38-11 
(Male-sterile 
single  cross 
used  as  ear 
parent;  does 
not  have  to  be 
detasseled) 


Hy2  x  Oh4l 
(Normal  single 
cross  used  as 
pollen  parent) 


Hybrid  seed  for  farmer 


Because  of  environmental  or  genetic  var- 
iation, a  small  percentage  of  tassels  in 
the  male-sterile  ear  parent  may  shed 
pollen.  These  tassels  must  be  removed, 
but  that  should  not  serve  as  a  reason 
for  criticizing  the  hybrid  seed  that  is 
being  produced.  Even  xhough  some  vari- 
ation in  sterility  exists,  the  seed  par- 
ents may  still  be  uniform  for  their  de- 
sirable agronomic  characteristics. 


by  scattered  seed  set  on  the  ears  at  har- 
vest. However,  scattered  seed  set  may 
result  from  environmental  as  well  as  ge- 
netic factors. 

A  few  facts  concerning  the  use  of  cyto- 
plasmic male  sterility  to  eliminate  de- 
tasseling,  including  both  the  advantages 
and  the  disadvantages,  are  summarized 
below: 


Although  a  high  degree  of  sterility  is 
desirable  during  the  production  phases, 
sufficient  pollen  production  to  assure  a 
full  seed  set  is  a  necessity  when  a  hy- 
brid is  grown  by  the  farmer.  Adequate 
pollen  shedding  in  the  field  may  be  ob- 
tained by  (l)  producing  the  hybrid  on 
both  male-sterile  and  male-fertile  ver- 
sions of  the  ear  parent  and  mixing  the 
seed  or  (2)  using  a  single-cross  male 
parent  carrying  genes  which  counteract 
the  sterile  cytoplasm  so  that  pollen 
production  is  restored  in  the  resulting 
crop. 

With  either  method  of  restoring  pollen 
production,  male-sterile  plants  may  ap- 
pear in  the  farmer's  field.  Insuffi- 
cient pollen  shedding  may  be  indicated 


1.  In  the  future  most  of  the  hybrid 
seed  corn  will  be  produced  without 
detasseling  the  ear  parent  single 
cross. 

2.  Seed  cost  will  not  be  greatly  re-   I 
duced. 

3.  Cost  of  detasseling  will  be  elimi- 
nated, but  breeding  work  and  seed 
stock  maintenance  will  be  more  com- 
plicated and  expensive  than  at  pres- 
ent . 

k.  Hazards  of  unfavorable  weather  dur- 
ing the  detasseling  season  will  be 
lessened. 

5.  Male  sterility  in  itself  will  not  be 
likely  to  improve  hybrid  performance. 

L.  F.  Bauman 
1/12/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


C-2 


RATE  OF  PLANTING  CORN 


Several  factors  operate  to  determine  the 
proper  rate  of  planting  corn  to  obtain 
highest  grain  yield,  but  the  most  impor- 
tant one  is  the  productivity  of  the  soil. 
The  more  productive  the  soil,  the  great- 
er must  be  the  plant  population  in  order 
to  obtain  maximum  yield 

Thin  corn  on  productive  soil  will  pro- 
duce large  ears,  and  sometimes  single 
plants  will  produce  two  ears.  As  the 
number  of  plants  increase  on  a  given 
area,  the  amount  of  grain  produced  per 
plant  decreases.  To  a  certain  point, 
however,  the  decrease  in  production  per 
plant  is  less  than  the  increase  in  aggre- 
gate yield  resulting  from  the  increased 
number  of  plants. 

When  the  population  is  further  increased, 
a  point  is  finally  reached  where  the  de- 
crease in  ear  size  is  great  enough  to 
more  than  offset  the  gain  accruing  from 
the  larger  n\:imber  of  ears .  The  popula- 
tion that  produces  the  smallest  ears 
without  reducing  the  per  acre  yield  is 
the  correct  one  to  use  to  get  the  high- 
est yield. 

Size  of  ear,  then,  is  a  guide  to  whether 
or  not  corn  is  planted  at  the  optimum 
rate  for  maximum  yield.  For  the  central 
corn  belt  hybrids,  the  correct  size  of 
ear  is  somewhere  between  .^5  and  .55 
pound.  In  states  north  of  Illinois,  the 
ear  size  associated  with  highest  yield 
is  smaller  than  this  figure. 

With  optimum  ear  size  figured  as  l/2 
pound  and  plant  establishment  as  87  l/2 
percent  of  the  kernels  planted,  the 
chart  on  the  back  of  this  sheet  has  been 
constructed  as  a  guide  to  planting  rates 
for  maximum  yields. 

In  using  the  chart  the  first  thing  to 
consider  is  not  how  much  yield  is  wanted. 


but  how  much  the  field  will  produce 
per  acre  under  moderately  favorable  con- 
ditions. Locate  this  figure  on  the 
scale  at  the  bottom  and  then  look  up  to 
the  diagonal  line.  Then  from  this  point 
look  straight  to  the  left  to  get  the 
number  of  kernels  to  plant  per  acre. 

If  the  corn  is  checked  in  rows  Uo  inches 
apart  each  way,  planting  one  kernel  per 
hill  will  yield  25  bushels  per  acre  on 
land  with  that  yield  capability.  For 
each  additional  25  bushels  per  acre, 
step  up  the  rate  of  planting  one  kernel 
per  hill.  For  drilled  corn,  gauge  the 
distance  between  kernels  in  the  row  by 
the  inches  obtained  when  ^0  is  divided 
by  the  n\imber  of  kernels  that  would  be 
plantedper  hill  if  the  corn  were  checked. 

Thickly  planted  corn  has  more  slender 
stalks  than  the  same  kind  of  corn  in  a 
dense  stand.  The  result  is  more  plants 
on  the  ground  at  harvest  than  would 
otherwise  be  the  case.  Corn  planted  at 
high  rates  produces  smaller  kernels  as 
well  as  smaller  ears  and  also  a  lower 
percentage  of  flat,  blocky  kernels  than 
the  same  hybrid  planted  at  lower  rates 
on  soil  of  the  same  productive  level. 

Moisture  supply  and  distribution  have  an 
important  effect  on  soil  productivity. 
A  field  that  under  favorable  moisture 
conditions  has  a  productive  level  of  I50 
bushels  per  acre  might  be  lowered  to  a 
75-bushel  capacity  by  drouth.  If  it  had 
been  planted  at  the  rate  of  2*^,000  ker- 
nels per  acre  in  an  attempt  to  get  the 
150  bushels,  the  dry  season  would  be 
likely  to  pull  the  yield  down  below  the 
75-bushel  level.  Overplanting  will  harm 
corn  yield  just  as  underplanting  will. 
A  high  yield  cannot  be  attained  without 
a  large  corn  plant  population,  but  a 
large  number  of  plants  per  acre  is  no 
guarantee  of  high  yield. 

G .  H .  Dungan 
'+/20/53 


28,000 


2i+,000 


20,000 


c 

O 


^  16,000 


c 

ch     12,000 
o 


8,000 


i+,000 


// 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

25 


50 


75 


100 


125 


150 


175 


Present  Productivity  of  the  Soil 
(Bushels  per  Acre) 


UNIVERSITY  OF  ILLINOCi 


GRICULTURE 


AGRONOMY  FACTS 


C-3 


STEWART'S  DISFASE  LEAF  BLIGHT  AND  NORTHERN  LEAF  BLIGHT  OF  FIELD  CORN 


Symptcms .  These  two  diseases  are  dis- 
cussed  together  because  often  it  is  not 
possible  to  distinguish  between  them  by 
the  appearance  of  the  lesions  on  the 
leaves,  especially  when  only  a  leaf  or 
two  are  sent  in  for  identification. 

Although  these  diseases  can  be  identi- 
fied by  observing  characteristic  lesions, 
not  all  lesions  are  characteristic. 
Typically  Stewart's  disease  (also  called 
bacterial  wilt)  infection,  caused  by 
Bacterium  stewartii,  travels  along  the 
veins,  causing  first  a  pale  green  and 
then  a  straw-colored  appearance  of  the 
adjacent  affected  tissues.  The  spreading- 
out  at  right  angles  to  the  vein  is  ir- 
regular in  outline,  appearing  first  as 
long,  narrow  streaks  along  the  vein, 
with  irregiilar  margins.  In  the  advanced 
stages  it  sometimes  becomes  an  inch  or 
more  wide.  Several  local  infections  on 
a  leaf  may  kill  the  entire  leaf. 

Usiially  in  field  com  this  leaf  infec- 
tion is  the  principal  symptom,  there 
being  no  wilt  as  is  sometimes  noted  in 
yo^mg  susceptible  sweet  corn.  In  field 
corn  in  Illinois,  both  diseases  usually 
become  conspicuous  only  after  pollinat- 
ing time. 

Northern  leaf  blight,  caused  by  the  fun- 
gus HelminthosporiiJm  turcicm,  appears 
typically  as  elongated  eliptical  lesions, 
more  or  less  bliintly  pointed  at  both 
ends.  These  pointed  ends  may  be  on  the 
veins,  but  usually  there  is  not  a  long 
linear  extension  along  the  vein.  The 
lesions  start  as  very  small  spots,  be- 
coming 3  to  6  inches  long  and  l/2  to  1 
inch  wide.  ^iThen  there  is  a  considerable 
amovint  of  infection,  a  nxjmber  of  lesions 
may  coalesce  before  they  become  this 


large,  giving  a  very  irregular  outline 
to  the  infected  area. 

The  most  definite  symptom  is  the  devel- 
opment of  darker  eliptical  sporulating 
areas  in  the  central  part  of  the  lesions 
after  they  are  several  weeks  old.  A  mi- 
croscope is  needed  to  identify  the 
spores  accurately.  In  damp  weather 
areas  killed  by  Stewart's  disease  may 
also  develop  a  dark  fijngus  growth.  A 
saprophyte, usually  an  alternaria  species, 
grows  on  the  dead  tissue. 

In  both  diseases,  after  the  leaves  be- 
come badly  blotched  from  infection,  the 
remaining  green  leaf  tissue  begins  to 
die.  This  is  especially  true  where  the 
soil  does  not  contain  enough  potassium. 
This  unbalanced  condition  iflay  also  have 
a  direct  effect  in  increasing  suscepti- 
bility. Sorghum  or  brocmcom  growing 
nearby  may  give  a  clue  to  the  identity 
of  the  blight,  as  these  crops  are  sus- 
ceptible to  northern  leaf  blight  but  im- 
mune to  Stewart's  disease. 

Factors  determining  infection.  The  bac- 
teria causing  Stewart's  disease  live 
over  winter  in  the  bodies  of  flea  bee- 
tles, and  the  disease  is  carried  to  com 
plants  by  the  feeding  of  these  insects. 
The  late  N.  E.  Stevens,  former  head  of 
the  Botany  Department,  University  of  Il- 
linois, found  that  winter  temperatuares 
affect  the  carryover  of  the  disease. 
Ordinarily,  when  the  sum  of  the  mean 
temperatures  for  December,  January,  and 
February  is  90  oi-  less,  there  is  no 
likelihood  that  Stewart's  disease  will 
OGcixr  the  following  season:  when  it  is 
between  90  and  100,  the  chances  are  that 
there  will  be  moderate  infection;  and 
when  it  is  100  or  over,  the  disease  may 
be  serious. 


-2- 


Another  factor  is  the  prevalence  of  the 
disease  in  the  previous  season,  as  it 
tends  to  build  up  with  repeated  favor- 
able seasons.  So  far  as  is  known, weather 
conditions  during  the  summer  have  little 
influence  on  the  disease. 

Northern  leaf  blight  requires  high  hu- 
midities during  the  growing  season. 
Winter  temperatures,  so  far  as  is  known, 
are  of  no  importance.  The  fung\as  lives 
over  winter  on  corn  refuse,  and  the 
spores  are  carried  to  the  new  corn  crop 
by  the  air.  In  this  case,  also,  the  di- 
sease tends  to  build  up  after  several 
favorable  seasons.  This  accounted  for 
the  \inus\:ially  heaAry  damage  in  Illinois 
in  1951.  Higher  simmer  hinnidities  and 
more  damage  from  northern  leaf  blight 
occur  on  the  average  in  states  to  the 
east  of  us. 


Relative  importance. 


Seme  lesions  of 


both  of  these  diseases  can  be  found  on 
corn  leaves  somewhere  in  Illinois  in 
every  season.  Infection  severe  enough 
to  cause  damage  occurs  most  frequently 
with  Stewart's  disease,  especially  in 
south-central  Illinois.  Northern  Illi- 
nois is  relatively  free  from  Stewart's 
disease. 

Damage  caused  by  both  of  these  diseases 
is  aggravated  by  both  Diplodia  and  Gib- 
berella  stalk  rot.  The  reason  is  that 
anything  that  caxises  severe  loss  of  ef- 
fective leaf  surface  while  the  ears  are 
very  immature  increases  stallv  rot  sus- 
ceptibility. 

The  end  result  of  leaf  blight  and  stalk 
rot  together  has  occasionally  caused  a 
50  percent  loss  in  yield  on  some  Illi- 
nois farms.  Ordinarily  Stewart's  dis- 
ease and  northern  leaf  blight  are  the 
two  principal  leaf  diseases  in  Illinois, 
but  lender  unusual  conditions  other  path- 
ogens, such  as  Helminthosporium  maydis , 
H.  carbonum,  Leptosphaeria  maydis ,  etc . , 
or  rust  may  cause  serious  leaf  blight. 

Control.  Resistant  varieties  are  the 
principal  requirement  for  control.   It 


has  already  been  mentioned  that  unbal- 
anced soil  fertility  aggravates  the  ef- 
fects of  these  diseases,  but  even  on  the 
best  soils  either  one  may  cause  severe 
loss.  In  a  year  when  an  epidemic  occurs, 
the  most  susceptible  varieties  can  be 
recognized,  and  the  hybrids  most  suscep- 
tible to  Ste-^'ra.rt's  disease  are  no  longer 
gro^m  in  areas  of  Illinois  where  damage 
can  be  expected  frequently.  But  for  a 
breeding  program  to  develop  a  high  de- 
gree of  resistance  in  combination  with 
other  desirable  agronomic  characters,  it 
is  necessary  to  have  some  assurance  of 
an  epidemic  of  the  disease  in  the  breed- 
ing plot  every  year.  To  obtain  this 
condition,  breeders  have  used  two  ap- 
proaches . 

One  method  is  to  inoculate  the  plants  in 
such  a  way  as  to  obtain  an  epidemic. 
The  other  is  to  plant  the  breeding  plot 
at  a  geographical  location  where  the  di- 
sease is  very  damaging  and  recurs  con- 
sistently. || 

With  Stewart's  disease  neither  of  these 
methods  has  yet  worked  very  well.  Inocu- 
lation methods  on  an  extensive  scale  have 
not  been  developed.  Insect  transmission 
is  involved.  Simply  spraying  the  plants 
with  the  bacteria  is  not  successful.  The 
result  is  that  for  the  most  part  hybrids 
are  being  losed  that  have  only  a  moderate 
degree  of  resistance  and  considerable 
damage  occiors  when  the  disease  becomes 
heavy. 

Breeding  for  better  stalk  rot  resistance 
is,  however,  making  some  head^^ay  and 
will  reduce  the  final  damage  resulting 
from  the  Stewart's  disease — stalk  rot 

combination. 

In  northern  leaf  blight,  both  methods  of 
breeding  have  been  used  successfully. 
Inoculation  methods  have  been  developed 
and  are  being  widely  used.  Corn  groi/n 
during  the  winter  and  spring  in  parts  of 
Florida  or  Central  America  are  usually 
subjected  to  natiural  epidemics.  The  re- 
sult is  that  encouraging  progress  toward 
the  breeding  of  resistance  to  northern 
leaf  blight  has  been  made. 

Benjamin  Koehler 
9/1/53 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


C-4 


DRYING  CORN  GRAIN  AT  HIGH  TEMPERATURE  LOWERS  ITS  VALUE  FOR  PROCESSING 


About  80  percent  of  the  corn  kernel  is 
starch.  The  other  20  percent  is  made  up 
of  gluten  (protein),  the  germ,  and  the 
hull.  The  hull  and  the  germ  are  well 
defined  parts  of  the  kernel.  The  starch 
and  gluten  are  not  so  clearly  distinct 
from  one  another.  Just  under  the  hull 
is  a  thin  layer  known  as  the  aleurone, 
which  is  predominantly  gluten.  On  the 
sides  of  the  kernel  and  extending  toward 
the  center  is  horny  material  consisting 
of  a  mixture  of  gluten  and  starch. 
Filling  the  crown  of  the  kernel  and  ex- 
tending dowmrard  aroiond  the  germ  is  the 
white,  starchy  part.  This  is  not  wholly 
starch,  ho^rever,  as  it  contains  some 
protein  and  a  little  oil. 

In  the  processing  of  corn  by  the  wet  mill- 
ing method, the  kernels,  after  being  sifted 
and  cleaned,  are  first  soaked  in  water 
for  36  hours.  The  soft  kernels  are  then 
riin  through  the  degerminating  mills  which 
spread  and  tear  the  corn  into  pieces 
without  crushing  the  germs.  Being  high 
in  oil,  the  germs  float  to  the  surface 
of  the  tanlv,  and  the  other  constituents, 
being  heavier  than  water,  settle  to  the 
bottom.  It  is  an  easy  matter,  therefore, 
to  separate  the  germs  from  the  rest  of 
the  kernels. 

Separating  the  starch  from  the  gluten  is 
a  more  difficult  process,  as  starch  is 
only  slightly  heavier  than  gluten.  The 
material,  after  being  finely  ground,  is 
made  into  a  thin  soup  by  the  addition  of 
a  large  amount  of  water.  The  starch  and 
gluten  mixture,  which  looks  like  rich 
milk,  flows  onto  the  starch  tables  that 
are  long,  flat -bottomed,  shallow  troughs. 
These  starch  tables  slope  just  a  little 
to  make  the  flow  of  liquid  very  gradual 
and  to  give  the  s-^arch  granules  plenty 
of  time  to  settle  out  from  the  gluten. 

This  works  very  well  with  normal  corn, 
but  difficulty  may  arise  if  the  corn  has 
had  some  abnormal  treatment.  Here  is 
where  high  drying  temperatrxres  cause 
trouble.  Heat  above  a  certain  point 
tends  to  cause  starch  and  gluten  to  cling 
together  more  tenaciously. 


Cooperative  tests  made  by  the  Northern 
Regional  Research  Laboratory,  Peoria, 
and  the  Departments  of  Agriculttoral  En- 
gineering and  Agronomy,  Illinois  Agri- 
cultural Experiment  Station,  Urbana, 
show  that  drying  wet  corn  at  high  tem- 
peratures interferes  with  the  clear-cut 
separation  of  starch  from  gluten.  For 
instance,  when  soft  corn  containing  66 
percent  moisture  was  dried  at  l8o°  F. , 
the  recovery  of  starch  was  only  57  per- 
cent; but  when  a  sample  of  the  same  corn 
was  dried  at  110°  F. ,  the  recovery  of 
starch  was  72  percent. 

What  became  of  the  starch  in  the  sample 
dried  at  the  high  temperatture  ?  A  large 
part  of  it  came  out  with  the  protein. 
Here  are  the  results:  The  gluten  sepa- 
rated from  the  sample  dried  at  l80°  F. 
was  57  percent  starch,  and  that  from  the 
sample  dried  at  110°  F.  was  only  36  per- 
cent starch.  Drying  at  a  high  tempera- 
ture also  caused  a  relatively  high  per- 
centage of  starch  in  the  fiber  fraction. 

Since  a  high  yield  of  starch  is  vital  to 
the  success  of  the  wet  milling  industry, 
it  is  no  mystery  why  processors  object 
to  artificial  drying  of  corn.  One  corn 
refinery  will  not  buy  any  corn  for  proc- 
essing if  it  is  known  to  have  been  dried 
by  heated  air.  Most  companies  believe 
that  if  the  temperature  of  the  drying 
air  has  not  exceeded  135°  F.  the  corn 
will  not  be  harmed.  If  the  com  is  to 
be  used  for  livestock  feed,  drying  tem- 
peratures may  be  higher  than  135°  F. 

In  order  to  determine  more  definitely 
the  effect  of  drying  on  the  processing 
quality  as  well  as  the  feeding  value  of 
corn  grain,  experiments  are  being  con- 
tinued by  the  Departments  of  Agricultural 
Engineering,  Animal  Science,  and  Agronomy 
in  cooperation  with  the  Northern  Research 
Laboratory.  Drying  corn  by  heated  air 
is  looked  upon  as  a  practice  that  will 
increase  in  the  Corn  Belt,  and  its  ef- 
fects on  the  grain  should  be  fully  kno-im. 

G.  H.  Dungan 
9-1^-53 


AGRONOMY  FACTS 


CORNSTALK  ROT  DISEASES 


C-5 


A  number  of  parasitic  fungi  and  one  'bac- 
terium have  been  observed  to  cause  corn- 
stalk rot-  On  the  average,  stalk  rot 
has  been  the  most  important  disease  of 
corn  in  Illinois.  In  certain  cases,  how- 
ever, some  other  diseases  have  far  sur- 
passed it  in  causing  losses. 

Stalk  rota  are  important  because  they 
occur  very  frequently,  causing  serious 
lodging  and  often  losses  in  yield.  Lodg- 
ing is  very  detrimental  because  the  ears 
that  contact  the  ground  deteriorate  dur- 
ing wet  weather,  and  the  corn  picker 
leaves  many  ears  of  lodged  plants  in  the 
field. 

DIPLOPIA  STALK  ROT  is  the  most  prevalent 
type  in  Illinois.  It  is  caused  by  the 
fungus  Diplodia  zeae.  The  same  fungus 
also  causes  ear  rots,  but  it  does  not  at- 
tack any  other  crop  plants.  Stalk  infec- 
tion does  not  start  to  develop  until 
several  weeks  after  pollination,  and  most 
of  it  usually  starts  later  than  that. 

The  lowest  6  to  12  inches  of  the  stalks 
usually  rot  worst,  but  local  infections 
at  the  nodes  may  also  occur  higher  up. 
Infections  may  start  at  the  Junction  of 
the  main  roots  with  the  stalks  Just  below 
the  soil,  at  the  Junction  of  the  brace 
roots,  or  at  the  junction  of  the  leaf 
sheaths  or  axillary  buds  or  ear  shanks 
at  the  nodes. 

In  aboveground  infections  dark  brown 
streaks  or  areas,  seen  on  the  surface  of 
the  stalks,  extend  down,  or  both  up  and 
down,  from  the  place  where  infection 
started.  On  the  interior  of  the  stalks, 
the  rot  may  spread  far  beyond  these  dis- 
colored areas.  The  interior  becomes 
retted  and  hollow,  but  there  is  little 
discoloration.  When  squeezed,  the  stalks 
usually  feel  soft  where  the  rot  is  well 
advanced. 


When  Diplodia  rot  takes  place  compara- 
tively early,  plants  may  start  to  die 
prematurely  in  late  August.  Soon  after 
they  die,  the  fungus  usually  starts  to 
fruit,  and  it  is  only  from  these  fruit- 
ing bodies  that  the  disease  can  be  iden- 
tified in  the  field. 

The  fruiting  bodies  can  first  be  seen  as 
tiny  black  points,  ranging  from  300  to 
1,000  per  square  inch.  Just  beneath  the 
surface  of  the  stalk.  The  fruiting  area 
may  be  either  less  or  considerably  more 
than  a  square  inch.  As  the  bodies  ma- 
ture, they  break  through  to  the  surface. 

Diplodia  rot  does  not  attack  plants  un- 
til translocation  of  food  materials  to 
the  ears  becomes  active.  Plants  that 
fail  to  develop  ears  remain  inmune.  Too 
little  or  too  much  potassium  in  the  soil 
may  increase  the  susceptibility  of  plants 
to  Diplodia  rot.  Premature  killing  of 
leaves  from  various  causes,  such  as  dis- 
ease. Insects,  or  frost  (but  not  drouth) 
increases  susceptibility  to  both  Diplo- 
dia and  Gibberella  stalk  rot. 

Inoculation  techniques  for  producing  ar- 
tificial epidemics  of  Diplodia  rot  have 
been  developed  successfully  and  are  use- 
ful in  breeding  for  resistance.  Data  on 
differences  among  hybrids  dying  prema- 
turely from  stalk  rot  (primarily  Diplo- 
dia rot)  are  given  from  time  to  time  in 
bulletins  published  by  the  Illinois  Agri- 
cultural Experiment  Station. 

The  ranking  of  hybrids,  however,  is  not 
always  the  same.  In  one  year  stalk  rot 
susceptibility  may  be  aggravated  by  leaf 
blight  from  Stewart's  disease.  At  an- 
other time  it  may  be  promoted  by  northern 
leaf  blight,  while  at  still  another  time 
it  may  be  due  to  other  causes.  Thus  the 
resistance  of  a  hybrid  to  these  predis- 
posing factors  ie  as  much  a  part  of  the 
end  result  as  is  its  innate  resistance 
to  Diplodia  stalk  rot- 


GIBBEBELLA  STALK  EOT  is,  on  the  average, 
the  second  most  prevalent  type  in  Illi- 
nois. It  is  caused  hy  the  fungus  Glbber- 
ella  zeae,  which  may  also  cause  ear  and 
root  rots.  It  also  causes  scab  in  small 
grains  and  attacks  the  roots  of  several 
other  crop  plants  besides  corn.  In  19^6 
and  1951 >  Gibberella  caused  more  corn- 
stalk rot  in  the  state  than  any  other 
pathogen.  But  the  cause  and  severity  of 
stalk  rot  always  varies  considerably  from 
place  to  place.  Damage  occurs  after  mid- 
summer and  in  the  fall. 

The  symptoms,  including  discolo rations, 
location  of  rot,  and  loss  of  firmness, 
are  practically  identical  with  those  of 
Diplodia  rot.  When  the  stalks  are  cut 
open  after  the  rot  has  gone  far  enough 
to  kill  the  plants,  one  is  likely  to  see 
a  limited  amount  of  pink  coloration,  but 
this  color  does  not  usually  occur  through- 
out the  rotted  area. 

This  fungus  may  also  fruit  on  the  sur- 
face of  the  stalks.  With  a  good  hand 
lens,  an  experienced  person  can  make  a 
fairly  accurate  identification  in  the 
field.  As  in  Diplodia,  the  fruiting 
bodies  are  black,  but  they  are  borne  en- 
tirely on  the  surface  of  the  stalk,  where 
they  can  be  scraped  off  with  a  finger- 
nail. They  also  tend,  to  a  greater  ex- 
tent than  in  Diplodia,  to  bunch  at  the 
nodes  of  the  stalk.  Any  of  the  fungus 
rots  that  are  not  fruiting  or  that  do 
not  show  definite  diagnostic  symptoms 
may  still  be  identified  by  using  suit- 
able laboratory  techniques. 

Giberella  stalk  rot  appears  to  be  most 
prevalent  and  destructive  on  highly  pro- 
ductive soils  that  are  rich  in  nitrogen. 
With  the  trend  toward  heavier  fertilizer 
applications,  the  need  for  breeding  more 
resistant  hybrids  seems  evident.  No 
good  method  for  producing  artificial  epi- 
demics to  aid  in  the  breeding  program 
has  yet  been  developed. 

CHARCOAL  ROT  is  caused  by  the  f\angus 
Sclerotium  bataticola, which  also  attacks 
the  stems  and  roots  of  many  other  plants 
besides  corn.  It  causes  most  damage  in 
hot  and  moderately  dry  weather  and  ordi- 
narily is  more  prevalent  farther  west 


and  southwest  than  in  Illinois.  It  also 
occurs  oftener  in  southern  than  in  north- 
ern Illinois,  but  damage  is  light  in  nor- 
mal seasons.  In  the  hot  summer  of  1955^ 
however,  infection  was  unusually  high. 

This  rot  is  usually  limited  to  the  low- 
est 8  inches  of  the  stalk,  which  may  dis- 
integrate badly,  causing  plants  to  fall 
as  they  approach  maturity.  The  disease 
can  be  easily  identified  in  the  field  by 
the  presence  of  tiny  black  dots  that  look 
somewhat  like  fine  charcoal  dust.  They 
are  especially  noticeable  on  the  inside 
of  the  stalk,  on  the  loose  fibers  of  the 
vascular  strands  which  are  all  that  re- 
main in  badly  rotted  stalks.  These  dots 
are  much  smaller  and  more  numerous  than 
those  of  Diplodia  or  Gibberella,  and 
they  occur  especially  in  the  interior  of 
the  stalk,  while  those  of  Diplodia  and 
Gibberella  occur  only  on  the  exterior. 

PYTHIUM  STALK  ROT  is  caused  by  the  fun- 
gus Pythium  butleri.  Unlike  the  rots 
described  previously,  it  is  active  only 
during  the  heat  of  midsummer  and  may  oc- 
cur even  before  pollinating  time.  It 
requires  moist  weather.  It  is  -a  dark, 
soft  rot,  usually  not  more  than  5  to  6 
inches  long,  near  the  bottom  of  the 
stalk.  The  plants  fall  while  they  are 
still  completely  green,  retaining  their 
green  color  for  several  days  afterwards. 
This  indicates  that  the  infection,  af- 
ter gaining  a  foothold,  works  very  fast. 
Fortunately  the  disease  occurs  only 
sporadically. 

BACTERIAL  STALK  ROT  is  reported  to  be 
caused  by  Bacterium  dlssolvens.  The 
description  of  Pythium  stalk  rot  applies 
also  to  this  disease.  Since  it  does  not 
seem  likely  that  there  would  be  two  dis- 
eases that  look  and  behave  exactly  alike, 
more  study  of  the  causes  appears  neces- 
sary. Up  to  now  the  situation  is  puz- 
zling, because  specimens  collected  by 
the  writer  from  a  number  of  fields  show- 
ing these  symptoms  readily  produced  col- 
onies of  Pythium  butleri  by  laboratory 
techniques,  while  specimens  from  Just  as 
many  other  locations  produced  only  bac- 
teria resembling  Bacterium  dlssolvens. 

Benjamin  Koehler 
12-7-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


C-6 


EFFECT  OF  TIME  OF  PLANTING  ON  YIELD  OF  CORN 


Sometimes  the  weather  forces  farmers  to 
plant  corn  late.  At  other  times  they 
plant  late  from  choice.  No  matter  what 
the  reason  may  be,  they  need  to  know  the 
effect  of  planting  at  different  dates  on 
yield,  on  percentage  of  moisture  in  the 
grain,  and  on  capacity  of  the  plants  to 
remain  erect  until  harvest. 

The  Illinois  Agricultural  Experiment  Sta- 
tion has  conducted  tests  at  Urhana  on 
time  of  planting  corn  through  nine  sea- 


sons. Three  hybrids  were  used,  one 
adapted  to  northern,  one  to  central,  and 
one  to  southern  Illinois.  So  far  as  con- 
ditions would  permit,  six  planting  dates 
7  to  9  days  apart  were  used.  The  first 
was  May  3,  ^,  or  5-  In  five  of  the  nine 
years,  soil  conditions  permitted  plant- 
ings on  the  desired  dates  without  any 
skips.  The  data  from  these  five  years 
have  been  averaged  and  are  presented  in 
the  table  below: 


Average  Yield  of  Grain,  Percentage  of  Moisture  in  Grain  at  Harvest 

Time,  and  Percentage  of  Plants  Erect  When  Harvested,  for 

Three  Corn  Hybrids  Planted  at  Six  Different  Dates, 

Urbana,  Illinois  (19*+!+,  19^+5;  1950,  1951  and  I952) 


Average  date 

Moisture  in 

grain 
ti/ 

Plants  erect   ^ 

of  planting 

Yield  of  grain 

at  harves 

when 

harvested^:' 

bu./A 

perct. 

perct. 

May  k 

112 

18.3 

80. U 

May  12 

108 

19.5 

79.5 

May  19 

111 

20.7 

78.1^ 

May  27 

110 

21.5 

69.6 

June  5 

101 

23.5 

66.6 

June  12 

89 

25.5 

5I+.0 

a/  Data  for  1952  are  not  included  in  the  averages  shown  in  this 
column. 


In  this  table  the  grain  yield  showed  a 
drop  for  the  May  12  planting,  but  it  is 
believed  to  have  been  due  to  chance. 
The  "meat"  in  these  data  is  that  yield 
Is  high  for  all  plantings  made  in  May. 
A  significant  drop  in  yield  did  not  oc- 
cur until  the  June  3  planting.  And  the 
June  12  planting  produced  only  about  80 
percent  as  much  grain  as  the  May  k 


planting.  In  this  experiment  harvesting 
was  always  postponed  until  late  November 
or  early  December  to  allow  the  sappy  ears 
to  dry  out.  But  even  this  delay  was  not 
always  enough  to  bring  the  moisture  in 
the  kernels  of  corn  planted  on  May  27 
down  to  the  21  percent  that  is  consid- 
ered safe  for  cribbing.  So,  even  though 
our  modern  corn  hybrids  are  capable  of 


-2- 


maintaining  high  yields  when  planted  in 
late  May,  the  hazard  of  wet  corn  is  a 
real  one  for  the  grower  who  elects, 
through  choice  or  otherwise,  to  plant 
late  in  Jfey. 

Stalks  stand  a  little  "better  when  the 
crop  is  planted  early,  although  there 
was  not  much  difference  between  the  per- 
centages of  erect  plants  from  plantings 
made  on  the  three  first  dates  in  ^fey. 
Stalks  that  do  not  reach  full  maturity 
In  the  normal  growing  season  lack  the 
stiffness  required  to  resist  the  strong 
winds  of  late  autumn. 

Another  factor  that  may  play  a  part  here 
is  the  height  of  the  plant-  In  some 
years  late-planted  corn  grew  signifi- 
cantly taller  than  tiiat  planted  early. 
The  extra  height  of  plant  and  the  heavi- 
ness of  the  immature  tissue  in  the  green 
stalk  handicapped  the  corn  in  the  late- 
planted  plots  when  it  came  to  a  test  of 
lodging  resistance. 

The  results  obtained  at  Urbana  were  du- 
plicated in  an  experiment  conducted  by 
Ray  Dunn  in  Henderson  county,  Illinois, 
in  1951*  He  used  the  same  three  hybrids 
and  the  same  six  planting  dates.  In  ad- 
dition to  finding  the  same  general  trends 
in  yield  and  moisture  content  as  were 
obtained  in  the  experiments  at  Urbana, 
he  found  a  striking  difference  in  hybrids 
with  respect  to  time  of  planting. 


The  late-maturing  hybrid  yielded  dis- 
tinctly more  grain  than  the  early  one  at 
the  first  planting.  At  the  last  plant- 
ing, the  yields  were  not  widely  differ- 
ent, but  the  grain  of  the  early  hybrid 
contained  5  percent  less  moisture  than 
that  of  the  late  one.  These  results  em- 
phasize the  wisdom  of  the  common  prac- 
tice of  using  a  short-season  hybrid  for 
late  planting. 

In  all  of  these  tests,  stand  of  corn  did 
not  influence  the  results.  The  hills 
harvested  for  yield  were  perfect,  and 
they  were  bordered  by  hills  that  had  at 
least  two  stalks  in  them.  The  experi- 
ment was  designed  to  find  out  what  ef- 
fect time  of  planting  might  have  on  the 
productiveness  of  corn  plants  and  not  to 
see  what  effect  it  might  have  on  stand. 

By  way  of  summary  it  may  be  said  that  in 
central  Illinois  tests  with  early,  mid- 
season,  and  late  hybrids  (l)  the  yield 
of  grain  was  not  significantly  reduced 
by  plantings  made  as  late  as  May  27  com- 
pared with  plantings  made  earlier  in  May, 
(2)  the  yield  of  grain  was  significantly 
reduced  by  plantings  made  in  June, 
(5)  the  moisture  content  of  the  grain  at 
harvest  time  increased  with  lateness  of 
planting,  and  (h)  the  percentage  of 
plants  standing  erect  at  harvest  de- 
creased with  lateness  of  planting,  par- 
ticularly those  plantings  made  after  the 
third  week  in  May. 


George  H. 
2-8-5^+ 


Dungan 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SELECTING  AFLAFLA  VARIETIES 


F-1 


Two  main  points  to  consider  in  select- 
ing an  alfalfa  variety  are  (l)  time  you 
expect  the  alfalfa  to  stand  tef ore  plow- 
ing it  down  and  (2)  cost  of  seed.  If 
you  will  use  the  stand  several  years  for 
hay,  plant  certified  seed  of  a  winter- 
hardy,  wilt-resistant  variety,  such  as 
Ranger  or  Buffalo.  If  you  will  use  it 
only  one  or  two  years  for  hay,  plant  a 
winter-hardy,  wilt-susceptihle  variety, 
such  as  Kansas  Common. 

Bacterial  wilt  does  not  reduce  alfal- 
fa yield  until  about  the  third  year.  Be- 
cause the  common  alfalfas  are  as  produc- 
tive as  Ranger  and  Buffalo  the  first 
year  or  two, there  is  no  advantage  in  us- 
ing the  more  expensive  seed  in  short  ro- 
tations. 

Several  varieties  of  alfalfa  have  been 
developed  in  the  United  States.  There 
is  a  good  seed  supply  of  certain  varie- 
ties but  not  of  others.  Following  are 
descriptions  of  available  varieties  and 
the  acreages  of  seed  fields  certified  to 
each  in  1952: 

Ranger,  which  is  resistant  to  bacteri- 
al wilt,  was  developed  by  the  Nebraska 
Experiment  Station  by  intercrossing  se- 
lected strains  of  Cossack,  Ladak,  and 
Turkistan.  A  good  forage  and  seed  pro- 
ducer. Ranger  is  as  winter-hardy  as  the 
most  hardy  common  alfalfa.  The  flower 
color  is  variegated.  110,370  acres  of 
seed  fields  were  certified  this  year. 

Buffalo,  also  resistant  to  bacterial 
wilt,  was  developed  by  the  Kansas  Exper- 
iment Station  out  of  Kansas  Common.  A 
good  forage  and  seed  producer,  it  is  on- 
ly slightly  less  winter-hardy  than  Rang- 
er. Flower  color  is  purple.  30>893 
acres  of  seed  fields  were  certified. 


Atlantic,  a  high-yielding  variety  de- 
veloped by  the  New  Jersey  Experiment 
Station,  is  not  resistant  to  bacterial 
wilt.  Developed  especially  for  the  east- 
ern states,  where  bacterial  wilt  is  not 
serious.  It  is  about  as  winter-hardy  as 
Buffalo.  Flower  color  is  variegated. 
i+,219  acres  of  seed  fields  were  certi- 
fied this  year. 

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.  Seed  will  not  be  avail- 
able in  1953. 

Nomad  has  a  high  proportion  of  creep- 
ing plants  that  will  root  at  stem  nodes. 
It  is  from  an  old  field  in  Oregon  found 
to  have  this  type  of  plant.  Nomad  is 
susceptible  to  bacterial  wilt  and  has 
not  been  tested  enough  to  determine  its 
adaptability.  In  most  tests  it  has  not 
appeared  to  be  so  vigorous  as  other  va- 
rieties. Because  of  its  creeping  habit 
of  growth,  it  may  be  useful  in  pastures. 
A  limited  amount  of  seed  is  available 
commercially. 

Talent  was  selected  in  Oregon  from  a 
strain  of  common  alfalfa  introduced  from 
France.  It  is  resistant  to  stem  nema- 
tode, which  is  not  serious  in  Illinois. 
It  is  not  resistant  to  bacterial  wilt 
and  does  not  appear  to  be  so  winter-hardy 
as  Buffalo.  It  has  a  purple  flower.  On- 
ly a  limited  amount  of  seed  is  available 
commercially. 

Ladak,  introduced  from  northern  India, 
is  more  cold-  and  drouth-resistant  than 
Grimm.  It  recovers  slowly  after  cutting, 


begins  growth  late  in  the  spring,  and 
■becomes  dormant  early  in  the  fall. 
First -cutting  yield  is  usually  larger 
than  that  of  other  varieties, and  second- 
and  third-year  cuttings  are  smaller. 
Total  seasonal  yield  is  about  the  same 
as  for  Ranger  and  Buffalo.  Ladak  is 
somewhat  more  tolerant  of  bacterial  wilt 
than  the  common  alfalfa,  but  it  is  not 
so  resistant  as  Ranger  and  Buffalo. 
Flower  color  is  variegated.  25,872  acres 
of  seed  fields  were  certified  in  1952. 

These  varieties,  except  Ranger,  Buf- 
falo, and  Ladak,  have  not  been  tested 
long  enough  in  Illinois  to  determine 
their  merit.  Because  of  susceptibility 
to  bacterial  wilt,  Harragansett,  Atlan- 
tic, and  Talent  should  be  used  only  in 
short  rotations.  But  even  before  they 
are  used  for  this  purpose,  they  will 
have  to  prove  superior  in  yield  to  Kan- 
sas Common  and  other  common  varieties 
now  used.  The  creeping  habit  of  Nomad 
might  make  it  desirable  in  pastures,  but 
its  susceptibility  to  wilt  will  proba- 


bly make  it  less  desirable  than  Buffalo 
and  Ranger  for  this  purpose. 

Certified  seed  of  Ranger  and  Buffalo 
is  produced  outside  the  region  of  adap- 
tation of  these  varieties,  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  Rang- 
er and  Buffalo  produced  in  California  is 
only  one  generation  removed  from  plants 
that  grew  in  the  region  of  adaptation. 
Also,  in  fields  growing  certified  seed, 
precautions  must  be  taken  to  prevent  the 
grovrth  of  volunteer  seedlings.  V/inter- 
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  out- 
side the  region  of  adaptation  that  there 
is  serious  loss  of  winter-hardiness. 

J.  A.  Jackets 
1/12/53 


JNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


NONHARDY  ALFALFAS 


Except  for  certified  Ranger  and  Buffalo 
alfalfa,  the  adaptation  and  performance 
of  alfalfa  varieties  or  strains  in  Illi- 
nois can  be  predicted  by  state  or  region 
of  origin. 

The  term  hardy  has  been  assigned  to  va- 
rieties or  strains  originating  in  the 
northern  part  of  the  United  States,  such 
as  Minnesota,  Montana,   and  the  Dakotas. 

The  common  strains  originating  in  the 
central  area,  such  as  Oklahoma,  Kansas, 
Colorado,  and  Utah,  are  considered  less 
hardy  than  those  from  farther  north,  but 
they  are  sufficiently  winter-hardy  to 
use  in  short  rotations  in  Illinois. 

Strains  or  varieties  grown  in  the  warmer 
sections,  such  as  Texas,  New  Mexico, Ari- 
zona, and  California,  are  considered  to 
be  nonhardy  in  Illinois. 

For  catch-crop  purposes  in  Illinois,  the 
nonhardy  varieties, Arizona  Common,  Cali- 
fornia Common,  Chilean,  African,  Indian, 
and  Peruvian  are  preferred.  Texas  and 
New  Mexico  produce  some  seed  that  will 
approach  Oklahoma  approved  seed  in 
winter-hardiness,  as  well  as  some  that 
is  nonhardy.  Winter-hardiness  of  Texas 
Common  and  New  Mexico  Common  depends  en- 
tirely on  previous  history  and  altitude 
at  which  they  originated. 

Sweet  clover  is  probably  in  a  class  by 
itself  as  a  catch-crop  legume,  but  its 
use  for  this  purpose  has  declined  rapid- 
ly in  Illinois  because  of  the  sweet  clo- 
ver weevil  and  root  rot.  Where  root  rot 
is  not  a  factor,  farmers  should  be  en- 
couraged to  continue  to  use  sweet  clover, 
and  the  insecticide  necessary  to  control 
the  weevil,  in  preference  to  using  other 
legumes  as  a  catch  crop. 


If  the  use  of  sweet  clover  is  not  prac- 
tical, the  nonhardy  alfalfa  strains  or 
varieties  can  be  substituted.  They  are 
preferable  to  the  more  winter-hardy 
types  because  they  make  more  top  and 
root  growth  during  the  seeding  year. 

Demonstration  plots  throughout  the  state 
have  shown  the  superiority  of  the  non- 
hardy strains  in  this  respect.  Observa- 
tions show  that  they  may  produce  two  to 
three  times  as  much  top  growth  as  the 
hardy  by  fall  of  the  seeding  year. 

Recent  experiments  at  Ohio  indicate  that 
Ladino  may  also  be  used  as  a  catch-crop. 
But  in  Illinois  alfalfa  is  preferable  be- 
cause it  is  more  drouth  resistant.  La- 
dino does,  however,  make  a  good  addition 
to  nonhardy  alfalfa. 

One-half  pound  of  Ladino  will  increase 
seeding  costs  very  little.  If  dry  weath- 
er occurs,  the  loss  is  small.  If  the 
season  is  favorable,  the  Ladino  may  in- 
crease the  value  of  the  catch  -crop. 
Since  there  is  always  a  possibility  of 
losing  nonhardy  alfalfa  over  winter,  the 
addition  of  Ladino  may  provide  green  ma- 
terial to  be  plowed  down  in  the  spring. 

Nonhardy  alfalfa  to  be  used  for  a  catch 
crop  should  always  be  seeded  at  the 
heavier  rates.  The  Ohio  station  reports 
that  seeding  rates  above  8  pounds  have 
little  effect  on  hay  yields.  But  plant- 
ing at  rates  up  to  15  pounds  produces 
more  dry  matter  by  the  fall  of  the  seed- 
ing year. 

It  is  true  that  alfalfa  cannot  be  grown 
on  all  soils  in  Illinois.  But  where  it 
is  adapted,  the  nonhardy  strains  should 
be  first  choice  as  a  substitute  for 
sweet  clover  as   a  catch  -  crop  because 


they  make  more  top  and 
the  hardy  strains. 


root  growth  than 


Results  of  an  Ohio  experiment  (see  table 
below)  show  that  hardy  alfalfa  compared 
favorably  in  value  with  sweet  clover  as 
a  catch  crop.  It  is  logical,  then,  to 
assiime  that  the  nonhardy  strains  which 
make  more  growth  will  be  of  greater  val- 
ue as  catch  crops. 

In  this  test,  covering  a  period  of  lU 
years,  the  legumes  were  compared  in  a 
rotation  of  corn,   oats  (legume).   All 


straw  and  stover  was  removed,  and  200 
pounds  of  0-20-0  was  applied  each  year. 

The  soil  where  the  experiment  was  con- 
ducted needed  potash.  This  fact  may  be 
seen  by  comparing  the  results  when  the 
straw  and  stover  were  left  on  and  when 
they  were  removed.  Although  potash  was 
not  applied  to  the  soil  on  which  the  al- 
falfa and  other  legumes  were  grown,  it 
can  be  assumed  that  the  benefits  to 
these  crops  from  potash  would  have  been 
comparable  to  those  shown  for  sweet  clo- 
ver. W.  0.  Scott 

1/12/53 


Effects  of  Using  Various  Legumes  as  Catch  Crops 
Wooster,  Ohio,  193O-U3 


Increase 


Legume 


Corn 
bu/A 

8.0 
10.7 
13.1 
13.3 


Oats 


"buTA 

2.9 
k.O 

2.k 


Without  potash 

Medium  red  clover 
Mammoth  red  clover 
Alfalfa* 
Sweet  clover 


With  potash 

Sweet  clover  plus  stover 
and  straw  containing 
70  pounds  of  potash 


29.8 


9.5 


*Hardy  strains  used. 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-3 


BI[^DSFO0T  TREFOIL 


Many  livestock  men  are  enthusiastic  about 
■birdsfoot  trefoil  because  it  can  appar- 
ently be  used  to  graze  cattle  without 
danger  of  bloat.  Livestock  gains  and 
milk  production  have  been  equal  to  those 
obtained  with  other  good  legumes. 

Birdsfoot  trefoil  does  not  become  coarse 
so  early  in  the  season  as  alfalfa.  For 
this  reason  it  can  be  used  for  grazing 
in  June  and  again  in  July  or  August  by 
rotating  the  pastures. 

Plants  in  bloom  have  a  protein  content 
of  20  percent;  calcium,  1.1  percent; 
phosphorus,  .28  percent;  and  potash,  1.1 
percent . 

Species .  Of  several  species  tested  in 
Illinois, the  broadleaf  type  (L.  cornicu- 
latus  L.)  has  proved  to  be  best.  There 
are  two  strains  of  the  broadleaf  species. 
One,  a  native  of  England  that  has  become 
adapted  to  New  York  conditions  during 
the  past  75  years,  is  commonly  referred 
to  as  the  New  York  strain.  The  other, 
native  to  the  southern  European  coun- 
tries, is  commonly  known  as  the  Italian 
or  French  strain. 


The  Italian  species  has  more  seedling 
vigor,  blooms  earlier  in  the  spring,  and 
grows  more  upright  than  the  New  York 
type.  However,  the  New  York  strain  is 
longer  lived  than  the  Italian  under  graz- 
ing conditions.  Because  the  New  York 
strain  is  better  able  to  survive  the  ef- 
fects of  grazing,  it  is  recommended  for 
use  in  perennial  pastures.  The  Italian 
appears  to  be  satisfactory  for  meadows 
that  will  be  cut  for  hay. 

Both  strains  are  perennial  legumes  that 
have  a  deep-growing,  branching  taproot. 
The  leaves  have  five  leaflets  instead  of 
three,  as  in  clover 
flowers  are  bright 
like  a  pea  flower, 
ripe,  the  seed  pods  are  long,  cylindri- 
cal, and  brown,  and  they  extend  outward 
from  the  tip  of  the  flower  stem  like  a 
bird's  foot.  The  pods  shatter  easily 
when  ripe.  The  seed  is  small,  rounded, 
and  brovmish  in  color,  and  there  are 
about  ^+00,000  to  a  pound. 


and  alfalfa.   The 

yellow  and  shaped 

When  the  crop  is 


Management , 


Here  are  a  few  suggestions 


for  establishing  and  maintaining  a  stand 
of  birdsfoot  trefoil: 


Empire,  an  improved  variety  of  the  New 
York  strain,  was  selected  by  the  Cornell 
Agricultural  Experiment  Station.  Viking, 
also  selected  by  Cornell,  was  derived 
from  the  Italian  strain.  Other  vari- 
eties of  Italian  origin  are  Cascade  and 
Granger,  both  selected  in  the  Northwest. 
Each  of  these  new  varieties  will  be 
tested  in  Illinois  as  soon  as  possible. 


Lime  the  soil,  as  needed  several  months 
before  seeding,  and  start  preparing  a 
seedbed  at  that  time.  Prepare  a  good, 
firm,  grass-free  seedbed,  and  leave  a 
light  mulch  on  the  surface  if  possible. 
Use  liberal  amounts  of  a  complete  ferti- 
lizer, such  as  10-10-10,  according  to 
test.  Inoculate  with  special  birdsfoot 
trefoil  culture. 


Characteristics.  Birdsfoot  trefoil  will 
grow  throughout  Illinois  on  many  types 
of  soil.  It  is  more  drought  resistant 
than  red  clover  and  less  sensitive  to 
poor  drainage  than  alfalfa. 


Seed  early  in  the  spring  in  northern  Il- 
linois and  during  the  first  week  in  Au- 
gust in  southern  Illinois.  Pack  the  soil 
with  a  corrugated  roller  before  and  af- 
ter seeding.   Use  about  five  pounds  of 


seed  per  acre^  and  plant  about  one-half 
inch  deep.  Do  not  plant  with  "shotgun" 
mixtures  of  other  legumes.  Birdsfoot 
trefoil  can  he  seeded  with  a  grass,  such 
as  four  pounds  of  hromegrass  per  acre  in 
the  north  or  four  pounds  of  orchard 
grass  in  the  south. 

The  Italian  strain  is  satisfactory  for 
hay  production,  hut  the  New  York  is  su- 
perior for  perennial  pastures.  A  grain 
crop  (not  rye)  may  be  planted  with  it  to 
hold  weeds  in  check  and  reduce  soil  ero- 
sion, but  the  grain  should  be  planted  at 
the  rate  of  about  one -half  bushel  per 
acre  and  should  be  grazed  when  six  to 
eight  inches  high.  Grazing  and  mowing 
during  the  first  year  will  avoid  shading 
and  competition  to  the  birdsfoot  seed- 
lings. 

If  the  plants  are  protected  from  grazing 
during  September,  they  will  yield  better 
the  following  season.  Rotation  grazing 
of  established  stands  results  in  higher 
yields  than  continuous  close  grazing. 

Harvesting.  The  hay  crop  of  birdsfoot 
trefoil  can  be  cut  at  the  early  bloom 
stage  and  handled  like  alfalfa. 

Seed  is  usually  harvested  from  the  first 
crop  of  the  season.  On  old  fields  the 
second  crop  will  usually  produce  a  good 
seed  yield  in  Illinois  if  the  first  crop 
is  harvested  in  late  May.  The  seed  ri- 
pens unevenly.  Many  flowers  are  still 
open  when  the  first  pods  ripen.  The 
pods  shatter  easily  as  they  ripen.   For 


this  reason  care  must  be  taken  in  han- 
dling to  prevent  excessive  losses. 

One  method  of  harvesting  that  has  given 
satisfactory  results  in  some  cases  is  to 
mow  with  a  windrowing  attachment  when 
many  of  the  pods  are  light  brown.  As 
soon  as  the  forage  is  dry  enough,  it  is 
either  placed  in  a  stack  or  in  small 
cocks  or  is  baled  in  round  bales.  Upon 
drying,  it  is  threshed  with  a  clover 
huller  or  a  combine. 

History.  Birdsfoot  trefoil  was  first 
found  in  this  country  near  city  dumps  in 
New  Jersey  and  New  York  in  1877 .  The 
seed  was  probably  introduced  with  pack- 
ing materials  from  England. 

In  1929  a  small  planting  was  established 
on  the  University  South  Farm.  Several 
years  later  that  area  was  converted  into 
a  bluegrass  border  along  a  new  roadway. 
Although  it  was  mowed  repeatedly  for 
twenty  years,  many  trefoil  plants  can 
still  be  found  with  the  bluegrass. 

In  the  spring  of  19^2  a  pasture  planting 
of  New  York  strain  was  established  on  afc 
eroded  Clarence  silt  loam  near  Pontiac, 
Illinois.  Besides  maintaining  an  excel- 
lent stand  for  the  past  ten  years,  this 
planting  has  been  spreading  into  the 
bluegrass  next  to  it. 

Numerous  plantings  have  been  made  on 
both  University  and  private  land  in  Il- 
linois since  19^+3.      Joseph  J  .  Pierre 
Agronomist,  Nursery  Division 
Soil  Conservation  Service 
1/12/53 


INIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


ST,1«vlNS  OF  BROMEGRASS 


Brcmegrass  strains  have  tieen  divided  in- 
to two  categorieS'-southern  and  north- 
ern. The  southern  type  is  recommended 
in  Illinois  because  it  is  superior  to 
the  northern  type  in  resistance  to  both 
drouth  and  heat.  These  superior  char- 
acteristics pay  off  in  higher  yields  and 
better  and  longer  stands. 

Table  1  below  shows  the  results  of  an 
experiment  conducted  by  the  late  Doctor 
R.  F.  Fuelleman  on  the  Agronomy  South 
Farm  with  commercial  seed  of  eight 
bromegrass  strains  seeded  in  19^1.  These 
data  do  not  give  the  entire  picture, how- 
ever. On  November  20,  19^5 >  Doctor 
Fuelleman  made  a  botanical  analysis,  the 
results  of  which  are  given  in  Table  2. 

The  Montana,  Utah,  Parkland,  Minnesota, 
and  Washington  strains  are  classed 
either  as  northern  types  or  between  the 
northern  and  southern  types.  The  Illi- 
nois strain  is  a  selection  from  Achen- 
bach.  Both  it  and  the  Kansas  and  Nebras- 
ka strains  are  southern  types.   The  Ne- 


braska strain  used  in  this  experiment, 
which  was  a  commercial  seed  lot,  was 
probably  not  so  true  a  southern  type  as 
we  would  expect  certified  Lincoln  to  be. 
However,  in  this  analysis  Illinois,  Kan- 
sas, and  Nebraska  were  the  only  strains 
that  approached  a  full  stand  of  brome- 
grass. Also  the  weed  content  was  zero 
in  the  Illinois  and  Kansas  strains  and 
very  small  in  the  Nebraska  strain. 

An  experiment  recently  established  by 
Doctor  Jackobs  with  pure  seed  of  several 
different  varieties  and  strains  of 
bromegrass  shows  the  same  trend  in  su- 
periority for  the  southern  types.  It  is 
not  confined  to  central  and  southern  Il- 
linois, as  evidenced  by  results  from 
Wisconsin  showing  that  the  southern  type 
of  bromegrass  produced  higher  yields  of 
hay  and  pasture  than  the  northern  type 
under  their  conditions. 

Because  the  seed  supply  of  the  southern 
strain  is  likely  to  be  limited,  it  will 
be  necessary  to  make  substitutions  when 


Table  1. --Yields  of  Dry  Matter  From  Bromegrass  Strains 
S-200,  Agronomy  South  Farm,  Urbana,  Illinois 


Season  and  yields 


Strain 


19^2 


19'^3 


I9J+4 


19^^ 


19^6 


!? 

-year 

average 

5 

417 

5 

180 

k 

516 

h 

53^^ 

k 

639 

3 

877 

3  793 

k 

175 

Kansas 

Illinois 

Nebraska 

Montana 

Utah 

Parkland 

Minnesota 

Washington 


5  735 
7  076 

5  134 
5  U28 

5  ^+97 
5  718 
5  7^+5 
5  901 


lb.  per  acre 

6  0^7 

5  302 

5  152 

5  671 

k   813 

h   609 

5  037 

1^  792 

h   628 

k   123 

h  651 

k   898 

k  7k3 

k   i;l5 

5  390 

k   330 

3  326 

k   167 

3  716 

3  592 

h   102 

3  883 

i^  053 

k   121 

848^/ 
732£/ 
988a/ 
564i/ 
150^/ 
8i;2k/ 
812^/ 
916^/ 


3  732£ 
2 

3 
3 

1 
1 
2 


a/  Less  than  kO   percent  bromegrass,  rest  Kentucky  bluegrass. 

b/  Less  than  10  percent  bromegrass,  rest  Kentucky  bluegrass  and  weeds. 

c/  Over  90  percent  bromegrass. 


supplies  are  short.  We  therefore  sug- 
gest that  you  recommend  the  following 
procedure  to  growers  in  your  county: 

1 .  Use  only  southern-type  bromegrass  in 
permanent  pastures  to  be  left  down 
for  many  years . 

2.  Stretch  the  seed  supply  by  seeding 
at  lighter  rates  in  legume-grass 
mixtures. 

3.  In  pastures  to  be  left  down  for  only 
two  or  three  years: 

a.   Use  timothy  if  it  is  available. 


Use  orchard  grass  if  you  are 
willing  to  manage  it  properly. 

Northern-type  bromegrass  can 
be  substituted  for  southern  on 
a  limited  scale  in  the  north 
and  the  north-central  part  of 
central  Illinois,  but  we  rec- 
ommend that  you  do  not  go  "all- 
out"  in  suggesting  its  use  in 
this  section. 

Do  not  use  northern-type  brome- 
grass in  southern  Illinois. 
Under  certain  weather  condi- 
tions it  will  not  become  estab- 
lished or  after  establishment 
may  disappear  rapidly. 


Table  2. --Botanical  Composition  and  Bare  Space  on 
Bromegrass  Strain  Test  Plots 


Species 

and  perc 

entages 

Blue- 

Red- 

Brome- 

Strain 

grass 

top 

grass 

Alfalfa 

Clover 

Weeds 

None 

Kansas 

k 

0 

96 

0 

0 

0 

0 

Illinois 

0 

0 

100 

0 

0 

0 

0 

Nebraska 

2 

2 

70 

0 

0 

16 

10 

Montana 

12 

6 

UO 

0 

16 

20 

6 

Utah 

k 

0 

48 

0 

6 

26 

16 

Parkland 

16 

2 

2k 

0 

10 

36 

12 

Minnesota 

8 

0 

hk 

2 

8 

28 

10 

Washington 

22 

0 

kk 

0 

8 

26 

0 

W.  0.  Scott 
1/12/53 


NIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-5 


EFFECT  OF  SEED  TREATMENT  ON  SMALL-SEEDED  LEGUMES 


?reating  the  seed  of  small -seeded  legumes 
iith  certain  fungicides  will  protect  the 
yTOung  seedlings  from  what  is  called  pre- 
^mergence  damping-off.  That  is,  the 
plant  is  protected  from  attack  by  fungi 
until  about  the  time  it  appears  above- 
ground.  After  it  breaks  through  the 
soil,  it  has  grown  away  from  the  pro- 
tected area  around  the  seed.  Therefore, 
the  only  effect  of  seed  treatment  is  to 
increase  the  number  of  plants  that  come 
up  when  pre-emergence  damping-off  is 
present. 


It  is  known  that  pre-emergence  damping- 
off  does  occur  in  forage  crops, but  there 
is  little  evidence  that  it  causes  poor 
stands.  One  reason  may  be  that  it  is 
most  severe  in  the  small- seeded  legumes 
when  the  soil  is  warm  and  moist.  Most 
of  our  spring-seeded  legumes  are  planted 
as  early  as  possible  in  the  spring  when 
j the  soil  is  cold  and  wet  and  there  is  a 
minimum  of  damping-off.  Alfalfa  seeded 
in  August  is  planted  in  warm  soil,  but 
at  this  time  of  year  the  surface  soil  is 
usually  dry,  and  this  dryness  would 
probably  control  damping-off. 

Field  tests  conducted  by  various  experi- 
ment stations  have  given  results  that 
vary  from  slight  decreases  to  slight  in- 
creases in  stand  with  treatment.  The 
over-all  average  shows  a  slight  increase 
with  treatment.  From  a  practical  stand- 
point, what  do  these  results  mean? 

Tests  with  different  planting  rates  show 
that  the  number  of  plants  in  a  stand  may 
vary  a  great  deal  without  affecting 
yield.  A  thinner  stand  produces  larger 
plants  that  in  turn  produce  Just  as  much 
forage  as  a  thicker  stand  of  smaller 
plants.  Increasing  the  stand  by  only  a 
few  plants  through  seed  treatment  is 
therefore  probably  of  little  or  no  prac- 
tical significance  in  increasing  yield. 
At  this  point  one  might  ask  this  ques- 
tion: If  seed  treatment  increases  emer- 
gence, then  can't  rate  of  seeding  be  re- 
duced? 


That  is  doubtful.  Most  farmers  use  a 
very  high  seeding  rate.  They  do  it  be- 
cause there  are  many  hazards  that  may 
prevent  the  seed  from  germinating  or  kill 
the  seedlings.  Pre-emergence  damping- 
off  is  only  one  of  these  hazards,  and 
probably  not  the  most  important  one.  If 
the  surface  soil  dries  out  just  as  the 
seed  germinates,  causing  a  poor  stand, 
seed  treatment  actually  increases  the 
damage .  There  are  other  hazards  that 
seed  treatment  cannot  overcome,  and  a 
high  seeding  rate  does  provide  some  in- 
surance against  most  of  them. 

Now,  what  about  using  seed  treatment  as 
insurance  against  heavy  loss  from  pre- 
emergence  damping-off  when  treatment 
means  the  difference  between  a  thin, 
weedy  stand  and  a  good  stand? 

This  reason  is  the  best  arg-ument  for 
treating  legume  seed.  Seed  treatment  is 
relatively  inexpensive;  and  even  if  such 
losses  occur  only  occasionally,  seed 
treatment  can  be  considered  good  insur- 
ance. 

But  before  we  buy  insurance  of  any  kind, 
we  want  to  know  that  the  event  against 
which  we  are  insuring  ourselves  has  some 
chance  of  occurring.  To  date  I  have 
seen  no  data  from  any  experiment  station 
showing  a  case  where  treated  seed  pro- 
duced a  good  stand  and  untreated  seed  an 
unsatisfactory  one.  Lack  of  such  data 
does  not,  however,  prove  that  such  cases 
may  not  occur;  and  if  a  farmer  wants  to 
insure  against  this  possibility,  I  would 
advise  him  to  treat  his  seed. 

There  is  one  other  case  where  treatment 
might  be  desirable.  Because  poor  quality 
seed  germinates  slowly,  it  is  more  sus- 
ceptible than  good-quality  seed  to  pre- 
emergence  damping-off,  and  there  is  evi- 
dence that  a  fairly  good  increase  in 
stand  nay  result  from  treating  low-qual- 
ity seed. 


Another  point  to  consider  is  whether  the  tains  many  of  these  bacteria,  and  there- 
seed  should  be  inoculated  with  nodule  fore  this  difference  cannot  be  observed, 
bacteria.  While  seed  treatment  does  not  The  fact  remains,  however,  that  the 
kill  all  the  bacteria,  tests  in  steri-  farmer  should  make  up  his  mind  which 
lized  soil  have  shown  that  nodules  are  will  do  him  the  most  good,  inoculation 
considerably  reduced  by  such  treatment.  or  seed  treatment,  and  not  try  to  use 
Ordinary  field  soil  usually  already  con-  both.                  J.  W.  Gerdemann 

2/9/53 


Ur.iVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-6 


RED  CLOVER  DISEASES 


Root  rot  of  red  clover  causes  more  reduc- 
tion in  yields  and  loss  of  stands  than 
any  other  disease.  It  is  present  on  all 
red  clover  plants  and  is  responsible  for 
the  eventual  death  of  nearly  every  plant . 

Loss  of  stands  from  this  cause  is,  in 
fact,  so  universal  that  it  has  become  ac- 
cepted as  normal.  Few  persons  realize 
that  red  clover  is  a  true  perennial  and 
that  loss  of  stands  during  the  second 
summer  is  not  normal.  It  is  only  when 
the  disease  becomes  especially  severe 
and  causes  high  losses  before  the  sec- 
ond cutting  that  it  receives  particular 
attention. 


jury  from  extreme  cold, 
ice  sheets. 


and  injxiry  from 


Other  conditions  similar  to  ice  sheets, 
such  as  waterlogged  frozen  soil  and  heav- 
ily packed  snow,  may  also  cause  winter 
injury.  It  has  been  observed  that  clo- 
ver frequently  survives  winterkilling 
better  on  rolling,  well-drained  soil 
than  on  flat,  poorly  drained  soil.  The 
more  northern  types  of  clover,  such  as 
the  Canadian  variety  Dollard,  appear  to 
have  some  resistance  to  winterkilling. 
At  present,  however,  seed  of  these  vari- 
eties is  available  only  for  experimental 
use . 


Root  rot  begins  a  few  weeks  after  the 
clover  seed  germinates,  but  its  progress 
is  usually  slow  if  growing  conditions 
for  the  clover  are  good.  If  unfavorable 
growing  conditions,  such  as  a  drouth  or 
a  severe  winter,  occur,  the  disease 
spreads  more  rapidly  and  the  plants  die 
sooner. 

Not  a  great  deal  is  yet  known  about  the 
nature  of  root  rot,  although  more  infor- 
mation is  gradually  becoming  available. 
It  now  appears  that  it  may  be  a  complex 
group  of  root  diseases.  The  best  hope 
for  control  lies  in  the  development  of 
resistant  clover  varieties.  At  present 
one  variety,  Kenland,is  slightly  resist- 
ant, and  it  should  be  used  in  the  south- 
ern half  of  Illinois,  where  it  is  well 
adapted.  It  might  also  be  used  on  an 
experimental  basis  in  northern  Illinois, 
where  it  is  not  so  well  adapted. 


Southern  anthracnose  causes  a  crown  rot 
of  young  red  clover  plants  and  may  also 
attack  and  kill  stems  and  leaves.  It 
causes  high  losses  in  the  southern  part 
of  the  United  States  and  is  present  in 
the  southern  half  of  Illinois.  The  va- 
riety Kenland  is  resistant. 

Northern  anthracnose  kills  stems  and 
leaves  of  red  clover  in  the  northern 
half  of  Illinois.  This  disease  occurs 
in  the  spring  during  damp,  cool  weather. 
It  causes  reductions  in  yield  and  qual- 
ity of  hay  but  does  not  kill  the  plants. 
When  it  becomes  severe,  an  entire  field 
may  become  brown.  Usually,  however,  it 
is  present  in  only  a  few  fields  and  does 
not  cause  much  loss  except  in  unusual 
years.  Most  northern  varieties  have 
some  resistance.  The  variety  Dollard  is 
probably  the  best,  but  seed  of  it  is  not 
yet  available. 


Various  types  of  winter  injury  cause 
high  losses  in  red  clover  stands.  In  ad- 
dition,winter  injury  weakens  the  plants, 
causing  them  to  become  more  susceptible 
to  root  rot.  There  are  at  least  three 
types  of  winter  injury:  heaving  caused 
by  alternate  freezing  and  thawing,  in- 


Powdery  mildew  causes  the  leaves  of  red 
clover  to  become  white  and  dusty.  It  is 
most  severe  in  dry  weather  but  seldom 
causes  much  damage.  The  variety  Wiscon- 
sin Mildew  Resistant  is  resistant,  but 
its  hay  yields  in  Illinois  are  not  high 
enough  to  recommend  it. 


Aphids  and  leafhoppers  transmit  viruses  There  are  many  other  diseases  of  red  clo- 

that  produce  mosaic  diseases  on  red  clo-  ver,   such  as  black  stem,  black  patch 

ver.   The  leaves  become  mottled  and  rust,  and  a  number  of  leaf  spot  diseases. 

streaked  with  yellow,  and  the  plants  are  They  often  cause  an  important  loss  in 

stunted.   There  are  no  practical  methods  yield  and  quality  of  hay.   No  practical 

of  control,  but  losses  from  mosaics  are  control  is  known  for  them, 

relatively  low,  J.  W.  Gerdemann 

3/2/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-7 


■^■ED  ClCy.l  SEED  SUPPLIES  AND  VARIETY 
I^ECOMMENPATIONS  FO"?  ILLINOIS 


The  supply  of  red  clover  seed  for  Illi- 
nois in  1953  will  be  more  than  ample. 
Production  of  common  medium  red  clover 
seed  for  1952  was  above  the  10-year 
(19^1-1950)  average,  and  there  is  a  fair 
supply  of  certified  Kenland.  Seed  sup- 
plies of  Midland  and  Cumberland  have  be- 
come very  small  and  probably  will  not  be 
increased. 

Kenland,  a  new  variety  of  red  clover  de- 
veloped at  the  Kentucky  Experiment  Sta- 
tion, is  recommended  for  use  in  central 
and  southern  Illinois.  It  is  not  recom- 
mended for  northern  Illinois  because  it 
is  susceptible  to  northern  anthracnose, 
a  disease  of  the  stems  and  leaves  that 
lowers  hay  quality.  At  present,  locally 
produced  red  clover  seed  is  recommended 
for  northern  Illinois. 

Kenland  has  proved  superior  in  many  re- 
spects to  other  strains  of  red  clover  in 
central  and  southern  Illinois.   It  is 


resistant  to  southern  anthracnose,  a 
disease  whose  symptoms  are  similar  to 
northern  anthracnose,  but  which  is 
caused  by  an  entirely  different  organism. 
Besides  damaging  aboveground,  the  fungus 
that  causes  southern  anthracnose  fre- 
quently invades  the  root  through  the 
crown,  causing  the  plant  to  die.  In  ad- 
dition, Kenland  appears  to  be  less  sus- 
ceptible than  other  varieties  to  certain 
other  root  rots  that  are  causing  prema- 
ture death  of  plants  in  practically  all 
red  clover  fields  in  Illinois. 

Kenland  also  remains  productive  longer 
than  other  red  clover  and  frequently 
gives  a  second  cutting  when  common  red 
clover  does  not  because  the  stand  is  se- 
verely thinned  as  a  result  of  root  rot. 

In  trials  at  Urbana  in  1952,  the  per- 
formance of  several  varieties  of  red 
clover  was  as  follows: 


Weeds 
in  hay 
July  29 

Yield  of  hay 

Variety 

June  13 

July  29 

Seasonal 
total 

Kenland 

Midland 

Medium  red  (common) 

Maimoth 

pet. 

8 

32 
i^3 
97 

tons /A. 

1.73 
1.56 

1.3^ 
1.38 

tons/A. 

1.30 

.80 

1.05 

tons/A. 

3.03 
2.36 

2.39 
1.38 

J.  A. 


Jackobs 
3/2/53 


I 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


USE  AND  AMNAGEMENT  OF  GRASS-LEGUME  MIXTURE  IN  PASTURES 


F-8 


Why  are  grass -legume  •  mixtures  recom- 
mended for  pastures?  Usually  there  are 
four  reasons : 

1.  Adapted  legumes  are  more  productive 
and  give  better  seasonal  distribu- 
tion of  production  than  grasses. 

2.  Danger  of  bloat  in  grazing  animals 
is ■ greatest. on  pure  legume  pasture . V 

3.  Grass-legume  mixtures  control  ero- 
sion more  effectively  than  pure 
stands  of  legumes . 

h.  There  is  less  risk  of  losing  a  stand 
when  grasses  are  included  in  the  mix- 
ture. Grasses  are  also  more  resist- 
ant to  low  temperatures  and  heaving 
and  will  survive  after  most  legumes 
are  winterkilled. 

Legumes  are  more  productive.  \'Then  all 
nutrient  requirements  of  plants  (except 
for  nitrogen)  are  met.,  adapted  legumes 
are  more  productive  than  grasses.  The 
reason,  in  part,  is  that  legumes  do  not 
have  to  depend  on  the  soil  for  nitrogen, 
whereas  grasses  do.  Legumes  also  produce 
better  in  the  hot  summer  months  than  the 
perennial  grasses.  Even  when  large 
amounts  of  nitrogen  are  used  on  grasses, 
neither  total  seasonal  production  nor 
summer  production  approaches  that  of  pxire 
legume  stands  or  grass-legume  mixtures. 

Mixtures  reduce  danger  of  bloat.  Most 
cases  of  bloat  occur  while  animals  are 
grazing  on  pure  stands  of  legumes  or  on 
mixtiores  that  are  predominantly  legume. 
Although  the  causes  of  bloat  are  not 
well  understood,  it  is  known  that  cattle 

1/  Birdsfoot  trefoil  is  a  legume,  but  no 
cases  of  bloat  have  been  reported  from 
its  use.  Legumes  referred  to  include 
Ladino  clover,  alfalfa,  red  clover,  al- 
sike  clover,  sweet  clover,  and  common 
white  clover. 


seldom  bloat  when  grazing  on  grass.  The 
danger  of  bloat  is  not  great  until  over 
50  percent  of  the  herbage  is  legume.  For 
this  reason  it  is  desirable  to  have  a 
mixture  that  consists  of  half  grass  and 
half  legume.  The  leg-ume  will  then  keep 
production  up,  and  the  grass  will  reduce 
the  danger  of  bloat. 

Mixtures  control  erosion.  Grasses  have 
a  much  more  fibrous  root  system  than  the 
legumes.  Legumes  are  not  so  long-lived 
as  the  perennial  grasses  used  in  pas- 
tures; and  when  pure  stands  of  legumes 
are  winterkilled  or  otherv'/ise  destroyed, 
the  soil  sin-face  is  exposed  to  erosion. 
Grass -legume  mixtures  will  control  ero- 
sion nearly  as  effectively  as  straight 
grass  seedings. 

Grasses  reduce  risk  of  losing  stand. 
Legumes  are  not  so  long-lived  as  the 
perennial  grasses.  In  fact,  in  a  grass- 
legume  mixture,  the  proportion  of  grass 
increases  and  the  legume  decreases  as 
the  stand  becomes  older.  So  the  propor- 
tion of  grasses  grows  as  the  legijmes  die 
out.  Grasses  are  also  more  resistant  to 
low  temperatures  and  heaving  than  le- 
gumes and  will  survive  after  the  legumes 
are  winterkilled.  In  addition,  grass 
protects  the  legume  from  heaving.  Often 
when  legumes  in  pure  stands  heave  because 
of  alternate  freezing  and  thawing  in  the 
spring,  comparable  leg\;imes  in  a  mixture 
with  grass  remain  securely  in  place. 

One  of  the  objectives  of  pasture  manage- 
ment is  to  maintain  equal  proportions  of 
grasses  and  legumes  in  pasture  mixtures. 
It  is  difficult,  and  at  times  impossible, 
to  attain  this  objective. 

As  a  stand  becomes  older,  the  legimie  dies 
out  and  is  replaced  by  grass.  The  prob- 
lem generally  is  to  get  enough  grass  into 
the  mixture  the  first  year  after  seeding 
and  then  to  maintain  the  legume  as  long 
as  possible  as  the  stand  becomes  older. 


The  best  way  to  accomplish  both  of  these 
objectives  is  to  seed  the  right  propor- 
tion of  grass  and  legume,  to  seed  at  a 
time  that  will  favor  the  grass,  to  use 
or  withhold  nitrogen  fertilizer  accord- 
ing to  the  desired  shift,  and  to  follow 
a  grazing  management  program  that  will 
favor  the  legume  after  the  first  year. 

Seeding  rates .  Ladino  clover  is  seldom 
seeded  at  a  rate  of  more  than  l/2  pound 
per  acre.  At  a  higher  rate  it  may  be- 
come so  dominant  in  the  mixtiare  that  the 
danger  of  bloat  will  be  great .  Alfalfa 
is  seeded  at  a  lighter  rate  in  pastijre 
mixtures  than  in  hay  mixtures .  Eight  to 
10  pounds  per  acre  is  generally  suffi- 
cient in  a  past\Jire  seeding.  The  amount 
of  grass  to  seed  per  acre  will  depend  on 
the  fertility  of  the  soil.  For  example, 
on  some  dairy  farms  in  northern  Illinois , 
i|-  to  5  pounds  of  bromegrass  is  suffi- 
cient in  a  pastiire  mixture,  but  in  most 
cases  6  to  8  pounds  should  be  used. 

Time  to  seed.  Late  summer  and  fall  seed- 
ings  favor  grass  over  legume  in  a  mix- 
ture. For  example,  if  the  same  grass - 
legume  mixture  is  seeded  in  early  spring 
and  in  late  summer  or  early  fall  and  the 
spring  seeding  has  given  a  mixture  that 
is  90  percent  legume,  the  late  stimmer 
seeding  will  be  likely  to  give  a  mixture 
that  is  only  Uo  to  50  percent  legume. 
Grass  seeded  in  the  spring  starts  to 
grow  slowly  and  does  not  compete  well 
with  the  legume  and  with  weeds  during 
the  hot  summer.  On  the  other  hand,  when 
it  is  seeded  in  the  late  summer  or  fall, 
weeds  do  not  offer  much  competition  and 
the  grass  continues  to  grow  much  later 
in  the  fall  than  the  legume. 

Location  will  determine  whether  fall 
seedings  are  feasible.  In  northern  Il- 
linois the  growing  season  is  usually  not 
long  enough  for  late  summer  and  fall 
seedings  to  become  established  well 
enough  to  survive  the  winter. 


Use  of  commercial  fertilizer. 


The  use 


of  nitrogen  fertilizer  on  a  grass -legume 


mixture  will  increase  the  proportion  of 
grass  .in  the  mixture  and  may  even  elimi- 
nate the  legume  completely  if  high  enough 
rates  are  used.  Ten  to  15  pounds  of  ni- 
trogen per  acre  can  be  used  at  seeding 
time  to  stimulate  the  gras^.  Sometimes 
the  legume  is  also  stimulated,  but  not 
to  the  same  extent  as  the  grass. 

It  is  usually  not  practical  to  apply  ni- 
trogen to  increase  the  proportion  of 
grass  in  a  mixtxjire  after  it  has  become 
established  because  there  will  be  little 
increase  in  yield  and,  in  fact,  yield 
may  even  be  reduced  because  of  the  reduc- 
tion of  the  legume  in  the  stand.  As  the 
stand  becomes  older,  however,  and  produc- 
tivity declines  because  of  disappearance 
of  the  legume,  it  may  be  desirable  to 
use  up  to  Uo  pounds  of  nitrogen  per  acre 
the  last  year  before  the  stand  is  plowed 
out  and  reestablished. 

Legumes  can  be  maintained  longer  if  lib- 
eral top-dressings  of  phosphorus  and  pot- 
ash carriers  are  used  when  the  soil  is 
low  in  available  forms  of  these  elements. 
This  is  particularly  true  of  potash  in 
southern  Illinois,  whe're  applied  potash 
is  converted  to  an  xxnavailable  form  in  a 
year  or  two- -long  before  the  stand  should 
be  plowed  out.  TNjo  hundred  to  250  potands 
of  an  0-20-20  fertilizer  top-dressed 
every  other  year  will  meet  the  require- 
ments of  legumes  in  most  pastures. 

Grazing  management.  Time  and  intensity 
of  grazing  affect  the  legume  in  a  mixture 
more  than  the  grass.  Response  of  pros- 
trate legumes  like  Ladino  clover  to  graz- 
ing management  is  quite  different  from 
that  of  erect-growing  legumes  like  alfal- 
fa. Frequent  close  grazing  is  harmful  to 
most  species  of  grasses  and  leg\jmes,  but 
moderately  frequent  and  moderately  close 
grazing  will  favor  Ladino  clover  over 
grass.  Such  management  is,  however, 
harmful  to  alfalfa.  If  a  mixture  that 
includes  Ladino  is  left  to  grow  xintil  the 
hay  stage,  the  Ladino  will  decline  in  the 
mixt\:ire.  If  a  mixtxare  that  includes  al- 
falfa is  left  to  grow  until  the  hay  stage, 
the  alfalfa  will  become  more  prominent. 


J.  A. 


Jackobs 
1-18-5^ 


IIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


TALL  FESCUE  VS.  SMOOTH  BROME GRASS 


F-9 


Which  grass  is  better  for  pasture:  tall 
fescue  or  smooth  brome?  The  answer  de- 
pends on  where  the  pasture  is  located  in 
the  state  and  what  kind  of  livestock  is 
to  be  pastured. 

For  summer  grazing,  smooth  brome  is  su- 
perior to  tall  fescue.  It  is  as  produc- 
tive as  tall  fescue  and  is  much  more 
palatable . 

For  winter,  spring,  and  late  fall  graz- 
ing, tall  fescue  is  superior  to  smooth 
brome.  It  begins  to  grow  earlier  in  the 
spring  than  the  brome,  and  it  stays 
green  and  palatable  longer  into  the  fall 
and  winter.  While  tall  fescue  is  not  a 
true  sod-forming  grass,  it  holds  animals 
up  remarkably  well  on  wet  soils.  For 
this  reason  it  is  particularly  well 
adapted  to  winter  and  spring  grazing. 

The  soil  requirements  are  not  so  exact- 
ing for  tall  fescue  as  for  smooth  brome. 
Smooth  brome  reqxiires  a  well-drained  soil 
that  is  high  in  mineral  nutrients  as  well 
as  nitrogen  if  a  productive  stand  is  to 
be  maintained.  Tall  fescue,  on  the  other 
hand,  will  grow  well  on  poorly  drained, 
acid  soils  that  are  only  moderately  high 
in  mineral  nutrients.  Smooth  brome  has 
never  flourished  on  the  light-colored 
soils  in  the  southern  third  of  Illinois. 
Tall  fescue  has  produced  very  well  on 
these  soils  after  recommended  amounts  of 
lime  and  fertilizer  have  been  applied. 

The  question,  then — which  is  better  for 
pastiure:  tall  fescue  or  smooth  brome?  — 
can  be  answered  as  follows: 


because  of  low  temperatxires,  then 
smooth  brome  should  be  seeded  in- 
stead of  tall  fescue. 

2.  If  smooth  brome  does  not  thrive, 
then  tall  fescue  is  the  best 
grass  to  use. 

3.  If  smooth  brome  can  be  grown  and 
mild  winters  allow  winter  grazing, 
then  brome-legume  pastures  shoiold 
be  established  for  summer  grazing 
and  tall  fescue — legume  pasttires 
for  winter  grazing. 

In  general  it  can  be  said  that  smooth 
brome  is  better  than  tall  fescue  on  the 
dark-colored  soils  in  the  northern  two- 
thirds  of  Illinois.  The  brome  does  very 
well  on  these  soils,  and  winter  grazing 
is  not  commonly  practiced  here  because 
of  low  temperatures. 

On  the  light-colored  soils  in  south- 
central  and  southeastern  Illinois,  how- 
ever, where  smooth  brome  does  not  thrive, 
tall  fescue  appears  to  be  the  best  pas- 
ture grass  to  use.  In  southwestern  Illi- 
nois, where  smooth  brome  does  very  well 
on  many  soils,  both  it  and  tall  fescue 
should  be  used  in  pastiire  programs,  be- 
cause winter  grazing  is  practiced  through- 
out southern  Illinois. 

Beef  cattle  graze  tall  fescue  much  bet- 
ter than  do  dairy  cattle  or  sheep.  If 
tall  fescue  pastijre  is  to  be  used  for 
either  dairy  animals  or  sheep,  better 
than  average  grazing  management  will  be 
needed. 


If  smooth  brome  can  be  grown,  and 
if  winter  grazing  is  not  feasible 


A.  Jackobs 
10-19-53 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


F-10 


LADING  clover!^ 


1/ 


Ladino  clover  is  a  giant  form  of  white 
clover  that  yields  about  twice  as  much 
dry  matter  as  other  white  clover  types. 
It  makes  nutritious  forage  for  all 
classes  of  livestock  and  is  well  adapted 
in  Illinois^  growing  best  on  fertile, 
moist  soils . 

Although  Ladino  is  used  principally  for 
forage,  if  handled  carefully  it  makes 
good-quality  hay  and  grass  silage.  It 
needs  to  be  carefxilly  managed  to  keep 
the  stand  productive  and  also  to  make  it 
safe  for  cattle  and  sheep  to  graze.  Nor- 
mally it  should  be  grown  in  mixtures  with 
other  grasses  and  legumes. 

Danger  from  bloat.  Along  with  lush  al- 
falfa and  other  succulent  legumes,  ladi- 
no clover  has  been  blamed  for'"  numerous 
cases  of  bloat  in  livestock.  Range  cat- 
tle that  have  been  fed  on  short  prairie 
grasses  are  particularly  subject  to 
bloating.  Agronomists  and  veterinarians 
suggest  the  following  steps  to  help  cut 
down  chances  of  bloat: 

1.  Seed  only  l/2  poxond  of  Ladino  clover 
an  acre  with  a  well-adapted  'grass  or 
legume-grass  mixture. 

2.  Apply  adequate  fertilizers  And  fol- 
low proper  grazing  management  in  or- 
der to  maintain  a  good  proportion  of 
grasses  'in  the  stand. 

5.  Let  animals  graze  for  only  a  few 
hours  the  first  two  or  three  days. 


Feed  hay  or  other  roughage 
and  dixring  pasturing. 


before 


Don't  turh  cattle 
pastiure . 


or  sheep  onto  wet 


6.  Ee  especially  careful  to  full-feed 
range  cattle  before  pasturing  them. 

7.  Keep  a  close  watch  for  bloating  ani- 
mals so  that  they  can  be  removed  or 
treated  immediately. 

Maintaining  a  stand.  Ladino  clover  does 
not  persist  without  care  fill  management. 
Winterkilling,  drought,  heat,  overgraz- 
ing, and  other  hazards  make  reseeding 
necessary  during  the  year.  Rotational 
grazing  will  allow  one  plot  to  reseed 
itself  while  others  are  being  pastured. 

Pastures  mg,y  be  purposely  \mdergrazed 
early  in  the  season  when  growth  is  rapid. 
Deferred  grazing  not  only  permits  natur- 
al reseeding,  but  also  provides  a  growth 
of  highly  nutritious  forage  that  will  be 
ready  later  when  growth  is  slower. 

Distinguishing  Ladino  from  white  clover. 
Because  Ladino  yields  better  than  white 
clover,  a  pasture  mixtxxre  containing  on- 
ly Ladino  and  not  a  mixtxjre  of  white 
clover  types  is  desirable.  It  is  hard 
to  tell  Ladino  and  white  clover  apart 
because  they  are  similar  in  shape,  color, 
^nd  markings  of  leaves  and  flower  heads 
and  in  shape,  color,  and  size  of  seeds. 
However,  under  similar  favorable  condi- 
tions Ladino  will  be  two  to  four  times 
the  size  and  height  of « common  white  clo- 
ver and  will  usually  have  fewer  flower 
stalks.  Because  size  can  be  affected 
greatly  by  environment,  there  is  no  sixre 
way  to  distinguish  between  the  two  types 
by  their  vegetative  characteristics. 


l/  ■  Refer  to  Circular  65O,  Ladino  Clover  in  Illinois,  for  general  c.ultxa:al  practices. 


Vascular  "bimdle  number  varies.  Several 
investigators  have  conducted  studies  of 
the  number  of  vascular  bundles  in  the 
petioles.  Although  this  method  offers 
possibilities  of  distinguishing  the  larg- 
er Ladino  plants  from  the  medium-sized 
white  clover  plants,  it  does  not  help 
materially  in  identifying  plants  of  simi- 
lar size  of  the  tvo  types  (e.g.,  Ladino 
growing  under  poor  soil  conditions  and 
white  clover  xmder  very  favorable  condi- 
tions ) .  There  is  a  definite  correlation 
between  diameter  of  petiole  and  vascular 
bundle  number,  and  therefore  eqtial-sized 
petioles  of  Ladino  and  white  clover  gen- 
erally have  the  same  number  of  vascular 
bundles  per  petiole. 

Certification  of  seed.  Variations  in 
the  genetic  make-up  of  different  certi- 
fied Ladino  clover  seedlots  can  be  ob- 
sejTved  by  studying  the  cyanogenic  prop- 
erties of  the  X'jhite  clovers.  Cyanogenic 
property  is  the  ability  of  a  plant  to 
release  hydrocyanic  acid  gas  (prussic 
acid)  when  mascerated  or  cut.  No  cases 
of  hydrocyanic  acid  poisoning  have  been 


reported  for  Ladino  clover  as  has  occurred 
when  immature  Sudan  grass  is  pastured. 

Original  Ladino  clover  from  Italy  has 
appeared  to  be  almost  free  from  cyano- 
genic properties.  The  frequency  of 
plants  having  cyanogenic  properties  from 
U.  S.  seedlots  has  been  shown  to  vary 
from  0  to  87  percent.  This  variation 
may  be  due  to  (l)  a  difference  in  the 
original  seedlots  imported  from  Italy, 
(2)  shifts  occixrring  as  a  result  of  nat- 
laral  selection,  and  (3)  outcrossing  with 
other  white  clover  types. 

Whatever  the  reason,  there  have  been 
changes  in  genetic  mal<;e-up  that  point  to 
the  need  for  improving  the  method  of 
certifying  Ladino  clover  seed.  The  dif- 
f iciilty  of  identifying  plants  and  seeds 
is  the  major  problem  in  field  and  lab- 
oratory inspections.  No  observable  low- 
ering of  production  has  been  noted  because 
of  this  genetic  shift  in  certified  Ladi- 
no clover,  and  through  certification  it 
is  hoped  to  keep  Ladino  clover  a  high- 
producing,  nutritious  forage  crop. 


H.  L.  Portz 
10-26-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


COMMON  ALFALFA  DISEASES 


F-n 


Bacterial  vllt  may  cause  loseee of  stands 
of  susceptible  alfalfa  varieties.  Dis- 
eased plants  are  stunted  and  produce 
many  fine  stems j  giving  the  plants  a 
bushy  appearance.  Leaves  are  small  and 
light  green  or  yellow.  A  sure  sign  of 
wilt  infection  is  the  yellow-brown  color 
in  the  woody  tissue  of  the  root  Just  un- 
der the  bark.  Infected  plants  eventu- 
ally wilt  and  die. 

Two  wilt-resistant  varieties,  Buffalo 
and  Ranger,  are  available.  Buffalo  is 
adapted  to  southern  and  central  Illinois, 
and  Ranger  is  best  for  the  north. 

Wilt  seldom  causes  damage  during  the 
first  two  years  of  the  life  of  a  stand. 
Therefore,  if  a  stand  is  desired  for  only 
two  years,  it  may  be  desirable  to  seed 
a  wilt-susceptible  type,  since  seed  of 
resistant  varieties  costs  slightly  more. 

Common  leaf  spot  may  be  recognized  by  the 
small  circular  brown  spots  on  the  leaves. 
If  the  spots  become  nimierous,  the  leaves 
turn  yellow  and  fall.  In  the  center  of  each 
spot  is  a  small  raised  disk,  the  fruiting 
body  of  the  fungus  which  causes  the  dis- 
ease. When  infected  leaves  fall  to  the 
ground,  the  fruiting  body  shoots  its  spores 
up  into  the  leaves  and  causes  new  infection. 

If  possible,  heavily  infected  stands 
shoiild  be  cut  before  the  leaves  fall. 
Then  the  quality  of  the  hay  will  be  main- 
tained and  much  of  the  fungus  will  be  re- 
moved from  the  field,  giving  the  new  crop 
a  better  chance  to  remain  healthy. 

This  disease  appears  to  be  worst  on  acid 
or  low-fertility  soils.  On  good  soils 
the  plants  are  better  able  to  ''outgrow" 
the  disease.  Seedling  stands  often  be- 
come heavily  infected  with  2 enf  spot  but. 


although  the  plants  may  be  severely 
stunted  the  first  year,  it  does  not  seem 
to  cause  any  permanent  damage. 

Plant  breeders  are  attempting  to  develop 
leaf -spot-resistant  varieties. 

There  are  other  leaf  spot  diseases  of 
alfalfa--leaf  blotch,  Stemphylium  leaf 
spot,  and  rust — that  sometimes  cause  dam- 
age. The  control  measures  recommended 
for  common  leaf  spot  also  apply  to  them. 

Black  stem  causes  a  blackening  of  the 
lower  stems  and  may  stunt  the  plants  and 
kill  young  shoots.  It  is  most  common  in 
cool,  wet  weather.  There  are  no  satis- 
factory control  measures. 

Downy  mildew  seldom  damages  alfalfa 
stands,  but  it  often  causes  some  concern 
because  of  its  striking  symptoms.  This 
disease  appears  on  the  new  growth  in 
cool,  wet  weather.  Leaves  become  light 
yellow,  especially  at  the  tip  of  the 
stem,  and  a  grayish-white  moldy  growth 
can  be  found  on  the  underside  of  in- 
fected leaves.  Control  measures  are  usu- 
ally unnecessary. 

Boron  deficiency  causes  alfalfa  plants 
to  become  stunted.  The  leaves  are  yellow 
to  purplish  in  color.  The  terminal  buds 
may  die  and  the  lateral  branches  grow, 
causing  the  stems  to  appear  "broomed." 
Internodes  of  the  stem  are  much  shortened. 
Alfalfa  is  very  sensitive  to  boron  defi- 
ciency. Because  it  is  easily  confused 
with  leaf hopper  damage,  it  is  beat  to 
test  the  soil  for  boron  if  there  is  any 
doubt. 

J.  W.  Gerdemann 
l+-12-5lt 


¥ 


G-1 


OAT  VARIETIES  FOR  ILLINOIS 


Many  varieties  of  oats  are  adapted  to 
Illinois,  but  only  a  relatively  few  are 
commonly  used.  The  list  below  does  not 
include  all  of  the  varieties  that  are 
adapted  to  the  particular  section  indi- 
cated, but  it  does  give  those  that  are 
most  popular: 

Northern:   Clinton,  Bonda,  Nemaha, 

Missouri  0-205,  LaSalle 
Central:   Clinton,  Bonda,  Nemaha, 

LaSalle,  Missouri  0-205, 

Marlon,  Columbia 
Southern:   Benton,  Missouri  0-205, 

Nemaha,  Columbia,  LaSalle 

The  most  popular  variety  in  the  southern 
part  of  the  state  has  been  Clinton  be- 
cause of  its  ability  to  stand  until  har- 
vest. However,  experiments  at  Browns- 
town  and  Dixon  Springs  show  that  LaSalle, 
Missouri  0-205,  Benton,  and  Nemaha 
should  be  recommended  over  Clinton  in 
this  section  because  of  their  higher 
yields . 

Recommended  Varieties 

LaSalle  was  developed  at  Illinois  by 
0.  T.  Bonnett  from  the  cross  Clinton  x 
Marion.  Seed  will  be  distributed  to  ex- 
perienced growers  of  certified  seed  in 
the  spring  of  1953  •  A.  yellow-kerneled 
variety,  LaSalle  matures  three  or  four 
days  earlier  than  Clinton,  grows  to 
about  the  same  height,  and  is  less  re- 
sistant to  lodging,  although  it  is  supe- 
rior in  this  respect  to  Marion  and  An- 
drew. LaSalle  has  not  equaled  Clinton 
in  yield  at  the  DeKalb  field  but  has 
been  superior  to  it  at  both  Urbana  and 
Brownstown.  It  is  intermediate  in  re- 
sponse to  septoria  and  susceptible  to 
race  7  of  stem  rust,  but  somewhat  toler- 
ant to  ^5  and  similar  races  of  leaf  rust. 
Although  it  does  not  equal  Clinton  in 
test  weight,  it  is  satisfactory  in  this 
respect. 


Clintaf e,  a  new  variety, was  developed  by 
Iowa  from  the  cross  Clinton  x  Santa  Fe. 
Santa  Fe,  introduced  from  Argentina,  is 
late,  susceptible  to  lodging,  and  not 
adapted  to  the  Corn  Belt.  It  does,  how- 
ever, have  good  resistance  to  ^5  and 
similar  races  of  leaf  rust  and  to  sep- 
toria black  stem  disease.  Clintaf e  is 
the  result  of  a  breeding  program  having 
two  aims:  first,  to  obtain  the  disease 
resistance  of  Santa  Fe  by  crossing  this 
variety  with  Clinton  and,  second,  to  re- 
gain as  many  as  possible  of  the  desir- 
able qualities  of  Clinton  through  a  se- 
ries of  back-crosses  to  Clinton. 

Cllntafe  matures  two  or  three  days  later 
than  Clinton,  grows  about  two  inches 
taller,  and  appears  to  equal  it  in  yield 
in  northern  Illinois.  It  is,  however, 
lower  in  test  weight  and  not  quite  so 
resistant  to  lodging,  although  possibly 
better  in  this  respect  than  Missouri 
0-205  or  LaSalle.  Cllntafe,  when  avail- 
able, will  be  resistant  to  race  h^  and 
approach  Clinton  in  lodging  resistance. 
It  will  be  adapted  to  northern  Illinois. 
Seed  will  not  be  available  until  after 
the  1953  harvest. 

Benton,  selected  by  Indiana  from  the 
cross  D-69  X  Bond,  Is  similar  to  Clinton 
except  that  it  ripens  a  day  or  two  ear- 
lier in  southern  Illinois  and  grows  six 
to  eight  Inches  taller.  It  also  has  a 
higher  yield  record  than  Clinton  in  this 
area.  Benton  is  tolerant  to  septoria 
and  shows  some  tolerance  to  race  U5  but 
is  susceptible  to  race  7  of  stem  rust. 

Bonda,  selected  by  Minnesota  from  the 
cross  Bond  x  Anthony, has  a  white  kernel, 
grows  about  four  inches  taller  than  Clin- 
ton, matures  at  about  the  same  time,  and 
has  the  same  resistance  to  the  rusts  and 
septoria.  It  has  the  highest  test 
weight  of  any  oat  recommended  for  Illi- 
nois,  consistently  running  two  or  more 


pounds  heavier  than  Clinton  and  other 
varieties.  Bonda  yields  well  in  north- 
ern and  central  Illinois  hut  is  not  rec- 
ommended for  southern  Illinois. 

Andrew,  developed  by  Minnesota  from  the 
cross  Bond  x  Rainbow,  has  a  yellow  grain 
and  the  same  resistance  to  disease  as 
Clinton  except  that  it  is  susceptible  to 
races  8  and  10  of  stem  rust  rather  than 
race  7-  It  may  have  some  tolerance  to 
i+5  and  similar  races  of  leaf  rust  but  is 
susceptible  to  septoria.  Andrew  is  not 
so  resistant  to  lodging  as  Clinton,  and 
its  maturity  date  varies;  in  some  years 
it  will  mature  at  the  same  time  as  Clin- 
ton and  in  others  will  be  somewhat  ear- 
lier. It  has  a  good  yield  record  in 
both  northern  and  central  Illinois. 

Nemaha,  developed  by  Iowa  from  the 
double  cross  Victoria-Richland  x  Morota- 
Bond,  was  released  by  Kansas  and  Nebras- 
ka in  19^8.  It  has  a  reddish-yellow 
kernel  color,  grows  about  three  inches 
shorter  than  Clinton,  and  matures  two  or 
three  days  earlier.  It  is  not  so  resis- 
tant to  lodging  as  Clinton  but  is  slight- 
ly better  than  Andrew,  Nemaha  has  a 
good  test  weight  and  a  slightly  lower 
yield  than  Clinton  in  northern  and  cen- 
tral Illinois,  although  it  has  out- 
yielded  Clinton  in  southern  Illinois. 
It  is  intermediate  in  resistance  to  sep- 
toria, tolerant  to  k^  and  similar  races 
of  leaf  rust,  and  susceptible  to  race  7 
of  stem  rust. 

Marion,  from  Markton  x  Rainbow,  was  re- 
leased by  Iowa  in  1939-  It  has  white 
kernels,  is  resistant  to  stem  rust  ex- 
cept races  8  and  10,  has  some  tolerance 
to  race  h^  of  leaf  rust,  and  is  suscep- 
tible to  septoria  and  lodging.  Marion 
has  an  excellent  yield  record  in  north- 
ern and  central  Illinois  but  does  not 
yield  well  in  southern  Illinois.  It  ma- 
tures slightly  earlier  than  Clinton. 

Columbia,  selected  by  Missouri  from  Ful- 
ghum,  matures  about  five  days  earlier 
than  Clinton.  It  is  very  susceptible  to 
smut  and  rust  except  race  k^   and  similar 


races  of  leaf  rust,  and  is  resistant  to 
septoria.  In  spite  of  these  disadvan- 
tages, it  has  never  gone  completely  out 
of  the  picture  in  Illinois,  primarily 
because  of  its  earliness  and  relatively 
good  yield  record. 

Missouri  0-20^,  selected  by  Missouri 
from  the  cross  Columbia  x  Victoria-Rich- 
land, is  similar  to  Columbia  in  plant 
and  seed  characteristics  and  about  two 
days  later  than  Columbia  but  two  to  three 
days  earlier  than  Clinton.  It  grows 
three  cr  f our  inches  taller  than  Clinton. 
Missouri  0-205  is  comparable  to  Nemaha 
in  resistance  to  lodging.  It  is  resist- 
ant to  race  U5  of  leaf  rust  and  race  7 
of  stem  rust,  susceptible  to  races  8  and 

10  of  stem  rust,  and  tolerant  to  septo- 
ria.  It  has  a  good  test  weight. 

Clinton  and  derivatives,  such  as  Clinton 

11  and  59>  3.Te  from  a  cross  of  D69  x 
Bond.  Clinton,  released  in  19^6, is  sus- 
ceptible to  U5  and  similar  races  of  leaf 
rust  and  to  race  7  of  stem  rust.  It  is 
outstanding  in  lodging  resistance,  has 
good  test  weight  and  yield,  and  matures 
about  five  days  later  than  Columbia. 

Varieties  Not  Recommended 

Abegweit late;  low  test  weight 

Advance late 

Ajax susceptible  to  rust 

Beaver late;  low  test  weight 

Bonham low  yield 

Branch late 

Cherokee low  yield 

Colo late;  low  yield 

Craig late 

Eaton low  yield 

Exeter late;  susceptible  to  rust 

Fortune late;  susceptible  to  rust; 

low  test  weight 

James  Hulless  Bond low  yield 

Lorain susceptible  to  rust;  low 

yield 
Mo.  0-200.... low  yield;  susceptible  to 

lodging 

Shelby late 

Zephyr late;  light  test  weight 

W.  0.  Scott 
1/12/53 


/ERSITY  OF  ILL 


G-1  Revised 


1954  OAT  VARIETIES  FOR  ILLINOIS 


Although  many  varieties  of  oats  are 
adapted  to  Illinois,  only  a  relatively 
few  are  conmonly  used.  The  list  below 
does  not  include  all  varieties  that  are 
adapted  to  the  particular  section,  but 
it  does  give  those  that  are  new  and  most 
popular  in  each  section. 


Northern 

High  fertility: 

Medium  to  low 
fertility: 


Central 

High  fertility: 

Medium  to  low 
fertility: 

Southern 


Clintland,*  Clinton, 
Clintafe,  Bonda 

Same  as  above  plus 
Branch,  Mo.  0-205 
LaSalle ,  Nemaha 


Clintland,*  Clinton, 
Bonda,  Benton 

Mo.  0-205,  LaSalle, 
Andrew,  Nemaha 


Mo.  0-205,  Nemaha, 
LaSalle ,  Benton 

Oat  yields  in  1953  were  generally  disap- 
pointing. Disease  and  extremely  high 
temperattores  at  "filling"  time  reduced 
yields  and  quality.  Race  7  of  stem  rust 
damaged  susceptible  varieties  in  some 
sections.  Where  damage  occurred,  farm- 
ers may  be  discoiiraged  with  Clinton  and 
want  a  stem-rust-resistant  variety. 

At  present  all  resistant  varieties  are 
much  more  susceptible  to  lodging  than  Clin- 
ton. It  is  therefore  necessary  to  choose 
between  disease  resistance  and  stiff 
straw.  Bad  stem-rust  years  cotild  conceiv- 
ably follow  consecutively.  It  is  possi- 
ble that  195^  will  be  another  rust  year. 
But  the  records  show  that  severe  damage 
can  be  expected  only  once  every  5  to  10 
years.  Therefore  on  highly  fertile  soils 
rust  may  be  a  lesser  gamble  than  lodging. 
*Not  available  commercially  until  1955. 


Recommended  Varieties 

Clintland*  was  developed  at  the  Indiana 
Station  from  the  cross  Clinton  x  Land- 
hafer  after  it  had  been  backcrossed  to 
Clinton  3  times.  Seed  of  this  new  vari- 
ety will  be  increased  in  Illinois  and 
distributed  in  1955 ♦  Clint land  is  simi- 
lar to  Clinton  in  maturity,  plant  appear- 
ance, lodging  resistance,  and  grain  char- 
acteristics. It  is  resistant  to  Race  1+5 
and  all  other  crown  rust  races  now  found 
in  the  Corn  Belt.  It  is  susceptible  to 
Race  7  and  resistant  to  Race  8  of  stem 
rust  and  moderately  resistant  to  Septoria 
black  stem.  When  seed  is  available,  it 
is  expected  to  replace  a  large  part  of 
the  acreage  now  devoted  to  Clinton. 

Clintafe  was  developed  by  the  Iowa  Sta- 
tion from  the  cross  Clinton  x  Santa  Fe 
backcrossed  to  Clinton  2  times.  Seed  is 
available  in  Illinois  for  195^^-  planting. 
Clintafe  matures  2  to  3  days  later  than 
Clinton,  grows  about  2  inches  taller, 
and  is  about  comparable  in  lodging  resist- 
ance. But  it  is  slightly  lower  in  test 
weight.  Clintafe  is  resistant  to  Race  45 
and  susceptible  to  Race  7  of  stem  rust. 
It  is  highly  resistant  to  Septoria  black 
stem.  Because  it  matures  rather  late,  we 
recommend  it  primarily  for  the  northern 
part  of  Illinois. 

Branch  was  developed  at  the  Wisconsin 
Station  from  Forward  x  (Victoria-Richland) 
backcrossed  to  Forward.  Branch  matures 
5  to  7  days  later  than  Clinton,  grows  h 
to  5  inches  taller,  is  about  comparable 
to  Mo.  0-205  in  lodging  resistance,  and 
is  moderately  resistant  to  Race  k3  of 
crown  rust.  It  is  also  resistant  to 
Race  7  hut  susceptible  to  Race  8  of  stem 
rust.  It  is  one  of  the  most  resistant 
varieties  to  Septoria  black  stem.  Because 
it  matures  late,  it  should  be  confined  to 
the  northern  part  of  the  state. 


LaSalle  was  developed  at  the  Illinois 
Station  from  the  cross  Clinton  x  Marion. 
It  was  distrihuted  to  certified  seed  pro- 
ducers in  1953'  It  is  a  yellow  kerneled 
variety  that  matures  3  or  U  days  earlier 
than  Clinton,  grows  to  about  the  same 
height,  and  is  less  resistant  to  lodging, 
although  it  is  superior  in  this  respect 
to  Marion  and  Andrew.  laSalle  has  not 
equaled  Clinton  in  yield  at  the  DeKalb 
field  but  has  been  superior  to  it  at  both 
Urbana  and  Brownstown.  It  is  susceptible 
to  Race  7  of  stem  rust  but  is  somewhat 
tolerant  to  Septoria  and  Race  ^5  and  simi- 
lar races  of  leaf  rust.  Although  it 
does  not  equal  Clinton  in  test  weight, 
it  is  satisfactory  in  this  respect. 

Clinton  and  derivatives,  such  as  Clinton 
11  and  59^  are  from  a  cross  of  D69  x  Bond. 
Clinton,  released  in  19^6,  is  suscepti- 
ble to  U5  and  similar  races  of  leaf  rust 
and  to  Race  7  of  stem  rust.  It  is  out- 
standing in  lodging  resistance,  has  good 
test  weight  and  yield,  and  matures  about 
5  days  later  than  Columbia. 

Benton,  selected  by  Indiana  from  the 
cross  D69  X  Bond,  is  similar  to  Clinton 
except  that  it  ripens  a  day  or  two  ear- 
lier in  southern  Illinois  and  grows  6  to 
8  inches  taller.  It  also  has  a  higher 
yield  record  than  Clinton  in  this  area. 
Benton  is  tolerant  to  Septoria  and  shows 
some  tolerance  to  Race  U5  but  is  suscep- 
tible to  Race  7  of  stem  rust. 

Bonda,  selected  by  Minnesota  from  the  cross 
Bond  X  Anthony, has  a  white  kernel,  grows 
about  k  inches  taller  than  Clinton,  ma- 
tures at  about  the  same  time, and  has  the 
same  resistance  to  the  rusts  and  Septoria. 
It  has  the  highest  test  weight  of  any  oat 
recommended  for  Illinois,  consistently 
running  2  or  more  pounds  heavier  than 
Clinton  and  other  varieties.  Bonda  yields 
well  in  northern  and  central  Illinois  but 
is  not  recommended  for  southern  Illinois. 

Andrew,  developed  by  Minnesota  from  the 
cross  Bond  x  Rainbow,  has  a  yellow  grain 
and  the  same  resistance  to  disease  as  Clin- 
ton except  that  it  is  resistant  to  Race  7 
of  stem  rust  and  susceptible  to  Race  8. 
It  may  have  some  tolerance  to  U5  and  simi- 
lar races  of  leaf  rust  but  it  is  suscepti- 
ble to  Septoria.  Andrew  is  not  so  resist- 
ant to  lodging  as  Clinton,  and  its  maturity 


date  varies;  in  some  years  it  matures  at 
the  same  time  and  in  others  it  is  some- 
what earlier.  It  has  a  good  yield  record 
in  both  northern  and  central  Illinois. 

Kemaha,  developed  by  Iowa  from  the  double 
cross  Victoria-Richland  x  Morota-Bond, 
was  released  by  Kansas  and  Nebraska  in 
19^8.  It  has  a  reddish-yellow  kernel 
color,  grows  about  3  inches  shorter  than 
Clinton,  and  matures  2  or  3  clays  earlier. 
It  is  not  so  resistant  to  lodging  as  Clin- 
ton but  is  slightly  better  than  Andrew. 
Nemaha  has  a  good  test  weight  and  a  slight- 
ly lower  yield  than  Clinton  in  northern 
Illinois.  It  is  intermediate  in  resist- 
ance to  Septoria  black  stem,  tolerant  to 
45  and  similar  races  of  leaf  rust,  and 
susceptible  to  Race  7  of  stem  rust. 

Mo.  0-20^,  selected  by  Missouri  from  the 
cross  Columbia  x  Victoria-Richland,  is 
similar  to  Columbia  in  plant  and  seed  char- 
acteristics and  about  2  days  later  than 
Columbia  but  2  or  3  days  earlier  than  Clin- 
ton. It  grows  3  to  U  inches  taller  than 
Clinton.  Mo.  0-205  is  comparable  to  Nema- 
ha in  resistance  to  lodging.  It  is  resist- 
ant to  Race  U5  of  leaf  rust  and  Race  7  of 
stem  rust,  susceptible  to  Races  8  and  10 
of  stem  rust,  and  tolerant  to  Septoria 
black  stem.   It  has  good  test  weight. 

Varieties  Not  Recommended 

Abegweit  -  late;  low  test  weight 

Advance  -  late 

Ajax  -  susceptible  to  rust 

Beaver  -  late;  low  test  weight 

Bonham  -  low  yield 

Cherokee  -  low  yield 

Colo  -  late;  low  yield 

Craig  -  late 

Eaton  -  low  yield 

Exeter  -  late;  susceptible  to  rust 

Fortxine  -  late;  susceptible  to  rust; 

low  test  weight 
James  Hxill-less  Bond  -  low  yield 
Larain  -  susceptible  to  rust;  low  yield 
Mo.  0-200  -  low  yield,  susceptible  to 

lodging 
Shelby  -  late 
Zephyr  -  late;  light  test  weight 

The  following  varieties  are  not  recom- 
mended because  their  adaptability  to  Il- 
linois conditions  has  not  been  determined: 
Rodney,  Lanark,  Sauk,  Valor. 

¥.  0.  Scott 
I2-IU-53 


G-2 


CROWN  RUST  OF  OATS  (Pu 


Economic  Importance. 
rust,  as  it  is  often 
most  everywhere  oats 
amount  of  infection 
amount  of  inoculum  ( 
the  early  spring,  the 
tible  varieties,  and 
to  optimum  growth  and 
fungus . 


Crown  rust,  or  leaf 

called,  appears  al- 

are  produced.   The 

depends  on  the 

spores)  present   in 

acreage  of  suscep- 

weather  conducive 

development  of  the 


In  Illinois  the  annual  loss  from  crown 
rust  m  the  past  10  years,  as  estimated 
ty  Mr.  G.  H.  Boeve,  Natural  History  Sur- 
vey, has  ranged  from  2  to  I5  percent. 
Race  k^  and  similar  races  have  been 
largely  responsible. 

Symptoms.  Crown  rust  occurs  principally 
on  leaves  of  the  oat  plant,  although  it 
IS  often  present,  especially  in  suscep- 
tible varieties,  on  the  leaf  sheath, 
stems,  and  panicles.  There  are  two 
stages  of  the  disease:  the  orange- 
yellow  or  summer  stage  and  the  black  or 
winter  stage. 

The  rust  spots  (pustules)  of  the  summer 
stage  are  usually  more  or  less  circular 
although  some  of  them  are  much  longer 
than  they  are  wide.  The  number  and  size 
of  the  pustules  vary  greatly,  depending 
on  the  susceptibility  of  the  variety  and 
the  severity  of  the  infection.  The  pus- 
tules of  the  summer  stage  rupture  the 
epidermis. 

.ater  in  the  season  the  black  or  winter 
•>tage  appears.  This  stage  does  not  rup- 
■ure  the  epidermis  as  does  the  summer 
tage  of  black  stem  rust. 


ccinig  coronotQ  avenaej 

The  other  (alternate)  host  for  crown 
rust  IS  any  one  of  a  number  of  species 
of  buckthorn  (Rhamnus) .  On  this  host 
bright  yellow  or  orange  spots  first  ap- 
pear on  the  upper  surface  of  the  leaf- 
Opposite  these  spots,  usually  on  the 
undersurface  of  the  leaf,  the  cluster- 
cup  stage  appears.  This  stage  is  simi- 
lar m  appearance  to  that  of  stem  rust 
on  barberries. 

Mf|^y£le.  The  life  cycle  of  the  crown 
rust  fungus  is  similar  to  that  of  stem 
rust  except  that  the  cluster-cup  stage 
develops  on  buckthorn  instead  of  on  bar- 
berries. In  Illinois  the  summer  staee 
seldom,  if  ever,  winters  over.  Early 
spring  infection  develops  from  the  clus- 
ter-cup stage  on  buckthorn.  Also,  sum- 
mer spores  may  be  blown  in  from  the 
southern  states  where  they  live  through 
the  winter  on  fall-seeded  oats. 

Physiologic  races.  Over  100  distinct 
races  of  crown  rust  have  been  discovered 
They  differ  only  in  their  ability  to  at- 
tack certain  varieties  of  oats.  For  ex 
ample,  Race  45  attacks  the  Bond-type 
oats,  such  as  Clinton  and  similar  va- 
rieties, but  not  Vicland. 

Race  I15  was  first  discovered  about  1937 
but  was  of  little  consequence  at  that 
time  However,  since  the  introduction 
of  the  Bond-type  oats.  Race  ^5  and  simi- 
lar races  have  become  increasingly  wide- 
spread and  of  great  economic  importance 
At  present  these  races  constitute  about 
90  percent  of  the  rust  occurring  on 
oats  over  the  entire  United  States 


Like  barberry  for  stem  rust^  buckthorn 
serves  as  a  source  of  development  of  new 
races  of  crown  rust.  The  sexual  stage 
occurs  on  buckthorn,  and  this  plant  is 
the  common  host  for  all  the  races.  Con- 
sequently, if  two  races  infect  the  buck- 
thorn at  the  same  time,  it  is  possible 
for  them  to  cross  or  hybridize  and  pro- 
duce a  new  race  or  races. 

Control.  Some  states  recommend  eradica- 
tion  of  buckthorn  to  reduce  the  source 
of  new  races  of  rust.  At  present,  the 
only  practical  means  of  control,  how- 
ever is  the  use  of  resistant  varieties. 


A  few  new  varieties  are  being  introduced 
that  are  highly  resistant  to  all  the 
present  crown  rust  races;  and  until  new 
races  appear,  these  varieties  will  mate- 
rially reduce  the  loss  due  to  crown  rust. 

Considerable  work  is  being  done  in  test- 
ing different  antibiotics  and  fungicides 
for  use  in  controlling  rust.  These  tests 
are  not  being  carried  out  with  the  idea 
of  spraying  or  dusting  the  entire  oat 
acreage,  but  for  the  purpose  of  control- 
ling a  local  outbreak  and  preventing  the 
development  of  a  general  epidemic . 

W,  M.  Bever 
1/12/53 


DIAGRAl^MATIC  SKETCH  OF  LIFE 
CYCLE  OF  CROWN  RUST 


This  spore 
infects  buck 
thorn 


Winter  spore 
germinating  in 
early  spring 


Winter  stage  on 
oat  stubble 
forms  as  crop 
matures. 


.   Summer 
/^tage  repro 

/duces  itself  on 
oats  each  7-10 

\  days  until  oat 

\  mature 


Cluster  cup  stage  on 
buckthorn 


This  spore  from  buck- 
thorn infects  young 
oat  seedling 


Summer  stage  on  oats. 


This  is  the  stage 

when  damage  is  done  to  oat  crop. 


iMiVERSITY  OF  ILL 


,piri  iiTi  iPF 


GREY  SPOT  OF  OATS 


"Grey  spot,"  first  observed  in  local 
areas  in  1-9hQ,  was  general  throughout 
the  state  in  19^9-  Since  that  time  it 
has  occurred  each  year  but  has  not  been 
nearly  so  extensive  as  it  was  in  19^9- 
The  cause  is  not  yet  known. 


Sometimes  the  infested  areas  overlap, 
creating  a  much  larger  area.  All  plants 
within  an  infested  spot  are  ashy  gray  in 
color.  None  of  them  escape.  Grey  spot 
has  no  apparent  effect  on  seed  germina- 
tion, however. 


This  disease  is  best  observed  at  the 
time  the  oats  are  turning  from  green  to 
yellow,  a  few  weeks  before  they  are 
ready  to  harvest.  The  plants  in  the  in- 
fested part  of  the  field  are  ashy  gray 
and  a  little  shorter  than  the  healthy 
plants.  It  is  practically  impossible  to 
recognize  the  disease  before  this  stage 
of  growth. 

A  reddening  and  premature  dying  of  the 
leaves  may  occur  when  the  plants  are  1 
to  2  feet  high,  but  this  is  not  always 
true.  The  infested  area  is  usually  cir- 
cular and  from  k   to  20  feet  in  diameter. 


Experimental  tests  have  shown  that  yield 
is  reduced  as  much  as  10  bushels  per 
acre  and  test  weight  is  lowered  as  much 
as  '+.5  pounds  per  bushel  within  the  dis- 
eased spots.  The  seed  is  always  light 
and  chaffy. 

Until  a  technic  has  been  developed  for 
producing  grey  spot  artificially,  vari- 
etal resistance  on  susceptibility  cannot 
be  studied  in  detail.  Field  observa- 
tions indicate,  however,  that  all  vari- 
eties in  commercial  production  in  Illi- 
nois are  susceptible.  Crop  rotation  has 
no  effect  on  the  incidence  of  the  disease. 

W.  M,  Bever 


BLACK  STEM  DISEASE  OF  OATS  (Septoria  avenae) 


Black  stem  disease  of  oats  was  first  re- 
ported in  the  United  States  in  1922. 
Until  recently,  however,  it  was  not  con- 
sidered important,  and  relatively  little 
research  work  was  done  on  it.  Only  in 
the  past  few  years  has  it  become  econom- 
ically important,  and  even  now  no  fig- 
ures are  available  on  the  damage  it 
causes  in  Illinois. 

Symptoms.  The  first  noticeable  symptoms 
appear  in  the  early  spring  as  small  pur- 
plish brown  spots  on  the  leaves.  As  the 
spots  grow,  the  infected  leaf  tissue 
dies.  In  severe  cases  the  spots  may 
combine,  causing  the  leaf  to  die  prema- 
turely. 

Sometime  after  heading  the  black  stem 
symptom  begins  to  appear.  It  is  usually 
observed  first  on  the  leaf   sheath  and 


around  the  point  where  the  leaf  is  at- 
tached to  the  sheath.  From  there  it 
spreads  to  the  stem  of  the  plant.  Be- 
cause of  the  stem  lesions,  susceptible 
varieties  will  lodge  considerably  at  the 
points  of  infection. 

When  conditions  are  optimum  for  growth 
of  the  black  stem  fungus,  considerable 
browning  of  the  hulls  will  also  occur. 
This  brown  discoloration  has  no  notice- 
able effect  on  germination  of  the  seed, 
however . 

Control.  Not  too  much  is  known  at  pres- 
ent about  the  life  cycle  and  overwinter- 
ing habits  of  the  black  stem  fungus.  At 
present  no  oat  variety  appears  to  be  en- 
tirely immune,  although  some  varieties, 
such  as  Andrew,  Marion,  and  Colo,  seem 
more  susceptible  than  others. 

W.  M.  Bever 
1/12/53 


UNI 


,5  •  COLLl 


L. 


G-4 


ROW  SPACING  FOR  SMALL  GRAINS 


What  about  widening  small  grain  rows  to 
increase  legume-grass  stands?  This 
question  is  not  new  but  is  coming  more 
often  as  a  result  of  recent  articles  in 
farm  papers . 

Whenever  two  or  more  crops  are  seeded  on 
the  same  piece  of  ground,  they  must  com- 
pete for  moisture,  nutrients,  and  light. 
For  instance,  when  clover  is  seeded  in 
small  grain,  the  grain  is,  by  nature, 
far  the  more  aggressive  competitor.  Its 
rapid  top  growth  often  shades  the  legume 
before  its  first  true  leaf  is  out,  while 
its  extensive,  fibrous  root  system  rap- 
idly depletes  the  soil  of  moisture. 

Wider  spacing  of  small  grain  rows  is  a 
simple  cultural  method  of  reducing  com- 
petition. As  in  many  other  cultural  op- 
erations, however,  the  benefits  to  be 
gained  will  depend  on  the  growing  season . 
A  deficiency  of  soil  moisture  has  been 
found  to  be  by  far  the  most  important 
single  factor  in  retarding  plant  growth. 
The  period  when  the  moisture  is  defi- 
cient is  also  important. 


In  two  of  the  five  years  stands  were 
significantly  better  in  the  wide  rows. 
During  seasons  with  normal  or  above- 
normal  rainfall  individual  legume  seed- 
lings were  not  so  vigorous  in  narrow 
rows  as  in  wide  rows,  but  this  differ- 
ence generally  disappeared  after  small- 
grain  harvest. 

Several  disadvantages  of  wide  row  spac- 
ing might  be  pointed  out: 

First,  it  is  necessary  to  use  a  grain 
drill  rather  than  broadcast.  Many  Illi- 
nois spring  oat  growers  do  not  have 
grain  drills. 

Second,  grain  yields  are  generally  re- 
duced from  10  to  20  percent  when  rows 
are  widened  from  8  to  l6  inches  (see 
Table  2  on  page  2) . 

The  most  promising  row  spacing  for  ob- 
taining good  clover  stands  with  the 
least  sacrifice  in  grain  yield  appears 
to  result  from  plugging  every  third 
drill  hole  rather  than  every  other  hole. 


The  need  of  clover  stands  on  highly  fer- 
tile soil  at  Urbana  for  moisture  during 
May  and  June  is  shown  in  the  following 
table: 

Table  1. --Effect  of  Rainfall  During  May 
and  June  on  Glover  Stands  at  Urbana, 
Illinois,  191+8-52 


Rainfall 

Stand 

Year 

«"rows 

16"rows 

perct . 

perct. 

I9I+8 

Below  normal 

15 

50 

19^9 

Normal 

100 

100 

1950 

Below  normal 

30 

60 

1951 

Above  normal 

100 

100 

1952 

Normal 

90 

100 

Three  basic  problems  have  been  encoun- 
tered in  widening  winter  wheat  rows: 
(1)  erosion  is  increased, (2)  winterkill- 
ing is  increased, (3)  spring  seeding  con- 
ditions and  certain  soil  types  found 
particularly  in  southern  Illinois  some- 
times favor  establishment  of  the  clover 
in  the  grain  row  rather  than  between  the 
row.  Under  these  conditions  widening  the 
rows  actually  causes  a  decrease  in  clover 
stand  and  an  increase  in  weed  population. 

Should  the  same  amount  of  seed  be  used 
per  acre  in  wide  rows  as  in  regular 
spacing?  In  wheat,  seeding  at  the  same 
rate  seems  desirable  because  the  heavier 
seeding  increases  winter  survival.  In 
spring  oats,  little  or  no  yield  increase 


has  been  obtained  from  seeding  heavy 
amounts  per  row;  therefore  the  acre  rate 
can  be  decreased  when  rows  are  widened. 

Another  Interesting  result  of  the  row 
spacing  trials  is  the  consistently  high- 
er test  weight  of  grain  obtained  from 
closely  spaced  rows  than  from  wide  rov^s. 
The  difference  is  generally  small,  al- 
though in  certain  tests  it  has  approached 
2  pounds 

Summary.  Wide  grain  rows  reduce  the 
competition  between  grain  and  clover  for 


moisture,  nutrients,  and  light.  However, 
the  primary  factor  appears  to  be  the 
availability  of  soil  moisture  during  May 
and  June.  In  seasons  when  dry  periods 
occur  during  either  of  these  two  months, 
wide  grain  rows  may  make  the  difference 
between  success  and  failure  of  the 
clover  stand.  However,  grain  yields 
from  wide  rows  are  about  10  to  20  percent 
lower  than  yields  from  regular  8-inch 
rows.  The  most  promising  spacing  ar- 
rangement appears  to  be  plugging  every 
third  drill  hole  rather  than  every  other 
hold. 


il 


Table  2. --Yields  of  Spring  Oats  and  Winter  Wheat  From  Various  Row  Spacings 

at  Urbana,    Illinois,    1950-52 


Spring  oats 


Winter  wheat 


Row  spacing 


1950   1951   1952  Average  I95I   I952  Average 


bu. 


bu. 


bu. 


bu. 


bu. 


bu. 


bu. 


8-inch  rows  77-7  ^6.5  79-6  67.9  39-^   36.2   37.8 

16-inch  rows  63.6  37.9  68.3  56.6  28.2   35.0   31.6 

2U-inch  rows  50. 9  25.1  5i+.7  i+3.6  20. i+   3^.0   27.2 

Two  8-inch  rows  with  l6-inch  space  68.1  k3.k  72.9  6I.5  33.8   39. 1   36.5 

Two  U-inch  rows  with  l6-inch  space  69.8  4o.l  7^1.6  6I.5  35. U   Uo.O   37.7 

Broadcast  67.5  k^ .J  69.7  61.6  


J.  W. 


Pendleton 
1/12/53 


AGku 


G-5 


SOW  SPRING  GRAINS  EARLY 


Spring  small  grains  should  be  seeded  as 
soon  as  the  soil  is  in  condition  to  work. 
Early  sowing  is  particularly  essential 
for  success  with  spring  wheat,  especial- 
ly if  this  crop  is  being  attempted  in 
north-central  and  central  Illinois.  It 
is  not  advisable  to  sow  spring  wheat  at 
all  in  the  southern  part  of  the  state. 
The  data  on  seeding  dates  for  spring 
wheat  shown  in  the  table  below  were  ob- 
tained at  Urbana. 

Early  seeding  makes  for  deep  rooting  of 
plants  and  advances  the  maturity  of  the 
crop.  In  late-seeded  crops  the  partial- 
ly mature  plants  are  often  exposed  to 
unfavorably  high  temperatures  and  to  en- 
vironments that  are  conducive  to  infec- 
tion by  scab  and  rust  diseases. 

Although  spring  barley  is  not  so  sensi- 
tive to  late  seeding  as  is  spring  wheat, 
early  sowing  is  very  necessary  for  good 
results.  In  central  Illinois,  oats 
should  be  seeded  between  the  middle  of 
February  and  the  middle  of  March. 

Spring  oats  do  well  in  northern  Illinois 
when  seeded  any  time  during  the  last 
half  of  March  and  April  20;  but  in  the 
central  and  southern  parts  of  the  state 
April  seeding  distinctly  reduces  yield. 
Oats  seeded  in  May  are  so  poor  that,  if 
it  were  not  for  their  service  as  a  com- 
panion crop  for  legume  and  grass,  they 
would  be  considered  a  failure.   The 


graph  on  the  back  of  this  page  shows 
yield  trend  curves  taken  from  many  years 
of  experience  in  seeding  oats  in  central 
and  southern  Illinois. 

Yield  drops  off  more  sharply  with  late 
seeding  in  southern  than  in  central  Il- 
linois, and  it  drops  off  very  rapidly  as 
a  result  of  May  seeding.  From  the  first 
half  of  March  to  the  last  half  of  April-- 
U6  days--the  yield  fell  from  100  to  6k 
percent.  This  is  a  rate  of  about  3A 
percent  for  each  day  seeding  was  delayed. 
After  the  last  half  of  April,  yield 
dropped  1  l/2  percent  for  each  day  seed- 
ing was  postponed. 

In  southern  Illinois,  yield  fell  off 
about  1  percent  per  day  of  delay  in  seed- 
ing up  to  the  last  half  of  April,  and 
after  that  time  the  drop  in  yield  was 
about  1  3/k  percent  for  each  day  seeding 
was  delayed. 


These  statements  apply  to  an  average  of 
seasons.  Exceptionally  cool  seasons 
will  permit  oats  seeded  in  May  to  yield 
more  than  these  figures  indicate.  It  is 
not  harmful  even  in  such  seasons  to  seed 
oats  early.  They  will  always  perform 
well.  Hard  freezes  have  been  known  to 
kill  some  of  the  plants,  but  the  remain- 
ing ones  will  yield  more  than  later 
seeded  oats.  Therefore,  do  not  be 
afraid  of  seeding  oats  too  early. 

G .  H .  Dungan 

2/2/53 


Date  of 

Heads  in- 

seeding 

Yield 

Weight 

fected  with 

wheat 

per  acre 

per  bushel 

scab 

March  6 
March  l6 
March  29 
April  10 


bu. 

29.3 
2^.k 
22.8 
22. 2i/ 


lb. 

59.9 
58.7 
57.7,/ 


perct . 

1.5 
3.^ 
6.5,/ 
li^.Si/ 


1/  Data  for  Marquis  variety. 
Marquis  and  Illinois  1. 


Other  data  are  averages  of  both 


100 

90 

8o 

a 

70 

o 

U    tjD 

tM     C 

•H 

60 

M    <D 

0)    0) 

•H    in 

50 

liH    rH 

O       1 

H 

40 

C  ^ 

0)    o 

o    ^ 

0)  S 

30 

fi< 

20 


10 


v-~^^ 

«^ 

\ 

\ 

Central 
'""'--•^..^Illinois 

\ 

--.^lliiK 

)is                   ^^ 

\ 

__ 

\           \ 

\\ 

\^ 

\ 

March 

March 

April 

April 

May 

1-15 

16-31 

1-15 

16-30 

1-15 

Date  of  Seeding  Oats 


[:r<;ity 


F  AGRICULTURE 


G-6 


NIT^CGFN  FOR  ILLINOIS  WHEAT 


Most  of  the  wheat  grown  in  Illinois  is 
winter  wheat.  It  has  a  moderate  (but 
rather  exact)  requirement  for  nitrogen. 
Wheat  grown  on  soil  that  contains  too 
much  nitrogen  tends  to  produce  an  exces- 
sive amount  of  straw.  It  also  lodges 
and  the  quality  of  the  grain  is  poor. 
Wheat  grown  on  nitrogen-deficient  soil 
is  stunted,  ripens  prematurely,  and  pro- 
duces low  yields. 

In  Illinois,  winter  wheat  is  usually 
grown  in  rotation  with  corn,  soybeans, 
other  small  grains,  and  legumes.  The 
legumes  serve  as  the  main  source  of  ni- 
trogen for  the  other  crops .  Because  the 
wheat  is  an  excellent  nurse  crop  for 
legume  seedings,  it  usually  precedes  the 
legume  and  thus  occupies  a  place  in  the 
rotation  where  the  legume -supplied  ni- 
trogen is  low.  During  recent  years,  how- 
ever, a  fairly  large  part  of  the  wheat 
in  Illinois  has  been  seeded  after  soy- 
beans that  have  followed  at  least  one 
corn  crop. 

Whether  or  not  wheat  will  respond  to  ni- 
trogen fertilizer  depends  mainly  on  how 
far  in  advance  of  the  wheat  crop  the  leg- 
ume was  grown  and  how  successful  it  was. 

On  nitrogen-deficient  soils,  supplemen- 
tary nitrogen  has  usually  been  most  ef- 
fective when  20  to  30  pounds  per  acre 
were  applied  in  late  March  or  early 
April.  By  this  date  it  is  usually  pos- 
sible to  determine  whether  or  not  there 
has  been  any  winter  injury  to  the  wheat. 
If  its  survival  is  doubtful,  treatment 
should  be  delayed  to  avoid  wasting  the 


nitrogen  on  dead  wheat.  It  is  seldom 
profitable  to  fertilize  a  thin  stand. 

The  effect  of  the  previous  crop  on  wheat 
stands  is  shown  by  tests  in  Greene  coun- 
ty. There  wheat  after  oats  produced 
3^.0  bushels  an  acre  and  an  additional 
4.9  bushels  when  20  pounds  of  nitrogen 
were  added.  Wheat  after  corn  yielded 
25.*+  bushels  and  made  an  average  gain  of 
9.6  bushels  when  20  pounds  of  nitrogen 
were  added. i/ 

At  the  Carlinville  experiment  field, 
wheat  after  corn  in  a  two-year  rotation 
of  corn  and  wheat  with  a  catch  crop  has 
averaged  27  bushels  an  acre,  with  an  ad- 
ditional response  of  3  bushels  for  ni- 
trogen. Wheat  following  clover-alfalfa 
has  yielded  kk  bushels,  with  no  benefit 
from  extra  nitrogen. 

Many  comparisons  of  spring  and  fall  ap- 
plications of  nitrogen  on  crops  have 
shown  an  advantage  for  spring  treatment. 
In  tests  in  Macoupin  county  in  which  30 
pounds  of  nitrogen  were  applied  per  acre, 
fall  treatments  increased  yields  by  3-5 
bushels  and  spring  treatments  by  9-8 
bushels  over  the  27.2-bushel  yield  on 
untreated  land. 

Although  heavy  applications  of  nitrogen 
in  the  fall  have  sometimes  produced  good 
increases  in  yield,  equal  results  have 
usually  been  obtained  by  applying  small- 
er amounts  in  the  spring.  There  is  lit- 
tle evidence  that  fall-applied  nitrogen 
will  consistently  improve  winter-hardiness 
of  wheat  under  Illinois  conditions. 


1/  Illinois  Bulletin  503,  page  I96. 


Applications  on  nitrogen  in  the  fall  or 
very  early  spring  are  sometimes  justi- 
fied because  muddy  fields  make  treat- 
ments difficult  in  March  or  April.  If 
early  applications  are  made,  leaching 
losses  can  be  reduced  by  using  calcium 
cyanimid  or  a  material  that  contains  am- 
moniiun  nitrogen. 

With  normal  spring  applications,  re- 
sponses have  been  about  the  same  regard- 


less of  the  carrier  used.  The  "best  buy" 
is  therefore  the  material  that  can  be 
applied  at  the  lowest  cost  per  pound  of 
nitrogen.  For  spring  treatment  it  is 
seldom  practical  to  put  on  more  than  30 
pounds  of  nitrogen  per  acre .  Larger 
amounts  often  cause  lodging  and  injury 
to  legume  seedings  and  rarely  give 
enough  yield  advantage  to  warrant  their 
use . 

L.  B.  Miller 
2/16/53 


ivERSITYOF  ILLIt 


G-7 


DRILLING  VS.  BROADCASTING  OF  OATS 


Judging  by  recent  queries  many  oat  grow- 
ers are  not  sure  whether  it  is  better  to 
drill  or  broadcast  oats. 

This  is  an  old,  old  question  that  has 
been  put  to  the  Illinois  Agricultural 
Experiment  Station  many  times.  As  long 
ago  as  1909^  the  Station  published  Bul- 
letin No.  156,  "Methods  of  Seeding  Oats, 
Drilling  and  Broadcasting."  Since  that 
time  the  results  have  been  checked  a- 
gainst  those  of  other  varieties.  Other 
experiment  stations  in  the  Corn  Belt  have 
also  worked  on  this  subject  at  one  time 
or  the  other,  and  all  the  results  are  in 
rather  close  agreement. 


First,   let's   list  the  advantages 
drilling  over  broadcasting: 


of 


1.  A  uniform  spacing  and  depth  of  seed- 
ing is  insured. 

2.  An  even  stand  affords  a  more  even 
growth  and  ripening. 

5.  Less  seed  is  necessary. 
k.     Even  spacing  results  in  more  compe- 
tition for  the  annual  weeds. 

5.  Seeds  are  covered  in  the  seeding 
operation. 

6.  The  grass- legume  companion  crop  may 
be  seeded  simultaneously. 

7.  Seedlings  are   less  susceptible  to 
late  spring  freezes. 

8.  Yields  are  higher. 

The  bulletin  released  in  I9O9  showed  a 
net  gain  of  5.3  bushels  for  drilling  over 
a  three-year  period.   A  test  conducted 


from  1950- 1952  with  Clinton  oats  showed 
a  net  gain  of  6.3  bushels.  Seventeen- 
year  tests  in  Iowa  resulted  in  a  ^.1 
bushel  advantage  for  drilling. 

With  these  obvious  advantages,  why  are  so 
many  oats  broadcast  in  Illinois?  The 
real  reason  is  that  a  grain  drill  is  not 
a  common  implement  on  many  farms  in  cen- 
tral and  northern  Illinois.  The  oat 
crop  is  the  only  one  grown  on  these 
farms  for  which  a  drill  would  be  used. 
And  the  relatively  low  income  from  oats 
has  dictated  the  use  of  cheaper  seeding 
machinery  and  tools  already  on  hand. 

Whether  to  buy  a  drill  is  a  decision  for 
the  individual  farmer  to  make.  By  know- 
ing the  general  price  of  oats,  cost  of 
the  desired  drill  and  number  of  acres 
grown  each  year,  he  can  calculate  ap- 
proximately the  number  of  years  or  crops 
necessary  to  pay  for  a  drill.  (One  can 
assume  approximately  a  5-'bushel-an-acre 
increase  for  drilling.) 

For  example,  if  a  grower  averaged  kO 
acres  of  oats  and  the  price  averaged  75 
cents  a  bushel,  he  would  have  approxi- 
mately 200  extra  bushels,  or  $150,  to 
apply  to  the  cost  of  a  drill  annually. 

Agronomically,  drilling  of  spring  oats 
is  a  highly  recommended  practice  that  is 
supported  by  much  research  data.  Eco- 
nomically, it  is  still  an  unsolved  prob- 
lem for  many  growers . 

J.  W.  Pendleton 
2/1/5^^ 


1^1 


G-8 


LOOSr  SMUT  OF  Vv'HEAT 


The  amount  of  loose  amut  varies  from 
year  to  year  depending  on  environmental 
conditions  at  the  time  the  wheat  is  in 
flower.  Humid^  cool  weather  accompanied 
by  light  showers  and  dew  is  favorable 
for  infection. 

Infection  takes  place  only  during  the 
flowering  period  of  the  wheat  plant. 
The  wind  carries  the  spores  from  the 
smutted  head  to  the  floral  parts  of  the 
healthy  head,  where  they  germinate  and 
infect  the  young  embryo  (seed)  by  grow- 
ing down  through  the  stigma,  or  female 
part  of  the  flower.  The  smut  lies  in  a 
dormant  condition  inside  the  seed  during 
the  time  it  takes  it  to  mature. 

At  the  time  the  infected  kernel  is 
planted  and  germination  takes  place,  the 
smut  becomes  active  and  grows  into  the 
growing  point  of  the  wheat  plant.  By 
heading  time  the  smut  spores  have  com- 
pletely replaced  the  healthy  seed,  and 
nothing  but  a  black  smutty  head  appears. 
Consequently,  the  amount  of  infection 
that  occurs  in  any  one  year  is  the  re- 
sult of  infection  taking  place  the  pre- 
vious year. 

Control.  Ordinary  seed  treatment  will 
not  control  loose  smut.  There  are  some 
wheat  varieties  that  are  resistant  to 
certain  physiologic  races  of  the  loose- 
smut  fungus,  but  there  is  no  recommended 
variety  that  is  resistant  to  all  of  the 
races . 


The  only  control- -and  we  recommend  that 
it  be  used  only  by  certified  seed  pro- 
ducers--is  the  hot-water  treatment.  This 
treatment  may  be  applied  as  follows: 

1.  Soak  1  bushel  of  seed  in  a  2-bushel 
burlap  bag  in  water  at  ordinary  tem- 
perature for  6  hours. 

2.  Eemove  presoaked  seed  (after  6  hours) 
and  immerse  in  hot  water  ( 1?0''  F.) 
for  10  minutes.  (Seed  should  be 
agitated  during  immersion  in  the  hot 
water. ) 

3 .  Remove  seed  at  the  end  of  the  10- 
mlnute  period,  and  cool  immediately. 
To  cool,  run  cold  water  over  the 
heat-treated  seed,  or  empty  the  seed 
out  of  the  burlap  bags  and  spread  in 
a  thin  layer  on  a  concrete  slab  or 
canvas.   It  is  important  to  cool  the 

seed  as  quickly  as  possible a£ter_ 

treatment . 


Dry  the  seed  either  by  placing  it  in 
a  corn  dryer  and  forcing  unheated 
air  through  it  or  by  spreading  it 
out  in  a  thin  layer  and  turning  it 
with  a  scoop  every  two  hours  until 
it  is  dry  enough  to  resack. 

W.  M.  Bever 
3-22-54 


:p<;iTV  n 


G-9 


STINKING  SMUT  (BUNT)  OF  WHEAT 


Economic  importance.  Periodically  bunt 
of  wheat  TDecomes  a  serious  disease  prob- 
lem in  certain  sections  of  Illinois.  The 
primary  reason  is  that  the  farmer  becomes 
lax  in  his  seed  treatment  program  and  the 
infection  gradually  increases .  When  the 
amount  of  infection  reaches  the  point 
where  his  wheat  is  reduced  in  grade  and 
he  has  to  accept  a  lower  price,  he  starts 
to  worry  about  how  to  control  it. 

Symptoms .  The  signs  of  this  disease  are 
usually  not  evident  until  the  plant  is 
in  the  heading  stage.  Under  some  envi- 
ronmental conditions,  together  with  heavy 
infection,  the  plants  may  be  stimted  and 
the  leaves  mottled  as  though  they  were 
infected  with  the  soil-borne  wheat  mo- 
saic virus.  Ordinarily,  however,  the 
only  distinguishing  symptoms  are  the  slim 
heads  compared  with  healthy  ones.  The 
diseased  heads  retain  their  greenish 
cast  longer.  The  final  symptom  is  the 
distinctive  black  powdery  mass  of  spores 
that  occupies  the  entire  kernel. 

Life  cycle.  The  black  spores  (chlamydo- 
spore )  are  carried  on  the  wheat  kernels 
or  are  present  in  the  soil,  where  they 
germinate  simultaneously  with  the  wheat 
seed.  The  germinating  spores  penetrate 
into  the  tissues  of  the  young  wheat 
seedlings,  reach  the  growing  point,  and 
develop  along  with  the  host  plant  until 
it  begins  to  produce  heads.  At  this 
time  the  black  spores  are  produced,  re- 


sulting in  the  smutted  kernel.  In  the 
harvesting  process  the  smutted  kernels 
are  broken  and  the  black  smut  spores  be- 
come lodged  on  the  sound,  or  healthy, 
grain.  Also,  they  are  carried  by  the 
air  to  other  fields  and  lodged  in  the 
soil. 

Effect  on  quality  of  seed.  Grain  from 
badly  smutted  fields  is  conspicuously 
black,  and  its  value  for  milling  pur- 
poses is  greatly  reduced,  because  special 
scouring  machinery  must  be  used  to  clean 
it.  The  farmer  who  produces  smutty 
grain  suffers  a  loss  in  price  in  accord- 
ance with  the  amoiint  of  smut.  The  U.  S. 
Grain  Standards  Act  specifies  that  smut- 
ty wheat  must  be  so  designated  when  sold 
on  the  market. 

There  is  no  experimental  evidence  that 
smutty  wheat  is  poisonous  when  fed  to 
animals.  Some  evidence  has  been  pre- 
sented, however,  to  show  that  it  defi- 
nitely causes  egg  production  to  drop 
when  fed  to  laying  hens. 

Control.  Treating  the  seed  with  one  of 
the  mercixry  coupounds  will  effectively 
control  any  smut  that  is  on  the  seed. 
However,  no  compound  has  been  developed 
that  will  effectively  control  bunt  due 
to  soil  contamination.  For  specific  in- 
formation on  treating  seed  to  control 
bunt,  write  to  the  Department  of  Agron- 
omy, University  of  Illinois,  Urbana. 

W.  M.  Bever 
U-19-5I+ 


'_  v,/  L  L  I- 


AGRONOMY  J-m»-i3 


G-10 


SFFD  TRFATMFNT5  FOR  SMALL  GRAINS 


A  proper  fungicidal  seed  treatment  is  a 
sure  control  for  stinking  smut  (bunt)  of 
wheat,  the  smuts  of  oats,  and  two  of  the 
smuts  of  barley.  In  addition,  Illinois 
tests  show  that  it  is  usually  a  paying 
proposition  for  the  control  of  seedling 
blight. 

In  experiments  with  smut-free  wheat  and 
oats,  seme  of  the  treated  rows  have  im- 
mistakably  shown  better  vigor  in  occa- 
sional years.  Even  in  some  years  when 
such  differences  were  not  apparent,  yield 
increases  of  as  much  as  five  bushels  an 
acre  occurred.  In  some  other  years 
yields  did  not  increase,  but  these  cases 
were  in  the  minority. 

When  seed  is  used  that  came  from  a  field 
in  which  any  smut  (except  loose  smut) 
has  been  seen,  treatment  becomes  especi- 
ally \irgent.  A  small  percentage  of  smut 
in  one  year  may  mean  a  heavy  infection 
the  next  year.  Barley,  particularly  win- 
ter barley,  should  always  be  treated  be- 
cause it  is  subject  not  only  to  smut  and 
seedling  blight,  but  also  to  a  damaging 
disease  called  "stripe,"  which  can  be 
controlled. 

Loose  smut  of  wheat  and  barley  cannot  be 
controlled  by  fimgicidal  seed  treatment. 
The  principal  controls  are  resistant 
varieties  and  the  hot-^mter  treatment. 
The  latter  is  difficult  to  use  and  usu- 
ally causes  seme  injury  to  germination. 
These  loose  smuts  can  be  identified  by 
the  fact  that  practically  all  of  the  smut 
spores  have  blown  away  from  the  heads  by 
the  time  the  grain  is  mature,  leaving 
only  the  bare  rachis  (see  Agronomy  Facts 
G-8.) 

There  are  other  diseases  of  oats  and 
wheat  not  mentioned  above  that  can  be 
controlled  more  or  less  by  treatment, 
but  in  general  they  appear  to  be  of  mi- 
nor importance  in  Illinois  at  present. 


Sometimes  unforeseen  diseases  develop 
suddenly  and  severely,  as  was  the  case 
with  Victoria  (Helminthosporium)  blight 
of  oats  from  19^+6  to  1950. 

Improvements  have  been  made  during  the 
past  decade  in  fungicides  for  treating 
seeds  and  in  methods  of  applying  them. 
Ceres an  M  and  Fanogen  are  the  commercial 
names  of  the  two  ccmpoxinds  recommended 
by  the  Illinois  Agricultural  Experiment 
Station  for  treating  small  grains.  Both 
contain  merc\ary  and  are  therefore  poi- 
sonous. For  this  reason  they  should  be 
used  in  a  well-ventilated  place. 

Under  certain  conditions  Ceresan  M  may 
cause  seme  reduction  in  yield  by  damag- 
ing the  seed.  Wheat  is  more  sensitive 
to  mercury  damage  than  oats  are,  and  bar- 
ley appears  to  be  intermediate.  Damage 
may  occur  (a)  when  the  moisture  in  the 
grain  is  too  high  or  (b )  in  dry  grain 
(12  percent  moisture)  when  the  dosage  is 
too  high  in  relation  to  the  length  of 
time  the  grain  is  held  after  treating 
and  before  sowing.  In  no  case  should 
more  than  l/2  ounce  per  bushel  be  used; 
and  if  the  seed  is  treated  two  or  more 
weeks  before  sowing,  the  rate  should  be 
1/^  ounce.  The  two  methods  are  equally 
efficient  for  smut  control:  l/h  ounce 
acting  for  two  weeks  is  just  as  effective 
as  1/2  ounce  acting  for  two  days. 

Fanogen  causes  somewhat  less  injury  to 
the  grain  than  Ceresan  M,  according  to 
Illinois  tests.  But  it  is  also  somewhat 
more  volatile.  To  protect  the  workm.en, 
it  is  therefore  particularly  important 
that  Fanogen  be  used  in  a  well-ventilated 
place.  Because  there  is  little  danger 
of  injuring  the  grain,  a  dosage  of  3/^+ 
ounce  of  Fanogen  is  recommended,  regard- 
less of  how  long  the  treated  grain  is  to 
be  stored,  and  it  is  best  to  let  the 
treated  seed  remain  in  bags  or  a  pile  at 
least  three  days  before  planting. 


Both  Ceresan  M  and  Panogen  can  be  ob- 
tained in  a  double -strength  formula. 
When  this  stronger  material  is  used,  the 
dosage  should  be  cut  in  half. 

Ceresan  M  is  a  dry  powder  that  can  be 
used  either  dry  or  as  a  slurry.  When  it 
is  used  dry,  the  operator  should  wear  a 
respirator.  Fanogen  is  a  red  liquid  that 
can  be  diluted  with  water  for  the  slurry 
machine  or  used  full  strength  with  the 
special  Fanogen  treating  machine.  Either 
fungicide  can  also  be  used  in  a  batch 
treater,  such  as  a  small  concrete  mixer, 
a  barrel  churn,  or  a  steel  drxom  fitted 
with  a  diagonal  axle,  hinged  lid,  and 
crank.  In  this  case  Ceresan  M  should  be 
applied  dry,  using  a  suitable  measuring 
spoon,  but  Fanogen  should  first  be  di- 
luted, 1  part  to  h  parts  water,  and  l/2 
cup  {h  ounces)  of  the  dilution  should  be 
used  per  bushel  for  wheat,  oats,  and 
barley. 

The  sl\irry  m.achines  (there  are  several 
makes)  and  the  special  Fanogen  machine 
have  the  following  advantages  over  the 
machines  that  use  the  dry  powder: 

(a)  Liquids  can  be  metered  more  accu- 
rately than  powder,  making  it  pos- 
sible to  apply  the  desired  dosage 
more  precisely. 

(b)  Usually  materials  that  are  applied 
wet  stick  better  than  dusts . 


(c)  In  fungicides  that  are  sold  as  dry 
powders,  little  of  the  dust  gets 
into  the  air  to  bother  the  workmen 
when  the  slurry  machines  are  used. 
The  grain  moisture  is  increased 
about  1/2  of  1  percent  by  the  slxir- 
ry  treatment,  but  no  drying  is  nec- 
essary provided  the  moisture  content 
was  low  at  the  start. 

Besides  Ceresan  M  and  Fanogen,  there  are 
a  few  other  fungicides  that  maybe  equal- 
ly effective  for  wheat.  Some  of  them  are 
Agrox,  Vancide  51j  Setrate,  Fentrate,  and 
Geitrete.  However,  these  materials  are 
not  satisfactory  for  some  of  the  diseases 
of  oats  and  barley.  Making  additional 
reccmraendations  just  for  wheat  would 
only  cause  unnecessary  complications  and! 
might  lead  to  confusion,  Treatmentsj 
used  for  corn,  such  as  Arasan,  Grthocide 
75,  Ortho  Seed  Guard,  DuFont  I  and  D,J 
and  Thiram  Kaugets,  are  not  satisfactory! 
for  small  grains. 

Kergamma  is  a  seed  dressing  for  wheati 
that  combines  both  fungicidal  and  insec-j 
ticidal  ingredients.  The  latter  is  in-4 
eluded  especially  for  wireworm  control,; 
In  a  10-month  storage  test  of  treated 
seed,  Mergairma  caused  more  injury  to  ger- 
mination than  any  other  commercial  or  ex- 
perim.ental  treatment  in  the  test.  It  is 
doubtful  whether  there  is  sufficient 
wireworm  damiage  to  small  grains  in  Illi- 
nois to  warrant  the  use  of  an  insecticide. 

Benjamin  Koehler 
5-17-5^ 


AGRONOMY  i-«^>:. 


S-1 


SOYBEAN  VARIETIES 


The  following  varieties  of  soybeans  are 
adapted  to  Illinois: 

Northern:   Blackhawk,  Hawkeye 
Central:   Hawkeye,  Adams,  Lincoln, 

Chief 
Southern:   Chief,  Wabash,  Perry 

Short  descriptions  are  given  below  for 
the  varieties  .  recommended  for  Illinois, 
as  well  as  for  some  varieties  that  are 
not  recommended  but  are  receiving  pub- 
licity in  the  state. 

Recommended 


Adams , 


Selected  from  a  cross  between 


mini  and  Dunfield  by  Iowa  in  coopera- 
tion with  U.  S.  Regional  Soybean  Labora- 
tory. Pubescence  gray,  flowers  white, 
pods  two  to  three  seeded,  seed  medium 
in  size  and  straw  colored  with  buff  to 
light  brown  hilum.  High  oil  content. 
Adams  splits  the  difference  between  Hawk- 
eye  and  Lincoln  in  maturity,  being  two 
to  three  days  later  than  Hawkeye  and  two 
to  three  days  earlier  than  Lincoln.  It 
is  slightly  better  than  Lincoln  in  lodg- 
ing resistance,  grows  slightly  shorter, 
and  has  a  good  yield  record  in  north- 
central  and  central  Illinois. 


Blackhawk.  Selected  from  the  cross  Muk- 
den X  Richland  developed  by  Iowa  in  co- 
operation with  U.  S.  Regional  Soybean 
Laboratory.  Pubescence  gray,  flowers 
white,  pods  two  to  three  seeded,  seed 
medium  in  size  and  straw  colored  with 
light  brown  hilum.  Medium  oil  content. 
Matures  about  a  week  earlier  than  Hawk- 
eye,  grows  about  two  inches  shorter,  and 
is  comparable  with  Hawkeye  in  lodging 
resistance . 

Hawkeye.  Selected  from  the  cross  Muk- 
den X  Richland  by  Iowa  in  cooperation 
with  U.  S.  Regional  Soybean  Laboratory. 
Pubescence  gray,  flowers  purple,  pods 
two  to  three  seeded,  seed  large  in  size 
and  straw-yellow  with  black  hilum.  Me- 
dium oil  content.  Matures  about  a  week 
earlier  than  Lincoln  and  grows  about  the 
same  height.  Yield  has  been  excellent 
in  central  Illinois  but  disappointing  on 
the  light  soils  of  southern  Illinois, 
where  it  has  been  tried  as  an  early  va- 
riety to  precede  wheat.  Lincoln  appears 
to  be  much  better  adapted  to  this  pur- 
pose in  southern  Illinois. 


Lincoln.  Selected  from  a  cross  between 
Mandarin  and  Manchu  by  Illinois  in  co- 
operation with  U.  S.  Regional  Soybean 
Laboratory.  Pubescence  tawny,  flowers 
white,  pods  two  to  four  seeded,  seed 
medivun  sized  and  straw-yellow  with  black 
hilvim.   High  oil  content. 


Chief, 


Developed  by  Illinois  from  a 


cross  between  Illini  and  Illinois  type 
No.  95-  Pubescence  gray,  flowers  purple, 
pods  two  to  three  seeded,  seed  small 
and  straw-yellow  with  slate  to  brown  hi- 
lum. Medium  in  oil  content.  Chief  av- 
erages seven  to  eight  days  later  than 
Lincoln  in  maturity, normally  grows  tall- 
er, and  does  not  stand  so  well.  A  typi- 
cal field  of  Chief  may  look  somewhat 
lodged,  but  will  have  scattered  plants 
standing  erect. 

Wabash.  Selected  by  Illinois  and  Indi- 
and  in  cooperation  with  U.  S.  Regional 
Soybean  Laboratory  from  a  cross  between 
Dunfield  and  Mansoy.  Pubescence  gray, 
flowers  white,  pods  two  to  three  seeded, 
seed  medium  in  size  and  straw-yellow 


with  light-brown  hilum.  High  in  oil  con- 
tent. Wabash  averages  about  one  to  two 
days  later  than  Chief  in  maturity, stands 
better,  normally  grows  several  inches 
shorter,  and  equals  or  exceeds  it  in 
yield  in  southern  Illinois. 

Perry.  Developed  from  the  cross  Pato- 
ka  X  L7-1355  by  Indiana  in  cooperation 
with  U.  S.  Regional  Soybean  Laboratory. 
Pubescence  gray,  pods  dark  gray  and  two 
to  three  seeded,  flowers  purple,  seed 
large  and  yellow  with  black-brown  hilum. 
Oil  content  high.  Perry  averages  four 
to  five  days  later  than  Wabash  in  matu- 
rity. It  is  very  resistant  to  lodging, 
grows  about  the  same  height  as  Wabash, 
and  has  an  exceptionally  high  yield  rec- 
ord in  southern  Illinois 

Not  Recommended 

Eavender  or  Bavender  Special.  Selected 
by  Mr.  Bavender  of  Whitten,  Iowa,  from  a 
cross  between  Mukden  and  a  North  Caro- 
lina variety.  Pubescence  tawny,  flowers 
both  purple  and  white,  pods  three  and 
four  seeded,  seed  straw-yellow  with 
both  black  and  brown  hila,  seed  size  and 
oil  content  medium.  Bavender  matures 
two  to  three  days  earlier  than  Lincoln, 
has  about  the  same  height,  and  has  a 
good  yield  record  in  Illinois,  but  is 
not  recommended  because  it  is  extremely 
susceptible  to  lodging. 


Cypress  No.  1.  Selected  from  Korean  by 
Cypress  Land  Farms  Company,  St.  Louis, 
Missouri.  Matures  six  to  eight  days 
later  than  Lincoln,  grows  about  the  same 
height,  and  is  extremely  susceptible  to 
lodging.  Not  tested  long  enough  in  Il- 
linois to  be  compared  with  Lincoln  in 
yield. 

Early  Korean.  Introduced  from  the  Ori- 
ent by  the  Dominion  Experiment  Station, 
Ontario,  Canada.  Unusually  large  yellow 
seed  with  black  hilum.  Matures  two  or 
three  days  earlier  than  Hawkeye,  grows 
about  six  inches  shorter,  and  equals  it 
in  resistance  to  lodging.  Lower  in 
yield  and  oil  content  than  Hawkeye  in  Il- 
linois. 

Monroe .  Developed  from  a  cross  between 
Mukden  and  Mandarin  by  Ohio  in  coopera- 
tion with  U.  S.  Regional  Soybean  Labora- 
tory. Pubescence  gray,  flowers  purple, 
pods  two  to  three  seeded.  Medium-sized 
seed,  straw-yellow  with  colorless  hiltim. 
Low  oil  content.  Monroe  averages  three 
to  four  days  earlier  than  Blackhawk, 
does  not  stand  so  well,  and  has  not 
equaled  it  in  yield  in  Illinois.         '. 

f 

USDA  Farmers'  Bulletin  No.  1520  contains  , 
short  descriptions  of  most  of  the  soy-  . 
bean  varieties   grown  in  the  United 
States.  w.  0.  Scott 

1/12/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICUl, 


AGRONOMY  FACTS 


SOYBEAN  VARIETIES 


S-1 
Revised 


The  following  varieties  of  soybeans  are 
adapted  to  Illinois : 

Northern:   Blacldiawk,  Harosoy^  Hawkeye, 
Adams 

Central:   Harosoy,  Hawkeye,  Adams, 
Lincoln,  Clark 

Southern:   Clark,  VJabash,  Perry 

Short  descriptions  are  given  below  for 
the  varieties  that  are  recommended  for 
Illinois,  as  well  as  for  some  varieties 
that  are  not  recommended  but  are  receiv- 
ing publicity  in  the  state. 

Recommended 

Blackhawk.   Selected  from  the  cross  Miok- 


den  X  Richland  developed  by  Iowa  in  co- 
operation with  the  U.  S.  Regional  Soybean 
Laboratory.  Pubescence  gray,  flowers 
white,  pods  2-  to  3 -seeded,  seed  medium 
in  size  and  straw  colored irLth  light  brown 
hilum.  Medium  oil  content.  Matures  about 
a  week  earlier  than  Hawkeye,  grows  about 
2  inches  shorter,  and  is  comparable  with 
Hawkeye  in  lodging  resistance. 

Harosoy.  Developed  at  the  Harrow,  Ontario, 
Canada  Station  from  a  selection  Mandarin 
X  AK  backcrossed  to  Mandarin.  Pubescence 
gray,  flowers  piarple,  pods  dark  gray, 2- 
to  3-seeded,  seed  large  in  size,  yellow 
with  colorless  hilum.  Medium  oil  con- 
tent. Mattires  2  to  3  days  earlier  than 
Hawkeye,  grows  about  same  height  and  is 
slightly  less  lodging  resistant  than  Hawk- 
eye.  For  the  past  3  years  it  has  been  the 
highest  yielding  Variety  in  northern  Il- 
linois .  At  Urbana  it  has  equaled  Hawkeye 
in  yield. 

I  Hawkeye.  Selected  from  the  cross  Mukden 
X  Richland  by  Iowa  in 'cooperation  with 
the  U.  S.  Regional  Soybean  Laboratory. 


Pubescence  gray,  flowers  purple,  pods 
gray^2-  to  3-seeded,  seed  large  in  size 
and  straw-yellow  with  black  hilum.  Me- 
divim  oil  content.  Matures  about  a  week 
earlier  than  Lincoln  and  grows  about  the 
same  height.  Yield  has  been  excellent 
in  central  Illinois  but  disappointing  on 
the  light  soils  of  southern  Illinois, 
where  it  has  been  tried  as  an  early  va- 
riety to  precede  wheat.  Lincoln  appears 
to  be  much  better  adapted  to  this  p\xr- 
pose  in  southern  Illinois . 


Adams. 


Selected  from  a  cross  between 


mini  and  Diinf  ield  by  Iowa  in  coopera- 
tion with  the  U.  S.  Regional  Soybean 
Laboratory.  Pubescence  gray,  flowers 
white,  pods  gray,  2-  to  3-seeded,  seed  me- 
dium in  size  and  straw  colored  with  bTiff 
to  light  broi-m  hilum.  High  oil  content. 
Adams  splits  the  difference  between  Hawk- 
eye  and  Lincoln  in  maturity,  being  2  to 
3  days  later  than  Hawkeye  and  2  to  3  days 
earlier  than  Lincoln.  It  is  slightly 
better  than  Lincoln  in  lodging  resist- 
ance, grows  slightly  shorter,  and  has  a 
good  yield  record  in  north-central  and 
central  Illinois . 

Lincoln.  Selected  from  a  cross  between 
Mandarin  and  Manchu  by  Illinois  in  coop- 
eration with  the  U.  S.  Regional  Soybean 
Laboratory.  Pubescence  tawny,  flowers 
white,  pods  brown, 2-  to  4-seeded,  seed 
mediLim  sized  and  straw-yellow  with  black 
hilijm.   High  oil  content. 

Chief.  Developed  by  Illinois  from  a 
cross  between  Illini  and  Illinois  type 
Wo.  95-  Pubescence  gray,  flowers  ptirple, 
pods  gray, 2-  to  3-seeded,  seed  small  and 
straw-yellow  with  slate  to  brown  hilum. 
Medium  in  oil  content.  Chief  averages 
7  to  8  days  later  than  Lincoln  in  matu- 
rity, normally  grows  taller,  and  does 
not  stand  so  well.  A  typical  field  of 
Chief  may  look  somewhat  lodged,  but  will 
have  scattered  plants  standing  erect. 


Clark.  Clark  was  developed  by  Indiana 
in  cooperation  with  the  U.  S.  Regional 
Soybean  Laboratory  from  the  backcross 
Lincoln  x  (Lincoln-Richland) .  Pubescence 
bro^-m,  flowers  purple,  pods  broim^  2-  to 
3 -seeded,  seeds  medium  to  large  in  size 
and  straw-yellovr  with  black  hiliom.  High 
oil  corltent.  Clark  grows  to  about  the 
same  height  as  Lincoln  but  matures  about 
a  week  later.  It  is  superior  to  Lincoln 
in  lodging  resistance.  It  is  equal  or 
superior  to  Wabash  in  this  respect.  Un- 
der Illinois  conditions  Clark  has  been 
higher  yielding  than  Lincoln,  Wabash, 
and  Perry  at  the  follo^ving  test  loca- 
tions: Urbana,  Stonington,  Trenton,  and 
Eldorado,  Illinois.  Seed  is  available 
in  Illinois  for  195^  planting. 

Wabash.  Selected  by  Illinois  and  Indiana 
in  cooperation  with  the  U.  S.  Regional 
Soybean  Laboratory  from  a  cross  between 
Dunfield  and  Mansoy.  Pubescence  gray, 
flowers  white,  pods  gray,  2-  to  3-seeded, 
seed  medium  in  size  and  straw-yellow 
with  light  brown  hil\an.  High  in  oil 
content.  VJabash  averages  about  1  to  2 
days  later  than  Chief  "in  mat\;irity,  stands 
better,  normally  grows  several  inches 
shorter,  and  equals  or  exceeds  it  in 
yield  in  southern  Illinois. 

Perry.  Developed  from  the  cross  Patoka 
X  L-7-31355  by  Indiana  in  cooperation 
with  the  U.  S.  Regional  Soybean  Labora- 
tory. Pubescence  gray,  pods  dark  gray 
and  2-  to  3-seeded,  flowers  purple,  seed 
large  and  yellow  with  black-brown  hilum. 
Oil  content  high.  Perry  averages  4  to  5 
days  later  than  Wabash  in  maj^urity.  It 
is  very  resistant  to  lodging,  grows  about 
the  same  height  as  Wabash,  and  has  an  ex- 
ceptionally high  yield  record- in  southern 
Illinois . 


Not  Recommended 

Bavender  or  Eavender  Special.  Selected 
by  Mr.  Bavender  of  VThitten,  Iowa,  from  a 
cross  between  M-ukdenanda  North  Carolina 
variety.  Pubescence  tawny,  flowers  both 
purple  and  white,  pods  3- and  4-seeded, 
seed  straw-yellow  with  both  black  and 
bro\-m  hila,  seed  size  and  oil  content 
medium.  Bavender  matures  2  to  3  days 
earlier  than  Lincoln,  has  about  the  same 
height,  and  has  a  good  yield  record  in 
Illinois,  but  is  not  recommended  because 
it  is  extremely  susceptible  to  lodging. 

C;^^ress  No.  1.  Selected  from  Korean  by 
Cypress  Land  Farms  Company,  St.  Louis, 
Missouri.  Mat\jres  6  to  8  days  later  than 
Lincoln,  grows  about  the  same  height, 
and  is  extremely  susceptible  to  lodging. 
Not  tested  long  enough  in  Illinois  to  be 
compared  with  Lincoln  in  yield. 

Early  Korean.  Introduced  from  the  Orient 
by  the  Dominion  Experiment  Station, 
Ontario,  Canada.  Unusually  large  yellow 
seed  with  black  hilum.  Matxires  2  to  3 
days  earlier  than  Hav;keye,  grows  about  6 
inches  shorter,  and  equals  it  in  resist-, 
ance  to  lodging.  Lower  in  yield  and  oil 
content  than  Hawkeye  in  Illinois. 

Monroe .  Developed  from  a  cross  between 
Mukden  with  Mandarin  by  Ohio  in  coopera- 
tion with  the  U.  S.  Regional  Soybean 
Laboratory.  Pubescence  gray,  flowers 
piirple,  pods  2-  to  3-seeded.  Mediian- 
sized  seed,  straw-yellow  with  colorless 
hilum.  Low  oil  content.  Monroe  aver- 
ages 3  to  ^  days  earlier  than  Blackhawk, 
does  not  stand  so  well,  and  has  not 
equaled  it  in  yield  in  Illinois . 

USDA  Farmers'  Bulletin  No.  1520  contains 
short  descriptions  of  most  of  the  soybean 
varieties  grown  in  the  United  States . 

W-  0.  Scott 
1-25-5^ 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


S-2 


SOYBEAN  DISEASE  AND  THE  WEATHER 


What  can  we  expect  from  soybean  diseases 
this  season?  This  question  is  asked  al- 
most every  year  in  March  or  April.  Un- 
fortunately, there  is  no  ready  answer. 
From  past  experience  we  know  several 
diseases  that  appear  each  year,  hut  we 
cannot  foretell  how  prevalent  or  how  se- 
vere they  will  be.  The  weather  has  a 
definite  influence  in  certain  phases  of 
disease  development. 

Observations  over  the  years  show  that 
certain  diseases  are  closely  associated 
with  specific  conditions  of  rainfall  and 
temperature.  Once  a  particular  weather 
pattern  develops,  we  have  some  idea  of 
what  to  expect  in  the  line  of  disease 
outbreaks.  We  must  remember,  however, 
that  showers  may  be  extremely  localized 
and  thus  their  effect  may  be  limited  to 
small  geographic  areas.  Likewise  a 
disease-inciting  organism  must  be  present 
as  the  first  requisite  for  infection. 

With  these  reservations,  we  can  list 
c-ertain  conditions  as  they  apply  to  soy- 
bean diseases. 


Frequent  rain  and  cool  weather  favor  the 
development  of  bacterial  blight,  which 
usually  occurs  in  Illinois  in  June  and 
early  July.  If  cool  weather  persists 
and  showers  are  frequent,  new  infections 
may  be  found  throughout  July.  The  dis- 
ease recedes  rapidly  with  the  onset  of 
high  temperatures. 

If  rain  is  frequent  and  heavy  enough  to 
keep  the  soil  wet,  Rhizoctonia  root  rot 
is  likely  to  develop  on  young  soybean 
plants  in  June.  If  the  soil  remains 
overly  wet,  the  disease  may  kill  older 
plants  through  July,  since  it  operates 
over  a  wide  temperature  range. 


Warm,  moist  weather  is  likely  to  encour- 
age the  development  of  Septoria  brown 
spot,  which  first  appears  on  the  primary 
leaves  and  later  spreads  to  the  upper 
leaves . 

Rain  and  warm  weather  combine  to  favor 
the  development  of  bacterial  pustule, 
which  usually  appears  during  the  first 
two  weeks  in  July.  This  disease  per- 
sists through  mid-August,  although  maxi- 
mum infection  is  usually  attained  near 
the  end  of  July. 

Cool  weather  in  August,  especially  dur- 
ing the  first  half  of  the  month,  favors 
the  development  of  brown  stem  rot.  In 
this  period  the  fungus  progresses  inside 
the  stem.  If  such  conditions  are  fol- 
lowed by  a  warm,  dry  period  late  in  Aug- 
ust or  early  in  September, the  leaves  are 
likely  to  wither  and  turn  brown  as  a  re- 
sult of  the  disease.  Except  for  this 
latter  stage,  rain  has  little  to  do  with 
the  development  of  brown  stem  rot. 

Hot ,  dry  weather  is  unfavorable  for  most 
soybean  diseases.  Consequently  when 
such  conditions  prevail  throughout  much 
of  the  growing  season,  soybeans  show 
little  infection.  One  exception,  how- 
ever, is  charcoal  rot.  This  disease  is 
favored  by  hot,  dry  weather,  especially 
in  combination  with  poor  soil.  Charcoal 
rot  is  usually  found  after  midsummer, 
mostly  in  the  southern  half  of  Illinois. 

In  order  to  treat  these  disease-weather 
relationships  as  briefly  as  possible, 
the  diseases  are  listed  here  by  their 
common  names.  The  symptoms,  causal  or- 
ganisms, and  other  pertinent  facts  may 
be  found  in  Illinois  College  of  Agricul- 
ture Circular  676,  Soybean  Diseases  in 
Illinois . 

D.  W.  Chamberlain 

Pathologist,  U.S. 

Dept.  of  Agriculture 

I+/27/53 


f 


u; -,.... 


S-3 


WHFN  TO  SEFD  SOYBEANS 


For  years  farmers  have  debated  about 
what  is  the  best  date  to  seed  soybeans. 
Most  of  them  have  established  their  pat- 
terns of  seeding  on  the  basis  of  either 
experience  or  custom. 

In  the  early  years  of  soybean  production 
in  Illinois,  a  large  part  of  the  crop 
was  grown  solid,  like  oats  or  wheat. 
This  meant  that  two  or  three  crops  of 
weeds  had  to  be  killed  before  the  seed 
was  planted.  This  thorough  preparation 
usually  delayed  seeding  imtil  after  corn- 
planting  time.  Since  most  of  the  farm 
work  was  then  done  with  horses  or  mules, 
final  seedbed  preparation  was  often  not 
completed  until  about  the  first  of  June. 

Medium  Early  Yellow  or  Ito  San  was  the 
variety  that  \jas  grown  most  extensively 
in  that  early  period.  Because  of  its 
early  maturity,  Ito  San  could  be  planted 
in  June  and  it  would  still  mature.  This 
characteristic,  together  with  the  need 
for  more  time  to  prepare  the  seedbed, 
established  a  pattern  of  relatively  late 
seeding  for  soybeans. 

This  practice  has,  however,  gradually 
been  changing.  Introduction  of  power 
machinery,  the  combine,  and  new  and  bet- 
ter adapted  varieties  m.ade  it  necessary 
for  many  experiment  stations  to  examine 
cultural  practices.  As  a  result,  stud- 
ies were  undertaken  in  the  late  20 's  to 
determine  the  best  time  to  seed  soybeans. 


For  six  years  (1926-I931)  the  University 
carried  on  a  study  of  this  kind  with  12 
different  varieties  varying  in  maturity 
from  a  very  early  black  soybean  to  late- 
raaturing  yellow  and  green  beans.  Seed- 
ings  were  made  at  six  different  dates  be- 
ll tween  Kay  1  and  June  20  at  approximately 
10-day  intervals. 


Results  of  these  tests  sho\7ed  that,  for 
all  varieties  taken  together,  yields 
from  seedings  made  in  May  averaged  3«1 
bushels,  or  15  percent,  more  per  acre 
than  yields  from  the  three  June  seedings. 
In  fact,  with  the  single  exception  of  the 
very  early  Wisconsin  Black,  the  highest 
iaverage  yield  of  each  variety  was  also 
obtained  from  one  of  the  Kay  seedings . 

There  was  very  little  difference  in  yield 
among  the  three  Kay  seedings.  The  high- 
est was  from  the  May  20  seeding,  the 
second  highest  from  the  May  10,  and  the 
lowest  from  the  May  1.  But  the  differ- 
ence was  only  .5  bushel  between  the  high- 
est and  the  lowest. 

At  a  later  date  the  U.  S.  Regional  Soy- 
bean Laboratory,  located  en  the  University 
campus,  inaugurated  a  cooperative  test 
between  the  states  of  Iowa,  Illinois,  and 
Indiana.  These  trials,  conducted  for  a 
period  of  three  years,  compared  five  soy- 
bean varieties  seeded  at  five  different 
dates  in  three  locations  (Ames,  Iowa; 
Urbana,  Illinois;  and  West  Lafayette, 
Indiana).  Here,  as  in  the  earlier  Illi- 
nois trials,  the  test  included  an  early 
and  a  late  variety  as  well  as  three 
medium-maturing  varieties  that  were  more 
nearly  adapted  to  the  region. 

An  average  of  all  varieties  tested  showed 
relatively  little  difference  in  yield  for 
plantings  from  the  first  three  dates-- 
May  1,  12,  and  23.  There  was,  however, 
a  more  marked  drop  in  the  averages  for  the 
two  June  plantings.  The  early  variety. 
Mandarin^  which  is  about  one  week  earlier 
than  Blackhawk, produced  its  highest  yield 
for  the  June  l^t-  planting.  On  the  other 
hand,  the  latest  variety,  Boone,  when 
planted  on  June  I'l,  produced  only  61  per- 
cent of  the  top  yield  for  that  variety, 
which  was  pb1:ained  by  seeding  on  May  1. 


-2- 


The  three  varieties  (Richland,  Mulcden, 
and  Diinfield),  considered  to  be  adapted 
to  all  three  locations,  gave  highest  av- 
erage yields  for  the  May  1  seeding,  next 
highest  for  the  May  12,  and  third  highest 
for  the  May  23.  The  over-all  difference, 
however,  was  only  1.2  bushels.  This  would 
suggest  that  it  is  possible  to  destroy  at 
least  two  crops  of  weeds  by  additional 
seedbed  preparation  and  still  get  beans 
into  the  ground  by  about  May  20  without 
suffering  severe  losses  in  yield. 

Trials  made  by  the  U.  S.  Regional  Soybean 
Laboratory  and  cooperating  states  showed 
certain  other  results  that  will  be  of 
interest  to  the  farmer: 

1.  Maturity  was  retarded  about  one  day 
for  each  three  days '  delay  in  plant- 
ing. 


2.  All  dates  considered,  yields  were 
highest  for  varieties  adapted  to  use 
of  the  full  growing  season, 

3.  In  an  average  of  all  varieties, 
their  ma:cimum  height  was  reached  by, 
plants  from  the  second  planting  date,: 
May  12,  and  height  diminished  gradu- 
ally for  each  succeeding  date. 

h.  Amount  of  lodging  was  not  signifi- 
cantly affected  by  different  dates 
of  planting. 

5.  On  the  average,  oil  content  was  re- 
duced slightly  by  delayed  planting, 
but  there  was  also  some  difference 
due  to  varietal  reaction. 

6.  Protein  content  was  not  appreciably 
affected  by  delayed  planting. 


The  following  data  taken  from  USDA  Technical  Bulletin  1017  show  the  response  of  each; 
of  the  varieties  to  the  different  dates  of  planting: 


Mean  Seed  Yields  Per  Acre  of  5  Varieties  of  Soybeans 
Planted  on  5  Dates  at  3  Locations  for  3  Years 

I9UO-I9U2 


Yield  for 

variety  planted- - 

Variety 

May  1 

May  12 

May  23   Jxone  3 

J\me  14 

Mean 

Mandarin 
Richland 
Mukden 
Diinfield 

Boone 

bu. 

25.5 
32.2 

3^.1 
33.6 
30.3 

bu. 

26.6 
31.5 
33.9 
33.1 
28.0 

bu.     bu. 

26.2  26.5 

32.3  30.5 
31.9     31.^ 
32.6     29.8 
26.8     22.2 

bu. 

26.1 
29.0 
28.2 
27.6 
18.7 

bu. 

26.2 
31.1 
31.9 
31.3 
25.2 

Mean 


31.2 


30.6 


30.0 


28.1 


25.9 


29.1 


The  most  recent  date- of -planting  studies  from  which  data  are  available  were  carried 
on  by  the  U.  S.  Regional  Soybean  Laboratory  at  Urbana,  Illinois,  during  the  seasons 
of  1951  and  1952.  The  following  data  are  of  special  interest  because  several  of  the 
currently  popular  varieties  were  included  in  these  studies  : 


Date 

planted 

Variety 

May  1 

May  15 

May  29 

June  12 

bu. 

bu. 

bu. 

bu. 

Blackhawk 
Hawkeye 
Adams 
Lincoln 

3'+.2 

38.9 
42.  U 
U3.U 

37.8 

43.5 
45.8 
43.2 

37.4 
38.7 
42.3 
38.6 

36.1 
38.3 
36.9 

39.0 

L6-2132 
VJabash 
Perry 
L6-5679 

46.6 
41.8 

43.9 
34.8 

44.8 
38.8 

39.9 
34.8 

40.4 
35.7 
36.9 
29.8 

4i.O 
31.2 
35.6 
25.1 

Mean 

40.8 

41.1 

37.5 

35.4 

The  highest  average  yield  for  the  eight  varieties  studied  indicates  that  mid-May  is 
the  best  planting  date.  A  study  of  the  individual  varieties  indicates  that  Black- 
hawk,  Hawkeye,  and  Adams,  the  3  earliest  in  this  group,  were  best  when  planted  on 
May  15  or  May  29,  the  former  date  having  a  slight  but  not  significant  advantage. 
Lincoln,  a  full-season  variety  at  Urbana,  yields  equally  well  May  1  or  May  15,  but 
later  seedings  reduce  yields.  The  other  four  varieties,  all  of  which  are  from  a  week 
to  10  days  or  more  later  than  Lincoln,  would  seem  to  require  early  May  planting  for 
maximum  yields. 

J.  C.  Hackleman 
4-26-54 


AGR 


S-4 


EFFECTIVE  METHODS  AND  RATES  OF  SEEDING  SOYBEANS 


When  soybeans  were  first  grown  in  Illi- 
nois ,  many  people  considered  them  either 
a  forage  or  hay  crop  and  used  them  as  a 
substitute  for  part  of  the  oats  in  the 
rotation.  In  either  case  the  crop  was 
seeded  with  a  grain  drill  in  rows  "J  or  Q 
inches  apart.  Harvesting  was  done  with 
the  mower  or  the  binder,  depending  on 
the  use  of  the  crop. 

As  soybean  acreage  increased  and  combin- 
ing became  the  preferred  method  of  har- 
vesting, producers  were  quick  to  ask  how 
row  seedings  would  compare  in  yield  with 
broadcasting  or  drilling,  because  it  was 
easier  to  control  weeds  in  row  seedings. 
This  interest  in  row  seeding  caused  the 
experiment  stations  to  set  up  tests  to 
compare  yields  of  rov;  and  solid  seedings 
and  to  determine  the  best  seeding  rates. 


More  recent  tests  at  Corn  Belt  experi- 
ment stations  have  attempted  to  deter- 
mine proper  width  of  row  and  optimum 
rate  of  seeding  with  present-day  vari- 
eties. Tests  made  at  Illinois,  Indiana, 
Iowa,  and  Ohio  show  that  beans  in  21-  to 
24-inch  rows  averaged  2  to  U  bushels 
more  than  those  in  kO-   to  i+2-inch  rows. 

Subsequent  trials  have  shovm  that  the 
character  of  growth  of  the  variety  under 
tests  affects  optimum  width  of  row.  The 
shorter  and  less  branching  the  plants,  the 
narrower  the  row.  Tall-growing,  branch- 
ing types  of  plants  can  be  seeded  in 
wider  rows  with  no  significant  reduction 
in  yield.  Varieties  with  growth  habits 
like  Lincoln,  Hawkeye,  Adams,  and  Clark 
will  not  suffer  serious  losses  in  rows 
up  to  36  inches  wide. 


In  an  experiment  conducted  at  the  Illi- 
nois Station  and  reported  in  Bulletin  k62, 
mini  soybeans  grown  in  24-inch  rows  at 
rates  varying  from  30  "to  110  pounds  an 
acre  were  compared  with  beans  drilled  in 
8-inch  rows  at  rates  of  50  to  210  pounds. 
The  following  conclusions  were  drawn 
from  these  tests,  which  covered  a  period 
of  five  years  (1928-I932): 

1.  Ro\T  seedings  outyielded  solid  or 
drill  plantings  by  an  average  of 
17.4  percent. 

2.  Optimum  seeding  rate  for  drilled 
beans  was  1  1/2  to  2  bushels  an 
acre. 

3.  Optimum  amount  of  seed  for  row 
plantings  ^^?as  50  to  70  pounds  an 
acre, 

h.  Row  seedings  had  a  higher  per- 
centage of  normally  mature  pods 
at  harvest  than  either  drilled 
or  broadcast  seedings. 

5-  Row  seedings  were  also  standing 
more  nearly  erect  at  harvest . 


Most  farmers  object  to  narrow-row  spacing 
because  they  have  to  change  the  adjust- 
ments on  their  planters  and  cultivating 
equipment.  Many  of  them  say  they  would 
rather  take  a  reduction  in  yield  of  beans . 

One  way  to  avoid  changing  your  machinery 
and  yet  reduce  the  average  width  of  rov, 
if  you  have  a  two -row  planter,  is  to 
plant  the  two  rows  of  beans  at  the  normal 
corn -row  width  and  shorten  the  gauge  or 
marker.  You  will  then  get  two  rows  of 
normal  width,  but  the  space  between  the 
pairs  of  rows  will  be  narrower .  The  exact 
amount  to  shorten  the  marker  will  depend 
on  the  width  of  the  tractor  tread — if 
you  expect  to  use  a  tractor  in  cultivat- 
ing. 

The  answer  to  how  much  seed  to  plant  per 
acre  will  depend  somewhat  on  width  of  row 
and  also  on  quality  of  seed.  On  soils 
that  tend  to  crust,  thicker  planting  will 
usually  insure  a  more  satisfactory  stand, 
as  the  seedlings  tend  to  help  one  another 
break  the  crust.  As  a  general  rule,  8  to 
12  seeds  per  foot  of  row  should  be  ade- 
quate. 


The  following  data  were  ottained  at  the 
Iowa  Experiment  Station  in  a  test  cover- 
ing five  years  (1939-19^3)  in  which,  five 
varieties  were  seeded  at  different  seed- 
ing rates  in  32 -inch  rows. 


Another  interesting  result  reported  t 
the  Iowa  investigators  was  that  each  l/2 
bushel  increase  in  seeding  rate  adde 
three  plants  per  foot  of  row,  and  wit 
this  increase  came  approximately  an 
percent  increase  in  amount  of  lodging. 


AG 


i-iate  of  planting   (pounds  per  acre)~ 


36 


60 


tik 


10b 


13 


Average  yield,  bushels 

Net  yield  (average  yield 
minus  seed  used) ,  bushels 

Plants  per  foot  of  row 


27.0 

26.4 
6 


28.1 


27.1 


28.6 


27.2 


11 


28.2 


26. ii- 


13 


28. 


26, 
16 


You  will  note  that  the  net  yield  (aver- 
age yield  minus  seed  used)  did  not  dif- 
fer for  the  60 -  and  8J+ -pound  rates  where 
the  stands  were  9  and  11  plants  per  foot 
of  row,  respectively.  Also  of  interest 
is  the  fact  that  net  yield  was  reduced 
only  .7  bushel  when  average  number  of 
plants  per  foot  of  row  was  reduced  by 
one -third,  from  9  plants  to  6,  at  36 
pounds  of  seed  per  acre. 


Since  extra-heavy  seeding  rates  do  no; 
increase  net  yield,  but  do  tend  to  ini 
crease  amount  of  lodging,  only  enoug; 
beans  should  be  seeded  to  make  the  seed, 
lings  thick  enough  to  help  each  othe| 
emerge.  This  will  probably  mean  plant; 
ing  8  to  12  good,  germinable  seeds  pei 
foot  of  row.  Such  a  stand  will  be  ade; 
quate  even  if  one  or  two  plants  per  fooj 
or  row  are  lost  during  early  cultivatior^ 

J.  C .  Hacklema 
5/3/5^^ 


k 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMEN 
CONSERVATION 


SM-1 


LOSS  OF  PLANT  NUTRIENTS  BY  LEACHING  FROM 
THREE  ILLINOIS  SOILS 


Plant  nutrients  are  removed  from  soils 
by  harvested  crops,  by  erosion,  and  by 
leaching.  Attempts  are  frequently  made 
to  estimate  the  total  amount  of  plant 
nutrients  removed  from  soils  to  use  as  a 
basis  for  fertilizer  recommendations. 
The  amount  of  nutrients  removed  by  crops 
can  be  determined  rather  accurately,  but 
losses  by  leaching  and  erosion  are  less 
easy  to  figure.  Improved  methods  for 
determining  nutrient   losses  are  needed. 

The  following  figures  on  leaching  losses 
from  three  Illinois  soils  were  obtained 
by  a  method  that  more  nearly  approaches 
field  conditions  than  those  previously 
used.  Because  in  this  method  the  natu- 
ral soil  structure  was  not  destroyed, 
the  results  should  be  more  reliable  than 
those  obtained  on  disturbed  soil. 

The  three  soils  for  which  results  are 
given  vary  widely  in  both  physical  and 
chemical  properties.  This  difference  is 
reflected  in  the  leaching  losses.  Run- 
off was  permitted  whenever  the  rate  of 
rainfall  exceeded  the  capacity  of  the 
soil  to  absorb  it. 


The  soils  have  been  kept  bare  since  1935- 
No  lime  or  fertilizers  have  been  added. 
Phosphorus  losses  are  not  included  in  the 
results  because  only  traces  of  this  nu- 
trient were  found  in  the  drainage  water. 

The  results  reported  here  are  for  silt 
loam  soils  that  have  been  developed  un- 
der grass  vegetation.  Saybrook  and  Mus- 
catine, which  are  dark  colored  and  high- 
ly productive  soils,  occur  extensively  in 
the  northern  two-thirds  of  Illinois. 
Saybrook  occurs  in  the  northeastern  part; 
and  Muscatine,  mostly  in  the  western  and 
northwestern  parts.  Cisne  is  a  gray- 
colored  soil  having  a  claypan  subsoil 
that  is  very  slowly  permeable  to  water. 
It  occurs  in  the  southern  one-third  of 
the  state . 

For  further  description  of  these  soils, 
see  Illinois  Mimeo.  AGli+U3,  Illinois 
Soil-Type  Descriptions.  For  further  in- 
formation on  this  project,  see  Journal 
of  American  Society  of  Agronomy,  volume 
29:917-923,  1937,  and  volume  3^:830-835, 
19^2.  A  complete  summary  of  the  entire 
project  will  be  published  in  1953- 


Average  Annual  Leaching  Losses,  Runoff,  and  Drainage, 
for  the  10-Year  Period  I9U2-I95I 


Soils 

Cal- 
cium 

Magne- 
sium 

Potas- 
sium 

So- 
dium 

Nitro- 
gen 

Sul- 
fur 

Run-   Drainage 
off   (Internal) 

Saybrook 

Muscatine 

Cisne 

181.2 

133.9 
15.0 

83.8 

70.3 

10.0 

(Pounds 

2.2 

l.k 
2.1+ 

per  acre) 

11.3 

9.8 

39.6 

103.6 
77.5 

31.^ 

50.3 

1+8.6 

l.k 

(Percent) 

9-3     3^.3 
ik.B          28.9 
32.3     3.0 

Note: Average  annual  precipitation,  40.76  inches. 


R.  S.  Stauffer 
1/12/53 


l^'« 


AG' 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT 
CONSERVATION 


SM~2 


KRILIUM  AND  OTHER  SOIL  CONDITIONERS 


Krilium  is  one  of  twenty  or  more  commer- 
cial soil  conditioners  manufactured  to 
treat  and  improve  soils  that  have  a 
tendency  to  become  hard,  compact,  crusty 
and  cloddy  when  dry.  These  soil  condi- 
tioners, which  are  all  similar,  have 
proved  to  he  extremely  effective  in  ful- 
filling their  purpose,  hut  they  are  too 
expensive  for  general  use  on  farm  land. 

What  Do  They  Cost? 

Although  exact  prices  will  not  be 
quoted,  it  appears  that  manufacturers  of 
the  polyacrylate  typei/  of  soil  condi- 
tioners must  sell  them  between  $1.00  and 
$2.50  per  pound  of  active  ingredients  in 
order  to  make  a  profit.  Experiments 
show  that  from  200  to  1,000  poiinds  are 
required  to  bring  about  the  desired 
changes  in  the  top  six  inches  of  an  acre 
of  clayey  soils.  At  these  prices  and 
rates  of  application,  it  is  obviously 
impractical  to  condition  the  plow  depth 
of  large  areas  of  farm  land. 

There  is  a  widespread  impression  that 
future  large-scale  production  of  these 
soil  conditioners  might  make  it  possible 
to  reduce  prices  to  a  small  fraction  of 
present  prices.  The  outlook  for  such 
reduction  is  not  good,  however,  espe- 
cially if  the  present  products  and  raw 
materials  continue  to  be  used.  Here  is 
the  reason: 

Acrylonitrile,  the  raw  material  used  in 
the  manufacture  of  the  most  commonly 
used  soil  conditioners,  is  very  expen- 
sive. Facilities  for  manufacturing  it 
are  not  sufficient  to  meet  the  demand, 
and  attempts  to  import  the  material  have 
)*ot  been  successful.  Acrylonitrile  is 
also  used  in  the  production  of  important 
plastics,  fibers,  and  fabrics.  Orion,  a 
much-desired  fabric  in  clothing,  is  one 
of  them.   The  demands  for  Orion  and 


other  similar  products  containing  acry- 
lonitrile may  actually  force  the  manu- 
facturers to  raise  prices  temporarily  on 
soil  conditioners. 

How  Long  Will  They  Last? 

The  polyacrylate  soil  conditioners  are 
extremely  resistant  to  decay.  Field  ex- 
periments show  that  applications  made 
over  three  years  ago  are  still  as  effec- 
tive as  when  they  were  first  applied. 
More  severe  laboratory  and  greenhouse 
tests  show  that  their  effects  will  last 
for  many  years. 

V/hat  Is  Their  Best  Use  at  Present  Prices? 

High  price  will  limit  the  use  of  soil 
conditioners  to  situations  where  special 
advantages  can  be  realized.  They  may  be 
expected  to  find  uses  in  lawns,  gardens, 
truck  farms,  golf  greens,  and  ornamental 
and  greenhouse  plantings.  They  may  also 
be  useful  in  protecting  small  spots  from 
erosion  while  grass  stands  are  being  es- 
tablished. Treating  small  areas  or 
strips  over  plantings  may  prove  practi- 
cal as  an  aid  to  emergence  of  certain 
seedlings  that  are  unfavorably  affected 
by  crust  formation  on  light-colored 
clayey  soils. 

How  to  Apply 

Soil  conditioners  may  be  applied  either 
in  solution  as  a  spray  or  in  powder 
form.  In  either  case  the  moisture  con- 
tent of  the  soil  must  be  such  as  to  per- 
mit the  conditioner  to  mix  immediately 
and  thoroughly  with  the  soil.  A  roto- 
tiller  is  the  most  effective  implement 
to  use  for  this  operation. 

Applying  soil  conditioners  to  cloddy  or 
crusted  soils  without  mixing  may  cause 
more  harm  than  good.   The  reason  is  that 


1/  The  most  common  type  of  soil  conditioner  on  the  present  market, 


t'rev 


=.~ -    ;r-j.=~  =  ,     ~.=  'r- -£     "jisz     r  =  sis'~£zi~     "tc       r.ssss-rcli     zn  soil     ccndi'ticners     iiES  t.z~ 
":rs=-!iEj:s   '.  :Ti~. ~   f— cs5~-czi~    c'^~i'."=.~icr.s .        "irc'."i.i£i.  &     scluticn  fcr     lar&s   acrss-ass 

"re  "bcr :'j.gi_L"  zix=i  vi-'-  t'ce    r::":scil.  ^bangizs     the       pi.ysic£-L     prrjerties      ;f 

Zcv  Tie'.'  Affe:":   ~.'zt  Szti.  ssarcb     in  crgar^ic     cbsiisxry  o£y     yield 

'leiter"     sjii  less     extensive   sciL     cc«i.i- 

:r   :r^5-.y  scils  r^re   -r-z:ly  a-i  fria:l5.      ::nverting  crop  resiiues  sri  sarure  into 
T'-e   £:il   .ecczes  z:re  trrcus.      zcre  ter-       rcre   effective   s:il   ::r.iiti:::ers . 

J.   Z.    3ie£e>ini 
1/12/5! 


NIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


\GRONOMY  FACTS 


MANAGEMENT  A 
CONSERVATION 


SM=3 


FUNDAyN^EiN'TALS  OF  (VaI 

Soil  physical  conditions  are  important 
primarily  as  they  zrake  it  possible 
fl)  for  air  and  water  xo  move  into  and 
through  the  soil, (2)  for  the  plant  roots 
to  pass  through  and  make  use  of  the  soil, 
and  (3)  for  the  soil to  hold  enough  water 
in  a  form  available  for  plants  to  use. 

These  conditions  are  affected  primarily 
"ry  the  texture,  degree  of  coEXaction, 
and  state  of  aggregation  of  the  soil. 

Since  cultural  practices  have  little  or 
no  effect  on  soil  texture,  attempts  to 
alter  air  and  water  relationships  and 
suitability  of  the  soil  for  effective 
plant  root  development  mus-  ce  r:eas"j.rei 
by  the  effects  of  such  practices  or.  soil 
compaction  and  aggregation. 

Soils  that  are  veJ._j  aggregated  have  a 
desirable  range  of  ?©©r'"  sizes  that  per- 
mit water  tc  infiltrate  readily  and 
spread  rapidly  through  the  rooting  zone. 
A  significant  proportion  of  large  pores 
also  allows  excess  water  to  ce  removed 
quickly  from  the  soil  and  remits  the 
exchange  of  gases  through  the  pores . 
This  exchange  is  essential  for  r:aintain- 
ing  in  the  soil  a  supply  of  ox^.'gen  ade- 
quate for  normal  root  development  and  for 
such  important  processes  as  nitrification 
and  nitrogen  fixation . 

If  there  is  not  enough  oxygen  in  the  soil. 
root  growth  and  extension  are  greatly  re- 
duced and  absorption  of  nutrients  and 
water  ty  the  roots  is  seriously  impaired. 
In  addition,  reduced  compounds  may  ap- 
pear in  quantities  suiTicient  to  disr-j.pt 
the  balance  between  the  plant  nutrients 
or  to  cause  the  soil  to  become  toxic. 

Soils  that  are  highly  cc~pact  either 
naturally  or  because  of  continued  mis- 
managerer.-t  ir  rrt  have  eno-jgh,  or  large 
enrui'r. ,  s:il  rrres  to  permit  water  and 
air  to  move  rapidly  into  and  tbrc\igh 


,!MNG  SOIL  TILTH 


them.   Thus 


arnear 


tns 


-,  oasica_-y, 
inadequate  soil  aggregation  and  exces- 
sive compaction  both  have  a  significant 
f-Por-+  on  plant  gro'S'Tth,  because  the  size 
distribution  of  the  soil  tores  in 


ej.  J. 

and 


One  of  the  most  important  factors  affect- 
ing soil  aggregation  and  the  susceptibil- 
ity of  the  soil  to  compaction  is  the 
amount  of  readily  decomposable  organic 
ratter  it  contains.  The  fact  should  be 
emphasized  that  it  is  the  rapidly  decern- 
nosi^^  f'*-ac~i~^  r^t"'"~r  "^'^a^  "^e  "^o^al 
terce^'ta^re  c^  er-'anic  ma'^'^er  '*'''^i!^~  i^  ~■^  — 
p  ortant . 

There  is  plenty  of  experimental  evidence 
to  show  that  the  rate  of  organic  matter 
decomposition  is  highly  correlated  with 
soil  aggregation.  The  reason  is  that 
certain  intezTtediate  biological  decomto- 
sition  products  that  are  formed  luring 
the  breakdown  of  plant  residues  are  very 
effective  aggregating  agents.  In  fact, 
it  was  the  discovery  of  the  remarkable 
effectiveness  of  these  products  that  led 
to  the  intensive  research  on  related 
synthetic  compounds,  such  as  the  poly- 
acrylonitriles,.  polyvinylacetates,  etc. 
This  research  in  fuz^  led  to  the  devel- 
opment of  Krili'jm  and  other  sjtnthetic 
soil  conditioners . 

Vnf ortunately,  these  naturally  produced 
aggregating  compounds  are  rather  un- 
stable and  hence  not  permanently  effec- 
tive. The  res"JLlt,  of  course,  is  that 
readily  decomposable  organic  materials 
must  be  inccrp crated  into  the  soil  at 
frequent  intervals  if  they  are  to  be 
effective  in  supplementing  these  pro- 
duced nat-urally. 


Tillage  and  impact  of 
soil  also  destroy  th 


raindrops  on  the 
soil  aggregates 
and  increase  compaction.  Eamage  from 
tilla^re  is  greatest  when  the  soil  is 


excessively  moist.  Although  tillage 
usually  reduces  soil  compaction  temporar- 
ily, the  resultant  increase  in  biologi- 
cal activity  hastens  the  hreakdown  of 
the  aggregating  compounds  in  the  soil, 
causing  a  net  reduction  in  aggregation. 

Soil  aggregates  have  their  lowest  stabil- 
ity or  strength  when  saturated  with  water. 
This  lowered  stability,  coupled  with  the 
impact  exerted  on  the  soil  by  raindrops, 
causes  considerable  destruction  of  aggre- 
gates in  the  surface  soil.  Upon  drying, 
this  dispersed  soil  frequently  forms  a 
compact  crust  that  makes  it  difficult 
for  air  and  water  to  enter  the  soil  and 
in  some  instances  prevents  seedlings 
from  emerging. 

In  light  of  these  principles,  it  is  pos- 
sible to  evaluate,  in  relative  terms, 
the  probable  effects  that  cropping  sys- 
tems or  soil  management  practices  will 
have  on  soil  physical  conditions,  Prac- 
tices that  cause  large  amounts  of  read- 
ily decomposable  organic  matter  to  be 
incorporated  into  the  soil  will  do  most 
to  improve  soil  aggregation  and  reduce 
susceptibility  to  compaction. 

Similarly,  management  systems  that  mini- 
mize intensive  tillage,  particularly  dur- 


ing periods  of  high  soil  moisture,  and 
that  maintain  a  vegetative  cover  on  the 
land  during  a  large  part  of  the  year 
will  be  most  conducive  to  the  mainte- 
nance of  good  soil  physical  condition. 

At  present  there  is  not  enough  informa- 
tion to  make  it  possible  to  predict  the 
effects  of  varying  soil  conditions  on 
plant  growth  and  crop  yields .  It  seems 
clear,  however,  that  as  we  raise  the  fer- 
tility level  of  our  soils,  increase  the 
yield  potentials  of  varieties,  and  learn 
more  effective  methods  of  planting  and 
harvesting  crops  and  controlling  plant 
diseases  and  pests,  we  shall  find  it  nec- 
essary to  give  more  attention  to  the 
physical  conditions  of  soils  as  factors 
which  determine  the  ceiling  on  crop 
yields. 

Only  when  we  have  developed  effective 
methods  of  characterizing  the  signifi- 
cant soil  physical  conditions  and  have 
established  tolerance  limits  and  re- 
sponse curves  for  those  conditions  will 
it  be  possible  to  make  a  completely  ra- 
tional approach  to  the  problem  of  evalu- 
ating management  practices  in  relation 
to  soil  condition. 

M.  B.  Russell 
3/16/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-4 


PUBLISHED  INFOPs(V\ATION  ON  THE  CHARACTERISTICS  AND  DISTRIBUTION  OF 
DIFFERENT  KINDS  OF  SOILS  IN  ILLINOIS 


Soil  reports  and  detailed  soil  maps  have 
been  published  for  7^  Illinois  counties 
(listed  at  end).  The  detailed  soil  maps 
indicate  the  distribution  of  the  differ- 
ent soil  types  in  the  county.  In  the 
text  of  each  county  soil  report,  the 
different  soil  types  shown  on  the  map 
are  described,  and  suggestions  are  made 
concerning  their  use  and  management. 
Mimeographed  descriptions  of  soil  types 
accompany  the  detailed  soil  maps  for 
Alexander,  Henderson,  and  Pulaski  coun- 
ties. There  is  also  a  soil  association 
map  and  mimeographed  publication, AGIU9U, 
entitled  "Soils  of  Cook  County,"  which 
describes  the  soils  in  that  area. 

Much  new  information  about  soils  has 
been  obtained  since  the  older  soil  maps 
and  reports  were  printed.  This  is  es- 
pecially true  of  Soil  Reports  Nos.  1  to 
53,  inclusive,  and  the  detailed  soil 
maps  without  soil  reports  for  Crawford, 
Franklin,  Monroe,  and  White  counties, 
which  were  published  before  1933-  For 
many  areas  this  newer  information  is 
necessary  if  the  maps  and  other  soil  in- 
formation in  the  reports  are  to  be  cor- 
rectly interpreted.  Help  in  making 
these  interpretations  can  be  obtained  by 
studying  Illinois  Publication  AGlkk^  en- 
titled "Illinois  Soil  Type  Descriptions" 
or  by  writing  to  the  Department  of 
Agronomy,  University  of  Illinois, Urbana. 

The  soils  in  northeastern  Illinois  are 
quite  variable  and  those  which  are  de- 
veloped from  thin  loess  over  fine-tex- 
tured glacial  till  present  some  manage- 
ment problems  that  are  more  difficult  to 
correct  than  in  many  other  parts  of  the 
state.  Some  of  the  characteristics  and 
management  requirements  of  these  slowly 
permeable  soils  are  discussed  in  the 
following  three  publications: 

C663  -  Handling   Northeastern  Illinois 

Soils 
C60i|  -  Shall  We  Fall-Plow  or  Spring-Plow 

in  Northeastern  Illinois? 


B5i^0  -  Costs  and  Benefits  From  Soil  Con- 
servation in  Northeastern  Illinois 

Information  on  the  productivity  and  rel- 
ative earning  capacity  of  different 
kinds  of  soil,  which  will  be  helpful  to 
operators,  owners,  and  prospective  pur- 
chasers of  farm  land,  is  published  in 
the  two  bulletins  listed  below: 


B522  -  How  Productive  Are 
Central  Illinois? 

B55O  -  How  Valuable  Are 
Central  Illinois? 


the  Soils  of 


the  Soils  of 


The  distribution  and  general  character- 
istics of  the  broad  soil  regions  in  Il- 
linois are  indicated  in  Illinois  mimeo- 
graph AGI397  entitled  "Principal  Soil 
Association  Areas  of  Illinois." 

Publication  AGIUI+3  entitled  "Illinois 
Soil  Type  Descriptions"  gives  comprehen- 
sive information  on  the  characteristics 
of  Illinois  soils.  This  293-page  volume 
was  prepared  primarily  for  agricultural 
technicians,  but  it  will  also  be  useful 
to  others  who  wish  to  become  familiar 
with  the  characteristics  of  the  soils  in 
Illinois.  In  addition  to  the  detailed 
soil-type  descriptions,  it  contains  a 
generalized  "Soil  Association  Map  of  Il- 
linois," Diagrams  of  soil  profiles  and 
landscapes  are  included  that  should  make 
it  much  easier  for  persons  to  become  fa- 
miliar with  the  relations  between  asso- 
ciated soil  types.  Estimated  yields  of 
grain  crops  are  given  for  various  soil 
types  under  a  moderately  high  level  of 
management.  Production  indexes  for 
grain  crops,  forage  crops,  and  timber 
are  also  given  for  the  different  soils. 

There  is  no  charge  for  single  copies  of 
the  publications  except  AGlUi+3.  Re- 
quests should  be  limited  to  those  publi- 
cations which  will  be  immediately  useful 
and  should  be  ordered  from  Agricultural 
Information  Office,  University  of  Illi- 
nois, Urbana,  Illinois 


COUNTY  SOIL  REPORTS  PUBLISHED 


Adams,  2k 
Bond,  8 
Boone,  65 
Bureau,  20 
Calhoun,  53 
Cass,  71 
Champaign,  18 
Christian,  73 
Clay,  1 
Clinton,  57 
Coles,  kk 
Cumberland,  69 
DeKalb,  23* 
DeWitt,  67 
Douglas,  h^ 
DuPage,  16 
Edgar,  I5 
Edwards,  k6 
Effingham,  US 
Fayette,  52 
Ford,  5^* 
Fulton,  51 
Grundy,  26 
Hancock,  27 
Hardin,  3 


Henry,  ^4^1 
Iroquois,  7^ 
Jackson,  55 
Jasper,  68 
Johnson,  30 
Kane,  17 
Kankakee,  13 
Kendall,  75 
Knox,  6 
Lake,  9 
LaSalle,  5 
Lee,  37 

Livingston,  72 
Logan,  39 
Macon,  U5* 
Macoupin,  50 
Marion,  3^+ 
Marshall,  59 
Mason,  28 
McDonough,  7 
McHenry,  21 
McLean,  10 
Menard,  76 
Mercer,  29 
Morgan ,  ^4-2 


Moultrie,  2 
Ogle,  38 
Peoria,  I9 
Piatt,  J+7 
Pike,  11 
Putnam,  60 
Randolph,  32 
Rock  Island,  31 
Saline,  33 
Sangamon,  k 
Schuyler,  56 
Shelby,  66 
St.  Clair,  63 
Stark,  6h 
Tazewell,  ik 
Vermilion,  62* 
Wabash,  6I 
Warren,  70 
Washington,  58 
Wayne,  ^9 
Whiteside,  ko 
Will,  35 
Winnebago,  12 
Woodford,  36 


*  No  longer  available  for  distribution. 


Detailed  soil  maps  without  soil  reports  are  available  for  seven  additional 
counties  as  follows: 


Alexander 
Crawford 


Franklin 
Henderson 


Monroe 

Pulaski 

White 


I 


R.  T.  Odell 
6/8/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-5 


EFFECT  OF  SOIL  TREATMENT  ON  CORN  ROOTS 


Corn  roots  developed  better  and  yield  was 

higher  on  a  plot  receiving  soil  treatment 
than  on  an  untreated  plot  on  Cisne  silt 
loam  on  the  soil  experiment  field  at  To- 
ledo, Illinois,  in  1952. 

The  treated  plot, which  had  received  resi- 
due (stover,  straws,  leg\:mes),  lime,  phos- 
phate, and  potash,  produced  75  bushels 
of  corn  an  acre  in  a  moderately  dry  sea- 
son. The  nearby  untreated  plot  made  only 
20  bushels  an  acre. 

Cisne  silt  loam  is  a  gray  claypan  soil 
that  is  acid  and  low  in  fertility.  It 
occurs  extensively  in  southern  Illinois 
and  was  developed  from  thin  loess  under 
the  influence  of  prairie  grass  vegeta- 
tion. The  claypan  or  subsoil  begins  at 
a  depth  of  about  16  to  l8  inches  and  ex- 
tends to  about  ^4-0  inches. 

The  general  idea  has been  that  crop  roots 
do  not  penetrate  it  to  any  great  extent. 
In  this  study,  however,  where  enough  of 
the  various  soil  treatments  (lime,  phos- 
phate, and  potash)  were  applied  to  the 
surface  soil  and  legumes  were  plowed 
down,  corn  roots  were  found  to  extend  to 
a  depth  of  60  inches  and  to  be  extensive- 
ly developed  in  the  claypan  or  subsoil. 
The  zone  of  most  limited  root  branching 
was  in  the  very  gray,  silty  subsurface 
layer  just  above  the  claypan.  (See  il- 
lustrations on  opposite  side.) 


The  total  weight  of  corn  roots  per  acre 
on  the  f \illy  treated  plot  was  1 .  3  tons . 
The  upper  11  inches  of the  soil  contained 
78  percent  of  the  roots.  Although  in  the 
treated  plot  the  amount  of  available 
phosphorus  below  the  s\irface  soil  was 
low,  the  roots  probably  received  some 
nourishment  from  the  claypan  and  were 
able  to  make  good  use  of  the  moisture 
available  in  that  soil  horizon. 

On  the  xmtreated  plot  corn  roots  extended 
to  a  depth  of  about  k2  inches  but  were 
weakly  developed  in  the  very  gray  sub- 
surface layer  just  about  the  claypan  and 
in  the  claypan  itself.  The  total  root 
weight  per  acre  was  0.4  ton,  and  82  per- 
cent of  the  roots  were  in  the  upper  9 
inches  of  surface  soil. 

Although  these  corn  root  distribution 
studies  cover  only  one  year,  it  is  prob- 
able that  the  results  are  representative 
of  these  that  would  be  obtained  on  treated 
and  untreated  Cisne  in  seasons  having 
normal  to  somewhat  dry  weather. 

The  results  suggest  that  not  only  do  soil 
treatments  increase  yields  on  such  soils 
as  Cisne  by  furnishing  needed  plant  nu- 
trients, but  by  furthering  root  penetra- 
tion and  development  in  the  lower  layers 
of  the  soil  they  also  make  it  possible 
for  plants  to  reach  and  use  moisture  at 
the  greater  depths. 


J.  B.  Fehrenbacher  and  H.  J.  Snider 

9-21-53 


CORN  ROOTS  IN   CISNE  ^ILT   LOAM-RLPK     PLOT 


CORN    ROOTS  IN   CISNE   SILT  LOAM- CHECK    PLOT 


SUBSTRATA 


I  FT 


2  FT 


3FT 


4FT 


5FT 


■■'"  lill 


hi 


13^ 


^ 


r  '1  wm  f^ii 


2F1 


3F 


4F" 


5F 


Com  roots  in  Cisne  silt  loam,  from  a  fertilized  plot  on  the  left  and  frcm  an  tinfer- 
tilized  check  plot  on  the  right.  Outside  root  panels  in  each  set  are  from  U"xl2"x  72" 
tray  sanrples  taken  directly  under  adjacent  3-8talk  hills  of  com.  Center  root  panels 
axe  frcm  h"   x  6"  x  72"  tray  samples  taken  balfway  between  the  two  hllla. 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


MULCH  COVER  SAVES  AGGREGATES  IN  THE  SURFACE  SOIL 


SM-6 


Numerous  experiments  have  demonstrated 
that  a  raiilch  of  crop  residues  on  the 
surface  of  soil  is  very  effective  in  re- 
ducing runoff  and  erosion.  Less  empha- 
sis has  been  given  to  the  fact  that  such 
a  mulch  also  reduces  the  destruction  of 
soil  aggregates.  This  is  a  desirable 
feature  of  mulches. 

To  be  productive, a  soil  must  be  open  and 
porous  enough  to  drain  freely  and  to  ad- 
mit air  readily.  To  have  these  proper- 
ties, most  Illinois  soils  (silt  loams  and 
finer)  must  be  aggregated.  The  individ- 
ual soil  particles  must  exist  in  groups 
or  clusters  instead  of  each  particle  ex- 
isting alone. 

If  the  soil  aggregates  are  broken  down, 
the  soil  will  be  heavy,  impermeable,  and 
hard  to  handle.  It  will  not  produce  high 
crop  yields,  even  if  there  is  no  lack  of 
plant  nutrients.  But  if  a  soil  is  well 
aggregated,  it  will  drain  readily,  aera- 
tion will  be  satisfactory,  and  yields  will 
be  high  provided  sufficient  plant  nutri- 
ents are  supplied.  Any  practice  that 
promotes  or  protects  soil  aggregation  is 
therefore  desirable  from  these  stand- 
points. 

Soil  aggregates  can  be  destroyed  in  a 
number  of  ways.  One  way  that  has  not 
received  much  attention  until  recent 
years  is  by  the  impact  of  falling  rain- 
drops. Any  soil  that  is  left  bare  is 
subject  to  this  dispersing  action. 

Raindrops  strike  the  soil  with  consider- 
able force,  the  impact  depending  largely 
on  the  size  of  the  drop.  This  force  is 
sufficient  to  break  down  soil  aggregates, 
disperse  or  scatter  the  individual  soil 
particles,  and  form  a  compact  layer  con- 
taining little  pore  space.  When  dry, 
this  layer  forms  a  crust  that  on  many 
soils  may  seriously  interfere  with  the 


emergence  of  young  seedlings.  When  moist, 
the  "puddled"  layer  will  not  admit  water 
readily  and  thus  causes  more  runoff. 

This  damage  from  falling  rain  can  be 
largely  eliminated  by  protecting  the 
soil  with  some  kind  of  cover.  The  de- 
gree of  protection  will  depend  on  how 
completely  the  soil  surface  is  covered. 
The  cover  can  absorb  the  impact  of  the 
falling  raindrops  without  being  damaged, 
whereas  there  is  a  great  deal  of  damage 
when  the  bare  soil  is  exposed. 

The  results  given  in  the  following  table 
were  obtained  on  a  good  corn-belt  soil 
on  a  4  percent  slope.  The  samples  were 
taken  in  the  spring  after  the  soil  had 
been  exposed  to  three  different  condi- 
tions over  winter.  All  of  the  plots  were 
planted  to  corn  in  the  previous  season. 
On  one  series  wheat  straw  was  spread  on 
the  surface  at  the  rate  of  2  tons  per 
acre.  On  the  other  two  series,  the  corn 
was  planted  and  ciiltivated  in  the  usual 
way. 

When  the  corn  was  harvested,  the  stalks 
on  one  series  wens  broken  down  across  the 
slope.  On  the  other  series,  the  stalks 
were  removed  at  the  time  the  corn  was 
harvested.  Each  figure  in  the  table  is 
an  average  of  8  or  more  single  determi- 
nations. The  samples  included  about 
one-half  inch  of  surface  soil. 

Percentage,  by  Weight,  of  Aggregates 
Larger  Than  I/50  Inch  in  Diameter 


Wheat 
straw 


Corn- 
stalks 


"Bare 
soil 


18.9 


9.2 


6.7 


These  figures  show  the  effectiveness  of 
the  straw  mvilch  in  protecting  the  soil 
aggregates. 

R.  S.  Stauffer 
10-5-53 


f 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-7 


IMPORTANCE  OF  SOIL  CLAYS  IN  PLANT  GROWTH 


The  clays  are  composed  of  the  extremely 
small  mineral  particles  in  soils.  Be- 
cause of  their  fineness ^  they  are  by  far 
the  most  active  fraction  of  the  soil. 
They  play  an  important  part  in  providing 
a  better  growing  medi\am  for  plants.  They 
bind  the  soil  together  and  thus  prevent 
wind  and  water  erosion.  They  adsorb  water 
and  plant  nutrients  throughout  the  year 
and  hold  them  in  a  form  available  for 
plants  to  use  diaring  the  growing  season. 

Some  clays  have  very  high  water-holding 
capacities,  while  others  have  intermedi- 
ate or  low  capacities.  Most  Illinois 
clays  have  high  capacities.  Unfortunate- 
ly, in  the  absence  of  soil  organic  mat- 
ter, the  high-capacity  clays  hold  large 
amounts  of  water  too  tenaciously  to  make 
it  available  to  plants.  In  fact,  these 
clays  may  actually"  compete  with  plants 
for  water. 

The  high-capacity  clays  adsorb  soil  or- 
ganic matter  more  tenaciously  than  water. 
These  stable  organic -clay  complexes  may 
have  higher  water-holding  capacities  than 
the  same  clays  that  are  devoid  of  organ- 
ic matter.  The  organic -clay  complexes, 
however,  do  not  hold  much  water  tena- 
ciously enough  to  prevent  plants  from 
taking  it  away  from  them.  For  this  rea- 
son it  can  be  said  that  organic  matter 
changes  an  undesirable  property  of  the 
! clays  into  a  desirable  property. 

Organic  matter  also  helps  to  develop 
good  structure  in  clayey  soils  and  thus 
increases  the  rate  of  water  and  air 
movement . 

Clays  adsorb  calcium,  magnesium,  and  po- 
tassium by  an  exchange  mechanism  through 
which  these  elements  replace  other  ele- 


ments previously  adsorbed  by  a  similar 
mechanism.  Growing  plants  produce  hydro- 
gen in  the  form  of  carbonic  and  organic 
acids.  Plants  can  exchange  this  hydro- 
gen for  calcium,  magnesium,  potassium, 
and  other  basic  elements  that  are  ad- 
sorbed by  clays.  In  this  way  growing 
plants  make  soils  more  acid.  The  farm- 
er reverses  this  process.  He  replaces 
hydrogen  on  the  clays  by  adding  manure, 
plant  residues,   lime,  and  fertilizers. 

The  weathering  of  minerals  in  soils  fur- 
nishes some  of  the  basic  elements  that 
saturate  the  clays.  These  clay-adsorbed 
elements  are  not  released  by  water  unless 
the  water  contains  similar  dissolved  ele- 
ments to  exchange  for  those  already  on 
the  clay.  The  clays  therefore  serve  as 
a  "trading  and  storage  center"  where 
plants  can  select  the  nutrient  elements 
they  need.  If  this  were  not  so,  we 
would  need  to  anticipate  and  supply  the 
balanced  nutrients  in  the  form  of  ferti- 
lizers as  fast  as  these  elements  were  re- 
moved by  leaching  and  crop  removal.  If 
there  were  absolutely  no  clay  or  organic 
matter  in  a  soil,  it  would  certainly 
need  to  be  fertilized  after  every  heavy 
rain  in  order  to  support  plant  growth. 

Soils  that  are  high  in  clay  and  low  in 
organic  matter  are  not  favorable  for 
plant  growth  because  they  do  not  let 
water  and  air  move  freely  through  their 
profiles  and  because  most  of  their  ad- 
sorbed water  is  not  available  for  plant 
growth.  But  soils  that  are  high  in  clay 
and  high  in  organic  matter,  when  proper- 
ly limed  and  fertilized,  do  provide  a 
favorable  medium  for  plant  growth  because 
they  hold  and  conserve  large  amounts  of 
water  and  nutrient  elements  in  a  readily 
available  form. 

J.  E.  Gieseking 
10-12-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-8 


SLICK  SPOTS 


The  80-oalled  slick  spots  of  south-central  and 
southern  Illinois  are  light-colored  silt  loam  soils 
that  are  very  low  In  productlYlty.  They  have  thin 
surface  and  subsurface  horizons  and  very  slowly  per- 
meable subsoils  that  are  usually  high  In  replaceable 
and  total  sodium.  Those  slick  spots  that  have  well 
developed  silt  loam  surface  and  subsurface  horizons 
10  to  16  Inches  thick  (total  depth  to  top  of  sub- 
soil or  claypan),  and  subsoils  with  a  high  pH  and 
high  sodium  content,  have  been  given  the  name  of 
Huey  el  It  loam. 

Occurrence.  The  slicks  occur  ee  spots  of  variable 
size  with  many  soils  but  are  most  commonly  associ- 
ated with  Cisne,  Cowden,  and  Herrlck  silt  loams. 
They  are  largest  In  the  Clsne  and  Cowden.  In  some 
places,  particularly  the  western  half  of  southern 
IlllnolE,  they  may  occupy  over  50  percent  of  Cowden 
and  Clene  areas. 

In  general,  slick  spots  are  confined  to  that  part 
of  Illinois  having  soil  parent  materials  conslGting 
of  less  than  100  Inches  of  loess  overleached  1111- 
nolan  glacial  till.  Most  of  them  have  developed 
under  grass,  although  occasionally  they  have  devel- 
oped under  forest  vegetation. 

They  are  frequently  found  along  or  near  the  head  of 
shallow  dralnageways.  They  may  also  occur  on  or 
near  the  base  of  steep  elopes,  on  "dead"  flats,  or 
sometimes  in  depressions.  In  general,  they  have  de- 
veloped under  poor  drainage  conditions  and  usually 
have  mottled  gray  subsoils.  However,  occasionally 
one  may  have  a  brownish-colored  subsoil  similar  to 
that  of  soils  developed  under  moderately  well- 
drained  conditions. 


sodium  for  four  Cowaen  profiles,  five  Clsne  pro- 
files, and  five  slick  spot  profiles. 


Characteristics.  Slick 


spots  have  lighter  colored 
nonelick  grassland  soils, 
and  they 


surfaces  than  adjacent 

thej-  !)re  lower  in  organic  matter  content, 
have  shallower  depths  to  the  top  of  the  claypan  sub- 
soil. The  subsoil  often  contains  lees  clay  than 
adjacent  soils,  but  the  sodium  content  and  pH  are 
usually  higher.  Occasionally  spots  are  found  that 
have  all  of  the  physical  appearances  of  slicks  but 
that  differ  chemically  by  being  ecld  throughout 
their  profiles. 

Slick  spots  tend  to  be  higher  in  sodium  content  In 
the  layers  below  the  surface  soil,  but  there  Is 
usually  little  difference  between  slick  and  non- 
slick  soils  in  pH  or  sodium  content  in  the  surface 
layers.  However,  in  slicks  that  occur  at  the  base 
of  slopes,  where  seepage  is  pronounced,  white,  pow- 
dery, alkaline  salts  may  accumulate  on  the  surface 
during  dry  periods.  The  most  common  salt  appears 
to  be  sodium  sulphate.  Figure  1  shows  the  varla- 
[  tion  with  depth  of  average  content  of  replaceable 


; 


0  12  3  4  5  6  7 

M.E     OF   REPLACEABLE    SOOIUM    PER    100  GMS.  SOIL 
( I  ME    OF   SOOWM .  460  LBS    OF   SOOIUM  PER    ACRE    OR    PER 
2   MILLION     LBS     OF     SOIL    ) 

Figure  1 

Besides  having  lighter  colored  surface  horizons  and 
shallower  depths  to  the  top  of  the  subsoil,  many 
clicks  have  in  their  subsoils  pray  concretions  of 
calcium  carbonate  varying  in  shape  and  ranging  from 
1/8  to  1  Inch  in  diameter.  The  presence  of  calcium 
carbonate  can  be  checked  by  dropping  dilute  hydro- 
chloric acid  on  subsoil  samples  and  noting  whether 
bubbling  occurs.  The  pH  of  the  subsoils  that  do 
not  effervesce  with  acid  can  be  checked  with  field 
pH  test  kits,  which  are  much  qrlcker  and  easier  to 
use  than  present  field  tests  for  replaceable  sodium. 
If  the  pH  of  the  subsoil  of  a  suspected  spot  is 
above  7.0  at  a  depth  as  shallow  as  2k  inches,  the 
area  is  probably  slick. 

Figure  2  on  the  back  of  this  page  shows  the  rela- 
tion between  pH  and  replaceable  sodium  content  of 
the  subsoil  of  some  slick  and  nonelick  samples. 
While  there  was  some  variation,  the  samples  having 
a  pH  greater  than  about  7.0  and  a  replaceable  sodi- 
um content  of  acout  3  or  more  mllllequlvalents  were 
slick. 

Figure  5,  also  on  the  back  page,  shows  the  relation 
between  average  replaceable  sodium  content  of  the 
subsoil  of  slick  and  nonslick  soils  and  average 
depth  to  subsoil.  As  depth  to  subsoil  (or  thick- 
ness of  surface  and  subsurface  layer)  decreases, 
average  replaceable  sodium  content  IncreaeeB. 

Because  of  the  high  sodium  content,  the  physical 
condition  of  the  subsoil  is  very  poor.  The  sodium 
keeps  the  clay  dispersed,  and  as  a  result  permea- 
bility to  water  is  very  slow.  When  dry,  the  subsoil 


ME-    OF    REPLflCEiBLE    SODIUM 


4  5  6 

IN  SUBSOIL  PER    100  GMS    SOIL 


(I  ME     Of    SOOIUM=  460  LBS    OF    SODIUM    PER    ACRE    OR    PER    2 
MILLION    LBS    OF    SOIL    1 

Figure  2 

la  quite  hard  and  slow  to  wet  up  follovlng  rains; 
and  when  wet,  it  is  very  slow  to  dry  out.  Its  abil- 
ity to  supply  moisture  to  crops  is  low,  and  this  in 
part  accounts  for  the  very  low  productivity  of 
these  spots. 

The  other  major  factor,  besides  the  high  sodium 
content  of  the  subsoil,  contributing  to  low  produc- 
tivity is  the  acid,  low  nitrogen,  phosphorus,  and 
potassium  content  of  the  surface  soil.  The  degree 
of  toxicity  of  plants  to  varioue  amounts  of  sodium 
in  these  soils  has  not  been  determined.  From  the 
available  data  it  appears  that  a  soil  having  over 
about  3  m.e.  of  replaceable  sodium  per  100  grams  of 
subsoil  or  a  soil  in  which  sodium  takes  up  over  10 
to  15  percent  of  the  capacity  of  the  subsoil  to 
hold  bases  should  be  clasplfled  as  slick.  Such  a 
soil  will  have  a  lower  productivity,  because  of 
more  adverse  physical  and  chemical  properties,  than 
adjacent  nonslick  soils. 

Origin.  The  origin  of  slick  spots  has  been  vari- 
ously-attributed to  the  accumulation  of  bases  under 
an  arid  or  semiarid  climate,  to  interruption  of 
leaching  of  a  shallow  loess  by  an  underlying  highly 
impervious  Illinoian  glacial  till,  to  interruption 
of  drainage  by  a  high  water  table,  and  to  lateral 
movement  of  drainage  water  that  is  relatively  high 
In  sodium  and  subsequent  accumulation  of  the  sodium 
because  of  evaporation  of  the  water.  Seepage  or 
hydrostatic  pressure  or  capillary  rise  may  account 
for  movement  of  the  water  to  points  at  the  surface 
of  the  soil  where  evaporation  would  follow.  The 
source  of  the  sodium  has  been  attributed  to  weather- 
ing of  primary  minerals  in  the  loess. 

The  Idea  that  slick  spots  are  relics  of  a  formerly 
arid  climate  is  questionable.  It  does  not  explain 
the  influence  of  parent  materials  on  their  occur- 
rence. The  other  ideas  presented  above  all  involve 
the  accumulation  of  sodium  under  the  present  cli- 
mate by  lateral  movement  of  ground  water  or  by  in- 
terruption of  leaching.  That  the  movement  of 
ground  water  is  involved  in  the  accumulation  of  the 
sodium  and  the  formation  of  the  slick  spots  is  a 
certainty,  but  the  exact  mechanism  and  processes 
involved  are  not  fully  known.  Mineraloglcal  and 
chemical  studies  in  progress  to  determine  the  re- 
placeable and  total  sodium,  possibly  the  source  of 
the  sodium,  and  the  type  of  clay  minerals  present 


SUCK 

fo"  OR  LESS  TO  suesau 


Hl^Y  SILT  LOAM 

(loroe'TO  suBSoiLi 
NONSLICK 
OUNKEL  SILT  LOAM 
(OVER  «"  TO  SUBSOtU 

AVERAGE  ME    OF  REPLACEABLE   SOOIUW  IN  SUBSOIL   PER   100  GMS.  SOIL 
(I  ME     OF    S00IUM=460  LBS.  Of   SODUJM   PER    ACRE   OR   PER    2  MILLION  LBS.  SOIL) 

Jigure  * 

may  help  to  explain  further  the  genesis  or  origin 
of  these  soils. 

Use  and  management.  Soil  treatment  to  improve  the 
productivity  of  elick  spots  often  gives  disappoint- 
ing results  because  it  does  not  remedy  the  poor 
physical  properties  nor  the  high  sodium  content  of 
the  subsoil.  Some  Improvement  can  be  made  on  most 
of  these  spots,  particularly  where  the  depth  to  the 
subsoil  is  more  than  12  inches.  If  the  subsoil  is 
very  shallow  or  has  been  exposed  by  erosion,  little 
can  be  accomplished  with  soil  treatment. 

One  of  the  first  steps  in  the  management  of  these 
soils  is  to  provide  adequate  drainage.  Tile  will 
not  draw  satisfactorily,  but  sometimes  an  open  in- 
let into  a  tile  line  can  be  used  to  remove  excess 
eurfece  water.  Ordinarily  an  open  ditch  is  the 
cheapest  and  most  practical  means  of  drainage.  If 
suitable  drainage  can  be  provided,  the  surface  soil 
should  be  treated  according  to  needs  as  determined 
by  soil  tests. 

In  addition  to  lime,  phosphate,  and  potassium,  the 
need  for  nitrogen  on  these  spots  Is  generally  great. 
If  the  spots  are  small  and  not  too  numerous,  they 
must  ordinarily  be  farmed  with  surrounding  soils. 
However,  if  they  are  large  enough  to  be  farmed  sep- 
arately, they  can  often  be  used  more  successfully 
for  winter  small  grains  or  pasture  than  for  summer 
crops,  such  as  corn  and  soybeans. 

Use  of  gypsum  or  some  other  chemical  agent  to  re- 
place the  sodium  in  the  slick  ppots  might  warrant 
further  investigation.   However,  one  of  the  major  , 
difficulties  of  such  a  method  is  to  get  adequate] 
underdrainage  for  flushing  or  washing  out  the  so- 
dium. A  few  farmers  have  tried  burying  such  mate- 
rials as  corncobs  in  slick  spots  to  Improve  their 
permeability  to  water,  but  the  benefits  of  such  | 
treatments  are  generally  temporary.   Others  who 
have  only  a  few  small  slick  spots  have  hauled  in  | 
dirt  removed  from  highway  shoulders  and  ditches. 
Building  up  the  thickness  of  more  permeable  mate- 
rial above  the  subsoil  will  reduce  the  adverse  ef- 
fects of  this  horizon  on  crops. 

One  good  thing  can  be  said  for  ellck  spots.   Where j 
they  are  suitably  located,  as  In  a  dralnageway, , 
they  make  excellent  pond  sites.   Their  high  sodium 
content  keeps  the  clay  dispersed  or  puddled  and 
consequently  very  slowly  permeable  to  seepage  of 
water. 

J.  B.  Fehrenbacher 
11-23-55 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-9 


HOW  MUCH  WATER  AND  PLANT  NUTRIENTS  ARE  LOST  BY  RUNOFF  AND  EROSION  FROM 
GENTLY  SLOPING,  PERMEABLE,  DARK-COLORED  SOILS  IN  ILLINOIS? 


These  results  are  'based  on  data  obtained 
on  the  Agronomy  farm  at  the  Illinois  Ag- 
rictiltijral  Experiment  Station,  Urbana, 
Illinois.  The  soil  is  Flanagan  silt 
loam,  a  highly  productive,  permeable  soil 
on  a  2  percent  slope.  The  land  had  been 
owned  by  the  Illinois  Agricultural  Ex- 
periment Station  for  more  than  30  years 
before  the  project  was  started.  Lime  and 
fertilizers  had  been  applied  and  a  rota- 
tion of  corn,  oats,  clover,  and  wheat  had 
been  followed.  The  soil  was  in  good  con- 
dition and  runoff  and  erosion  were  not  a 


serious  problem. 

From  19^1, when  this  project  was  started, 
until  19^^  inclusive,  a  rotation  of  corn, 
oats,  with  a  sweet  clover  catch  crop, 
was  followed.  Since  19^5  the  rotation 
has  been  corn  and  soybeans  with  no  catch 
crop.  Since  19^7  heavy  applications  of 
fertilizers  have  been  made. 

The  following  tables  give  the  amount  of 
rimoff  and  the  loss  of  some  plant  nutri- 
ents in  the  soil  removed  by  erosion. 


Average  Annual  Rimoff  in  Inches 
Up  and  down^ 


^= 


Contoure 


Highest    Lowest 


Av. 


Highest    Lowest 


Av. 


Corn  (12  yr. ) 
Soybeans  (8  yr. ) 
Oats  (4  yr. ) 


in. 

h.66 
k.dQ 
2.79 


in. 

1.01 
1.18 
0.77 


in. 

2.30 
2.19 
1.80 


in. 

3.23 

1.99 
2.28 


in. 

0.02 
0.01 
0.88 


in. 

1.32 
0.75 
I.I19 


"  17  Farmed  up  and  down  the  slope 
2/  Farmed  on  the  contour 

Average  Annual  Losses  of  Organic  Matter,  Nitrogen,  and  Phosphorus 

in  PoTonds  per  Acre 


Organic  matter 

Up  and  downj^/  Contoured2/ 
lb. /A. 


i\irrogen 

Up  and  downl/  Contoured^/ 


Phosphorus 

Up  and  downl7~Contoured2/ 


306 


lb. /A. 


112 


lb. /A. 


15.2 


lb. /A. 
5.8 


lb. /A. 
3.8 


lb. /A. 
1.4 


T/  Farmed  up  and  down  the  slope 
li  2/  Farmed  on  the  contour 


R.  S.  Staxiffer 
Nov.  2,  1953 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


SM-10 


MANAGEMENT  PRACTICES  AND  CROPS  ADAPTED  TO  SANDY  SOILS 


Proper  management  of  sandy  soils  requires 
a  thorough  knowledge  of  the  physical  and 
chemical  properties  of  the  different 
soils  in  each  field  or  crop  area.  The 
reason  is  that  soils  vary  in  their  capac- 
ity to  absorb  and  retain  water  and  to 
furnish  plant  nutrients  and  store  them 
for  future  use,  as  well  as  in  many  other 
factors  that  are  important  to  satisfac- 
tory plant  growth  and  crop  yield. 

Some  sandy  soils  have  subsoils  in  the 
upper  3-foot  section  that  contain  large 
amounts  of  clay,  some  have  moderate  clay 
accumulation,  and  others  have  little  or 
no  clay.  Milroy  sandy  loam  is  an  exam- 
ple of  a  soil  whose  subsoil  is  too  heavy 
and  impermeable  for  favorable  water  move- 
ment and  root  penetration.  Ridgeville 
fine  sandy  loam,  which  has  a  moderate 
amount  of  clay  in  the  subsoil  and  other 
favorable  features,  represents  the  best 
of  the  sandy  soils.  Plainfield  sand  is 
an  example  of  a  soil  with  no  clayey  sub- 
soil to  a  depth  of  3  or  U  feet, 

Ridgeville  soils,  even  when  untreated, 
often  produce  moderately  good  crops  of 
corn  and  soybeans,  especially  in  years 
of  favorable  weather.  Without  full 
treatment,  however,  Milroy  and  Plain- 
field  seldom  or  never  produce  satisfac- 
tory yields  of  these  two  crops. 

I  Similarly  those  sandy  soils  that  have  a 
large  proportion  of  fine  or  very  fine 
sand,  like  Onarga  fine  sandy  loam,  are 
better  storehouses  for  water  and  plant 
nutrients  than  those  made  up  mostly  of 
medium  or  coarse  sand,  like  Sumner  sandy 
loam.  Also,  soils  having  dark-colored 
surface  layers  that  are  8  to  10  inches 
or  more  thick,   such  as  Disco  fine  sandy 


loam  and  Hagener  loamy  fine  sand,  con- 
tain larger  amounts  of  organic  matter 
and  thus  more  nitrogen  and  other  plant 
nutrients  than  soils  in  which  the  dark 
surface  is  thin  or  absent,  such  as  Alvin 
sandy  loam,   Roby  fine  sandy  loam,  etc. 

Furthermore,  sandy  soils  that  have  a  mod- 
erate to  high  proportion  of  organic  mat- 
ter or  of  clay  particles  are  less  easily 
moved  by  the  wind  and  are  therefore  less 
hazardous  to  use  for  growing  clean-tilled 
crops  than  are  the  excessively  sandy 
soils. 

Most  sandy  soils  are  medium  to  strongly 
acid  and  usually  need  some  limestone  to 
produce  the  best  growth  of  clovers  and 
alfalfa.  However,  sandy  soils  have  a 
lower  capacity  to  retain  bases  than  have 
the  finer  textured  silt  loam  and  clay 
loam  soils.  This  means  that  less  lime- 
stone is  needed  to  neutralize  the  indi- 
cated acidity,  although  it  also  means 
that  limestone  should  be  added  more  of- 
ten. In  the  excessively  sandy  types,  the 
potassium  thiocyanate  test  for  acidity 
often  requires  the  addition  of  iron  to 
show  the  proper  test  color. 

Phosphate  and  potash  fertilizers  should 
be  applied  according  to  test,  but  prima- 
rily to  meet  the  needs  of  the  immediate 
crop,  since  sandy  soils  do  not  hold  large 
amounts  of  these  materials  for  any  length 
of  time.  Nitrogen  is  also  an  important 
plant  nutrient  that  is  usually  deficient, 
particularly  in  the  lighter  colored  and 
excessively  sandy  soils. 

large  amounts  of  organic  matter- -barn- 
yard manure,  green  manure,  crop  residues, 
or  other  organic  materials- -are  valuable 


additions  to  sandy  soils  not  only  for 
supplying  plant  nutrients,  but  also  for 
increasing  their  water-  and  base-holding 
capacity  and  their  stability  against 
wind  movement . 

There  are  a  number  of  special  practices 
that  may  be  used  to  help  reduce  wind 
movement  of  sandy  soils  and  thus  tend  to 
increase  crop  yields.  Among  them  are 
keeping  the  soil  surface  covered  by  grow- 
ing vegetation  or  by  crop  residues  as 
much  as  possible;  leaving  the  plowed 
surface  rough;  plowing  in  such  a  way  as 
to  leave  some  plant  residues  on  the  sur- 
face; covering  the  soil  surface  with  ma- 
nure; plowing  ridges  and  furrows  at 
right  angles  to  prevailing  west  winds  so 
far  as  possible;  planting  clean-tilled 
crops  in  strips  with  small  grains  and 
forage  crops  at  right  angles  to  prevail- 


ing winds; 
the  slope 
belts. 


contouring  strip  crops  where 
warrants;  and  using  shelter 


As  has  been  pointed  out,  many  sandy 
soils,  when  untreated,  are  not  particu- 
larly well  suited  to  growing  corn  and 
soybeans.  Returns  from  these  crops  do 
not  consistently  repay  the  cost  of  pro- 
duction. The  data  given  below,  however, 
indicate  that  applying  adequate  amounts 
of  manure,  with  limestone,  phosphorus, 
potassium,  and  nitrogen  as  needed,  will 
greatly  increase  yields  of  these  two  im- 
portant crops,  perhaps  even  to  the  point 
where  they  will  return  a  moderate  profit. 

Other  crops  that  are  better  suited  to 
sandy  soils  are  such  early-maturing  crops 
as  rye  and  wheat,  deep- rooting  crops 
like  alfalfa,  and  probably  some  special 
crops  like  melons  and  cowpeas. 


Oquawka  Soil  Experiment  Field* 

Average  Annual  Acre  Yields  of  Corn,  Soybeans, 

Wheat  and  Alfalfa,  I915-I952,  Inclusive 


Corn 

Increase 

Soybeans 

Wheat 

Alfalfa- 

38 

for  W,  k 

38 

37 

hay  35 

Treatment 

crops 

crops** 

crops 

crops 

crops 

Manure 

Manure -lime stone 

Manure-limestone-rock  phosphate 


bu. 


bu. 


bu. 


bu, 


tons 


~~^ 

37 

•  • 

12 

13 

1.0 

hi 

•  • 

16 

19 

2.4 

hi 

16 

20 

2.k 

27 

20 

8 

10 

.7 

43 

19 

13 

16 

2.1 

1^3 

12 

13 

16 

2.0 

hi 

21 

17 

17 

2.6 

No  treatment 

Residues- lime stone 

Residues- lime stone -rock  phosphate 

Residues- limestone-rock  phosphate -potash 


^Located  primarily  on  Oquawka  sand  and  Hagener  loamy  sand. 
**A  side-dressing  of  60  pounds  per  acre  of  nitrogen  was  applied  19^9-1952,  inclusive, 


H. 


L.  Wascher 
11-30-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


MANAGEMENT  & 
CONSERVATION 


mi^ 


SM-ll 


WHAT  DO  WE  KNOW  ABOUT  DEEP  TILLAGE? 


A  great  deal  has  been  said  and  written 
about  deep  tillage.  Its  benefits  have 
been  described  in  glowing  terms  in  popu- 
lar agricultural  journals  and  magazines 
and  in  literattire  published  by  commer- 
cial companies.  However,  scientific  ag- 
rictiltural  literature,  based  on  careful- 
ly conducted  experiments,  does  not  bear 
out  these  extravagant  claims.  There  may 
be  exceptions  like  plowing  an  area  in 
California  5  feet  deep  to  turn  under  xm- 
desirable  sandy,  gravelly  material  that 
had  washed  onto  the  sxjrface  of  very  val- 
uable land.  Sometime  a  method  to  make 
compact,  impervious  soils  open  and  por- 


ous by  mechanical  means  may  be  foxind. 
To  the  present,  however,  for  the  usual 
conditions  encountered  in  farming  there 
is  a  very  definite  lack  of  acceptable 
data  to  show  that  deep  tillage  greatly 
benefits  the  soil  long  enough  to  pay  for 
its  cost. 

In  this  discussion  deep  tillage  means  10 
inches  or  more  in  depth  and  includes  any 
method  of  penetrating  the  soil  to  that 
depth.  Some  results  on  deep  tillage  are 
given  in  the  following  tables,  with  de- 
scriptions of  the  soils  and  the  conditions 
xinder  which  the  results  were  secured. 


Illinois  Results  -  Corn  Yields,  Bushels  per  Acre 
(111.  Agr.  Exp.  Sta.  Bui.  258.  1925) 


Flanagan  silt  loam  -  Av.  6  yr. 

Yield 

Depth        1st  yr.     2nd  yr. 
plowed corn corn 


Cisne  silt  loam  -  Av.  "13  yr. 


Depth  plowed 

No  feiitilizer              RLPKl/     ~ 
Ordinary^/     Sub-^^/     Ordinary^     Sub- 
plowing soiled plowing soiled 


12 


7 


65.9 
65. 7 


62.3 

63.6 


16.1 


15.6 


39.6 


36.4 


Rotation  on  Flanagan  silt  loam  -  corn,  com,  oats,  sweet  clover. 
Rotation  on  Cisne  silt  loam  -  corn,  soybeans,  wheat,  red  clover. 

1/  RLPK  means  residues,  lime,  phosphorus,  and  potassitan  had  been  applied  to  the  sur- 
face of  this  area. 
2/  About  7  inches  deep. 
3/  About  l4  inches  deep. 

Flanagan  silt  loam  is  a  dark-colored  corn-belt  soil  occurring  extensively  in  east- 
central  Illinois. 

Cisne  silt  loam  Is  a  gray  prairie  soil  with  a  relatively  impermeable  claypan  subsoil. 

The  author  of  the  bxilletin  concluded,  "That  such  methods  (deep  tillage)  are  not  supe- 
rior to  ordinary  or  medium  depth  plowing  has  been  indicated  ty  subsoiling  experiments . . . .  " 


(Continued  on  other  side) 


Tennessee  Results  -  Yields  of  Corn  in  Bushels  per  Acre 
(Tenn.  Agr.  Exp.  Sta.  Bui.  191.   19*+^) 


Depth  of  plowing 


6  inches  and 
10  inches  subsoiled  6  inches 


6  inches 


Olivier  silt  loami/        , 
Huntington  fine  sandy  loam^' 
Cumberland  loam3/ 
Baxter  silt  loamZ' 


1|8.2 

73.9 
hi. 3 
52. i^ 


^9.7 
lh.5 
ki.k 
53.0 


h9.7 


l/  Ik   years'  resiolts;  2/  3  years'  results;  3/  2  years'  results;  k/  k   years'  results 

Olivier  silt  loam,  a  residual  soil,  grayish-yellow  surface,  yellow  silty  clay  loam 
upper  subsoil,  heavy  but  friable  Huntington  fine  sandy  loam  bottomland  soil. 

Cijmberland  loam,  grayish-yellow  surface,  heavy  red,  compact  subsoil. 

Baxter  silt  loam,  grayish-yellow  siirface,  reddish  subsoil,  from  cherty  limestone  and 
dolomitic  limestone.   •    • 


The  author  of  this  btilletin  concluded  that  "Neither  subsoiling  or  extra-deep  disk 
plowing  proved  profitable." 

Missoiari  Results  -  Grain  Yields,  Bxoshels  per  Acre 


i<--year  av. 
I9U3-I946 


TlowedT 
normal 


Shattered   Shattered  subsoil  plus^ 
subsoil    lime  and  fert.  in  subsoil 


Corn 
Gats 
Barley 


2U.5 

31.9 
20.3 


29.7 
30.9 
16.7 


32.0 

32.9 
20.1 


1/  Two  tons  limestone  and  200  pounds  8-20-10  fertilizer  in  shattered  subsoil. 

Putnam  silt  loam,  slowly  permeable  soil  with  claypan  subsoil.  Two  rotations:  corn, 
barley,  sweet  clover  as  green  manure  and  corn,  oats,  lespedeza  as  green  manure.  To 
shatter  subsoil,  a  regular  l8-inch  tractor  plow  was  used  to  a  depth  of  10  or  12  inches, 
followed  by  a  12-inch  walking  plow  in  first  furrow.  Total  depth  ranged  from  16  to 
20  inches. 


I  have  been  i^nable  to  secure  more  recent 
results  from  this  project,  but  I  under- 
stand that  the  effects  of  the  subsoil 
shattering  were  rapidly  disappearing 
even  where  the  limestone  and  fertilizer 
had  been  added  to  the  subsoil.  The  re- 
sults given  in  the  table,  which  were 
secxjred  at  the  beginning  of  the  experi- 
ment, are  more  favorable  to  the  treat- 
ments than  later  results  wotxld  be.  Even 
these  resxilts  are  not  a  strong  recommen- 


dation for  subsoil  shattering  and  ferti- 
lizing. It  requires  an  increased  yield 
of  more  than  7.5  bushels  of  corn  to  pay 
for  the  treatment,  especially  if  its  ef- 
fects last  only  four  or  five  years. 

An  article  published  recently  (Soil  Sci., 
Apr.  1953)  gives  some  results  of  subsoil 
shattering  in  the  sugar  cane  soils  of 
Puerto  Rico.  The  authors  state  that 
shattering  the  subsoil  without  adding 


■3- 


fertilizers  generally  reduced  yields. 
Where  lime  and  fertilizers  were  added  to 
the  shattered  subsoil,  yields  were  in- 
creased by  about  ik  percent.  These  soils 
are  fine  texttired  and  have  grown  sugar 
cane  for  years.  They  are  usually  in 
very  poor  condition  and  should  benefit 
from  subsoiling  more  than  most  soils. 
However,  the  increase  in  yield  of  sugar 
is  not  phenomenal,  and  there  is  no  indi- 
cation how  long  the  results  may  last. 

Many  other  references  on  subsoiling  could 
be  cited,  but  the  conclusions  would  still 


be  the  same  as  the  one  reached  in  1918 
(Jotir.  Agr.  Res.  lU:U8l-52l)  and  quoted 
in  a  recent  book  (Soil  Conditions  and 
Plant  Growth,  1952):  "Yields  cannot  be 
increased  nor  the  effects  of  drought  miti- 
gated by  tillage  below  depth  of  ordinary 
plowing.  The  quite  general  popxilar  be- 
lief in  the  efficiency  of  deep  tillage  as 
a  means  of  overcoming  drought  or  of  in- 
creasing yields  has  little  foundation  of 
fact,  but  is  based  on  misconceptions  and 
lack  of  knowledge  of  the  form  and  extent 
of  the  root  system  of  plants  and  of  the  be- 
havior and  movement  of  water  in  the  soil." 


R,  S.  Staxoffer 
12-28-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND              ^ 
TESTING       ^ 

M 

^ 

SF-l 


THE  NATURE  OF  SOIL  ACIDITY 


One  cannot  discuss  soil  acidity  without 
talking  about  the  available  soil  forms 
of  three  very  important  plant  foods, cal- 
cium, magnesium,  and  potassium. 

Soil  reaction  or  acidity  is  caused  by 
positively  charged  hydrogen  ions  which 
are  attached  to  the  negatively  charged 
surfaces  of  the  billions  of  small  clay 
and  humus  particles  in  the  soil.  But 
positively  charged  calcium,  magnesium, 
and  potassium  ions  are  also  attached  to 
these  negatively  charged  surfaces. 

Every  negatively  charged  spot  on  the 
clay  and  humus  must  be  occupied  by  a 
positively  charged  atom.  If  there  are 
no  bases  like  calcium,  magnesium,  and 
potassium  to  satisfy  these  negatively 
charged  spots,  then  hydrogen,  the  acid 
ion,  must  be  there  and  must  satisfy  the 
negative  charge. 

So  the  acidity  of  a  soil  depends  on  the 
balance  or  proportion  between  the  acid 
ions  and  the  basic  ions  on  the  clay-hu- 
mus. If  80  percent  of  the  clay  -  humus 
particles  are  covered  with  bases,  then 
the  soil  will  be  in  the  sweet  range.  If 
only  25  percent  of  the  clay-humus  is  base 
covered,  then  75  percent  will  be  acid 
i  ions  and  the  soil  will  be  highly  acid. 

When  a  soil  is  too  acid,  liming  material 
is  applied  to  sweeten  it.  If  this  mate- 
rial is  a  dolomitic  limestone,  as  it  of- 
ten is,  then  it  supplies  both  calcium 
and  magnesium.  As  the  small  limestone 
particles  slowly  dissolve,  the  calcium 
and  magnesium  ions  displace  the  acid 
ions  from  the  clay-humus  surfaces;  that 
is,  they  exchange  places.  The  calcium 
and  magnesium  ions  are  then  on  the  clay- 
humus,  and  the  hydrogen  ions  are  in  the 
soil  water  as  carbonic  acid,  a  harmless 
acid  normally  present  in  all  soils. 


As  this  process  continues,  the  soil 
around  each  little  limestone  particle 
becomes  charged  with  calcium  and  magne- 
sium and  the  number  of  acid  hydrogen 
ions  decreases. 

Although  plant  roots  feed  very  efficient- 
ly from  these  bases,  leaching  rains  can 
remove  them  only  slowly.  As  calcium  and 
magnesium  are  removed,  the  hydrogen  ions 
again  take  the  place  left  vacant  by 
their  removal.  With  time  these  small 
removals  mount  up,  and  the  soil  be- 
comes acid  enough  to  make  reliming  neces- 
sary. 

In  order  to  be  sweet,  a  soil  need  not 
contain  any  limestone.  Limestone  itself 
is  not  the  cause  of  sweetness.  It  is  a 
high  proportion  of  calcium  and  magnesium, 
principally  calcium,  on  the  clay-humus 
surfaces  that  causes  the  soil  to  have  a 
favorable  reaction  (as  measured  by  its 
pH) .  It  can  contain  unused  limestone 
and  still  be  acid  if  the  limestone  has 
not  had  either  the  time  or  the  opportu- 
nity to  react  with  the  soil. 

The  acid  soil  particles  cannot  move  to 
the  limestone  particles  or  vice  versa. 
A  large  particle  of  limestone  will  react 
with  the  nearby  soil  and  then  practical- 
ly stop  dissolving  because  it  has  neu- 
tralized all  of  the  nearby  acid.  So  it 
is  important  for  limestone  to  be  fine. 

(The  agricultural  limestone  used  in  Il- 
linois is  a  compromise  between  fineness 
and  price.  A  grind  containing  both  fine 
and  some  coarse  particles  is  less  expen- 
sive in  the  long  run  than  all  finely 
ground  material.  Enough  lime  should  be 
applied  to  permit  the  fine  material  to 
neutralize  sufficient  soil,  leaving  the 
coarse  to  keep  it  sweet  as  plants  and 
rains  slowly  remove  the  bases.) 


Since  the  limestone  particles  cannot  move 
around  to  where  they  are  needed,  they 
must  te  put  where  they  are  needed.  If 
they  are  broadcast  on  the  surface  and 
left  there,  they  can  sweeten  only  a 
quarter  of  an  inch  or  so  of  the  surface 
soil  and  the  rest  will  remain  acid  no 
matter  how  much  lime  is  applied.  If 
they  are  broadcast  and  then  plowed  un- 
der, without  first  being  mixed  with  the 
soil,  they  can  also  sv^eeten  only  a  very 
little  soil.  The  surface  will  still  be 
acid  and  clovers  will  not  nodulate. 


A  properly  limed  soil  is  not  necessarily 
one  that  is  sweet  throughout.  Even  with 
good  mixing,  both  sweet  and  acid  areas 
will  remain.  But  with  continued  culti- 
vation the  sweet  and  acid  soil  will 
gradually  merge.  A  sample  from  a  soil 
limed  during  the  past  five  years  or  so 
may  not  give  a  sweet  reaction  because 
the  test  is  made  to  determine  the  acidi- 
ty and  the  reaction  will  be  with  the 
acid  spots.  Nevertheless,  the  clover 
roots  find  the  sweet  spots  and  are  nodu- 
lated. 


But  if  they  are  broadcast  and  mixed 
vfell  with  the  soil,  then  all  through  the 
soil  will  be  sweet  areas  which  can  serve 
as  centers  for  the  legume  bacteria  to 
nodulate  the  legume  roots.  The  princi- 
ple to  use  is:  Put  the  limestone  where 
the  roots  will  be.  Time  and  opportunity 
for  reaction  will  produce  a  properly 
sweetened  soil,  but  really  coarse  lime- 
stone takes  too  much  time  to  react,  and 
poor  mixing  gives  well-ground  limestone 
no  opportunity  to  react. 

The  best  way  to  apply  limestone  is  to 
broadcast  and  mix  it  well  by  disking, 
harrowing,  etc.,  before  sowing  legumes. 
But  do  not  plow:  Plowing  brings  up  acid 
soil  and  puts  most  of  the  sweet  soil 
down  below.  If  the  land  is  plowed  after 
liming,  it  must  be  plowed  again  before 
legumes  are  planted  in  order  to  bring 
the  sweet  soil  back  to  the  top. 


The  pH  scale  is  merely  a  numerical 
method  of  expressing  the  balance  between 
acid  and  base  in  terms  of  the  hydrogen 
ion  concentration.  A  pH  of  7  is  neutral, 
a  pH  of  around  6.3  is  sweet,  or  adequate 
for  sweet  clover  and  alfalfa;  a  pH  of 
around  5-^  is  too  acid  for  most  clovers 
but  not  very  harmful  for  the  more  acid- 
tolerant  plants  like  soybeans,  corn,  and 
wheat;  and  a  pH  of  i+.  5  to  U.l  is  highly 
acid  and  harmful  to  any  but  acid-loving 
plants. 

The  exact  pH  range  that  any  one  plant 
will  tolerate  also  depends  on  other  un- 
known factors.  Sometimes  clovers  are 
found  growing  where  the  pH  is  supposedly 
too  low  for  their  successful  growth. 
Liming  recommendations  attempt  to  adjust 
the  pH  to  a  range  where  all  legumes  can 
always  be  successfully  grown. 

Roger  H.  Bray 
1/12/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF--2 


THE  NATURE  OF  AVAILABLE  POTASSIUM  IN  SOILS 


The  clay  minerals  and  the  soil  humus 
possess  the  property  of  holding  on  their 
surfaces  the  ions  of  such  nutrients  as 
potassium,  magnesium,  and  calcium  as 
well  as  the  acid  hydrogen  ions.  These 
surface-held  ions,  which  are  the  avail- 
able forms  of  potassium,  calcium,  and 
magnesiiJim,  are  called  exchangeable  ions. 
The  clay  minerals  and  humus  are  called 
base-exchange  materials. 

The  exchangeable  ions  are  held  on  the 
clay-humus  surfaces  by  electrical  bonds. 
The  clay-humus  is  negatively  charged 
(-),  and  the  exchangeable  ions  are  posi- 
tively charged  (+).  They  attract  each 
other,  and  the  positive  ions  cling  to 
the  negative  clay-humus  surfaces.  But 
if  a  salt  or  acid  is  present  in  the  sur- 
rounding water  and  ionizes  into  +  and  - 
ions,  the  +  ions  can  displace  (exchange 
with)  the  +  ions  on  the  clay-humus  and 
force  the  exchangeable  ions  into  the 
soil  water. 

For  example,  when  small  amounts  of  ni- 
tric, sulphuric,  and  carbonic  acids  are 
formed  in  the  soil  by  decomposition  of 
soil  organic  matter,  the  hydrogen  (acid) 
ion  displaces  exchangeable  Ca,  Mg,  and 
K  ions,  which  go  into  the  soil  water  as 
companions  for  the  sulphate,  nitrate, 
and  bicarbonate  ions.  In  a  sweet  soil, 
nitric  acid  is  changed  into  calcium, mag- 
nesium, and  potassium  nitrates,  leaving 
only  traces  of  the  acid. 

The  proportion  of  any  one  base  (positive 
ion)  in  solution  depends  on  the  composi- 
tion of  the  exchangeable  bases  held  on 
the  base -exchange  surfaces  (the  clay  min- 
eral and  humus  surfaces).  Usually  cal- 
cium is  so  abundant  that  the  salts  are 
mainly  calcium  salts.  A  common  propor- 
tion in  our  brown  silt  loam  soils  would 
be  60  percent  Ca,  30  percent  Mg,  3  per- 
cent K  and  7  percent  H. 


Plant  roots  feed  on  this  mixture  of 
salts  and  acids  in  the  soil  solution. 
They  do  not,  however,  feed  on  them  in 
this  same  proportion,  but  take  out  rela- 
tively more  potassium.  As  the  plant 
roots  remove  the  potassium,  more  ex- 
changeable potassium  is  displaced  in  or- 
der to  readjust  the  composition  of  the 
soil  water. 

Thus,  through  this  equilibrium,  the  ex- 
changeable potassium  is  the  source  of  K 
for  plant  feeding,  and  for  this  reason 
it  is  called  available  potassium.  The 
exchangeable  calcium  and  magnesium  are 
also  the  principal  available  forms  of 
these  nutrients  in  soils  of  humid  re- 
gions. 

In  Illinois  soils  containing  much  illite 
(a  clay  mineral  containing  potassium), 
the  surf ace -exchangeable  potassium  is 
also  in  equilibrium  with  a  part  of  the 
potassium  v/ithin  the  clay  particle.  So 
\7hen  potassium  is  removed  by  plant  feed- 
ing, more  of  it  is  slowly  released  to 
the  surface.  When  potassium  is  added  to 
the  surface  soil,  part  of  it  goes  slow- 
ly into  the  interior  and  is  no  longer 
immediately  exchangeable. 

We  call  this  potassium  in  the  interior 
the  storehouse  form,  because  excess  K 
goes  into  it.  But  as  plants  remove  too 
much  of  the  surface  potassium,  it  is 
slowly  renewed  from  the  storehouse  form. 
This  equilibrium  prevents  leaching  of 
excess  potassium  and  regulates  the  potas- 
sium at  a  level  that  reflects  the  abil- 
ity of  the  storehouse  to  renew  it  once 
equilibrium  is  established. 

For  example,  when  the  equivalent  of  100 
pounds  of  K  per  acre  is  added  to  a  soil 
already  containing  I50  pounds  and  is  al- 
lowed to  stand  for  a  long  time  without 
cropping  or  any  chance  of  leaching,  the 


exchangeable  potassium  at  first  will  be 
the  sum  of  that  present  plus  what  is 
added,  or  250  pounds.  In  time,  however, 
it  will  go  do\v-n  to  200  pounds  or  less. 
That  is,  part  will  go  into  the  store- 
house, and  the  amount  which  would  be  re- 
covered in  a  soil  test  would  be  less 
than  the  sum  of  the  amount  already  there 
and  the  amount  added,  even  though  no 
cropping  or  leaching  took  place. 

On  the  other  hand,  if  a  soil  containing 
150  pounds  of  K  per  acre  is  cropped  and 
the  crop  removes  50  pounds, the  exchange- 
able K  at  the  beginning  of  the  next  sea- 
son will  not  be  100  pounds,  but  may  be 
as  much  as  l4o  or  1^5  pounds  because  of 
the  release  from  the  storehouse. 

So  a  soil  test  value  gives  the  results 
of  the  equilibrium  between  the  store- 
house and  the  available  potassium,  pro- 
vided enough  time  has  elapsed  to  produce 
the  equilibriijm.  For  this  reason  it  is 
good  practice  to  avoid  taking  samples 
from  areas  where  potassium  has  been  very 
recently  applied  or  from  the  dense  part 
of  the  root  system  of  a  growing  plant. 
The  equilibrium  value  is  the  one  that 
should  be  measured. 

When  potash  salts  are  added,  they  react 
with  the  first  soil  clay  they  contact. 
For  example,  if  100  pounds  of  muriate  of 
potash  is  added  to  the  surface  soil  and 
not  mixed  in,  over  80  percent  of  the  K+ 
will  be  adsorbed  in  the  top  quarter  inch. 
When  400  pounds  are  added,  over  50'  per- 
cent will  be  adsorbed  in  the  first  quar- 
ter inch. 

The  final  result  of  adding  a  fertilizer 
such  as  potassium  chloride  is  that  the 
added  potassium  is  now  held  safe  from 
immediate  leaching  on  or  in  the  soil 
clay,  while  the  calcium  joins  the  chlor- 
ide ion  in  the  soil  water  and  both  are 
eventually  leached  away,  carrying  with 
them  only  traces  of  potassium  and  some 
magnesium. 

But  because  the  potassium  reacts  with 
the  first  clay  soil  it  contacts,  it  must 
be  put  where  it  is  wanted.  If  broadcast 
on  the  surface,  it  must  be  disked  into 
the  soil  in  order  to  be  effectively  used. 


If  drilled,  it  must  be  drilled  near  the 
seeds  and  yet  not  near  enough  to  cause 
burning,  especially  in  soybeans.  If 
used  for  top  dressing, the  potassi\im  will 
be  only  partially  effective  because  it 
will  attach  itself  to  the  surface  clay, 
which  often  dries  out  and  then  cannot  be 
used  by  the  plant.  ' 

To  measure  the  amount  of  exchangeable  ■ 
(available)  potassium  in  a  soil,  all  one 
has  to  do  is  first  thoroughly  air-dry 
the  soil  and  then  add  enough  of  another 
salt  to  cause  the  positive  ions  of  the 
salt  to  displace  all  of  the  exchangeable 
potassium.  After  filtering,  the  ex- 
changeable potassium  is  in  the  filtrate 
and  can  then  be  measured.  But  if  the 
soil  is  not  thoroughly  air-dried  (for 
over  10  days  after  it  is  dry  enough  to 
screen) ,  the  salt  cannot  replace  all  of 
the  exchangeable  potassium. 

Because  of  the  storehouse  phenomena,  the 
same  soil  test  value  for  available  K  may 
have  different  long-range  interpreta- 
tions . 

On  the  dark-colored  soils  where  the  . 
storehouse  is  still  fairly  well  filled,  ; 
a  l80-pound  test,  for  example, is  an  ade- 
quate value  for  most  crops  and,  because 
of  renewal  from  the  storehouse,  will  not 
decrease  rapidly. 

But  a  l8o-pound  test  on  a  light-colored 
clay  pan  soil  in  southern  Illinois  does 
not  mean  the  same  thing.  These  untreated  ] 
soils  almost  always  have  very  little  K 
in  the  storehouse.  A  l80-pound  value 
may  mean  that  potash  has  recently  been 
supplied  and  little  of  it  has  yet  gene 
into  the  storehouse.  Or  it  may  mean 
that  the  continuous  use  of  K  has  built 
up  both  the  storehouse  supply  and  the 
exchangeable  potassium  supply. 

I 
This  means  that  the  l80-pcund  test  value 

can  be  interpreted  in  three  different 

ways: 

1.  On  a  dark-colored  silt  or  clay  loam 
soil  in  central  and  northern  Illinois, 
where  the  storehouse  is  large  and  fairly 
well  filled,  it  means  that  K  is  not  now 
deficient,   will  not  become   seriously 


deficient  over  the  next  few  years,  need 
not  be  returned  in  an  amount  equal  to 
that  removed  in  crops,  and  is  required 
in  only  a  small  amount  in  drilled  or 
hill-dropped  fertilizers  for  balance  and 
starter  effect. 

2.  On  the  highly  weathered,  originally 
highly  acid  and  potash-deficient  soils 
of  southern  Illinois  (for  example,  the 
light-colored  clay-pan  soils)  that  have 
had  previous  treatment  with  K  extending 
over  10  to  15  years,  this  test  value 
means  that  the  storehouse  has  been  at 
least  partly  renewed  and  that  only  main- 
tenance amounts  should  be  used  to  keep 
the  level  adequate. 

3.  On  the  same  kind  of  soils  as  are  de- 
scribed in  (2)  above,  but  which  have  had 
only  one  or  two  recent  treatments  with 
potash,  then  this  test  value  should  be 
regarded  as  showing  sufficient  K  for 
that  year  only.   Any  recomnendations  for 


future  treatments  should  be  made  on  the 
basis  that  the  soil  is  deficient  in  pot- 
ash. 

It  is  therefore  obvious  that  for  soils 
that  are  naturally  deficient  in  potas- 
sium a  history  of  previous  treatments  is 
needed  as  a  guide  in  interpreting  soil 
tests. 

Because  the  exchangeable  potassium  is  re- 
newed only  slowly  after  plant  roots  re- 
move it,  the  highest  soil  tests  will  be 
obtained  in  the  spring.  Partial  renewal 
of  the  potassium  used  by  previous  crops 
will  then  have  occurred.  It  is  however, 
impossible  to  give  correlations  for  soil 
tests  for  every  month  of  the  year  and 
for  every  cropping  history.  The  corre- 
lation used  in  the  soil  testing  labora- 
tory to  interpret  the  soil  test  value  is 
for  the  average  situation  rather  than 
for  either  extreme,  and  it  is  adequate 
for  samples  taken  any  time  of  year. 

Roger  H.  Bray 
1/12/53 


ttlE 


s 


I 


FORMS  OF  POTASSIUM  IN  ILLINOIS  SOILS 
MD  THEIR  EQUILIBRIUMS 


Mineral  form  of  potassium 

Varies  from  over 

^5,000  pounds  per  acre  in  northern 

Illinois 

soils  to  less  than 

20,000  pounds  per  acre  in  southern 

Illinois 

soils. 

Release  less  than  5  pounds 
per  acre  annually 


^ 


c 
a 


Storehouse  form 

Varies  from  over  I5OO 
pounds  K  per  acre 
Northern  Illinois 

To  less  than 

200  pounds  K  per  acre 
Southern  Illinois 


C 
D 


— > 


Ex- 
change- 
able 
K 

over 
300 
North 
less  ^0 
South 


Water- 
soluble 
K    — 


■n 


3- 


o 

o 
o 


Leaching 
loss,  less 
than  5  pounds 
K  per  acre 
annually 


A  =  Added  K.  Most  potash  fertilizers  are  water 
soluble.  When  added  to  the  soil,  they  dis- 
solve in  the  soil  water. 

B  =  Immediate  equilibrium  level  -  The  dissolved 
fertilizer  reacts  with  the  soil  colloid  and 
all  of  the  added  K  becomes  exchangeable, 
giving  a  big  increase  in  total  exchangeable 
K  in  the  soil. 

C  =  Final  equilibrium  levels  -  With  time  exchangeable  K  reaches  an  equi- 
librium with  the  storehouse  form.  Much  of  the  added  K  goes  to  this 
form  if  the  soil  is  low  in  the  storehouse  form. 


D  =   Original  equilibrium  levels  in  the  soil. 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-3 


THE  NATURE  OF  AVAILABLE  PHOSPHORUS  IN   SOILS 


The  available  soil  forms  of  phosphorus 
are  the  least  understood  of  the  three 
principal  major  nutrients.  It  is  cer- 
tain that  two  or  more  forms  are  present 
in  most  soils,  and  they  can  be  discussed 
under  two  headings:  (a)  the  adsorbed 
forms  and  (b)  the  acid-soluble  forms. 

The  adsorbed  forms:  When  soluble  phos- 
phate is  released  through  the  decomposi- 
tion of  soil  humus  and  plant  organic 
matter  or  is  added  as  a  soluble  phos- 
phate like  superphosphate,  a  good  share 
of  it  is  adsorbed  by  the  colloidal  clay 
minerals  in  the  soil,  and  perhaps  by  the 
hydrous  oxides  of  iron  and  aluminum  or 
concretionary  material .  This  adsorption 
greatly  reduces  its  solubility  and  hence 
its  mobility  in  the  soil.  It  will  not 
leach  out  and  yet  plants  can  feed  on  it. 

The  larger  the  amount  of  adsorbed  phos- 
phate in  any  one  spot,  the  higher  its 
solubility  and  the  more  readily  plant 
roots  can  feed  on  it.  Therefore,  in 
practice,  it  is  advantageous  to  add  sol- 
uble forms  of  phosphates  to  a  soil  in 
such  a  way  that  they  will  not  be  thor- 
oughly (evenly)  mixed  with  the  whole 
soil.  Broadcasting  and  disking,  for  ex- 
ample, mix  the  phosphates  unevenly  e- 
nough  to  leave  small  patches  or  areas 
that  are  very  high  in  adsorbed  phospho- 
rus. That  means  that  the  phosphate  ad- 
sorbed in  these  areas  will  have  rela- 
tively good  solubility  and  hence  higher 
availability  for  root  feeding.  The  sol- 
uble phosphates  are  adsorbed  even  less 
strongly  when  put  into  the  row  or  hill 
than  when  broadcast . 

Plant  roots  develop  more  extensively 
within  these  patches  and  feed  much  more 
effectively  than  if  the  solubility  and 
positional  availability  were  further  re- 
duced by  thorough  mixing.  This  unused 
phosphate,  however,  gradually  mixes  with 


more  and  more  soil  as  repeated  plowing 
and  cultivating  stir  the  soil.  Although 
it  will  still  be  available,  its  availa- 
bility will  finally  be  reduced  to  that 
of  the  more  evenly  distributed  forms. 

The  distribution  of  the  available  form 
of  a  nutrient  in  the  soil  is  called  its 
fertility  pattern.  An  uneven  or  irregu- 
lar fertility  pattern  can  increase  the 
availability  (both  chemical  and  posi- 
tional)of  such  available  soil  forms  as 
adsorbed  and  acid-soluble  phosphate 
(rock  phosphate  is  an  exception)  and  ex- 
changeable potassium. 

The  acid- soluble  forms  in  turn  consist 
of  two  types,  the  naturally  occurring 
acid-soluble  forms  and  rock  phosphate. 
The  natural  acid-soluble  forms, so-called 
because  dilute  mineral  acids  can  dis- 
solve them,  would  probably  be  better 
called  the  calcium  forms.  Mono-calcium 
phosphate  (the  form  in  superphosphate) 
is  a  soluble  form.  When  added  to  the 
soil,  the  part  that  is  not  adsorbed  (see 
above)  is  apparently  changed  to  less  sol- 
uble forms  that  are  higher  in  calcium. 
In  sweet  soils  that  are  high  in  ex- 
changeable (available)  calcium,  the  wa- 
ter solubility  of  these  higher  calcium 
forms  is  still  further  reduced. 

Sweet  or  near-neutral  soils  contain  a 
relatively  higher  proportion  of  the 
acid-soluble  (higher  calcium)  forms  and 
relatively  less  of  the  adsorbed  forms 
than  do  acid  soils.  Liming  a  soil 
changes  much  of  the  adsorbed  phosphorus 
into  the  easily  acid-soluble  forms.  Be- 
cause in  highly  acid  soils  it  is  diffi- 
cult for  most  cultivated  plants  to  feed 
on  phosphorus,  liming  has  another  func- 
tion besides  making  the  soil  favorable 
for  legume  nodulation  or  furnishing  cal- 
cium and  magnesium:  it  makes  the  phos- 
phorus uptake  easier. 


Although  rock  phosphate  is  probably 
present  in  the  unweathered  till  and 
loess ;  it  is  not  found  in  detectable  a- 
mounts  in  surface  soils  in  a  natural  a- 
vailable  form.  Rock  phosphate  is  solu- 
ble in  dilute  mineral  acids,  and  in  very- 
acid  soils  the  soil  acids  slowly  attack 
and  dissolve  it,  causing  it  to  go  into 
the  naturally  available  forms  described 
above.  In  very  sweet  soils  (pH  6.5  to 
7) ,  and  especially  those  on  the  alkaline 
side,  as  carbonate -containing  soils, 
rock  phosphate  dissolves  only  very  slow- 
ly, being  retarded  by  the  large  supply 
of  calcium  associated  with  a  high  pH,  as 
well  as  by  a  lack  of  acid. 

But  in  the  pH  range  usually  found  in 
carefully  limed  soils,  plant  roots  can 
feed  on  the  rock  phosphate,  and  it  is 
therefore  classed  as  available,  although 
for  many  plants  its  availability  is  lim- 
ited. Unlike  the  other  forms,  its  solu- 
bility--and  hence  its  availability--is 
not  increased  by  concentration.  For 
these  reasons  all  the  root  hairs  should 
be  given  a  chance  to  feed  on  particles 
of  rock  phosphate. 

The  application  of  relatively  small  a- 
mounts  of  rock  phosphate  by  drilling  or 
hill-dropping  does  not  increase  its  sol- 
ubility or  effectiveness.  This  is  the 
reason  it  is  necessary  to  broadcast  the 
full  requirement  and  to  mix  it  thorough- 
ly. Only  in  this  way  can  most  of  the 
roots  get  a  chance  to  feed  on  the  slowly 
soluble  rock  phosphate.  The  roots  in 
one  area  cannot  obtain  extra  phosphate 
to  make  up  for  the  lack  of  phosphate  in 
another  area,  as  is  true  with  the  ad- 
sorbed and  other  acid-soluble  forms. 
The  roots  in  all  areas  must  have  a 
chance  to  feed  on  rock  phosphate. 

But  even  when  rock  phosphate  is  well 
mixed  throughout  the  soil,  some  kinds  of 
plants  do  not  use  rock  phosphate  effi- 
ciently and  the  early  stages  of  growth 
may  be  retarded  because  of  a  lack  of 
phosphorus.  Wheat  and  tomato  yields 
are  likely  to  be  low  unless  some  super- 
phosphate is  used  for  "starter"  effect. 
The  superphosphate  will  give  the  young 
plants  a  good  start  and  they  will  feed 
rather  effectively  on  the  rock  phosphate 


during  the  rest  of  their  growth  period. 
Wheat  can  be  set  back  from  3  to  10  or 
more  bushels  per  acre  if  soluble  phos- 
phates are  not  applied,  even  when  four 
or  more  tons  of  rock  phosphate  per  acre 
have  been  used. 

Most  phosphate  fertilizers  (rock  phos- 
phate is  an  exception)  are  readily  solu- 
ble and  react  with  the  soil  as  described 
above.  The  proportion  of  the  so-called 
acid-soluble  and  adsorbed  forms  appears 
to  be  controlled  by  the  pH  (acidity)  of 
the  soil.  The  relative  availability  of 
these  forms  is  not  known.  Liming  changes 
part  of  the  adsorbed  forms  over  to  acid- 
soluble  forms  and  thus  increases  the  a- 
mount  removed  by  those  soil  tests  which 
dissolve  principally  the  acid-soluble 
forms.  This  makes  it  appear  as  though 
liming  has  increased  the  amount  of  a- 
vailable  phosphorus,  whereas  it  may  be 
only  an  alteration  within  available 
forms . 

The  amounts  of  these  natural  available 
forms  of  phosphorus  needed  for  optimum 
yields  are  surprisingly  large.  This  is 
true  for  untreated  cropped  soils  where 
the  available  phosphorus  is  more  or  less 
evenly  distributed  (not  concentrated  in- 
to patches  of  higher  availability) .  A- 
round  16O  to  300  pounds  per  acre 
(2,000,000  pounds)  of  phosphorus  (P,  not 
P2O5)  are  required  when  this  amount  is 
rather  thoroughly  mixed  with  the  soil  as 
is  the  case  with  cropped  soils  which 
have  not  had  recent  applications.  On 
the  other  hand  "low"  testing  soils  con- 
tain around  60  pounds  of  available  P . 
(The  soil  test  (P2)  removes  only  about 
one -third  of  the  total  available  amount 
so  the  soil  test  value  must  be  multiplied 
by  3  to  obtain  the  actual  value.) 

But  if  a  soil  contains  60  pounds  of  a- 
vailable  phosphorus  (tests  low)  and  if 
the  amount  which  should  be  present  (thor- 
oughly mixed  with  the  soil)  for  optimum 
yield  is  200  pounds,  it  does  not  follow 
that  the  soil  must  be  treated  with  lUO 
pounds  of  soluble  phosphorus. 

Soluble  phosphates,  when  first  added, 
especially  when  extreme  mixing  has  not 
occurred, are  much  higher  in  availability 


due  to  the  fact  that  concentration  in- 
creases the  solubility  of  the  adsorbed 
forms  as  well  as  the  positional  availa- 
bility for  root  feeding.  So  instead  of 
l40  pounds  of  phosphorus  an  amount  as 
low  as  ko  or  30  pounds  or  less  may  be 
sufficient  depending  upon  how  it  is 
used  and  the  kind  of  crop.  But  it  must 
be  repeatedly  used  until  the  soil  level 
is  sufficiently  high  to  permit  just  the 
application  of  maintenance  amounts. 
Recommendations  for  the  use  of  soluble 
phosphates  (superphosphate  is  an  example) 
are  thus  not  generally  designed  to  build 
up  the  soil  level  all  at  once.  They  are 
mainly  for  the  crop  to  which  they  are 
applied.  Usually  more  is  added  than  is 
■  removed  and  a  build  -  up  of  available 
phosphorus  gradually  occurs.  But  this 
build-up  is  a  natural  by-product  of  the 
practice,  not  the  objective.  Only  highly 
soluble  phosphates  can  be  used  in  this 
way.  Slightly  soluble  and  slowly  solu- 
ble phosphates  like  rock  phosphate  can- 
not be  used  in  this  way. 

Large  amounts  of  rock  phosphate  must  be 
broadcast  and  thoroughly  mixed  with  the 
soil  for  satisfactory  results.  But  even 


when  added  in  the  proper  amounts  and 
thoroughly  mixed,  rock  phosphate  does  not 
satisfy  all  crops  and  for  some  a  "start- 
er" of  soluble  phosphate  is  necessary. 

The  Soil  Organic  Matter  (humus) 

Soluble  phosphate  is  liberated  when  soil 
organic  matter  decomposes.  This  phos- 
phate goes  into  the  natural  available 
forms  and  helps  explain  why  the  soil 
test  values  on  untreated  soils  do  not 
decrease  proportionally  with  crop  remov- 
als. Because  this  release  of  phosphorus 
from  the  soil  organic  matter  is  uniform 
throughout  the  soil,  it  is  not  concen- 
trated into  patches  as  happens  when  sol- 
uble phosphates  are  added.  The  phos- 
phate released  will  have  no  higher  an  a- 
vailability  than  the  naturally  occurring 
available  forms  into  which  it  changed. 
This  release  may  amount  to  only  3  or  i| 
pounds  a  year,  and  it  adds  very  little  to 
the  effectiveness  of  the  6q  to  I30 
pounds  of  available  phosphorus  already 
present  in  deficient  soils.  But  it  can 
have  a  relatively  large  effect  on  the 
maintenance  of  phosphorus,  since  some  ro- 
tations remove  not  much  over  10  pounds 
of  phosphorus  each  year. 

Roger  H .  Bray 
3/23/53 


p.e 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-4 


THE  NATURE  OF  AVAILABLE  NITROGEN  IN  SOILS 


The  natural  available  forms  of  nitrogen 
in  soils  are  ammonia  and  nitrate,  which 
are  present  as  the  ammoniiim  ion  (NHi[) 
and  the  nitrate  ion  ("NOn).  Both  forms 
can  be  taken  up  from  the  soil  and  uti- 
lized by  most  plants.  A  few  plants-- 
rice  is  an  example--must  have  the  ammo- 
nium form  almost  exclusively.  But  most 
plants, although  they  absorb  and  can  uti- 
lize both  forms,  must  have  a  great  part 
of  their  nitrogen  in  the  nitrate  form 
and  do  not  actually  have  to  have  any  in 
the  ammonium  form. 

This  may  or  may  not  be  related  to  the 
fact  that  nitrate  nitrogen  is  the  ulti- 
mate available  form  in  soils.  All  other 
fertilizer  forms,  through  the  action  of 
soil  microorganisms, can  be  converted  in- 
to ammonia  and  ultimately  into  nitrate 
nitrogen. 

The  nitrogen  in  soil  hiunus  is  not  in  an 
available  form,  but  its  decomposition  by 
soil  organisms  slowly  releases  some 
available  nitrogen  each  year,  the  amount 
varying  with  the  amount  of  nitrogen  in 
the  humus  and  the  favorableness  of  the 
soil  and  season.  The  protein  in  organic 
matter,  such  as  crop  residues,  green 
manures,  or  barnyard  manures,  goes 
through  a  decomposition  cycle  which  fi- 
nally liberates  a  good  share  of  its  ni- 
trogen as  ammonia  and  nitrate  nitrogen. 

The  most  common  nitrogen  fertilizers  are 
ones  consisting  either  of  the  nitrate  or 
the  ammonium  form  or  both.  Organic  fer- 
tilizers like  guano  or  dried  blood  de- 
compose to  ammonia  and  then  to  nitrate. 

Urea  and  cyanamid  likewise  decompose  to 
ammonia  and  nitrate  (cyanamid  can  harm 
crops  and  must  be  added  10  days  before 
planting. 


But  regardless  of  what  fertilizer  or  or- 
ganic form  is  added,  it  is  changed  to 
ammonia  and  nitrate  before  it  is  used  by 
plants. 

Difference  Between  Ammonia  and  Nitrate 

There  is  a  fundamental  difference  in  the 
way  ammonia  and  nitrate  react  in  the  soil: 

The  negatively  charged  nitrate  ion  re- 
mains free  and  mobile  in  the  soil.  Not 
being  adsorbed  by  the  soil  clay,  it  is 
free  to  move  In  and  with  the  soil  water. 
It  will  move  into  the  root  as  the  root 
adsorbs  water  or  will  move  up  to  the  sur- 
face of  the  soil  and  be  deposited  as  a 
salt  as  the  soil  dries  cut. 

This  salt  will  be  mainly  calcium  nitrate 
with  some  magnesium  and  potassium,  de- 
pending on  the  relative  amounts  of  Ca, 
Mg,  and  K  on  the  base-exchange  surfaces 
of  the  soil.  The  relative  amounts  of  the 
exchangeable  bases  control  the  propor- 
tion of  these  bases  that  will  be  part- 
ners of  the  nitrate  ion. 

Because  of  its  high  mobility  in  relation 
to  the  mobility  of  the  adsorbed  forms  of 
nutrients,  nitrate  nitrogen  is  highly 
available  and  crops  can  remove  it  almost 
quantitatively  from  moist  soils.  Leach- 
ing rains  can  also  remove  it.  However, 
in  the  silt  and  clay  loam  soils  of  the 
corn  belt,  loss  of  nitrogen  thru  leach- 
ing does  not  appear  to  be  a  very  serious 
problem,  particularly  while  crops  are 
growing.  Because  nitrate  depends  on 
water  for  its  mobility,  dry  periods  can 
immobilize  it  before  the  plant  gets  it 
and  cause  a  drought-induced  nitrogen  de- 
ficiency. 

The  ammonium  ion  (NHlJ;)  is  positively 
charged  and  reacts  with  the  clay  mineral 


and  humus  base -exchange  surfaces.  This 
adsorption  by  (reaction  with)  the  clay- 
humus  exchange  surfaces  results  in  al- 
most all  of  the  ammonium  ions  being  held 
on  these  surfaces  and  protected  against 
leaching.  Being  adsorbed  in  this  way, 
ammonia  is  much  less  mobile  in  the  soil 
and  hence  is  a  temporarily  less  avail- 
able form  than  nitrate  nitrogen.  But 
this  does  not  mean  that  any  more  of  the 
ammonium  form  is  needed  for  equal  results; 
its  change  to  nitrate  is  rapid  when  grow- 
ing conditions  are  favorable.  As  soil 
temperatures  fall  somewhere  below  60°  to 
55°  in  the  fall  or  spring,  the  ammonia 
present  in  the  soil  is,  for  practical 
purposes,  no  longer  changed  to  nitrate 
and,  being  held  on  the  clay  humus  sur- 
faces, is  protected  against  leaching  dur- 
ing cold  periods. 

Because  all  nitrogen  fertilizers,  except 
those  used  by  soil  microorganisms,  are 
eventually  changed  to  nitrate  nitrogen, 
which  is  mobile  in  moist  soils,  it  usu- 
ally does  not  matter  what  method  of  ap- 
plication is  used.  Plowed  under  or 
broadcast  and  disked  ahead  of  planting, 
drilled  alongside  the  rows  or  in  the  mid- 


dle of  the  rows --all  of 
are  generally  effective. 


these  methods 


Timeliness  of  application  is,  however, 
important  in  the  utilization  of  added  ni- 
trogen by  microorganisms  or  its  possible 
loss  by  leaching.  Delaying  part  or  all 
of  the  application  could  give  a  somewhat 
more  efficient  use  under  some  conditions. 
But  if  late  applications  are  broadcast 
or  side-dressed  on  dry  soil  surfaces, 
they  will  be  ineffective  until  rains 
wash  them  into  the  soil. 

When  soils  are  sandy  and  (or)  leach  read- 
ily, the  nitrogen  application  may  be 
split  into  two  or  three  applications  to 
reduce  the  chances  of  its  being  parti- 
ally lost  by  leaching. 

Wet  and  (or)  cold  springs  delay  nitrate 
formation,  as  does  dry  weather. 

When  ammonia  is  added  as  a  gas  (anhy- 
drous ammonia),   it  must  be  released  be-' 
low  the  surface  in  such  a  way  as  to  give! 
it  a  chance  to  react  with  sufficient 
clay-humus  surfaces.   This  reaction  is' 
rapid  because  it  is  a  neutralization; 
reaction  and  the  soil  is,   for  the  time 
being,  somewhat  sweeter. 

Roger  H.  Bray 
i^/6/53 


I  I 


flL 


Ci 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND 
TESTING       w 

m- 

SF-5A 


PRINCIPLES  OF  FERTILIZER  USE  BASED  ON  SOIL  REACTIONS 


1.   Phosphates 


The  way  in  which  fertilizers  react  with 
the  soil  and  the  products  that  result  de- 
termine in  large  part  how  fertilizer  ma- 
terials should  be  used. 


ihy 
lie 
dm 

iet 
Di 
tio 
til 


'% 


The'  simplest  example  is 
phate.  In  highly  acid 
phosphate  particles  disso 
making  the  phosphate  more 
plants  cannot  grow  well 
soils  to  make  use  of  the 
less  acid  soils  the  part 
less  slowly,  and  in  normal 
main  largely  as  they  were 


round  rcckphos- 

soils     the  rock 

Ive  very  slowly, 

available,   but 

enough  in  such 

phosphate.      In 

icles  dissolve 

soils  they  re- 

when  applied. 


Plants  can  feed  to  varying  extents  on 
rock  phosphate.  Because  it  is  so  insol- 
uble and  reacts  so  slowly,  the  root  hairs 
that  contact  and  feed  on  the  particles 
have  difficulty  in  obtaining  enough  phos- 
phate for  the  plants.  VJhen  the  root  hair 
first  contacts  the  phosphate  particle, 
it  can  rather  rapidly  remove  the  thin 
surface  film  of  already  dissolved  phos- 
phate. But  from  that  time  on,  the  roots 
feed  only  as  fast  as  the  particles  can 
dissolve. 

For  this  reason  some  crops  never  get 
enough  phosphate  from  rock  phosphate 
alone.  The  small  grains,  particularly 
wheat,  and  probably  the  grasses  need 
supplemental  additions  of  soluble  phos- 
phates. V/heat  following  soybeans  may 
produce  only  two-thirds  of  a  normal  yield 
with  rock  phosphate  alone.  To  get  a 
good  yield,  it  is  necessary  to  drill  sol- 
uble phosphate  in  at  seeding  time. 

Instances  where  large  amounts  of  rock 
phosphate  have  produced  as  high  yields 
as  adequate  amounts  of  superphosphate 
are  rare  and  do  not  disclose  the  true 
differences  between  the  two  forms.  Vfhen 
tests  show  yields  to  be  as  high  vrith 


rock  phosphate  alone  as  with  superphos- 
phate, it  is  because  the  natural  forms 
are  helping  out,  the  soil  has  become  acid 
enough  to  help  dissolve  the  rock  phos- 
phate, or  the  soluble  phosphates  were  not 
used  in  adequate  amounts. 

Because  the  rock  phosphate  particles 
dissolve  so  slowly,  as  many  root  hairs 
as  possible  must  feed  on  them  in  order  to 
make  most  efficient  use  of  the  phosphate. 
This  means  that  the  rock  phosphate  should 
be  broadcast  and  thoroup:hly  mixed  with 
the  soil  by  repeated  diskings.  Broad- 
casting and  plowing  without  mixing,  or 
drilling  in  small  amounts  in  the  row 
with  the  seed,  permits  only  a  small  part 
of  the  root  hairs  to  feed  on  the  phos- 
phate. A  small  number  of  root  hairs 
feeding  luxuriantly  on  rock  phosphate 
cannot  make  up  for  a  larger  number  get- 
ting a  deficient  supply.  Broadcasting 
followed  by  thorough  mixing  allows  the 
roots  to  make  maximum  use  of  the  phos- 
phate. 

Another  problem  in  using  rock  phosphate 
is  that  calcium  and  a  high  pH  decrease 
the  rate  of  solution  of  the  rock  phos- 
phate particles.  Soils  containing  cal- 
cium carbonate  therefore  require  soluble 
phosphates.  When  rock  phosphate  is  ap- 
plied at  the  same  time  as  limestone,  the 
limestone  markedly  reduces  the  soil's 
response  to  the  rock  phosphate.  This  re- 
duction can  be  prevented  by  adding  super- 
phosphate at  the  same  time.  The  adverse 
effect  wears  off  in  time  as  the  lime- 
stone does  its  job  of  neutralizing  the 
soil. 

Soluble  phosphates  present  an  entirely 
different  problem.  Superphosphate,  treb- 
le super,  and  meta  phosphate  are  exam- 
ples of  soluble  phosphates.   VThen  a 


soluble  phosphate  is  added  to  the  soil^ 
it  dissolves  in  the  soil  water  and  is 
changed  almost  ircmediately  into  the  nat- 
ural available  soil  forms.  Although  the 
chemistry  of  these  natural  soil  forms  is 
not  fully  understood;  their  division  in- 
to adsorbed  and  acid- soluble  forms  seems 
warranted  (see  S.F.-3). 

An  adsorbed  form  will  be  used  for  illus- 
tration. A  phosphate  ion  from  the  dis- 
solved phosphate- -for  example ^  an  ~H2P01| 
ion- -moves  to  a  broken  edge  of  a  clay 
mineral  lattice  and  changes  places  with 
an  "OH  ion  on  the  lattice  edge.  Now  the 
phosphate  ion  is  tightly  held  and  is  no 
longer  in  solution.  But  as  more  phos- 
phate is  adsorbed,  the  phosphate  ions 
are  held  less  tightly.  In  short,  the 
phosphate  ions  on  the  clay  are  in  equi- 
librium with  the  phosphate  ions  in  the 
soil  water.  The  larp:er  the  amount  ad- 
sorbed ,  the  larger  the  amount  in  the 
soil  water. 

For  this  reason  if  the  phosphate  is 
broadcast  and  thoroughly  mixed  with  the 
soil,  only  a  small  amount  will  be  pres- 
ent on  the  clay  surfaces  throughout  the 
soil,  and  equilibrium  will  result  in  a 
low  concentration  of  phosphate  in  the 
soil  water. 

Such  thorough  mixing  is,  however,  prac- 
tically impossible.  What  actually  hap- 
pens is  that  the  soluble  phosphate 
reacts  with  the  first  soil  it  contacts 
and  becomes  highly  concentrated  in  small 
areas,  leaving  large  areas  untouched. 
When  numerous  enough,  these  small  areas 
of  phosphate  concentration  serve  as  ade- 
quate feeding  areas  for  the  plant  roots. 


In  contrast  to  rock  phosphate,  the  added 
natural  available  forms  of  phosphate  dis- 
solve readily  enough  to  permit  the  root 
hairs  to  feed  luxuriously  and, by  obtain- 
ing more  than  their  share,  to  make  up  for 
the  deficiency  in  the  untreated  areas. 
The  higher  this  deficiency,  the  larger 
will  be  the  amount  of  soluble  phosphate 
used,  and  hence  the  greater  v;ill  be  the 
number  of  areas  that  are  high  in  ad- 
sorbed phosphate. 

Soluble  phosphates  should  therefore  not 
be  mixed  thoroughly  with  the  soil.  If 
large  amounts  are  applied,  they  should 
be  broadcast  and  disked  into  the  soil. 
I^/hen  possible,  smaller  amounts,  like  100 
to  200  pounds,  should  be  drilled  or 
banded  near  the  seed. 

Broadcasting  without  mixing  causes  the 
soluble  phosphates  to  be  adsorbed  mostly 
in  the  surface  quarter  to  half  inch  or 
so.  Even  though  the  phosphate  were  dis- 
solved in  water  before  being  added  to 
the  soil,  it  would  still  be  adsorbed  in 
the  immediate  surface.  Roots  can  feed 
on  it  effectively  when  the  surface  is 
moist,  but  not  when  the  surface  is  dry, 
as  it  so  often  is.  For  pastures,  how- 
ever, this  method  is  often  necessary  and 
practical. 

The  objective  is  to  use  the  soluble  phos- 
phates in  such  a  way  that  they  will  be- 
come available  to  the  greatest  extent 
both  chemically  and  positionally.  High 
solubility  increases  chemical  availabil- 
ity. Placing  the  phosphate  close  to  the 
seed  increases  positional  availability. 
For  example,  soluble  phosphates  will  not 
be  so  effective  if  drilled  in  the  middle 
of  corn  rows. 

Eoger  H.  Bray 
5-11-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-5B 


PRINCIPLES  OF  FERTILIZER  USE  BASED  ON  SOIL  REACTIONS 

1.   Potassiiim,  Sulfur  and  Boron 


The  chemistry  of  potassiiiin  is  the  chem- 
istry of  base-exchange,  because  the  dom- 
inant natural  available  form  of  potassi- 
um is  the  exchangeable  potassium.  Potas- 
sium is  added  to  the  soil  as  soluble 
salts  that  dissolve  and  ionize  in  the 
soil  water.  Muriate  of  potash  (potas- 
siiim  chloride)  is  the  most  common  ferti- 
lizer form. 

Muriate  of  potash,  KCl,  dissolves  in  the 
soil  water  as  a  positively  charged  potas- 
sium ion,  K+,  and  a  negatively  charged 
chloride  ion,  "CI.  The  chloride  ions 
cannot  react  with  anything  in  the  soil 
to  make  them  become  less  abundant  in  the 
soil  water.  But  the  positively  charged 
potassiiim  ions  can  take  part  in  base- 
exchange  . 

As  positive  ions  the  potassium  ions  can 
replace  other  positive  exchangeable  ions 
on  the  surfaces  of  the  clay  minerals  and 
soil  organic  matter.  They  are  then  held 
immobile  on  these  surfaces  unless  or  un- 
til other  ions  displace  them  and  release 
them  again  into  the  soil  water.  How 
much  of  the  potassium  remains  in  the 
soil  water  at  equilibrium  depends  on  how 
much  is  added  and  what  the  base-exchange 
capacity  of  the  soil  is. 

Because  in  most  agricultural  soils  cal- 
cium and  magnesium  ions  are  most  abun- 
dant on  the  exchange  surfaces,  they  are 
the  ones  that  exchange  most  readily  with 
the  potassiiom  and  are  released  most 
abundantly  into  the  soil  water  after  pot- 
ash salts  are  added.  This  is  particu- 
larly true  of  calci\im.  Exchangeable  hy- 
drogen, the  acid  ion  that  causes  soil 
acidity,  dominates  only  in  highly  acid 
soils. 


Therefore,  when  muriate  of  potash  is 
added  to  a  soil,  the  K+  exchanges  with 
the  positive  ions  on  the  base-exchange 
surfaces,  and  the  soil  water  contains 
mainly  calcium  chloride  with  a  smaller 
amount  of  magnesium  and  very  small 
amounts  of  potassium  and  hydrogen  chlor- 
ides. Most  of  the  potassium  attaches 
itself  to  the  surfaces  of  the  soil  clay 
and  organic  matter  as  exchangeable  potas- 
sium. 

While  this  exchange  reduces  the  availa- 
bility of  the  potassium,  it  does  not 
make  it  unavailable  (see  Agronomy  Facts 
SF-2)  because  exchangeable  potassium  is 
the  natural  available  form.  As  the 
plant  roots  feed  on  the  potassium  in  the 
soil  water,  more  potassium  is  released 
to  reestablish  the  equilibrium.  By  this 
process  the  potassium  is  effectively  re- 
moved by  the  plant  roots  in  the  denser 
part  of  the  root  system  feeding  zone. 

Just  as  soluble  phosphates  remain  more 
highly  available  if  concentrated  into 
small  areas  instead  of  being  mixed  thor- 
oughly with  all  of  the  soil,  so  potassi- 
um is  more  available  if  it  is  not  thor- 
oughly mixed.  This  means  that  soluble 
potash  fertilizers,  when  used  in  small 
amounts,  should  also  be  drilled  or  hill- 
dropped  near  the  seed.  Large  amounts 
should  be  broadcast  and  disked  into  the 
soil  with  as  little  mixing  as  possible. 

Here  again,  as  with  phosphates,  broad- 
cast surface  applications  for  pastures 
are  a  practical  and  often  necessary  expe- 
dient rather  than  an  ideal  way  to  apply 
the  fertilizer. 


In  contrast  to  phosphate  use,  caution 
must  be  observed  in  applying  potash  salt 
close  to  the  seed.  Phosphates  do  not 
leave  soluble  salt  or  acid  residues  aft- 
er reacting  with  normal  agricultural 
soils,  and  therefore  they  may  be  used 
rather  freely.  But  potassium  chloride 
leaves  as  much  soluble  salt  after  react- 
ing with  the  soil  as  before  the  reaction. 
The  only  difference  is  that  afterwards 
the  salt  is  mostly  calcium  chloride  in- 
stead of  potassium  chloride.  The  amount 
that  can  be  placed  near  the  seed  is 
therefore  limited. 

Some  crops  are  less  sensitive  to  salt 
than  others.  Soybeans  appear  to  be  es- 
pecially sensitive.  Recommendations  for 
the  use  of  muriate  of  potash  should,  and 
usually  do,  recognize  this  fact.  No 
recommendations  for  amounts  to  use  are 
being  given  because  our  purpose  here  is 
only  to  explain  the  nature  of  the  soil 
reactions  and  to  show  how  they  influence 
the  amounts  used  and  the  way  in  which 
they  are  used. 


Boron  and  sulfur.  Besides  the  ultimate 
available  form  of  nitrogen,  nitrate  ni- 
trogen, there  are  two  other  nutrients, 
boron  and  sulfur,  that  soils  do  not  ad- 
sorb to  any  marked  degree.  Boron,  in 
the  form  of  borax,  NagBi^Oy,  probably 
changes  in  the  soil  to  boric  acid,  HoBOo, 
which,  because  it  is  not  adsorbed,  will 
eventually  be  lost  by  leaching  if  not 
taken  up  by  crops . 

The  available  soil  form  of  sulfur  is 
sulfate,  ~"SOj^^.  In  soils  it  is  present 
mostly  as  CaSOlj..  While  calcium  sulfate 
is  not  very  soluble,  it  is  sufficiently 
soluble  to  make  it  appear  doubtful  that 
there  is  any  undissolved  calcium  sulfate 
in  normal  soils  of  humid  regions.  The 
so-called  slick  spots  of  southern  Illi- 
nois are  one  exception.  So  far  as  we 
know,  the  sulfur  resulting  from  the  de- 
composition of  the  soil  humus  and  from 
coal  smoke  in  industrial  areas  is  suffi- 
cient for  crops,  and  the  sulfate  in  the 
drainage  water  is  proportional  to  the 
amount  in  the  rainfall. 


Potassium  sulfate  is  another,  but  less 
common,  form  of  potassium  fertilizer. 
It  is  obtainable  commercially  only  in 
limited  amounts.  When  soils  contain  a 
large  amount  of  exchangeable  calcium, 
the  danger  of  damage  to  crops  from  the 
effect  of  the  salt  should  be  lessened  by 
using  potassium  sulfate  instead  of  po- 
tassium chloride.  The  reason  is  that, 
although  calcium  chloride  is  highly  sol- 
uble, calcium  sulfate  is  not.  It  will 
precipitate  out  when  the  concentration 
in  solution  exceeds  the  solubility  of 
the  calcium  sulfate. 


The  information  on  fertilizer  use  given 
here  does  not  include  directions  on  how 
to  use  fertilizers;  rather,  it  is  an  ex- 
planation of  the  principles  behind  the 
use  of  fertilizers.  Knowing  the  prin- 
ciples makes  it  possible  to  use  ferti- 
lizers intelligently--to  modify  standard 
recommendations  to  fit  local  situations 
without  violating  the' principles .  At  the 
same  time  expediency  of  use  must  also  be 
considered.  The  "perfect"  use  of  a  fer- 
tilizer must  often  give  way  to  the  "ex- 
pedient" use,  such  as  broadcasting  fer- 
tilizer on  pastures  without  working  it  in. 


Roger  H.  Bray 
5/11/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-5C 


PRINCIPLES  OF  FERTILIZER  USE  BASED  ON  SOIL  REACTIONS 


Nitrogen  and  Mixed  Fertilizers 


Nitrogen.  All  nitrogen  fertilizers  have 
one  thing  in  common:  if  they  are  not  al- 
ready nitrate  in  form,  they  finally  end 
up  as  nitrates  in  the  soil--except  for 
the  small  part  which  the  plant  absorbs 
as  ammonia  (SF-^) . 

In  the  soil  all  organic  forms  of  nitro- 
gen, such  as  urea  and  cyanamid,  are 
changed  first  into  ammonia  and  then  into 
nitrate  nitrogen.  If  ammonia  were  the 
ultimate  available  form  used  by  the  plant 
and  the  change  to  nitrate  did  not  occur, 
then  nitrogen  fertility  would  be  similar 
to  potassium  fertility  and  we  would  be 
concerned  with  nitrogen  as  ammonia, which 
is  an  exchangeable  base.  Placement  in 
the  soil  would  then  become  important,  as 
it  is  with  soluble  phosphate  and  potash 
salts . 

But  because  all  nitrogen  fertilizers  can 
be  ultimately  changed  into  nitrate  nitro- 
gen, and  because  the  nitrate  ion  is  not 
adsorbed  by  the  soil,  nitrogen  fertili- 
zers can  be  applied  in  almost  any  way 
and  they  will  still  be  almost  completely 
available  for  use  by  plants.  An  excep- 
tion is  the  part  used  in  biological  re- 
actions or  lost  by  leaching. 

This  means  that  nitrogen  fertilizers  can 
be  broadcast  and  plowed  under,  broadcast 
and  disked,  broadcast  or  side-dressed  on 
the  surface  without  disking,  drilled  in 
the  row,  or  drilled  between  rows  or  be- 
tween alternate  rows.  Usually  these 
methods  are  about  equally  effective. 
Time  of  application  does,  however,  make 
some  difference.  Theoretically,  in  av- 
erage seasons,  corn  should  be  able  to 
make  most  efficient  use  of  nitrogen  when 
it  is  applied  at  the  second  cultivation. 
Actually,  however,  too  often  wet  weather 


makes  it  impossible  to  apply  the  ferti- 
lizer at  this  time,  or  dry  weather  pre- 
vents its  efficient  use  by  the  plant. 
In  other  words,  too  often  the  season  is 
not  "average." 

Because  nitrates  are  not  adsorbed  by  the 
soil,  the  nitrate  forms  of  fertilizer 
should  be  used  with  caution,  and  large 
amounts  should  not  be  placed  near  the 
seed. 

Soil  organisms  use  the  available  forms 
of  nitrogen  in  decomposing  organic  mat- 
ter. For  example,  bromegrass  sods  con- 
taining only  a  little  alfalfa  will  use 
up  soil  nitrogen  rather  than  serve  as  an 
immediate  source  of  available  nitrogen. 
This  biological  reaction  must  always  be 
considered  in  estimating  nitrogen  re- 
quirements. On  sandy  soils  the  possible 
loss  of  nitrogen  by  leaching  must  also 
be  considered.  Leaching  is  not  due  to  a 
soil  reaction  but  results  from  failure 
of  nitrates  to  react  with  the  soil. 

Mixed  fertilizers  are  combinations  of 
various  fertilizer  materials  except  rock 
phosphate.  These  mixtures  should  be 
used  according  to  their  composition.  If 
they  are  high  in  soluble  phosphates  and 
low  in  muriate  of  potash,  the  salt  ef- 
fect will  be  low  (the  phosphate  has  no 
salt  effect)  and  larger  amounts  can  be 
applied  in  the  row  or  hill.  If  they  are 
high  in  muriate  of  potash  or  nitrate  ni- 
trogen, or  both,  correspondingly  lower 
amounts  should  be  used.  How  much  soluble 
salt  they  will  leave  in  the  soil  and  how 
sensitive  the  crop  is  to  the  salt  will 
mainly  determine  how  much  of  the  mixed 
fertilizer  can  safely  be  applied  near 
the  seed. 


J 


The  method  of  applying  the  fertilizer 
also  helps  to  determine  how  much  should 
be  used.  For  example,  if  a  soil  is  not 
too  deficient,  a  small  amount  of  ferti- 
lizer applied  in  the  row  or  hill-dropped 
may  be  as  effective  as  a  much  larger 
amount  broadcast  eind  disked  in. 


AG 


But  if  the  deficiency  is  great,  the  soil 
may  need  more  fertilizer  than  can  safely 
be  applied  by  this  method.  Broadcasting 
and  disking  then  become  necessary. 
Whether  part  of  the  fertilizer  should  be 
drilled  in  the  row  for  "starter  effect" 
depends  on  the  kind  of  crop  and  the  soil 
deficiencies  involved.  | 


Roger  H.  Bray 
5/11/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


I 


AGRONOMY  FACTS 


SF-6 


KINDS  OF  NITROGEN  FERTILIZER 


Different  nitrogen  fertilizers  when  used 
properly  and  under  comparable  conditions 
and  at  equal  amounts  of  nitrogen  can  be 
expected  to  give  similar  crop  responses. 
In  some  cases,  however ;  differences  in 
the  properties  of  the  various  carriers 
may  influence  their  use.  Some  informa- 
tion about  these  different  properties 
and  the  behavior  of  nitrogen  in  the  soil 
is  given  below: 

1.  Nitrate  nitrogen  is  the  form  uti- 
lized most  extensively  by  field 
crops,  but  considerable  amounts  of 
ammonium  nitrogen  are  also  readily 
used. 

2.  Nitrate  nitrogen  is  released  from 
the  soil  organic  matter  by  micro- 
organisms. The  nitrate  formed  by 
this  decomposition  is  identical  with 
that  added  in  fertilizers.  The 
amount  of  nitrate  present  or  being 
formed  in  a  soil  at  a  particular 
time  depends  on  the  kind  and  amount 
of  organic  matter  that  is  present. 
Activity  of  the  microorganisms  is 
also  influenced  by  soil  conditions-- 
little  nitrate  is  formed  if  the  soil 
is  too  wet,  too  dry,  too  cold,  or 
very  acid. 

5-  Nitrate  nitrogen  is  not  held  tightly 
by  the  soil  and  can  move  with  the 
soil  water.  When  water  moves  through 
the  soil,  any  nitrates  that  are  pres- 
ent can  be  expected  to  leach  in  con- 
siderable amounts. 

k.  The  ammonium  form  of  nitrogen  is  at- 
tached to  soil  particles  and  does 
not  leach  appreciably.  Aiuaonium 
nitrogen  is  converted  by  soil  micro- 
organisms to  nitrate  nitrogen,  which 
is  not  held  by  the  soil.  This  con- 
version is  probably  complete  in  two 
weeks  if  the  temperature  and  mois- 
ture conditions  are  favorable. 


In  a  cold  soil,  the  conversion  is  very 
slow,  and  little  change  of  ammonium  to 
nitrate  nitrogen  occurs  at  soil  tempera- 
tures below  55°  to  60°  F. 

In  general,  greater  efficiency  of  nitro- 
gen fertilizer  (more  response  per  pound 
of  nitrogen)  is  obtained  when  the  nitro- 
gen is  applied  shortly  before  it  is  used 
by  the  crop.  larger  amounts  of  nitrogen 
will  probably  be  required  for  similar 
returns  If  the  fertilizer  is  applied  at 
longer  periods  ahead  of  the  crop. 

Frequently  convenience  and  market  condi- 
tions almost  dictate  that  nitrogen  fer- 
tilizer be  applied  for  corn  during  the 
preceding  winter.  Efficiency  of  such 
fall  and  winter  applications  has  not 
been  established.  Soil  permeability, 
form  of  nitrogen  applied,  soil  tempera- 
ture, and  amount  of  rainfall  would  ap- 
parently influence  efficiency. 

Losses  would  be  expected  to  be  smaller 
when  such  applications  are  made  after 
cold  weather  begins  and  when  the  nitro- 
gen is  in  the  ammonium  form.  Greatest 
flow  from  tile  drains  usually  occurs  in 
the  spring  before  soil  temperatures  are 
high  enough  for  extensive  nitrate  forma- 
tion. A  reduction  in  losses  ^rould  also 
be  expected  if  the  nitrogen  were  plowed 
down  with  crop  residues,  such  as  straw 
or  cornstalks, which  are  low  in  nitrogen. 

Nitrogen  fertilizer  may  be  applied  to 
sod  and  pasture  crops  at  almost  any  time 
of  year,  since  little  leaching  occurs 
under  sod  crops. 

Nitrogen  in  fertilizers  is  on  the  market 
in  solid  materials,  in  anhydrous  ammo- 
nia, and  in  nitrogen  solutions. 

Solid  materials  are  usually  either  pel- 
lets or  salt-like  crystals  packed  in 
moisture-resistant  bags.  These  materials 


are  usually  applied  with  conventional 
fertilizer  spreaders  or  side-dressing 
equipment-   Some  of  these  carriers  are  : 

AmmoniLmi  nitrate,  MI+NO5,  contains  about 
55  percent  nitrogen,  of  which  one-half 
is  in  ammonium  form  and  one-half  in  ni- 
trate form. 

Ammonium  sulfate,  (Mij.)2S0^,  contains  20 
to  21  percent  nitrogen,  all  of  which  is 
In  ammonium  form.  It  may  be  of  synthet- 
ic origin  or  a  by-product  of  coke  pro- 
duced in  the  steel  industry. 

Urea,  i'M.2)2^^!  ^  synthetic  product,  may 
contain  up  to  k6  percent  nitrogen  ("Nu- 
Green"  is  largely  urea;  Uramon,  a  coated 
granular  urea,  k2'fo  N) .  Urea  reacts  with 
water  in  the  soil  and  is  converted  in  a 
few  days  to  the  ammonium  form. 

Cyanamld,  a  synthetic  product  containing 
around  20  percent  nitrogen,  is  black  in 
color  and  is  usually  pelleted.  The  ni- 
trogen is  present  as  the  compound  CaCWg; 
which  is  diluted  by  the  manufacturing 
process  with  carbon  and  hydrated  lime. 
CaCNg  is  not  used  directly  by  plants  but 
must  first  decompose  in  the  soil. 

Normally  in  this  decomposition  urea  and 
then  ammonium  nitrogen  ia  formed.  Under 
some  conditions  (alkaline  or  poorly 
drained  soils)  temporary,  intermediate 
compounds  that  are  toxic  to  plants  are 
formed  during  the  decomposition. 

Cyanamld  is  usually  broadcast  or  plowed 
down  ahead  of  the  crop  rather  than  banded 
near  the  row  ao  that  any  toxic  materials 
will  not  be  concentrated  and  injure  the 
crop. 

Sodium  nitrate,  NaNO^,  which  may  be  syn- 
thetic (Arcadian)  or  refined  Chilean  ni- 
trate (Champion),  contains  I6  percent 
nitrogen,  all  in  the  nitrate  form. 

Modified  forms  of  the  different  carriers 
mentioned  above  are  also  on  the  market. 
A.N.L.^  containing  20  percent  nitrogen, 
is  ammonium  nitrate  that  has  been  mixed 
and  pelleted  with  dolomite  to  improve 
handling  characteristics.  Cal-nitro  and 
nitro-lime  are  similar  products. 

Nitrogen  in  mixed  fertilizers  is  usually 
in  the  ammonium  form,   although  carriers 


containing  other  forms  are  also  used  to 
some  extent. 

Anhydrous  ammonia  is  shipped  and  handled 
as  a  liquid  under  pressure.  When  pres- 
sure ia  released,  the  liquid  evaporates 
very  quickly  to  ammonia  gas.  The  liquid 
is  released  by  the  applicator  machinery 
in  the  soil,  where  it  reacts  with  the 
soil  water  and  the  clay  particles.  Be- 
cause of  the  special  pressure  equipment 
that  is  required,  anhydrous  ammonia  is 
usually  applied  by  the  dealer. 

Nitrogen  solutions  are  ammonia,  ammonium 
nitrate,  or  urea,  or  a  mixture  of  two  or 
more  of  these  in  water.  These  solutions 
are  usually  sprayed  on  the  soil  surface 
and  disked  or  plowed  into  the  soil.  Ni- 
trogen solutions  are  also  used  for  aide- 
dressing  row  crops  where  the  solution 
runs  from  a  small  pipe  behind  the  culti- 
vator shovel.  Because  these  solutions 
are  corrosive,  stainless  steel  or  alumi- 
num equipment  is  ordinarily  used. 

A  nitrogen  material  in  water  solution 
will  be  no  different  from  the  solid  ma- 
terial in  ita  reaction  with  the  aoil  and 
its  effect  on  crop  growth. 

Some  nitrogen  solutions  are  listedbelow. 
similar  solutions  put  out  by  different 
companies  may  have  different  names. 

Nitrogen  solution  52  contains  around 
15  1/2  percent  nitrogen  as  ammonium  ni- 
trate and  16  1/2  percent  nitrogen  as 
urea,  or  a  total  of  52  percent  nitrogen. 

Nitrogen  solution  k  contains  57  percent 
nitrogen,  about  two-thirds  of  which  ia 
ammonium  nitrate  and  one-third  anhydrous 
ammonia.  This  solution  has  about  1  pound 
pressure  at  10U°  F.  Salt  will  begin  to 
crystallize  out  at  k8°   F. 

Nitrogen  solution  2A  contains  kCfo  nitro- 
gen and  is  also  a  mixture  of  ammonium 
nitrate,  ammonia,  and  water.  It  con- 
tains more  ammonia  and  has  around  10 
pounds  pressure  at  100°  F.  and  begins  to 
salt  out  at  25°  F. 

Other  nitrogen  solutions  are  also  being 

manufactured.   One  group  containing  urea 

and  ammonia  in  water  is  known  as  U.A.L. 

solutions  (urea-ammonia  liquors). 

L.  T.  Kurtz 

5/V53 


NllVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND              ^^ 
TESTING       -^^ 

'"■""■ '1 

w'. 

SF-7 


THE  ILLINOIS  SOIL  TESTING  PROGRAM 


The  farmer  gets  from  his  farm  adviser  a 
sheet,  "Directions  for  Collecting  Soil 
Samples  From  a  Forty-Acre  Field,"  de- 
scribing how  to  sample  his  fields.  He 
also  gets  an  "Information  Sheet"  to  fill 
out,  giving  the  farm  adviser  information 
about  the  kinds  of  soil  and  previous 
treatment . 

After  he  has  taken  his  samples  and  com- 
pleted the  information  sheet,  he  takes 
the  samples  to  the  farm  adviser  to  be 
tested  in  the  county  soil  testing  labor- 
atory for  limestone  (acidity),  available 
phosphorus,  and  available  potassium. 
Counties  that  have  no  laboratories  send 
their  samples  to  the  University  Soil 
Testing  Laboratory. 

lA  technician,  trained  at  the  University 
laboratory,  runs  the  samples  and  gives 
the  results  to  the  farm  adviser  who,  in 
conference  with  the  farmer,  outlines  a 
program  of  limestone  and  fertilizer  to 
be  used  for  each  field  tested.  The  farm 
adviser  uses  pamphlets  AGII98  and  AG1220 
as  guides  in  interpreting  the  tests. 


How  Technicians  Are  Trained 

Because  of  limited  staff  and  facilities 
at  the  University  laboratory,  acceptance 
of  applicants  for  training  must  be  lim- 
ited to  persons  and  laboratories  plan- 
ning a  complete  and  regular  soil  testing 
service  for  acidity,  phosphorus, and  pot- 
ash. No  one  will  be  trained  who  expects 
to  test  only  occasionally. 

iln  order  to  maintain  an  accurate  and  de- 
pendable soil  testing  service,  those  who 
are  accepted  for  training  will  be  ex- 
pected to  agree  to  the  following: 


15 


iTt! 


1.  To  spend  at  least  two  days  in  the 
University  laboratory  for  training 
in  testing  soils  (unless  they  can 
submit  satisfactory  evidence  of  pre- 
vious training) . 

2.  To  submit  eight  check  samples  to  the 
University  laboratory  every  month 
while  the  county  laboratory  is  test- 
ing soils.  No  charge  will  be  made  by 
the  University  laboratory  for  running 
check  samples  for  acidity,  phos- 
phorus, and  potassium. 

Anyone  who  plans  to  establish  and  oper- 
ate a  soil  testing  laboratory  should 
first  write  for  information  and  an  appli- 
cation blank  to 

A.  U.  Thor 

Agronomy  Soil  Testing  Laboratory 

Davenport  Hall 

Urbana,  Illinois 

As  of  December  1952,  there  were  80  coun- 
ty soil  testing  laboratories  and  I8  com- 
mercial soil  testing  laboratories  on  our 
accredited  list.  The  University  labora- 
tory also  tests  soil  samples  for  acidity, 
available  phosphorus,  and  available  po- 
tassium. In  addition  to  these  standard 
tests,  the  soil  can  be  tested  for  boron, 
but  an  additional  charge  is  made. 

Available  Information  on  Soil  Testing 

On  the  back  of  this  page  is  a  list  of 
pamphlets  describing  how  we  take  and  pre- 
pare soil  samples,  run  the  samples  in 
the  laboratory  by  the  quick  methods,  and 
interpret  the  results  in  terms  of  lime- 
stone, phosphate,  and  potash  needs  for 
corn-belt  conditions. 


M  397 
3-^8-38074 


AGI275 
AGI306 
AG878 
AGIO28 

AGI268 


AGI388 
AGI342 
AGI257 


11- J+7- 36976 

AF1220 

AGll98a-h 

AGI359 

AGI374 

2-J+6-37572 


PAMPHLETS  Mm   LEAFLETS  DESCRIBING  THi,  TESTING  PROGRAI'I 

For  th^-  Farmer 

-  Directions  for  Collecting  Soil  Samples 

-  Information  Sheet  and  Soil  Test  Report 

For  the  Technician 

-  Photometer  Method  for  Determining  Available  Potassium  in  Soils 

-  Photometer  Method  for  Determining  Available  Phosphorus  in  Soils 
'  -  Potassium^  Phosphorus  and  Other  Tests  for  Illinois  Soils 

-  Rapid  Tests  for  Measuring  and  Differentiating  Between  Adsorbed 
and  Acid-Soluble  Forms  of  Phosphate  in  Soils 

-  Leaflet  Describing  Acidity  and  Phosphorus  Tests 

For  the  Farm  Adviser  and  Farmer 

-  The  Illinois  Soil  Testing  Program 

-  Nitrate  Tests  for  Soils  and  Plant  Tissues 

-  Directions  for  Using  Nitrate  Powder  on  Corn  Plants 

For  the  Farm  Adviser 

-  Soil  Test  Maps 

-  Soil  Test  Interpretation  and  Fertilizer  Use 

-  Standard  Rotation  Requirement  Tables 

-  Maintenance  Requirements  for  Fertile  Soils 

-  Equipment  Needed  for  Complete  Soil  Testing  Laboratory 

-  Soil  Treatment  Recommendations  Based  on  Soil  Tests 

Book  on  Soil  Testing 


Diagnostic  Techniques  for  Soils  and  Crops,  1155  l6th  Street,  N.  W. ,  Washington, 
D.  C,  published  by  American  Potash  Institute. 


A,  U.  Thor 
5/18/53 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND 
TESTING       w 

PIS 

Wk 

SF-8 


LEGUMES  AS  NITROGEN  FIXERS 


One  way  in  which,  leguminous  crops  im- 
prove soil  productivity  is  by  taking 
part  of  their  nitrogen  from  the  air  and 
giving  some  of  it  to  the  soil  v;hen  all 
or  part  of  the  crop  is  plowed  under. 

How  much  nitrogen  do  legumes  add  to  the 
soil?  The  answer  to  this  question  de- 
pends on  several  conditions. 

One  of  these  conditions  is  the  propor- 
tion of  nitrogen  which  the  legume  takes 
from  the  air.  Although  it  is  often  said 
that  legumes  obtain  two-thirds  of  their 
nitrogen  from  the  air  and  one-third  from 
the  soil,  this  proportion  is  not  always 
the  same . 

Recently  a  new  method  was  found  for  eval- 
uating the  contribution  of  leguminous 
crops  to  soil  nitrogen.  In  this  method 
two  sister  selections  of  soybeans  that 
are  alike  in  all  characteristics  except 
nodule  formation  are  used  to  measure  the 
amount  of  nitrogen  the  nodule  bacteria 
contribute  to  the  soil.  One  of  these 
selections,  designated  as  R,  is  well 
nodulated,  whereas  the  other,  designated 
as  r,  bears  no  nodules. 

Results  of  two  experiments  in  which 
these  two  soybean  selections  were  com- 
pared are  given  below.  The  crops  were 
grown  on  limed  soils  to  which  phosphate 
and  potash  had  been  applied  according  to 
soil  tests.  The  soils  differed  in  their 
nitrogen- supplying  power,  however. 

Where  there  was  an  adequate  supply  of 
available  nitrogen  in  the  soil,  yields 
were  the  same  for  the  two  selections. 
Where  the  available  nitrogen  supply  was 
low,  however,  the  R  selection  yielded 
more  than  the  r  selection. 


Table  1.   Yields  of  Two  Soybean  Selec- 
tions on  Soils  Differing  in  Nitrogen 

Nitrogen  fer-  Soybean  selection  Dif fer- 
tility of  soil    R r  ence 

bu/A     bu/A    bu/A 


1. 

High 

36.6 

33.1 

3.5 

2. 

Medium 

36.0 

29.2 

6.8 

3. 

Low 

35.5 

20.9 

14.6 

Selection  R,  which  was  well  nodulated, 
had  practically  the  same  yield  on  all 
soils  regardless  of  nitrogen  fertility] 
but  selection  r,  which  was  not  nodulated, 
declined  in  yield  as  nitrogen  fertility 
declined. 

An  analysis  of  the  plant  tops  and  roots 
and  comparison  of  the  results  made  it 
possible  to  estimate  the  proportion  of 
total  nitrogen  that  the  soybean  selec- 
tion R  had  obtained  from  the  air. 

Table  2.  Nitrogen  Content  of  R  and  r 
Soybean  Selections  on  Three  Soils 


Soil 

Total  nitrogen 
in  selection 
R                      r 

Air-derived 
nitrogen  in 
selection  R 

1 
2 
3 

lb/A 

199 
192 

177 

lb/A 

158 

102 

65 

perct. 
21 
63 

As  the  nitrogen  fertility  in  the  soil  de- 
creased, the  proportion  of  nitrogen  se- 
cured from  the  air  increased  and  the 
value  of  the  nodule  bacteria  increased. 


If  vre  assume  that  a  corn  crop  could  take 
the  same  amount  of  nitrogen  from  these 
soils  as  the  r  selection  (unnodulated) 
and  that  1  l/2  pounds  of  nitrogen  are 
sufficient  to  produce  1  bushel  of  corn, 
we  can  then  conclude  that,  on  soils  hav- 
ing a  nitrogen  fertility  sufficient  for 
100  bushels  of  corn  per  acre,  only  one- 
fifth  of  the  nitrogen  in  soybean  crops 
grown  on  such  soils  would  come  from  the 
air.  On  soils  having  a  nitrogen  fertil- 
ity sufficient  for  only  kO  bushels  of 
corn,  under  favorable  conditions  nearly 
two-thirds  of  the  nitrogen  in  the  soy- 
bean crop  would  be  air-derived. 

Although  we  have  no  tools  for  measuring 
exactly  the  effect  of  available  nitrogen 
on  the  ability  of  other  leguminous  crops 
to  fix  nitrogen,  it  is  reasonable  to  as- 


sume that  the  same  principle  would  apply 
to  them. 


Thus  it  would  appear  that  natural  proc- 
esses set  a  ceiling  on  nitrogen  fixation 
for  each  environment  and  that,  as  the 
nitrogen  content  of  the  soil  approaches 
this  ceiling,  it  becomes  more  difficult 
for  nodulated  legumes  to  add  nitrogen  to 
the  soil.  As  the  nitrogen  fertility  of 
soils  decreases,  other  factors  being  fa- 
vorable, the  contribution  of  nodulated 
legumes  increases.  But  as  the  nitrogen 
fertility  increases,  the  amount  of  ni- 
trogen added  by  legumes  decreases.  Thus 
it  is  difficult  to  raise  the  level  of 
soil  nitrogen  beyond  a  certain  amount 
by  using  legumes,  and  this  fixed  amount 
will  vary  with  different  soils. 


0. 


H.    Sears 
6/1/53 


hj 


t 
fc 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-9 


FOLIAR  SPRAY  APPLICATION  OF  FERTILIZER  MATERIALS 


Since  it  has  been  shown  that  a  large 
niunber  of  the  essential  plant  nutrients 
can  be  absorbed  through  leaves  of  plants, 
considerable  interest  in  adding  nutri- 
ents to  plants  in  this  way  has  occurred 


during  the  past  few  years.  Most  of  the 
available  experimental  data  on  the  com- 
parison of  foliar  spray  and  soil  appli- 
cation of  nitrogen  on  the  yield  of  corn 
and  wheat  are  presented  here. 


Comparison  of  Foliar  Spray  and  Soil  Application  of  Nitrogen^/  on  Yield  of  Wheat 

(Hauck  and  Earley,  Illinois.  1951) 


Method  of 
application 


Date 
applied 


Cone,  of  fert. 
in  spray 


Urea 


Yield  (bu.TAT 


(NHtj.)pSOU 


Check 

Top-dressed 

Sprayed 

Top-dressed 

Sprayed 

Top-dressed 

Sprayed 


April  26 
April  26 
May  12 
May  12 
May  22 
May  22 


1  lb. /gal. 
1  lb. /gal. 
1  lb. /gal. 


26 
36 
35 
33 
32 

•  • 

30 


30 
i^5 
k2 
iv3 
37 
37 
27 


1/  40  pounds  of  N  per  acre  added. 

Authors'  conclusion:   Spraying  nitrogen 
on  wheat  plants  had  no  adveuitage  over 


top-dressing.  In  both  methods  the  earli- 
est applied  nitrogen  gave  highest  yields. 


Comparison  of  Foliar  Spray  and  Soil  Application  of  Nitrogen^/  on  Yield  of  Wheat 

(Smith,  Kansas.   1952) 


Method  of 

Date 
applied 

Cone,  of  fert. 
in  spray 

Yield  (bu./A) 

application 

Urea         NHPIO:! 

Top-dressed 

Sprayed 

Top-dressed 

Sprayed 

Top-dressed 

Sprayed 


April  25 
April  25 
May  3 
May  3 
May  17 
May  17 


8  lb. /gal. 
8  lb. /gal. 
8  lb. /gal. 
8  lb. /gal. 
8  lb. /gal. 
8  lb. /gal. 


33 

•  • 

29 

•  • 

27 


37 
33 
33 
30 
29 
28 


1/  50  poionds  of  nitrogen  per  acre  added. 

Author's  conclusions:  (l)  Nitrogen  fer- 
tilizer may  be  sprayed  on  wheat  foliage, 
but  this  type  of  application  is  less  ef- 
fective, especially  with  respect  to 
yield,  than  are  applications  made  to  the 
soil.   (2)  Since  financial  returns  for 


the  use  of  nitrogen  fertilizer  on  wheat 
normally  depend  on  increases  in  yield 
rather  than  on  increases  in  protein  con- 
tent, there  is  no  good  reason  to  recom- 
mend foliar  sprays  rather  than  the  con- 
ventional dry  applications  for  wheat. 


Comparison  of  Foliar  Spray  and  Soil  Application  of  Nitrogen  on  Yield  of  Com 

(Montenegro,  Foy  emd  Barber,  Indiana o  1952) 


Fertilizer 


NH4NO3 
Urea 
ITH4NO3 
Urea 


Method  of 
application 


Nitrogen  added  Cone,  of  ferto 
per  acre       in  spray 


Side "dressed 
Sprayed 
Side -dressed 
Sprayed 


20  , 
20I/ 
40  , 


Yield  increases 

Field 

A  B 

bu./A  bUo/A 


'    O     O     O    O     O     D     I 


1/2  ibVsaio 

000000000000 

1/2  ibc/galo 


7.0 
606 
9»3 
7.5 


13A 
13.8 
20.6 
ll^<,8 


1/     Single^ application o 


of  nitrogen  as  ammonium  nitrate  side' 
dressedo  At  the  UO-poxind  rate,  side- 
dressing  gave  the  best  resxiltSo 


Authors"  conclusions  Application  of  20 
pounds  of  nitrogen  per  acre  as  a  urea 
spray  vas  no  more  effective  in  increas- 
ing yield  of  com  than  an  equal  amount 

Comparison  of  Foliar  Spray  and  Soil  Application  of  Ni^rogeni/  on  Yield  of  Com 

(Hauck  and  Ear ley,  Illinois o  1951) 


Method  of 

Ifete 
applied 

Cone,  of  ferto 
in  spray 

Yield  ,bu./A 

) 

application 

Urea 

tNHl4.  ,12304 

NHlOTO^ 

Check 

oooooSdoooooo 

OOOOOOOOOOOO 

81 

81 

81 

Side -dressed 

July  2 

Dooeoooooooo 

102 

116 

114 

Sprayed 

July  17 

1  Ibo/galo 

95 

71 

66 

Sprayed 

July  2  and  17 

1/2  lbo/gal» 

10i+ 

88 

92 

1,/  40  pounds  of  nitrogen  per  acre'  added 

Authors'  concl*usionss  (1,3  These  nitro- 
gen fertilizers  sprayed  on  com  plants 
at  the  rate  of  ko  pounds  of  nitrogen  per 
acre  and  1  pound  per  ^llon  of  solution 
caiised  marginal  burning  of  the  leaves 
and  reduction  in  yield  compared  to 
side-dressingo  Urea  caused  the  sma.llest 
amount  of  leaf  damage  aoad  the  smallest 
reduction  in  yieldo  (2)  Two  sprayings 
of  20  pounds  of  nitrogen  per  acre  at  l/2 
pound  of  fertiliz,er  per  gallon  of  sola- 
tion  ^ve  higher  yield  than  one  spray- 
ing of  ko  po'unds  of  nitrogen  per  acre  at 
1  pound  of  fertilizer  per  gallon  of  so- 
lutiono  (3)  Side^dressing  40  pounds  of 
nitrogen  per  acre  gave  higher  yields  of 
com  than  spraying,  except  for  the  two 
sprayings  of  -area,  which  equaled  side- 
dressingo 


Thus  far  there  is  little  evidence  to 
show  that  foliar  spray  application  of 
nutrients  to  agronomic  plants  is  more 
efficient  in  increasing  yield  than  soil 
applicationo  Until  this  is  shown,  it  is 
suggested  that  soil  application  of  fer- 
tilizers be  continued  according  to  pres- 
ent reconmiendations  o 

Only  a  few  experiments  have  been  report- 
ed where  phosphorus  and  potass iium  com^ 
pounds  have  been  sprayed  on  plants.  The 
results  indicate  that  these  substances 
must  be  added  in  very  dilute  solutions 
in  order  to  prevent  burning  the  leaves » 

Foliar  spray  applications  can  easily  be 
made  to  horticultural  and  truck  crops, 
but  the  cQiffiiiercial  value  of  this  prac- 
tice remains  to  be  seen. 

Ee  B=  Earley 
June  29,  1953 


JNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


AND              -^^ 
TESTING       -3^ 

"'■'■■■"■    '  ■"  ■■■■'jr 

W    ■ 

SF-10 


ILLINOIS  SOIL  EXPERIMENT  FIELDS 


The  University  of  Illinois  has  experi- 
ment fields  located  on  most  of  the  im- 
portant soils  throughout  the  state. 
These  fields  are  providing  information 
on  the  responsiveness  of  soils  to  live- 
stock and  grain  systems  of  management 
under  different  liming  and  fertility 
practices.  The  results  are  measured  in 
terms  of  crop  yields  and  economic  re- 
turns. In  some  cases  the  physical  and 
chemical  changes  of  the  soil  have  also 
been  measured. 

The  location,  soil  association,  and  soil 
types  (AGIUU3)  of  the  present  experiment 
fields  are  presented  in  the  table  below. 
Results  for  each  location  are  siimmarized 
annually.  The  results  for  any  field  can 
be  obtained  from  the  Department  of 
Agronomy.  One  or  two  field  meetings  are 
held  at  most  locations  each  year  during 


the  summer  or  fall.  These  meetings, 
under  direction  of  University  personnel, 
provide  an  opportunity  for  the  public  to 
see  how  research  is  conducted  and  how 
agronomic  practices  affect  crop  growth. 
In  addition,  agricultural  workers  may 
use  the  fields  for  tours  or  educational 
programs  or  meetings  of  their  own. 

Other  publications  based  on  results  at 
the  soil  experiment  fields  are  Illinois 
Bulletin  516  and  Agronomy  mimeograph 
AGI512.  Bulletin  516  contains  a  compre- 
hensive summary  of  the  research  on  soil 
experiment  fields  from  the  establishment 
of  the  Morrow  plots  in  I876  through  I9U2. 
The  effects  of  maniire,  crop  residues, 
limestone,  phosphate,  and  potash  on  crop 
yields  and  net  income  are  discussed. 
AGI512  gives  a  brief  report  of  experi- 
ment field  resTilts  from  1888  through  1950' 


Soil 

assoc. 

Experiment 

County  and  date 

area 

field 

established 

Description  of  soils  and  types 

E 


Joliet 


Will  -  19li^ 


H 


Urbana 


K 


K 


K 


Aledo 


Kewanee 


Dixon 

Mt.  Morris 


Champaign  -  1903 
and  1928 


Mercer  -  1910 


Henry  -  I9I5 


Lee  -  1910 
Ogle  -  1910 


Dark  soils  with  slowly  permeable 
subsoils  on  calcareous  slowly  per- 
meable till.   Chiefly  Elliott  silt 
loam. 

Moderately  dark  to  very  dark  soils 
with  moderately  permeable  subsoils. 
Chiefly  Flanagan-Catlin-Sidell  silt 
loams  and  Drummer  silty  clay  loam. 

Very  dark  soils  with  moderately  per- 
meable subsoils.  Sable  silt  loam  to 
silty  clay  loam. 

Dark  soils  with  moderately  permeable 
subsoils.   Chiefly  Muscatine  silt 
loam. 

Moderately  dark  to  dark  soils  with 
moderately  permeable  subsoils.  Tama- 
Muscatine  silt  loams. 


Soil 

assoc . 

Experiment 

County  and  date 

area 

field 

established 

Description  of  soils  and  types 

K 


K 


K 


M 


M 


0-P 


McNabb 


Hartsburg 


Carthage 


Carlinville 
Clayton 


Lebanon 


Enfield 


Sparta 


Raleigh 
West  Salem 


Oblong 


Ewing 
Toledo 


Putnam  -  I907 


Logan  -  1911 


Hancock  -  I9II 


Macoupin  -  I9IO 
Adams  -  I9II 


St.  Clair  -  I910 


White  -  1912 


Randolph  -  I916 


Saline  -  I9IO 
Edwards  -  I912 


Crawford  -  1912 


Franklin  -  I9IO 
Cumberland  -  I913 


Moderately  dark  to  dark  soils  with 
moderately  permeable  subsoils. 
Atterberry-Muscatine  silt  loams. 

Very  dark  moderately  heavy  soils  with 
moderately  permeable  subsoils.   II- 
liopolis  silty  clay  loam. 

Dark  soils  with  moderately  permeable 
subsoils.   Ipava  silt  loam  and  II- 
liopolis  silty  clay  loam  borderline 
to  Herrick  silt  loam  and  Virden  silty 
clay  loam,  respectively,  of  Soil  As- 
sociation Area  M. 

Moderately  dark  soils  with  grayish 
subsurface  and  slowly  permeable  sub- 
soils.  Chiefly  Herrick  silt  loam. 

Moderately  dark  soils  with  grayish 
subsurface  and  moderately  slowly  per- 
meable subsoils.   Borderline  Herrick- 
Jarvis  silt  loam  (latter  soil  mapped 
only  by  SCS  to  date.) 

Yellowish -gray  strongly  leached  soils 
with  slowly  to  very  slowly  permeable 
subsoils.   Bluford  and  Wynoose  silt 
loams. 

f 
Yellowish-gray  strongly  leached  soils. 

with  slowly  to  very  slowly  permeable 

subsoils.   Chiefly  Bluford  and  Wynoose 

silt  loams  with  frequent  slick  spots. 

Gray  to  yellowish -gray  strongly 
leached  soils  with  very  slowly  per- 
meable subsoils.  Bluford,  Wynoose, 
Hoyleton  and  Cisne  silt  loams. 

Dark  gray  moderately  leached  soils 
with  slowly  permeable  subsoils. 
Chiefly  Newberry  silt  loam.  I 

Gray  strongly  leached  soils  with  very 
slowly  permeable  subsoils.  Cisne  and 
Hoyleton  silt  loams. 


Soil 

assoc . 

Experiment 

County  and  date 

area 

field 

established 

Description  of  soils  and  types 

Newton 
Brownstown 


Jasper  -  I912 
Fayette  -  19^+0 


Q 


Elizabethtown  Hardin  -  1917 


Oquawka 


Henderson  -  1915 


Gray  strongly  leached  soils  with  very 
slowly  permeable  subsoils.   Chiefly 
Cisne  silt  loam  and  Hoyleton  silt 
loam  with  frequent  slick  spots. 

Yellow  soils  with  slowly  permeable 
subsoils.  Similar  to  Clement  silt 
loam,  immature  phase. 

Light  brown  medium  sand  with  slight 
to  no  subsoil  development.  Oquawka 
sand. 


V 


Minonk 


Woodford  -  I9IO 


Dixon  Springs  Pope  -  1937 


Dark  to  very  dark  moderately  heavy 
soils  with  moderately  permeable  sub- 
soils. Mostly  similar  to  Ashkum 
silty  clay  loam  but  deeper  to  calcar- 
eous slowly  permeable  till. 

Yellowish-gray  strongly  leached  soils 
with  very  slowly  permeable  subsoils. 
Chiefly  Grenada-like  silt  loam  (simi- 
lar to  Ava  silt  loam  of  Soil  Associa- 
tion Area  0.) 


A.  L.  Lang  and  H  L.  Wascher 

6/15/53 


;  31^ 


« 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


(■ 


AGRONOMY  FACTS 


NITROGEN  AND  SOIL  ORGANIC  MATTER 


SF-ll 


Soil  organic  matter  is  usually  thought 
of  as  a  residual  product  consisting  of 
decomposable  residues  and  microbial  tis- 
sue. The  organic  matter  is  essentially 
the  only  source  of  nitrogen  in  soils. 

By  analysis,  organic  matter  contains 
about  5  percent  of  nitrogen  and  O.5  per- 
cent each  of  phosphorus  and  sulfur.  Or, 
stated  in  another  way,  the  ratio  of  car- 
bon to  nitrogen  to  phosphorus  to  sulfur 
in  soil  organic  matter  is  about  100  to 
10  to  1  to  1.  Most  soil  organic  matter 
has  a  carbon-nitrogen  ratio  varying 
roughly  from  8  or  12  to  1. 

Since  soil  organic  matter  is  the  major 
source  of  nitrogen  for  crops  on  untreated 
land,  it  follows  that  the  more  intensive 
the  nitrogen  removal  in  crops,  the  more 
rapid  the  organic  matter  loss.  Any 
treatment  that  tends  to  reduce  the  de- 
mand of  a  crop  for  soil  nitrogen,  such 
as  growing  legumes  or  adding  manures  or 
nitrogen  fertilizers,  tends  to  decrease 
the  rate  of  loss  of  both  soil  nitrogen 
and  soil  organic  matter.  The  longer 
soils  are  cropped  without  adding  nitro- 
gen in  some  form,  the  less  the  amount  of 
organic  matter  in  the  soil. 

How  low  may  the  organic  matter  in  a  giv- 
en soil  be  allowed  to  drop  v/ithout 
causing  loss  of  productive  capacity  due 
to  poor  physical  condition  of  the  soil? 
The  answer  will  vary  with  the  soil  and 
its  location.  Critical  levels  have  not 
been  well  established,  but  it  is  felt 
that  good  farm  management  programs 
should  aim  at  maintaining  soils  at  their 
present  organic  matter  levels. 

The  maintenance,  or  build-up,  of  soil 
orgcinic  matter  is  determined  essentially 
by  the  following  factors: 


5. 


Nature  and  amount  of  organic  materi- 
als returned  to  the  soil.  Legumes 
are  better  for  this  purpose  than 
stover;  stover  is  better  than  straw. 

Rate  of  decomposition  of  residues  is 
influenced  by  their  nitrogen  content. 
Residues  that  are  high  in  nitrogen 
(or  to  which  nitrogen  has  been  added) 
decompose  faster  than  residues  that 
are  low  in  nitrogen.  But  the  total 
soil  organic  matter  formed  increases 
as  the  nitrogen  content  of  the  resi- 
due increases. 

Soil  moisture.  Wet  soils  are  more 
favorable  for  the  formation  of  or- 
ganic matter  than  dry  soils. 

Soil  temperature.  In  general,  cool- 
er temperatures  favor  the  formation 
and  retention  of  soil  organic  matter. 

Soil  aeration.  In  general,  a  well- 
aerated  soil  is  less  favorable  for 
the  build-up  of  soil  organic  m.atter 
than  a  poorly  aerated  soil. 

Sands  and  coarse-textured  soils  are 
less  favorable  for  soil  organic  mat- 
ter build-up  than  are  the  heavier 
soils. 

Cultivation  causes  a  breakdown  of 
soil  organic  matter  and  tends  to  pre- 
vent its  build-up  in  the  soil. 

Soil  nutrients.  Since  soil  organic 
matter  is  the  residual  product  of  mi- 
crobiological activity,  it  follows 
that  fertile  soils  are  more  favorable 
for  organic  matter  build-up  than  in- 
fertile soils. 


Millar  and  Turk^  on  page  257  of  their 
1951  edition  of  Soil  Science,  state: 
"The  accumulation  of  organic  matter  in 
soils  is  primarily  a  nitrogen  problem. 
Theoretically,  there  can  be  no  increase 
in  effective  soil  organic  matter  without 
first  a  proportionate  increase  in  soil 
nitrogen.  This  implies  that  there  is  a 
very  constant  and  close  relationship  be- 
tween the  nitrogen  and  organic  matter 
contents  in  soils.  This  close  relation- 
ship does  actually  exist.  Since  the  ra- 
tio of  C  to  N  in  humus  is  roughly  10  to 
1,  it  must  be  concluded  that  neither 
carbon  nor  nitrogen,  and  hence  soil  or- 
ganic matter,  can  be  permanently  or  ap- 
preciably increased  or  decreased  without 
a  corresponding  change  in  the  other. 

"If  the  nitrogen  content  of  plant  resi- 
dues is  low,  added  nitrogen  will  be  re- 
quired to  meet  the  demands  of  the  soil 
organisms  which  produce  the  soil  humus. 


We  must,  therefore,  come  to  the  con- 
clusion that  the  accumulation  or  restor- 
ation of  soil  organic  matter  is  a  problem 
of  utilizing  nitrogen  as  a  means  of  hold- 
ing carbon  and  other  materials  that  con- 
stitute humus." 

Soil  tilth  and  aeration  are  influenced 
by  soil  organic  matter.  It  is  not 
enough  that  a  soil  contains  fairly  large 
amounts  of  total  soil  organic  matter,  it 
must  have  relatively  large  amounts  of 
"active"  organic  matter  or  residues  go- 
ing through  the  process  of  decomposition. 
It  is  the  actively  decomposing  residues 
that  seem  to  be  essential  for  the  forma- 
tion and  maintenance  of  good  soil  struc- 
ture and  tilth.  A  good  soil  management 
program  maintains  the  level  of  total ^ 
soil  organic  matter  and  maintains  an 
adequate  supply  of  actively  decomposing: 
material  for  optimum  microbiological  ac- , 


tivity  in  the  soil. 


r 


h  5 


S.  W.  Melsted 


6/22/53 


E 


s^s: 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-12 


USING  BORAX  FERTILIZER  ON  ILLINOIS  SOILS 


To  develop  normally,  plants  must  have 
"boron  in  small  amounts.  '  Because  the 
amount  is  so  small,  boron  is  called  a 
minor  plant  nutrient  or  a  trace  element. 
Too  much  of  it  will  poison  plants;  for 
this  reason  excess  boron  is  said  to  be 
toxic . 

Alfalfa  shows  symptoms  of  boron  deficien- 
cy more  often  than  any  other  crop  in  Il- 
linois. But  other  legumes  (except  soy- 
beans) and  some  vegetable  crops  like  to- 
matoes, celery,  cabbage,  and  beets  are 
also  sensitive  to  lack  of  boron. 

In  alfalfa  the  symptoms  vary  with  degree 
of  deficiency  and  age  of  the  plant.  Al- 
falfa yellows  is  a  common  symptom,  but 
rosetting  is  a  more  reliable  one. 

When  rosetting  occurs,  the  stems  of  the 
upper  branches  are  usually  short,  giving 
the  plant  a  bushy  appearance.  Plant 
growth  is  stunted.  The  terminal  bud 
dies.  The  leaves  become  yellow  or  red. 
Leaf  discoloration  may  also  be  caused  by 
insect  damage,  certain  diseases,  and  de- 
ficiency of  other  nutrients.  But  dis- 
coloration due  to  boron  deficiency  is 
always  confined  to  the  terminal  or  upper 
growth . 

Boron  deficiencies  have  been  reported 
throughout  all  of  Illinois.  The  soils 
of  southern  Illinois  are  particularly  de- 
ficient. Sandy  and  coarse-textured 
soils  are  also  likely  to  lack  boron,  as 
are  those  that  have  lost  most  of  their 
available  boron  through  crop  removal. 
For  example,  a  field  that  has  had  a 
heavy  legume  rotation  (as  in  dairy  farm- 
ing) may  be  expected  to  be  low  in  avail- 
able boron. 

Boron  deficiency  in  alfalfa  is  most  ap- 
parent in  dry  years  and  on  the  second- 
cutting  of  alfalfa  hay.  When  boron  fer- 


tilizer is  applied,  yields  may  increase, 
especially  on  soils  that  are  highly  de- 
ficient. On  soils  that  are  only  moder- 
ately deficient,  the  primary  effect  will 
be  to  increase  forage  quality.  In  re- 
cent tests  in  southern  Illinois,  borax 
applications  have  caused  remarkable  in- 
creases in  alfalfa  seed  set.  With  the 
proper  use  of  borax, alfalfa  seed  produc- 
tion may  therefore  become  a  distinct  pos- 
sibility in  Illinois. 

Improper  use  of  borax  may,  however,  ruin 
a  crop.  If  your  soil  has  not  been 
tested  for  available  boron,  use  borax 
only  with  extreme  caution.  Do  not  apply 
more  than  6o  pounds  per  acre  (in  some 
states  the  usual  rate  is  only  15  to  30 
pounds) .  Never  apply  it  at  seeding  time, 
but  top-dress  it  on  established  stands. 
Do  not  use  it  on  small  grains,  corn,  or 
soybeans.  These  crops  are  less  tolerant 
than  the  legumes,  and  borax  can  easily 
injure  them.  The  grasses,  however,  are 
quite  tolerant,  and  borax  can  be  used  on 
legiame-grass  mixtures  as  well  as  on  pure 
legume  stands . 

In  most  soils  boron  toxicity  rarely  oc- 
curs naturally.  But  certain  conditions 
may  cause  such  symptoms  to  appear.  Soy- 
beans are  especially  susceptible  to  high 
concentrations  of  boron,  and  there  are 
indications  that  roses  and  chrysanthe- 
m\ims  may  also  be  susceptible.  In  all  of 
these  cases  the  main  symptom  seems  to  be 
the  dying  of  a  narrow  margin  of  the  leaf 
edges.  It  usually  appears  first  in  the 
older  leaves . 

Borax  and  fertilizer  borate  are  the  ma- 
terials that  are  commonly  used  to  sup- 
ply boron;  they  contain  about  11  percent 
of  boron.  Because  they  are  dry  and  gran- 
ular, they  may  be  spread  directly  from 
broadcast  spreaders,  by  tractor-mounted 
grass  seeders,   or  by  hand.   Or  they  may 


be  mixed  with  some  other  material,  such 
as  phosphate  or  potash  fertilizer  or  dry 
sand,  and  applied  with  a  regular  ferti- 
lizer spreader. 

It  is  possible  to  buy  commercial  mixed 
fertilizers  containing  borax.  But  they 
should  be  used  only  for  top-dressing  es- 
tablished stands  of  legumes  and  not  at 
planting  time.  Often,  too,  they  do  not 
contain  enough  boron  to  overcome  the  de- 
ficiency unless  excessive  amounts  of 
phosphorus  and  potassium  are  also  ap- 
plied. Such  mixtures  as  0-9-27B  (origi- 
nally 0-10-30),  to  which  10  percent  of 
borax  has  been  added,  are  probably  suit- 
able for  use  on  all  but  the  most  boron - 
deficient  fields. 

You  can  take  soil  samples  for  the  avail- 
able boron  test  at  any  time  of  the  year. 
The  sample  may  be  a  composite  of  three 


or  four  samples  taken  for  acidity,  phos- 
phorus, and  potash  tests.  Or  it  may  be 
a  separate  sample  made  up  of  six  to  ten 
borings  from  a  10-  to  15 -acre  area. 
Send  the  samples  to  the  Soil  Testing 
Laboratory,  Davenport  Hall,  University 
of  Illinois,  Urbana. 

The  boron  test  costs  $2.00  per  sample. 
Because  borax  fertilizer  is  of  little 
value  if  the  phosphate  and  potash  re- 
quirements of  the  crop  are  not  fully  sat- 
isfied, all  samples  are  also  tested  for 
acidity,  available  phosphorus, and  avail- 
able potassium.  The  $2.00  charge  in- 
cludes these  tests.  I 

At  present  the  University  Soil  Testing 
Laboratory  is  making  the  following  rec- 
ommendations for  applying  borax  ferti- 
lizers to  soils  growing  legumes  when  the 
tests  show  them  to  have  the  indicated 
amounts  of  boron  deficiency. 


Soil 

test 

Borax  recommended  for  top-dres 
(pounds  per  acre 

>sing 
) 

on  legumes 

Pounds  of 

available 

boron  per  acre 

Test 
rating 

Slowly 
permeable 
soils 

Moderately 
permeable 
soils 

Excessively 

permeable 

soils 

0-1 

Low 

60 

Uo 

20 

1  -  2 

Medium 

ko 

20 

0 

2  + 

High 

0 

0 

0 

Darrell  A.  Russel 
6/29/53 


Postage  paid 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-13 


FALL  VS.  SPRING  PLOWING 


Nearly  three  million  acres  of  leguminous 
crops,  grown  alone  or  in  grass  mixtures, 
are  used  annually  in  Illinois  for  forage 
and  for  soil  improvement  purposes.  They 
occupy  the  land  from  one  to  several 
years  and  are  usually  followed  by  corn. 

The  time  of  year  at  which  to  plow  these 
legumes  under  varies  greatly  from  farm 
to  farm.  The  farmer  must  consider  many 
conditions  before  deciding  what  is  the 
best  time  for  this  operation. 


become  available  for  plant  use  through 
biological  and  chemical  changes  that  oc- 
cuT  natiirally.  Actually,  however,  these 
changes  are  relatively  insignificant 
where  the  supply  of  nutrients  is  main- 
tained by  adding  fertilizers  as  soil 
tests  indicate  a  need  for  them. 


It  lessens  insect  hazards. 


Although 


fall  plowing  alone  will  not  control  in- 
sects, there  is  some  evidence  that  it 
does  reduce  damage  to  corn  from  insects. 


These  five  reasons  are  often  given  for 
plowing  legxmes  under  in  the  fall: 

It  improves  soil  tilth.  Many  fanners 
prefer  to  fall-plow,  particularly  on 
heavy  soils  like  clay  loams,  because 
they  think  winter  freezing  helps  to  make 
a  better  seedbed  than  can  be  obtained 
after  spring  plowing. 

If  spring-plowed  soils  are  to  have  good 
tilth,  they  must  be  plowed  when  the 
moisture  content  is  right.  On  heavy 
soils,  moisture  conditions  are  rarely 
favorable  in  the  spring.  For  this  rea- 
son spring  plowing  is  often  done  when 
the  soil  is  too  wet  or  when  the  season 
is  too  far  advanced. 

Moisture  conditions  are  more  favorable 
in  the  fall.  And,  even  if  the  soil  is 
wet  when  the  plowing  is  done,  freezing 
and  thawing  will  improve  the  soil  struc- 
ture and  consequently  res\alt  in  a  better 
seedbed. 

It  replenishes  available  soil  nutrients. 
The  idea  back  of  this  reasoning  is  that 
resting  the  land  permits  some  of  the  un- 
available plant  nutrients  in  the  soil  to 


It  permits  better  distribution  of  farm 
labor  by  leaving  more  time  in  the  spring 
for  other  urgent  jobs. 

It  destroys  weeds.  To  avoid  a  heavy  in- 
festation of  weed  seeds,  it  is  necessary 
to  plow  occasionally  in  either  late  sum- 
mer or  fall  or  to  clip  the  weeds. 

But  there  are  some  points  on  the  other 
side  of  the  ledger.  Fall  plowing  may 
also  do  these  things: 

It  may  increase  soil  losses  from  erosion. 
Groirnd  cover  helps  to  cut  down  losses 
from  erosion.  On  land  that  is  subject 
to  erosion,  the  losses  from  this  soiirce 
may  more  than  offset  any  gains  in  yields 
obtained  through  fall  plowing. 

It  may  cause  plant  nutrients  to  be  lost 
in  the  drainage  water.  Nitrogen  in  par- 
ticular may  be  lost;  and  the  earlier  the 
plowing,  the  greater  the  loss.  Most  of 
the  nitrogen  in  plant  residues  is  in  a 
form  that  will  not  move  freely  in  soil 
water.  But  if  plowing  is  done  when  the 
soil  temperature  is  above  50°  F. ,  the 
soil  microorganisms  readily  convert  the 
plant  nitrogen  into  nitrate  nitrogen,  a 


from  that  does  move  readily  with  soil 
water.  Thus  early  fall  plowing,  when 
temperatures  are  favorable  for  microor- 
ganic  activity,  may  cause  a  considerable 
amoxmt  of  loss  in  the  nitrogen  that  leg- 
uminous plants  take  from  the  air. 

It  may  decrease  nitrogen  fixation.  The 
quantity  of  nitrogen  that  nodulated  leg- 
lames  add  to  the  soil  depends  in  part  on 
the  amoiint  of  growth  the  leguminous  crop 
is  able  to  make.  If  the  legume  is  plowed 
under  in  the  same  year  in  which  it  is 
seeded,  early  fall  plowing  will  prevent 
the  plants  from  fixing  the  maximum  amc\mt 
of  nitrogen. 


on  what  objective  is  to  be  achieved.  If 
a  farmer  wants  to  control  erosion,  he 
should  not  do  his  plowing  in  the  fall. 
If  he  wants  to  reduce  insect  damage  in 
his  corn,  he  might  fall-plow  at  the  ex- 
pense of  losing  some  nitrogen  by  leach- 
ing and  perhaps  by  erosion. 

Yield  is,  however,  the  main  criterion 
that  most  farmers  use  in  evaluating  the 
worth  of  any  farming  practice.  And  so 
far  there  is  not  much  evidence  to  show 
that  fall  plowing  is  any  better  than 
spring  plowing  in  increasing  com  yields, 
although  there  may  be  a  slight  trend  in 
favor  of  fall  plowing. 


From  these  statements  it  appears  obvious 
that  the  best  time  to  plow  will  depend 


R.   S.   Staiiffer  and  0.   H.    Sears 

9-7-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-14 


SOIL  TESTS:  THEIR  CHANGES  WITH  FERTILIZER  APPLICATIONS 


Interpretations  of  soil  test  values  must 
be  based  in  part  on  a  knowledge  of  fer- 
tilizer and  limestone  applications  dur- 
ing the  past  five  or  six  years,  and  pref- 
erably longer.  It  is  not  possible  to 
obtain  representative  samples  from  re- 
cently treated  soils.  Even  with  the  best 
sampling  techniques ,  the  test  result 
must  be  interpreted  not  only  with  due 
consideration  of  (l)  the  amount  of  a  fer- 
tilizer material  added,  but  also  (2)  the 
kind  or  form  of  the  material,  (3)  its 
.  reaction  with  the  soil, and  (U)  the  meth- 
od of  application  used. 

The  test  of  a  soil  soon  after  treatment 
is  not  a  check  on  whether  or  not  enough 
has  been  used.  Rather,  it  is  a  value 
Influenced  not  only  by  the  original  con- 
tent, but  also  by  the  four  factors  men- 
tioned above. 

Acidity.  The  acidity  in  an  unlimed  soil 
is  fairly  uniform  in  local  areas .  A  com- 
posite soil  sample  adequately  represents 
the  situation  in  the  local  area.  But 
this  uniformity  disappears  with  liming. 
Even  the  best  of  mixing  leaves  a  mixture 
of  neutralized   (sweet)  and  acid  spots. 

If  there  are  enough  neutralized  spots 
within  the  legume's  root  systems,  ade- 
quate nodulation  of  the  roots  can  take 
place.  The  whole  soil  does  not  have  to 
be  neutralized.  A  sample  from  such  a 
soil  may  be  "acid"  by  the  pH  measurement 
and  give  a  red  thiocyanate  test.  But  in 
time,  with  plowing  and  cultivating,  the 
limed  soil  becomes  more  uniformly  neu- 
tral. 

Because  of  the  lag  in  neutralization  and 
mixing,  the  testing  of  recently  limed 
soils  can  give  no  useful  information. 
One  cannot  add  limestone  and  then  test 
to  see  whether  enough  has  been  added. 
Five  or  six  years  after  liming,  fairly 


reliable  tests  can  again  be  secured. 
But  even  then  the  tests  can  be  better 
interpreted  if  one  Icnows  the  previous 
liming  history.  The  best  procedure  is 
to  have  the  soil  tested,  broadcast  the 
recommended  amount  of  limestone,  thor- 
oughly mix  it  into  the  soil,  and  not 
test  again  for  five  or  six  years. 

Rock  phosphate .  Erratic  soil  test  val- 
ues for  phosphorus  are  usually  found 
when  soils  are  tested  after  the  recom- 
mended rates  of  rock  phosphate  have  been 
applied.  If  the  rock  phosphate  was  thor- 
oughly mixed  with  the  soil,  as  it  should 
be  for  good  results,  one  should  theoret- 
ically obtain  tests  around  medium  or 
above.  But  complete  mixing  is  difficult, 
if  not  impossible,  and  wide  variations 
in  test  value  are  found.  Too  wide  vari- 
ations indicate  that  the  rock  phosphate 
was  not  properly  applied  and  mixed. 

Soluble  phosphates  are  changed  in  soils 
into  the  natural  available  soil  forms  of 
phosphorus .  Because  soluble  phosphates 
are  so  much  more  highly  available  when 
properly  applied  (see  SF-5)^  ordinarily 
not  enough  is  used  to  markedly  change 
the  soil  test  value.  Furthermore,  when 
properly  applied,  the  soluble  phosphates 
are  not  thoroughly  mixed  with  the  soil. 
This  results  in  very  efficient  plant 
feeding  but  also  makes  it  difficult  to 
obtain  representative  samples. 

An  amoiJnt  that  is  adequate  to  produce 
maximum  yields  is  not  necessarily  enough 
to  make  the  soil  test  "high. "  The  added 
phosphate  is  more  available  when  not 
thoroughly  mixed  than  when  rather  evenly 
mixed.  A  soil  does  not  have  to  test 
"medium  to  high"  in  order  to  give  opti- 
mum yields  if  part  of  the  available 
phosphate  is  concentrated  in  patches  or 
spots  where  it  has  a  markedly  higher  sol- 
ubility and  is  also  positionally  more 


available  for  plant  feeding.  It  is  pos- 
sible for  two  different  soils  to  give 
the  same  soil  test  value  and  yet  vary  in 
their  phosphate  sixfficiency,  provided 
one  of  them  has  been  treated  recently 
with  soluble  phosphates. 

Each  100  pounds  of  20  percent  superphos- 
phate contains  only  8.7  pounds  of  actual 
P,  the  element  phosphorus.  The  soil 
test  extracts  only  about  one-third  of 
the  available  phosphorus.  A  soil  test 
value  of  25  pounds,  therefore,  means  an 
actual  value  of  aroxmd  75  pounds.  Even 
though  the  8.7  pounds  of  phosphorus  was 
mixed  thoroughly  and  a  representative 
test  was  secured,  the  actual  soil  test 
value  would  be  increased  by  about  2.9 
pounds  for  each  100  pounds  of  superphos- 
phate (O-20-O),  assuming  no  plant  remov- 
al. Thus  the  addition  of  200  or  300 
pounds  of  superphosphate  woxild  increase 
the  actual  test  value  only  slightly. 
However,  uneven  mixing,  which  is  the 
correct  way  to  use  soluble  phosphates, 
can  result  in  widely  varying  test  values 
until  plowing  and  cultivating  cause  more 
even  mixing. 

Potass iijm  is  likewise  more  available  to 
plants  when  not  thoroughly  mixed  with 
the  soil.  When  it  has  been  recently  ap- 
plied, representative  samples  are  diffi- 
cult to  secure.  The  soil  test,  however, 
extracts  all  (not  a  proportionate  part) 
of ,  the  immediately  available  potassium 
in  the  sample  that  has  not  been  ex- 
tracted by  plant  feeding  or  adsorbed  in- 
to the  "storehouse"  (see  SF-2).  But  the 
sample  will  not  be  representative  until 
after  plowing  and  cultivating  mix  the 
applied  potash. 

Nitrogen.  The  natural  available  forms 
of  nitrogen  are  ammonia  and  nitrate  ni- 
trogen (see  SF-U).  It  is  easy  to  meas- 
ure both  of  these  forms.  Additions  of 
commercial 'nitrogen  fertilizers  will  in- 
crease these  forms  temporarily  until  the 
plants  remove  them,  as  will  also  clovers 
and  other  crops  that  are  high  in  nitro- 
gen. But  a  soil  test  at  any  one  time 
gives  only  the  level  at  that  time.  Many 
factors  influence  the  level  of  these 


forms  in  the  soil.  This  makes  it  impos- 
sible to  interpret  soil  tests  accurately 
for  available  forms  of  nitrogen.  Sever- 
al states  are  using  methods  that  try  to 
predict  how  much  will  be  released  during 
the  year.  But  this  is  not  a  direct  meas- 
ure of  the  available  form. 

Summary.  Reasons  why  the  previous  treat- 
ment history  of  a  soil  shoxold  be  known 
have  been  given  above.  The  soil  test 
measures  the  amounts  of  available  forms 
present  in  a  sample .  But  the  plant  avail- 
ability or  effectiveness cf  one  amoxmt  of 
a  form  will  depend  not  only  on  the  chemi- 
cal properties  of  the  form,  but  also  on 
its  distribution  throughout  the  soil — 
that  is,  its  fertility  pattern  or  even- 
ness of  distribution. 

At  present  the  soil  tests  are  calibrated 
on  the  basis  of  the  natural  type  of  dis- 
tribution resulting  from  plant  feeding 
where  no  fertilizers  have  been  added. 
This  is  a  fairly  even  distribution,  with 
no  sharp  variations  in  amount.  After 
fertilizers  have  been  applied  and  mixed 
and  plowed  and  cultivated  for  several  sea- 
sons, a  somewhat  similar  fertility  pat- 
tern will  finally  result. 

But  if  soluble  fertilizers  (P  and  k)  have 
been  recently  added,  allowance  must  be 
made  for  the  extra  availability  of  the 
amounts  added  in  interpreting  the  soil 
test.  There  is  no  "rtile  of  thumb"  or 
scale  by  which  to  judge  how  much  signifi- 
cance should  be  given  to  recently  applied 
fertilizers.  If  the  amotmts  added  were 
relatively  small,  they  can  be  almost  ig- 
nored. But  if  the  amounts  were  consider- 
ably in  excess  of  subsequent  plant  remov- 
als, the  effectiveness  of  the  soluble 
nutrient  will  be  higher  than  will  be  in- 
dicated by  the  charts  for  the  soil  test 
interpretations . 

After  soils  are  tested  for  phosphorus  and 
potassium  and  a  program  of  soluble  ferti- 
lizer use  has  been  decided  upon,  it  shoxild 
be  continued  for  six  to  eight  years.  Then 
retesting  is  reconmended  to  adjust  the 
treatments  for  any  change  in  the  soil  test 
values. 

Roger  H.  Bray 
9-28-53 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-15 


SOIL  FERTILITY  MAINTENANCE 


A  fertilizer  maintenance  program  implies 
(l)  that  enough  fertilizer  will  be  used 
to  maintain  either  soil  test  at  optimtjm 
levels  or  yields  at  optirnxm,  and  (2)  that 
the  quantity  of  fertilizer  used  will  con- 
tain nutrients  equal  to,  or  less  than, 
those  removed  by  crops. 

Fertility  maintenance  is  usually  prac- 
ticed only  on  soils  that  have  an  average 
crop  nutrient  sufficiency  rating  of  over 
90  percent.  At  the  90  percent  level,  the 
use  of  fertilizer  nutrients  equal  to  that 
removed  by  crops  will  give  optirnxm 
yields . 

Maintenance  fertilization,  then,  is  the 
practice  of  using  a  quantity  of  fertili- 
zer, largely  determined  by  the  amount  of 
nutrients  removed,  to  get  optimum  crop 
yields  or  to  maintain  soil  test  levels 
at  their  optimum. 

The  following  table  may  be  used  to  de- 
termine the  amount  of  nutrients  removed 
by  some  conanon  farm  crops: 

Nutrients  Removed  by  Common  Farm  Crops 


Crop 


Yield  level    N   P2O5  KpO 
lb/A  lb/A  lb/A 


Corn 

100  bu.  grain 

92 

37 

2k 

Wheat 

35  hu.  grain 

h3 

18 

11 

Oats 

TO  bu.  grain 

h3 

18 

11 

Soybeans 

32  bu.  grain 



27 

35 

Legumes 

3  tons  hay 

—  — 

32 

102 

The  first  pTjrpose  of  the  maintenance  pro- 
gram is  to  keep  the  productive  level,  or 
yield  capacity,  of  the  soil  at  optimum. 
For  each  soil  nutrient  there  is  a  minimum 
level  that  is  just  high  enough  to  give 


optimxjm  yields  when  it  is  supplemented  by 
enough  fertilizer  to  provide  the  nutri- 
ents equivalent  to  those  removed  by  crops . 

For  phosphorus  the  soil  test  level  at 
which  the  use  of  phosphate  fertilizers 
equal  to  that  removed  by  plants  will  give 
optimum  yields  and  maintain  the  test  lev- 
el is  slight  plus  (S+).  For  potassium  the 
minimum  test  level  for  maintenance  will 
depend  on  the  soil  (see  SF-2).  In  gener- 
al, for  northern  Illinois  this  minimum  is 
about  120  pounds  per  acre,  while  for 
southern  Illinois  it  is  about  I50  pounds. 

The  second  purpose  of  maintenance  ferti- 
lization is  to  maintain  a  given  level  of 
a  nutrient  in  the  soil.  Almost  all  soils 
that  test  higher  than  the  indicated  mini- 
mtan  can  be  maintained  at  this  level  by 
adding  enough  fertilizer  to  replace  the 
nutrients  removed  by  crops.  The  amoiint 
may  need  to  be  modified  slightly  with 
differences  in  leaching  losses  or  weath- 
ering. Soils  testing  below  minimum  lev- 
els for  maintenance  will  need  more  ferti- 
lizer than  is  removed  by  the  crop  to  give 
optimum  yields. 

Thus  soils  that  are  naturally  at,  or  have 
been  built  up  to,  the  90  percent  level 
are  best  suited  to  a  maintenance  program. 
On  soils  testing  higher  than  the  indi- 
cated minimum,  maintenance  of  test  levels 
will  require  more  fertilizer  than  is 
needed  for  optimum  yields. 

The  table  on  the  next  page  gives  the  quan- 
tities of  phosphate  fertilizers  needed  to 
maintain  yield  and  soil  nutrient  levels 
ijinder  average  conditions .  Yield  can  be 
maintained  temporarily  with  much  less 
fertilizer  than  is  needed  to  maintain 
nutrient  levels. 


-2- 


Phosphorus  Maintenance  Requirements 


Rock  phosphate 

program 

r-Iainte nance  of 

Superphosphate 

program 

Maintenance  of 
nutrient  level 

yield  level 

Maintenance 

of 

I':aintenance  of 

800  of  rock 

Soil 

nutrient  level 

yield  level 

6-  to  8-year 

pliis  extra 

test 

^-year  rotation 

k 

-year  rotation 

requirement 

soluble  phos. 

level 

0-20-0 

0-20-0 

rock  phos. 

0-20-0 

lb. /A. 

lb. /A. 

lb. /A. 

lb. /A.  yearly 

S+ 

6001/ 

6ool/ 

8002/ 

75 

M- 

600 

600 

800 

75 

M 

6oo 

300 

Boo 

Starter 

m- 

600 

300 

Boo 

Starter 

H- 

6oo 

starter 

Boo 

Starter 

H 

600 

Starter 

800 

Starter 

H+ 

600 

Starter 

Boo 

Starter 

T/    These  quantities  are  equivalent  to  crop  removals  for  average  4-year  rotations  at 

the  100-bushel  corn  level. 
2/  These  quantities  are  equivalent  to  crop  removals  for  average  rotations  for  an  8-year 

period . 


To  maintain  yield  at  various  potassium 
test  levels,  it  is  necessary  first  to 
distinguish  between  soils  that  have  a 
large  amount  of  the  "storehouse"  form  of 
potassium  and  those  that  contain  little 
of  this  form.  Because  some  of  the  added 
potassixjim  vrLll  go  into  the  "storehouse" 
form  (see  SF-2)  and  the  soil  tests  do 


not  measure  this  form,  there  is  no  ac- 
curate way  to  determine  how  much  potash 
fertilizers  are  needed  to  maintain  test 
levels.  For  potassiian,  therefore,  only 
yield  maintenance  is  considered.  The 
following  table  may  be  used  as  a  guide 


in  determining  potash 
for  Illinois  soils: 


maintenance  needs 


* 


Potash  Maintenance  Requirements 


Soil  test  level 
(lb. /a.) 


Percent  of  4-year  rotation  crop  removal 


Northern  Illinois 


Southern  Illinois 


120  to  150 
150  to  170 
170  to  190 
190  to  210 
210  and  over 


100 

75 

50 
Starter 
Starter 


Build-up 
100 
75 
50 

Starter 


The  table  below  assumes  levels  for  con- 
ditions of  equilibrium;  that  is,  they 
are  not  temporary  as  the  result  of  a 
large  application  of  potash  the  year  be- 
fore the  sample  was  taken.  Soils  should 
be  retested  every  6  to  8  years  to  check 
their  reaction  to  treatment. 


The  concept  of  maintenance  fertilization 
is  not  the  same  for  nitrogen  as  for  phos- 
phorus and  potass iimi.  A  level  of  soil 
nitrates  or  ammonia  that  will  produce 
optimtan  yields  cannot  be  maintained  over 
any  length  of  time.  Nor  is  it  possible 
to  maintain  a  level  of  organic  matter 


-3- 


high  enough  to  furnish  enough  nitrogen 
to  give  optimum  yields. 

Actually,  since  some  crops,  like  legumes 
and  soybeans,  can  fix  part  of  the  nitro- 
gen they  need,  it  is  not  desirable  to 
maintain  very  high  nitrogen  levels.  In 
the  use  of  fertilizer  for  nitrogen  main- 
tenance, therefore,  the  object  is  to  sup- 
ply the  soil  with  just  enough  to  produce 
high  yields  with  little  or  no  loss  of  ni- 
trates due  to  leaching  or  with  no  reduc- 
tion in  soil  organic  matter. 

The  program  of  nitrogen  maintenance  fer- 
tilization is  essentially  oneof  estimat- 
ing the  needs  of  the  expected  crop  and 
then  applying  the  needed  amount  before 
or  as  the  crop  is  grown.  The  nitrogen 
need  is  determined  by  calculating  the 
crop  requirement --essentially  the  amotmt 
removed  by  the  crop — and  subtracting  the 
estimated  amount  plowed-under  legumes 
or  residues  may  be  able  to  furnish.  The 
difference  is  the  amount  that  must  be  sup- 
plied to  produce  the  expected  yield. 

Corrections  must  be  made  for  soils  that 
are  subject  to  severe  leaching  of  ni- 
trates. For  most  soils,  except  sands, 
peat,  or  soils  that  are  subject  to  ex- 
cessive leaching,  use  of  crop -removal 
quantities  of  nitrogen  will  about  main- 
tain the  soil  organic  matter  level.  In 
general  nitrogen  leaching  is  not  serious 
on  Illinois  soils  (see  SF-U). 

Soluble  mixed  fertilizers  are  usually 
best  for  maintaining  soil  fertility,  with 


the  extra  nitrogen  need  supplied  as  a 
straight  carrier.  Man^a:e  may  be  used  as 
part  of  the  maintenance  fertilizer;  its 
value  will  depend  solely  on  its  nutrient 
content. 

Plowed-under  legumes  will  furnish  nitro- 
gen and  maybe  considered  a  straight  car- 
rier. In  a  maintenance  program,  not  more 
than  half  of  the  total  nitrogen  in  the 
legume  may  be  considered  new  nitrogen, 
however.  For  practical  purposes,  each 
ton  of  the  legume  plowed  under  may  be  ex- 
pected to  furnish  about  20  pounds  of  ni- 
trogen per  acre.  Plowing -down  legtmes 
does  not  add  any  new  potass iirni  or  phos- 
phorus to  the  soil. 

Maintenance  fertilizers  are  usually  most 
effective  when  applied  as  starter  ferti- 
lizers for  crops  that  have  high  fertil- 
ity requirements,  with  the  extra  nitrogen 
plowed  under  or  side-dressed  after  the 
crop  is  up.  In  a  maintenance  program  the 
soil  should  be  retested  every  6  to  8  years 
to  check  the  adequacy  of  the  fertilizers 
that  have  been  used. 

Obviously  the  highest  testing  soils  that 
receive  less  nutrients  in  fertilizer  than 
the  crops  remove  will  sometime  drop  to 
lower  test  levels.  Since  weathering  can- 
not be  stopped,  it  becomes  sound  practice 
on  these  high-testing  soils  to  take  ad- 
vantage of,  and  use,  the  nutrients  that 
become  available  each  year  from  the  un- 
available forms.  The  retesting  program 
will  permit  modification  of  maintenance 
needs  to  meet  changing  soil  conditions. 

S.  W.  Kelsted 
11-9-53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-16 


PRINCIPLES  OF  TESTING  FOR  AVAILABLE  SOIL  PHOSPHORUS 


There  are  two  groups  or  forms  of  soil 
phosphorus  that  contribute  significantly 
to  crop  gro\rth.  These  are  the  "acid- 
soluble"  or  calcium  forms  and  the  adsorbed 
or  exchangeable  forms.  Both  shoiild  be 
measured  as  a  basis  for  making  fertili- 
zer recommendations  (see  Agronomy  Facts 
sheet  SF-3).  Corn-belt  soils  contain 
both  kinds,  naturally  as  well  as  from  the 
additions  of  rock  and  s.oluble  phosphates . 

The  more  acid  soils  usually  have  a  higher 
proportion  in  the  adsorbed  forms.  The 
less  acid  to  neutral  soils  usually  have 
a  higher  proportion  (naturally  occurring) 
in  the  acid-soluble  forms.  Almost  25 
percent  of  the  dark-colored  prairie  soils 
natixrally  tested  "high"  in  acid-soluble 
forms  around  1930-  Since  then  hundreds 
of  thousands  of  acres  have  been  treated 
with  rock  phosphate,  also  an  acid-soluble 
form.  Few  of  these  soils  test  high  na- 
turally as  a  result  of  adsorbed  forms, 
and  not  enough  soluble  phosphates  have 
beed  added  to  create  a  "high"  test  for 
adsorbed  forms. 

A  soil  testing  medium  to  high  in  the  ad- 
sorbed forms  is  more  effective  than  one 
containing  high  amounts  of  the  acid- 
soluble  forms.  The  latter  forms  have  a 
limited  effectiveness  in  that,  to  obtain 
maximum  yields  of  some  crops,  some  solu- 
ble phosphate  must  be  added  as  a  starter. 
Wheat,  following  soybeans,  may  be  as  much 
as  10  bushels  short  in  yield  imless  solu- 
ble phosphate  is  drilled  with  the  seed, 
even  though  k  tons  of  rock  phosphate  per 
acre  have  already  been  added. 

The  P2  test  was  designed  to  extract  both 
forms  of  available  phosphorus.  It  con- 
sists of  0.10  normal  hydrochloric  acid 
in  0.03  normal  ammonium  fluoride.  The 
acid  dissolves  the  acid-soluble  forms. 


including  rock  phosphate.  The  fluoride 
ion  displaces  adsorbed  forms.  The  test 
extracts  about  one -third  of  the  total, 
probably  the  more  available  one -third. 

A  high  P2  test  may  be  due  to  high  amounts 
of  the  acid -soluble  forms, to  high  amounts 
of  the  adsorbed  forms,  or  to  a  combina- 
tion of  both  forms .  Thus ,  medium  to  high 
test  values  do  not  indicate  whether  or 
not  a  starter  is  needed.  The  Pi  test 
was  designed  to  distinguish  between  these 
situations.  It  is  a  solution  of  0.025 
normal  hydrochloric  acid  in  0.03  normal 
ammonium  fluoride.  The  small  amoxmt  of 
acid  is  buffered  by  the  exchangeable 
bases;  the  fluoride  displaces  the  ad- 
sorbed phosphates.  Wo  factor  has  been 
worked  out  to  determine  the  proportion 
of  adsorbed  forms  removed.  Generally, 
it  is  only  the  soils  that  have  been 
treated  with  soluble  phosphate  that  test 
high  by  the  ?]_  test. 

A  soil  that  tests  low  by  the  Pp  test  will 
always  test  as  low  or  lower  by  the  Pi 
test,  showing  a  need  for  large  amounts 
of  phosphate  fertilizers.  A  soil  that 
tests  high  by  the  P2  test  will  also  test 
high  by  the  P-]_  test,  provided  the  result 
is  due  to  adsorbed  phosphates,  and  no 
phosphate  is  needed.  But  when  a  high  P2 
test  is  due  mainly  to  the  acid-soluble 
forms,  the  Pi  test  will  be  low  and  only 
starter  soluble  fertilizer  will  be  needed. 
The  table  illustrates  these  sitiiations 
with  experimental  field  data. 


In  the  Illinois  soil  testing  program, 
only  the  P2  test  is  used  because  of  the 
scarcity  of  soils  testing  high  mainly 
because  of  adsorbed  forms.  The  record 
of  previous  treatments  should  show  which 
forms  of  fertilizers  have  been  added. 
In  the  absence  of  records,  a  high  P2  test 


(Continued  on  other  side) 


is  assigned  to  te  iue  tc  acid-sol\ible 
forms,  either  nat-urp." " y  present  or  re- 
sulting frrr  added  reck  phosphate,  and 
starter  ;  :  1  - :  le  phosphate  shovild  be  used 
on  those  crops  that  recuire  it.  Low  F2 
tests  indicate  the  need  for  general  use 
of  relatively  large  anoxmts  of  phosphate 
fertilizers . 

It  is  procacle  that  as  the  use  of  solu- 
cle  phosphates  increases  and  the  adsorted 
fcrr^  are  built  up,  and  as  treatment  rec- 
03rds  became  lost  or  confused,  the  use  of 
both  P]_  and  Fp  tests  on  each  sanple  nay 
beccne  standard  rractice. 


usi: 


"-.res  „n 


tsecen~_y  severa_  sc:l_  cnenisxs  nave  sug- 
gested that  only  the  adsorbed  forms  of 
phcsphcr'-LS  be  meas'-red  as  a  g'oide  to  fer- 
tilizer use.  Beth  the  r-_  solution  and 
an  alkaline  solution  cf  sodiim  bicarbon- 
ate have  been  sioggested  f  cr  this  purpose. 

"ivhere  the  adsorbed  forms  are  dominant 
and  the  acid-soluble  forms  are  present 
in  cnly  negligible  amounts,  this  proce- 
dure might  be  feasible.  For  calcarec^ 
soils,  vhere  it  is  difficult  to  evaluate 
the  acid-soltible  forms,  it  might  be  jus- 
tified as  an  expedient.  But  to  recom- 
mend either  cf  these  tests  as  a  general 
test  for  calcareous,  neutral,  and  acid 
soils,  '.d-thout  qualification,  is  to  ig- 


icre  the  fact  thai 


crops  can  ap- 


proach, if  not  achieve,  their  maximxaa 
j'i.elds  -»rhen  only  the  acid-soluble  forms 


are  rreser 


SIS 


Such  a  prcced^'L^re  ' :  ,li 
betveen  soils  needir^-  ;: 


ant  amcTznts. 

:'.:"  distinguish 
ly  a  smaZ-1  amount 


of  starter  soluble  phosphate  and  ones 
needing  the  general  use  of  large  amounts 
of  phosphorus.  It  could  lead  to  the  use 
of  large  amounts  of  fertilizers  where 
only  small  amounts  are  needed. 

In  contrast,  the  F2  test  -used  without 
the  F]_  test  may  indicate  the  need  for 
small  aEO\ants  of  fertilizer  vhere  none 
is  needed.  But  it  will  not  indicate  the 
need  for  large  amounts  vhere  only  small 
amo\ints  are  needed.  It  is  because  the 
acid-soluble  forms  contribute  signifi- 
cantly to  crop  growth  in  corn-belt  soils 
that  neither  the  Tj^  nor  the  alkaline  so- 
dium bicarbonate  test  is  recommended  for 
general  use  as  the  only  guide  for  phos- 
phorus fertilizer  recommendations. 

The  table  below  illuistrates  the  fact 
that  the  P]_  test  for  adsorbed  phosphorus 
does  not  distinguish  betveen  high,  medi- 
um, low,  and  starter  needs. 

Phosphate  Needs  and  the  P]_  and  P2 
Test  Values 


:iXT:eriment 

Limei 

■clots 

Relative  need 

field 

?! 

F2 

for  phosphorus 

l^-/2  M 

of  soil 

Enfield 

14 

16 

High 

Raleigh 

15 

15 

Hieh 

Carl invi  lie 

20 

31 

High 

Joliet 

21 

31 

High 

Clayton 

21 

5h 

Medium 

Hartsburg 

22 

62 

Low 

Minonk 

26 

71 

Lov 

Clayton  +  rP 

22 

200+ 

Starter  only 

Des  Plaines 

+  sp 

177 

200+ 

None 

Roger  H.  Bray 
12-21-53 


UNIVERSITY  OF  ILUNOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-17 


•.■;\  ,\C-  N,""  CC-:N 


:S' 


auccessruj-  les's  za-.-e 
wtining:  tbe  e'.-allsile  r-: 


*-  =  ".=        "^CT^     c.-;"g  '  '  e,'~  '  P 


Ts'trtcri-  In  crcsr  to 


S   rO^ES-iCi  z^- 


"2    *""'?    32"S^C        ' 


g  ,  -  -'-jC - 


as  veil  as  nitrogen,     are  -"    ijicrss 
end  -'*.       rrils     ra.7  crntain     fran 


-J     -  ^-.c-,. 


^cre     lnTcl'«*^s     n^rel^*  8>rirs.ctl.n^     ncTe   r 


:cr     "ne  ns>r 
£ssi-.r:  tnsre- 


ei.       icr  esszEle,     if  past  :.-ields  rs-re  eTsragsd 


■::«r   r-jsne. 


-  —  — ■•  —  —  T  ■»- 


IS  i-  =£;■•  "re  cc-isicsr; 


ces.   -■irrer- 
t  "js  ancunx 


Ftcsrncrus  and  rctassi-,Ti     i:  n:-  deper 

ing  Hcrel;''  ~c  s^ni^ct  and  nfia-S'^i^  *n£  T:r^srn" 
aawumt  of  svsilarle  nitrrgen,  as  is  dens  f;r 
'ctcsT^CT'JS   and  "ciassl'.m.    rri'rr'r  t** c-*"' r- ~  e   ct'CT 

avsiXabie  to  fu-ure   ;rcrs. 

for  skepticisn  regarding  the  value  cf  existing 
■tests  fCT  deteminini:  a'i~ailarle  niTrc-^^n  sni  5rr 
fail-v3«  to  reccnneni  tnen  r.:-    ,-:i^;     in     Illinris. 

Several  nefn^ds  -cr  estins'in;:  =ril  r.itmen  re- 
qtiiresents  are,  hcrire-.-er,  l;.  .j?  ::■  — .v;  r-een 
proposed.  .ts/  can  '- -"  — •:v.7ei  as  -cHo4-s: 
(l)  predict irns     "rsssi  :.;-r'rir-.3  ;.-ields     smd 

(3)  ls"J  erst  cr;-'  inoursti.;. 


rsstner  arc  rai 


:£   sxr<e;"-e 


•.rur  r  _- ■_=    -^ :  rratcry 


:^cvn 
=  cil 


isents  a_so 


--  ■_ :  ■■-  -  ^  nat^  c. —  -  - ::  ~f  availan_^5  ni.Trc<^i^3 
(?•  Jfe,  A31?59).  In  spite  cf  tils  evidesas,  ni- 
trocen  recaaasndsticis  "issed  solely  rsn  rr-gsnic 
:Latt.sr  dstajniz^stlcns  are  not  relisirls. 


Act 


Lne  isstrur: 


^c  _  .  r.  -  _ 


over  E  period  ci"  ;."esrs  (All-; 
used  in  naking  nitrogen  reccr 
ncis  (AGlr56>  and 


nese  ^  c.c  are 


^tner  states. 


This  approach  is  net  inf all-i'cle . 
tive,  it  i'ecv-ires  csref"-il  ana'"''s: 


v^  eff eo - 
-"■     -5-ts-- 


soi-i  or«zan2.2     nsttisr  ^f^"^^*"*/)'  '"rc'^^  ~— <;  are     "nart  dx 

in;crpcrsted  resii-Jiss  are  also  car-st^:' ', v  ;cinsid- 

nsniati  ens  are  sade  free  psst  ;.-islds  sad  cropping 
=  f  ;•.:■/:■  :;=  v!iich  la  tijesE-elTes  reflect  curgssnlc 
zl:.''z~  levels  an"    ""■"'■■~tv, 

gen  test  that  has  net  teen     tested  for  reliatil- 

itv  in  et'r.er  states.       ^Ttis  metiiod  differs     from 

tie  re-.ilar     tctsl.  er-gsndc  nattsr  aetiied  in  tist 

''  "  "••--■   "      "   '     ',  / "  "   "      -■ "     "    ■"-=  solit  cjff  froBB 


the  organic  matter  as  ammonia  and  the  amount  is 
determined.  It,  ho\rever,  would  seem  to  have 
many  of  the  limitations  of  the  organic  matter 
detenninatlons.  For  example,  from  the  test  re- 
sults it  is  not  possible  to  predict  the  effects 
of  residues,  particularly  those  of  wide  carbon- 
nitrogen  ratios,  on  net  nitrogen  availability. 
Again  it  woiJ-d  seem  to  be  necessary  to  co:isider 
past  yields  and  cropping  sequence  in  arriving  at 
a  satisfactory  recommendation. 


Laboratory  incubation  methods. 


Incubation  of 


soils  \jnder  stemdard  laboratory  temperatures  and 
moisture  conditions  represents  one  of  the  first 
attempts  to  assess  nitrogen  fertility.  Theoreti- 
cally this  approach  is  sound.  Activity  of  the 
microbes  that  naturally  release  available  nitro- 
gen determines  nitrogen  fertility.  But  release 
of  nitrogen  under  laboratory  conditions  can  be 
quite  different  from  that  occurring  under  field 
conditions,  where  both  temperature  and  moistxare 
may  vary.  As  these  limitations  became  apparent, 
interest  in  microbial  methods  naturally  declined. 

In  the  past  few  years,  however,  workers  at  the 
Iowa  Experiment  Station  have  reactivated  Inter- 
est in  the  microbiological  approach.  A  major  ob- 
jection to  the  method  had  been  the  30-day  incuba- 
tion period.  Iowa  has  been  able  to  cut  this  time 
to  I'l-  days,  which  is  comparable  with  the  10-day 
drying  inteirval  required  for  the  potassium  test. 

Iowa  workers  have  also  not  overlooked  the  impor- 
tance ■  of  unincorporated  residues  and  stand  on 
the  reliability  of  nitrogen  recommendations. 
They  report  greater  reliability  in  predicting 
nitrogen  needs  of  second-year  corn  than  of  first 
year,  as  might  be  expected  because  of  differ- 
ences in  managing  legume  and  grass  stands. 


cles  and  the  adequacy  of  nitrogen  fertilization 
programs  arrived  at  by  other  methods. 

In  com  the  main  symptan  of  nitrogen  deficiency 
is  yellowing  of  the  lower  leaves  from  the  tip 
back  through  the  midrib  section.  Unless  the  de- 
ficiency is  severe,  symptoms  do  not  appear  until 
just  before  or  after  shooting,  and  then  it  is 
too  late  to  correct.  They  are,  however,  useful 
in  pointing  out  the  need  for  nitrogen  fertiliz- 
ers. The  U.S.D.A.  reports  that,  for  each  nitro- 
gen deficient  leaf  at  shooting  stage,  com  yields 
are  decreased  15  bushels  an  acre,  assuming  that 
all  plants  show  deficiency  symptoms. 

Hidden  nitrogen  starvation,  in  which  no  deficien- 
cy symptoms  are  apparent,  is  cammon  In  Illinois. 
The  best  way  to  detect  it  is  by  plant  analyses 
or  tissue  tests,  which  detennlne  the  amount  of 
nonasslmilated  nitrate  nitrogen  in  the  plant. 
A  positive  test  indicates  sufficient  nitrogen; 
a  negative  test  Indicates  a  deficiency. 

Nonasslmilated  nitrate  nitrogen  may  or  may  not 
indicate  sufficient  nitrogen.  For  example,  free 
nitrate  may  accumulate  when  potassium  or  some 
other  essential  element  or  growth  factor  is  lim- 
iting plant  growth.  For  this  reason  nitrogen 
tests  should  always  be  accompanied  by  tissue 
tests  for  phosphonis  and  potassiim. 

Nitrate  nitrogen  tends  to  disappear  as  plants 
mature.  An  early  tissue  test  may  Indicate  a 
sufficiency;  a  later  test  may  show  nitrogen 
starvation.  For  this  reason  tissue  tests  shoxild 
be  made  at  varioiis  stages  of  growth.  To  obtain 
maximum  yields,  assuming  adequate  minerals,  the 
tests  shoxild  show  positive  until  the  moisture 
content  of  ear  corn  is  about  50  percent. 


« 


I 


The  Iowa  resiilts  look  promising.  If  the  method 
should  prove  applicable,  it  will  not  be  particu- 
larly adapted  for  county  testing  laboratories. 
The  microbiological  test  would  need  to  be  run  in 
adequately  equipped  and  staffed  central  labora- 
tories. Interpretation  of  results  would  require 
a  laio\-fledge  of  past  yields  and  cropping  history 
and  exercise  of  good  judgment. 

Deficiency  symptoms  and  plant  tests.  So  far  we 
have  tallied  about  methods  of  estimating  nitrogen 
needs  prior  to  seeding.  Obviously  deficiency 
symptoms  and  plant  tissue  tests  cannot  be  used 
for  this  purpose.  They  do,  hoi-rever,  serve  as 
valuable  aids  in  determining  nitrogen  deficlen- 


In  conclx:islon,  the  dependence  of  nitrogen  avail- 
ability on  microbial  activity  makes  testing  for 
available  nitrogen  a  more  difficult  problem  than 
testing  for  available  phosphoms  and  potassium. 
The  probable  response  of  grain  crops  to  nitrogen 
fertilizers  can  be  determined  only  by  taking  in- 
to account  previous  yields  and  cropping  history, 
kinds  of  residues  returned  to  the  soil,  axid  ade- 
quacy of  natural  or  applied  phosphorus  and  po- 
tassium fertility.  Tests  for  available  nitrogen 
can  serve  only  as  partial  guides.  In  the  final 
analysis  considerable  attention  must  be  given  to 
all  of  the  aforementioned  factors  in  translating 
the  results  of  a  nitrogen  test  into  specific  ni- 
trogen recommendations. 


Edward  H. 
l-lt-5it 


Tyner 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-18 


ROTATIONS 


Determining,  establishing,  and  maintain- 
ing suitable  cropping  sequences  on  farm 
lands  is  not  easy.  Sequences  are  affected 
by  such  factors  as  land  suitability, 
land  use,  economies,  labor,  continuity 
of  management,  potential  of  applied  pro- 
ductivity, and  many  hazards .  Also  seme 
of  the  factors  that  cause  conflicts  fre- 
quently have  changing  impacts.  So  it  is 
not  surprising  that  interpretations  and 
use  of  sequences  often  do  not  agree 
among  individuals  whose  desires,  needs, 
objectives,  abilities,  and  points  of 
view  differ.  Even  the  conditions  of  the 
individual  change  frequently.   Standard 


patterns  and  proportional  units  need  to 
be  established  for  each  specific  situa- 
tion. 

Table  1  gives  factual  data  from  rotation 
experiments  showing  the  use  of  land  and 
the  consequences  of  such  use.  These 
data  can  be  interpreted  in  several  ways . 
Since  first-year  corn  is  common  to  all 
systems,  it  can  be  used  as  a  comparative 
measure  of  the  effect  of  the  system  on 
productivity  of  the  soil.  From  this 
vievrpoint,  systems  with  standover  leg- 
umes have  been  superior  to  those  with 
catch  crops .   Systems  with  catch-crop 


Table  1. --Effect  of  Cropping  Sequence  on  Crop  Yields  -  Drummer  Clay  Loam 
Department  of  Agronomy  -  South  Farm,  Urbana,  Illinois 


Mean  acre 

yield 

Average 

19^0-1951 

current 

1st.  yr 

.  2nd.  yr 

values 

Location 

Rotation^:/ 

corn 

corn 

Beans 

Wheat 

Oats 

Hay 

19U8-51 

bu. 

bu. 

bu. 

bu. 

bu. 

tons 

l-C-0£/ 

86b/ 

53 

$  81.18 

M-9 

2-C-W£/ 

86b/ 

23 

93.02^ 

500  -  6oo 

3-C-B 

U-C-O 

72 

28 

J^9 

91.19 
6i^.76 

5-C-W-Cl(alf . ) 

6-c-c-w£/ 

7-C-0-w£/ 

90 

30 

2.1|i+ 

84.52 

M-19 

83 

68 

26 

92.72 

500  -  TOO 

72^/ 

31 

56 

73.8ii 

8-c-o-w 

29 

52 

63-73 

9-C-B-W-Cl  , 

10-c-o-ci-wy 

11-C-C-B-W£/ 

i2-c-B-o£/w£/ 
l3-c-c-o£/w£/ 

93^/ 

33 

29 

l.OU 

76. U5 

M-19 

87 

37 

61 

1.51 

69.20 

100  -  Uoo 

86 

78 

3^ 

27 

95.79 

85 

33 

32 

63 

79.05 

83 

76 

33 

61 

85.33 

a/  All  plo 

ts  treated  uniform 

ly  with 

limestone 

,  phosphate , 

and  potash. 

The  average 

organic  matter  content  is  5.5  percent, 
b/  Rotations  1  and  2  significantly  higher  than  3  and  h.        Rotation  8  significantly 

lower  than  5,  6,  and  7.   Rotation  9  significantly  higher  than  10,  11,  12,  andl3. 
c/  Green  manure  catch  crop. 


-2- 


legianes  have  been  superior  to  those 
without  catch  crops .  In  no  case  where 
second-year  corn  occurs  did  the  system 
maintain  as  high  a  yield  for  second-year 
corn  as  for  first.  Whether  this  was  due 
entirely  to  nutrient  supply  or  physical 
breakdown  has  not  been  determined.  Soy- 
beans have  not  been  significantly  af- 
fected by  sequences. 

Clover  seems  to  be  the  best  crop  to  pre- 
cede wheat,  and  corn  the  poorest.  Oats 
and  soybeans  are  intermediate.  What,  if 
any,  treatment  practice  might  improve 
this  relationship  has  not  been  deter- 
mined. Oats  have  fared  better  with  each 
additional  crop  added  to  the  sequence. 

Hay  production  on  the  plots  has  been 
poor  because  of  the  hazards  associated 
with  isolated  production  on  small  areas. 
This  seemingly  has  interfered  with  real- 
izing benefits  that  would  normally  be 
expected. 


Organic  matter  and  aggregate  stability 
are  physical  properties  of  soil  that  can 
be  measured  as  an  effect  of  crop  produc- 
tion. Preliminary  studies  of  these 
properties  indicate  that  the  soil  is 
naturally  high  in  organic  matter  (aver- 
age 5-5  percent),  and  during  the  short 
period  of  this  experiment  this  level  has 
not  been  changed  by  the  cropping  systems 
used.  Aggregate  stability  findings  thus 
far  indicate  that  standover  legumes  have 
been  significantly  better  in  maintaining 
stability  than  catch-crop  legumes  and 
that  likewise  catch-crop  systems  are  su- 
perior to  no  catch  crop. 

Annual  cin-rent  crop  prices,  averaged  for 
the  years  19^8-51  inclusive  in  the  last 
column  of  Table  1,  show  the  gross  annual 
acre  returns  for  each  system.  When 
these  fig\ires  are  compared  with  those  of 
first-year  corn,  the  conflict  between 
cash  income  and  soil  productivity  main- 
tenance is  evident. 


Table  2. --Effect  of  Various  Forage  Crops  and 
Hay  Removal  on  Crop  Yields 


Area 


Forage 


No.  of  hay 
crops  removed 


Corn 


Oats 


Wheat 


Hay 


M-9 

Red  clover 

0 

Red  clover 

1 

Series 

Red  clover 

2 

100  - 

Alfalfa 

2 

1+00 

Sweet  clover 

0 

Timothy 

1 

bu, 

93 
89 
87 

89 

76^/ 


bu. 


bu. 


tons 


70 

3h 

•  •  •  • 

66 

32 

1.37 

68 

31 

2.ii8 

6h 

3i^ 

1.87 

6k 

33 

•  •  •  • 

58 

28 

1.17 

a/  Significantly  lower  than  other  yields. 


Studies  comparing  various  forage  crops 
and  the  management  of  the  growth  are 
given  in  Table  2. 

Corn  following  timothy  (a  grass  crop)  is 
significantly  lower  in  yield  than  corn 
following  legumes. 

In  this  study  there  has  been  no  signif- 
icant difference  between  red  clover,  al- 
falfa, and  sweet  clover  as  standover 


legume  crops.  Likewise,  there  has  been 
no  significant  difference  whether  no, 
one,  or  two  crops  of  red  clover  have 
been  removed.  However,  the  trend  of  all 
crops  favors  plowing  all  the  growth 
down.  In  time  this  difference  may  be- 
come greater.  It  is  also  reasonable 
that  there  woxold  be  greater  differences 
on  soils  of  lower  native  productivity 
and  organic  matter  than  on  the  better 
soils. 


A. 


L.  Lang 
2-I5-5I+ 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-19 


THE  NATURE  OF  RESERVE  AND  ACTIVE  SOIL  ACIL.ITY 

Soil  acidity  is  due  to  exchangeable  hydrogen  on  soil  colloidal  surfaces  (SF~l). 
In  crop  production  two  types  of  acidity  are  of  practical  interest ,  namely,  reserve 
and  active  acidity.  An  important  difference  between  reserve  and  active  acidity 
lies  in  the  location  of  the  acid -producing  hydrogens.  This  difference  is  illus- 
trated in  Diagram  A. 


H   H 


H 


(a)    H  I  Soil  Colloid  |  H 
H   H   H 


—  H'*'  (in  solution) 


Exchangeable  H 
(Reserve  acidity) 


Hydrogen- ion 
(Active  acidity) 


The  rather  firmly  held  exchangeable,  hydrogen  on  colloidal  surfaces  represents 
the  reserve  soil  acidity.  Note  that  for  each  active  H-ion  in  solution  there  are 
numerous  reserve  exchangeable  hydrogens  still  attached  to  the  surface,  and  the 
reserve  hydrogen  and  active  hydrogen  tend  to  be  in  equilibrium.  The  lime  re- 
quirement of  a  soil  quantitatively  indicates  its  reserve  acidity. 

The  ionization  of  exchangeable  hydrogen  gives  rise  to  free  hydrogen  ions  in  the 
solutions  bathing  the  colloidal  surfaces.  The  free  hydrogen  ions  represent  ac- 
tive acidity.  The  concentration  of  active  acidity  or  free  hydrogen  ions  in  so- 
lution is  universally  expressed  in  pH  units.  Microbiological  activity,  plant 
nutrient  availability,  rock  phosphate  solubility,  and  numerous  other  factors  af- 
fecting plant  growth  are  closely  related  to  the  free,  active  hydrogen-ion  con- 
centration or  pH  of  soils. 

Pure  water  has  a  pH  of  7-  This  value  represents  neutrality.  A  pH  of  less  than 
7  is  in  the  acidic  range.  A  pH  greater  than  7  is  in  the  alkaline  range.  The  pH 
range  for  soils  may  vary  from  about  h  to  10.  If  the  acidity  of  a  soil  is  less 
than  U,  it  is  quite  probable  that  a  free,  strong  acid,  for  example,  sulfxxric,  is 
present.  The  low  pH  values  (2.3-2.5)  found  on  strip-mine  spoils  and  near  smelters 
is  due  to  free  sulfuric  acid  or  iron  and  aluminum  sulphate  produced  by  the  acid. 

Soils  containing  considerable  amounts  of  free  excess  calcium  carbonate  or  ex- 
changeable sodium  (shelly  spots,  marl,  slick  spots)  have  pH  values  of  about  7-5- 
8.0.  Very  strongly  alkaline  soils  (pH  9  to  10)  usually  contain  sodium  carbonate 
or  very  large  amounts  of  exchangeable  sodium.  These  general  relations  are  dia- 
grammatically  illustrated  below. 


il.O   i|.5   5-0 


pH  range  of  soils 

Illinois  soils  

5.5   6.0   6.5   7-0 


7-5  8.0 


9.0 


10.0 


Excess          Excess  Na2C03 
$9:^03 — Exchangeable  Na ^ 


Acidic 


-f>  Neutral 


Alkaline 


-2- 

Exchangeable  calcium,  magnesium,  potassium,  and  sodium  are  also  present  on  soil 
colloidal  surfaces.  These  elements  impart  alkalinity,  in  contrast  to  exchange- 
able hydrogen,  VThich  imparts  acidity.   This  is  illustrated  below  in  Diagram  B. 


(B) 


Mg   Mg   Ca 


Na 


Soil  Colloid  I  K 


K 


Ca   Ca 


Ca 


H   H   H   H 


H  j  Soil  Colloid   H 


H   H 


(Neutral  to  alkaline - 
base  saturated) 


(Acidic) 


The  total  number  of  reactive  spots  on  the  soil  colloidal  surface  where  exchange- 
able calcium,  magnesium,  potassitim,  sodium,  and  hydrogen  cations  can  be  held  is 
more  or  less  constant  for  a  given  soil.  The  capacity  of  soils  to  retain  ex- 
changeable cations  (Ca,  Mg,  K,  H,  and  Na)   is  termed  cation  exchange  capacity. 

The  cation  exchange  capacity,  however,  can  vary  for  different  soils  depending 
upon  their  humus  and  clay  content  and  the  type  of  clay  present.  Thus  sandy  soils, 
because  of  their  lower  clay  and  humus,  have  fewer  reactive  spots  where  exchange- 
able cation  can  be  held  and,  accordingly,  lower  cation  exchange  capacities  than 
heavy-textured  soils. 

The  average  soil  has  exchangeable  Ca,  Mg,  K,  and  H  absorbed  on  its  colloidal  sur- 
faces. From  Diagram  B  it  is  obvious  that  their  effects  on  soil  acidity  are  dif- 
ferent. It  is  the  ratio  of  the  sum  of  the  exchangeable  bases  to  exchangeable 
hydrogen,  therefore,  rather  than  the  total  amount  of  exchangeable  hydrogen,  that 
determines  the  pHof  soils.  This  principle  can  be  illustrated  by  considering  the 
examples  of  Soils  A  and  B  illustrated  below: 


Soil  A 


j 
X 

Total  cation 

Exch. 
H   (lA) 

.     Exch.     ^ 
,    Bases      , 

V///A 

Soil  B 

o 

Exch. 

H  riA) 

o 

Exch.     / 
Bases 
C(3A)    . 

The  exchange  capacity  of  A  is  twice  that  of  B. 
The  ratio  of  exchangeable  hydrogen  to  exchange- 
able bases,  however,  is  identical  for  both  A  and 
B,  namely,  l/i+  hydrogen  and  3/^  bases.  The  per- 
cent of  the  cation  exchange  capacity  or  react- 
ing spots  satisfied  by  exchangeable  bases,  or 
the  degree  of  base  saturation,  is  identical  for 
both  A  and  B.  Soils  A  and  B  therefore  have 
identical  pH  values,  since  the  pH  of  a  soil  is 
more  or  less  dependent  on  the  degree  of  satura- 
tion. The  approximate  relation  of  degree  of 
base  saturation  to  pH  values  for  Illinois  soils 
is  given  in  the  following  table: 


pH  5-5   pH  5-5 


Percent  of  base 
saturation 


Corresponding  pH 


95 

6.5-7-0 

90-95 

6.2-6.U 

85-90 

5.8-6.1 

75-85 

5.7-5.^ 

50-75 

5.3-i^.8 

25-50 

i+.7-^.2 

<25 

U.O 

-3- 

In  the  preceding  diagram,  the  active  acidity,  or  pH,  of  Soils  A  and  B  was  iden- 
tical because  of  similar  degrees  of  saturation.  Note,  hovever,  from  the  thick- 
ness of  the  bar  (Exch.  H)  that  the  reserve  acidity  of  Soil  A  is  twice  that  of 
Soil  B.  Lime  reduces  the  reserve  acidity.  Since  the  reserve  acidity  of  A  is 
twice  that  of  B,  Soil  A  will  need  to  have  twice  as  much  lime  applied  to  it  as 
Soil  B  will  in  order  to  get  a  similar  shift  in  pH  values.  Differences  in  base 
exchange  capacity  and  reserve  acidity  are  the  reasons  why  more  lime  is  needed  to 
correct  acidity  on  heavy-textured  soils  than  on  sandy  soils. 


When  lime  is  added  to  soils,  the  reserve  exchangeable  hydrogens  are  replaced  by 
calciian.  The  degree  of  satioration,  or  the  ratio  of  the  exchangeable  bases  to  ex- 
changeable hydrogen,  is  increased  and  the  soil  pH  shifts  in  the  direction  of 
neutrality.   This  process  is  diagrammatically  illustrated  below: 


75^0  Base 


Saturation  pExch., 


pH  5.5 


CaC03 


95'?^  Base  Saturation 


pH  7.0 


+  CO2  +  H20 


An  effective  neutralizing  agent  not  only  must  replace  the  exchangeable  hydrogen 
on  soil  surfaces,  but  must  also  deactivate  the  replaced  hydrogen  ion,  converting 
it  to  a  relatively  inert  product  which  on  ionization  gives  fewer  hydrogen  ions  than 
previously  existed  on  the  soil  surfaces.  This  requisite  is  fulfilled  in  the  pre- 
ceding diagram,  where  the  exchangeable  hydrogen,  through  reaction  with  lime,  gives 
rise  to  a  neutral  product --water. 

Such  substances  as  gypsum  ( CaSOl| . 2H2O )  supply  calcivm  but  will  not  neutralize 
soil  acidity  because  the  replaceable  hydrogen  is  not  converted  to  an  inert  or 
neutral  product.  This  process  is  illustrated  below: 


_H H 


H 


Ca 


Soil  Colloid 
H   H   H 


i  +  3  CaSOli    — ^ 


Soil  Colloid   ■  Ca  +  SHgSOi^ 


Ca 


In  the  above  illustration  the  exchangeable  hydrogen  is  replaced  and  forms  sulfu- 
ric acid.  The  sulfuric  acid  produced  in  this  reaction  is  a  much  stronger  acid 
than  the  acid  produced  when  the  hydrogen  exists  in  exchange  form  on  the  soil  col- 
loidal surfaces.  Any  tendency  for  the  reaction  to  move  toward  the  right,  in  the 
direction  of  neutrality,  is  immediately  counteracted  by  the  strong  production  of 
sulfuric  acid,  which  drives  the  reaction  back  to  the  left,  or  its  original  state. 
The  result  is  that  no  neutralization  can  occur  because  no  permanent  shift  in  de- 
gree of  saturation  is  possible. 


To  summarize:  The  soil  colloidal  fraction  is  the  seat  of  permanent  soil  acidity. 
The  primary  difference  between  reserve  and  active  acidity  lies  in  the  location 
of  the  acid-producing  hydrogens.  The  lime  requirement  is  a  measure  of  reserve 
acidity.  The  concentration  of  active  acidity  is  reported  as  pH.  Liming  controls 
active  acidity,  as  the  lime  that  is  added  causes  shifts  in  the  degree  of  satura- 
tion. Only  those  substances  that  react  with  soils  to  effect  real  changes  in  de- 
gree of  saturation  are  suitable  for  liming  purposes. 

Edward  H.  Tyner 
2-22-5^^ 


k 


' 

y 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-20 


THE  MINOR  ELEMENT  PROBLEM  IN  ILLINOIS  SOILS 


The  minor  or  trace  elements  boron,  cop- 
per, zinc,  manganese,  iron,  and  molyb- 
denum are  all  needed  for  plant  growth. 
Calcium,  magnesium,  and  sulfur,  while 
usually  regarded  as  major  elements,  are 
also  essential  to  plant  growth  and  will 
therefore  be  included  here.  Cobalt,  a 
nutrient  required  for  animal  growth, 
will  also  be  considered. 

Information  on  the  minor  or  trace  ele- 
ments in  Illinois  soils  is  somewhat  in- 
complete, but  certain  general  facts  are 
known.  A  summary  of  this  information  is 
presented  briefly  here. 

Boron.  Illinois  soils,  generally  speak- 
ing, are  all  low  in  boron  (see  SF-12). 
This  deficiency  is  most  noticeable  in 
alfalfa  and  clovers  and  has  been  observed 
in  all  of  the  major  soil  types  of  the 
state.  Boron  is  usually  recommended  for 
all  new  legume  seedings.  Boron  defi- 
ciencies have  never  been  observed  in  any 
of  the  grain  crops  in  Illinois. 

Copper.  There  are  no  known  areas  in  Il- 
linois where  the  soils  are  deficient  in 
copper  for  agronomic  crops.  Analyses 
show  that  most  of  the  soils  in  the  state 
contain  from  10  to  20  pounds  of  available 
copper  per  acre.  On  none  of  the  major 
soil  types  where  copper  fertilizers  have 
been  used  have  yields  of  agronomic  crops 
increased  because  of  the  treatments. 

Zinc.  Like  copper,  no  areas  of  zinc- 
deficient  soils  for  agronomic  crops  have 
yet  been  found  in  Illinois.  Our  soils 
seem  to  be  high  in  this  element,  usually 
containing  from  10  to  30  pounds  of  avail- 
able zinc  per  acre.  Where  zinc  fertili- 
zers have  been  used,   none  of  the  major 


soil  types  of  the  state  have  shown  yield 
increases  in  agronomic  crops  for  such 
treatments. 

Manganese.  The  only  part  of  the  state 
where  manganese  may  be  deficient  is  in 
the  Kankakee  sand  area.  However,  no  man- 
ganese deficiencies  in  agronomic  crops 
have  been  observed  in  this  area,  and 
crops  have  not  responded  to  manganese 
fertilizers.  In  many  areas,  especially 
in  the  older  and  more  weathered  soils  of 
the  southern  half  of  the  state,  manganese 
is  actually  present  in  quantities  high 
enough  (200  pounds  of  available  Mn  per 
acre)  to  be  toxic  to  agronomic  crops. 
Liming  such  soils  usually  reduces  the 
amount  of  available  manganese  to  such  ex- 
tent that  toxic  conditions  no  longer 
exist. 

Iron.  Iron  is  not  deficient  for  agro- 
nomic crops  in  any  Illinois  soil. 

Molybdenum.  Preliminary  surveys  have 
not  shown  any  indications  of  molybdenum 
deficiencies  for  agronomic  crops  grown 
on  any  major  soil  type. 

Cobalt.  Cobalt  is  not  known  to  be  essen- 
tial for  plant  growth.  Therefore  no 
cobalt-deficient  areas  exist  so  far  as 
the  production  of  agronomic  crops  is  con- 
cerned. Chemical  analyses  of  agronomic 
plants  grown  on  Illinois  soils,  however, 
show  that  the  cobalt  level  is  approach- 
ing the  critical  minimum  usually  assumed 
to  be  required  in  plants  for  animal 
needs.  Therefore,  a  cobalt  deficiency 
m  livestock  is  not  impossible  under  Il- 
linois conditions. 


-2- 


Mlnor  Element  Fertilizer  Recommendations 

Minor  element  fertilizers,  with  the  ex- 
ception of  borax,  are  not  recommended 
for  Illinois  soils  for  the  production  of 
agronomic  crops . 

Calcium.  Calcium  deficiencies  have  been 
found  in  southern  Illinois  on  the  older 
weathered  soils.  When  soils  are  limed 
for  agronomic  crops,  no  soil  in  Illinois 
will  be  deficient  in  calcium. 

Magnesium.  Magnesium  deficiencies  have 
been  observed  in  the  Kankakee  sand  area 
and  in  southern  Illinois  on  the  older 
weathered  soils.  Deficiencies  may  be  ex- 
pected to  occur  in  the  sand  areas  and 


I 


the  older  soils  of  the  state.  Need  for 
magnesium  fertilizer  can  be  determined 
by  testing.  Test  your  soils  before  buy- 
ing magnesium  fertilizers.  The  use  of 
some  dolomitic  limestone  in  the  regular 
liming  program  is  recommended  for  south- 
ern Illinois  and  the  sand  areas  of  the 
state . 

Sulfur.  Soils  deficient  in  sulfur  for 
agronomic  crops  have  not  been  found  in 
Illinois.  Usually  normal  rainfall,  as 
well  as  commercial  fertilizers,  contain 
more  sulfur  than  is  required  for  agro- 
nomic crops. 


S.   W. 


Me  Is ted 


AGI 


Dix 
Ear 
Jol 
Jew 
Lei! 
iHcS 
in 
Xt, 


Jolj 
Jevs 

liinc 

ft. 

Av 


itcv 


p. 
1 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-21 


CORN  YIELDS  -  ILLINOIS  SOIL  EXPERIMENT  FIELDS 

8- Year  Average,  19^^6-1953 


Field  location 

,    1 
Rotationl/    0 

2   3     ^ 
M    ML    MLP 

0 

R 

7 
RL 

b 
RLP 

9 

Town       County 

RLFK 

Dark-colored  soils 

-  first-year  corn 

bu. 

bu. 

bu. 

bu. 

bu. 

bu. 

bu. 

bu. 

bu- 

Aledo 

Mercer 

C-C-O-H 

78 

96 

102 

105 

52 

58 

77 

78 

80 

Carlinville 

Macoupin 

C-B-W-H 

49 

81 

100 

102 

55 

58 

80 

88 

101 

Carthage 

Hancock 

C-B-W-H 

6Q 

92 

100 

100 

Ik 

81 

98 

9k 

100 

Clayton 

Ar)a,m.s 

C-B-O-H 

53 

80 

88 

91 

kl 

57 

73 

83 

86 

Dixon 

Lee 

C-O-Cl-W 

58 

9h 

103 

105 

63 

7^^ 

87 

91 

100 

Hartsburg 

Logan 

C-C-O-H 

76 

98 

101 

99 

56 

78 

90 

93 

90 

Joliet   . 
Kewanee^,/ 

Will 

C-B-C-0-W-H 

kl 

60 

65 

79 

U3 

^+7 

56 

81 

86 

Henry 

C-C-O-H 

60 

77 

86 

92 

71 

79 

93 

95 

97 

Lebanon 

St.  Clair 

C-B-W-H 

36 

92 

lOU 

107 

kl 

52 

91 

91 

100 

McNabb 

Putnam 

C-C-O-H 

97 

112 

110 

112 

50 

101 

105 

106 

•  •  • 

Minonk 

Mt.  Morris^/ 

Woodford 

C-C-O-H 

87 

95 

95 

96 

57 

78 

82 

88 

87 

Ogle 

C-C-O-H 

6k 

86 

98 

97 

58 

69 

95 

99 

102 

Average 

5ir 

B9 

"9^ 

99 

5^ 

69 

86 

91 

3^ 

] 

Dark-colored  soils 

-  se 

cond-year  corn 

Aledo 

Mercer 

C-C-O-H 

73 

96 

102 

99 

57 

59 

65 

72 

73 

Hartsburg 

Logan 

C-C-O-H 

73 

98 

99 

98 

9^ 

65 

69 

72 

72 

Joliet 

Will 

C-B-C-0-W-H 

36 

65 

72 

77 

35 

39 

1+8 

62 

73 

Kewanee 

Henry 

C-C-O-H 

61 

86 

95 

95 

•  • 

.  , 

«  • 

*  • 

•  • 

McNabb 

Putnam 

C-C-O-H 

78 

107 

108 

111 

53 

90 

82 

91 

•  • 

Minonk 

Woodford 

C-C-O-H 

7U 

88 

85 

83 

52 

59 

60 

Gk 

GG 

Mt.  Morris 

Ogle 

C-C-O-H 

53 

97 

105 

101 

•  • 

•  • 

•  • 

•  • 

.  , 

Average 

m 

91 

95 

95 

50 

62 

65 

72 

71 

Light-colored  soils 

-  prairie 

Browns town 

Fayette 

C-B-W-H 

lh 

1+6 

67 

•  • 

29 

33 

1^7 

5^+ 

73 

Ewing 

Franklin 

C-B-W-H 

11 

39 

61+ 

66 

18 

29 

38 

k-i 

78 

Newton 

Jasper 

C-B-W-H 

6 

31 

75 

80 

15 

18 

kZ 

kl 

61+ 

Oblong 

Crawford 

C-B-W-H 

21 

50 

81+ 

88 

27 

3*+ 

58 

61 

92 

Toledo 

Cumberland 

C-B-W-H 

15 

52 

75 

Ik 

16 

23 

1+1 

37 

81 

Average 

15 

UU 

73 

11 

21 

27 

^5 

^ 

7B 

l/  The  rotation  on  plots  5-9  is  C-C-O-W  at  Aledo,  Hartsbxjrg,  McNabb  and  Minonk;  at 

Kewanee  and  Mt.  Morris  these  plots  have  a  C-O-W-H  rotation. 
2/  Yields  are  l+-year  averages  (1950-1953)  because  of  recent  rotation  change. 


(Continued  on  other  side) 


-2- 


8-Year  Average,  19^6-1953  (Cont. ) 


Field  location 

1    2 
Rotation     0    M 

3   k 
ML   MLP 

5 
0 

6 
R 

7 
RL 

8 
RLP 

9 

Tovm        Coimty 

RLPK 

Lisht -colored  soils  - 

timber 

Enfield 

White 

C-03/-W-H 

Raleigh 

Saline 

C-O-H-W 

Sparta 

Randolph 

C-03/-W-H 

Average 

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


56  Ik  iB  37  i^l  58 

50  Ik  18  38  ko  59 

63  ^  _8  J+0  37  65 

5^  10  15  3B  39  ^ 


10 

35 

57 

7 

26 

52 

8 

21 

62 

8 

27 

57 

Hilly  land  - 

southern  Illinois 

Elizabethtown 

Hardin 

C-03/-H-W 

..   39   55   58 

13 

Ik 

ko 

k9 

57 

Sandy  land  - 

western  Illinois 

Oquawka 

Henderson 

C-B-W-H 

51   65  6k 

37 

k3 

52 

52 

62 

3/  Winter  oats 

The  reported  corn  yields  are  for  the  8 
years  from  19^+6  to  1953  on  variously 
treated  plots  on  22  Illinois  soil  ex- 
periment fields  well  distributed  over 
the  state. 

The  indicated  crop  rotations  are  in  use 
at  the  present  time.  On  most  of  the 
older  fields  the  cropping  system  has  been 
changed  at  least  once  since  the  fields 
were  established. 

Soil  treatment  in  the  livestock  system 
(plots  l-**)  includes  barnyard  manure  (m) 
used  alone,  with  limestone  (ML),  and  with 
limestone  and  phosphate  (MLP).  In  the 
grain  system  (plots  5-9)  crop  residues 
(r)  are  used  alone;  with  limestone  (RL); 
with  limestone  and  phosphate  (RLP);  and 
with  limestone,  phosphate,  and  potash 
(RLPK).  a  check  or  untreated  plot  is  in- 
cluded in  each  system.  On  several  of  the 
fields  the  rotation  used  in  the  grain 
system  is  different  from  that  used  in  the 
livestock  system,  as  shown  in  footnote  1. 


A  detailed  explanation  of  the  treatments 
and  rotations  and  a  description  of  the 
soil  types  will  be  found  in  Illinois 
Bulletin  516,  "Effect  of  Soil  Treatment 
on  Soil  Productivity. " 


These  average  yields  were  produced  with 
bulk  applications  of  limestone,  rock 
phosphate,  and  muriate  of  potash  (on  re- 
spective plots)  lised  in  the  rotations  as 
described.  On  many  of  the  fields  addi- 
tional tests  have  been  made  with  starter 
fertilizers,  superphosphate,  mixed  fer- 
tilizers, and  nitrogen  used  in  various 
ways.  Mimeographed  pamphlets  are  avail- 
able for  each  field  giving  yields  and 
values  of  all  crops  and  amovuat  and  costs 
of  soil  treatments  under  several  systems 
of  management. 


Soil  Experiment  Field  Staff 

L.  B.  Miller 

3-8- 5U 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-22 


WIDE-ROW  SPACING  OF  CORN 


One  possibility  of  planting  corn  in  wide 
rows  is  to  ase-  the  corn  as  a  nurse  crop 
for  legumes  or  grasses  in  establishing 
pastures  or  atand-over  sods.  Trials 
with  wide-row  spacings  of  corn  without 
sod  seetiings  have  been  carried  out  by- 
several  experiment  stations.  But  very 
little  work  has  been  done  on  the  cultural 
practices  required  for  legume  and  grass 
seedings  when  corn  is  used  as  the  nurse 
crop.  The  practice  of  using  corn  in 
wide  rows  as  a  nurse  crop  is  new;  and 
the  available  information  is  therefore 
fragmentary. 

Trials  show  that  spacing  corn  in  rows  up 
to  60  inches  with  constant  seeding  rates 
does  not  materially  affect  yield.  As 
the  width  between  rows  increases;  how- 
ever ,  the  number  of  stalks  in  the  row 
must  increase.  Generally,  when  corn  is 
seeded  in  80-inch  rows  yield  has  de- 
creased slightly. 

Preliminary  trials  with  corn  as  a  nurse 
crop  show  that  the  stands  of  legumes  or 
grasses  improve  progressively  as  the  corn 
row  spacings  are  increased  from  kO  to  80 
inches.  The  wider  spacings,  60  to  80 
inches,  permit  small  tractors  and  equip- 
ment to  operate  between  the  rows  to  pre- 
pare seedbeds  and  seed  the  legume  or 
grass  crops.  With  proper  seedbed  prepa- 
ration good  stands  of  legumes  and  grasses 
have  been  obtained.  The  best  legume  and 
grass  stands  have  usually  come  from 
spring  plantings.  Eye  or  ryegrass  is 
usually  seeded  in  early  September,  when 
only  late  fall  and  early  spring  pastures 
are  desired  or  when  the  primary  objective 
of  the  grass  seeding  is  to  control  ero- 
sion. 


Corn  seeded  in  6O-  to  80-inch  rows  has 
several  advantages  over  the  small  grains 
as  a  nurse  crop: 

1.  Corn  is  worth  more  than  the  small 
grains . 

2.  The  legume  or  grass  sods  act  as  a 
cover  crop  for  the  corn  and  there- 
fore help  to  control  erosion  in  the 
cornfields . 

5.  When  small  grains  are  used,  the  heavy 
straw  residues  from  the  grain  har- 
vest may  smother  the  legume  or  grass. 

k.  Heavy  fertilization  of  the  ^nurae 
crop  will  not  retard  the  legume  or 
grass  stands. 

5.  With  corn  as  the  nurse  crop,  the 
farmer  can  carry  on  an  intensive 
corn- legume-livestock  rotation  on  his 
farm. 

There  are  also  several  disadvantages  to 
using  corn  as  a  nurse  crop  for  legumes 
or  grasses  at  this  time: 

1.  Small  or  special  equipment  i a  needed 
to  seed  legumes  or  grasses  in  the 
60  to  80  inches  between  the  corn 
rows . 

2.  Conventional  two-row  i|0-inch  equip- 
ment cannot  be  used  to  plant  or  har- 
vest the  corn  crop. 

3.  The  thick  cornstalk  population  in 
the  wide  rows  makes  picking  diffi- 
cult. 


(Continued  on  other  side) 


h.  There  will  be  narrow  banda  of  bare 
soil  in  the  legume  or  grass  stands 
where  the  corn  rows  were  the  year 
before . 

5.  More  work  is  required  to  seed  the 
legume  or  grass  in  the  established 
corn. 

6.  Corn  yields  will  be  reduced  to  some 
extent;  but  probably  not  so  much  as 
the  yield  of  the  small  grain  nurse 
crop  ia  now  reduced  to  keep  it  from 
smothering  the  sod  crop. 

Most  of  these  disadvantages  are  associ- 
ated with  adapting  present  equipment  to 
60  or  80  rows  for  corn.  If  the  practice 
of  using  corn  as  a  nurse  crop  proves 
practical,  farm  equipment  companies  will 
soon  develop  the  equipment  necessary  to 
do  the  work . 

Success  in  using  corn  as  a  nurse  crop 
will  depend  largely  on  proper  management 
and  adequate  fertilization,   especially 


with  nitrogen.  The  quality  of  the  legume 
or  grass  stands  will  vary  with  seasons, 
but  it  will  also  be  affected  by  time  of 
planting  and  seedbed  preparation.  V/eeds 
in  the  corn  rows  will  still  have  to  be 
controlled. 

There  does  not  seem  to  be  any  good  rea- 
son why  corn  spaced  in  6O-  to  80-lnch 
rows  should  not  make  a  satisfactory 
nurse  crop  for  legumes  or  grasses .  Whether 
a  farmer  elects  to  use  it  in  this  way 
will  depend  largely  on  the  type  and  size 
of  his  farm  equipment  and  on  his  economic 
situation.  If  the  increased  value  of 
the  corn  nurse  crop  will  offset  the  in- 
creased labor  and  reduced  sod  stands, 
then  the  practice  should  prove  profit- 
able. In  many  instances,  however,  using 
wide  rows  and  sod  aeedings  in  corn  can 
be  justified  solely  on  the  basis  of  its 
value  in  controlling  soil  erosion. 


I 


S.  W, 


Me  Is ted 
3-15-5^ 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-23 


NITROGEN  IS  THE  KEY  TO  GOOD  ORGANIC  MATTER  USE 


Soil  organic  matter  is  replenished  by 
the  aae  of  green  manures  and  crop  resi- 
^naa.  This  recharging  of  organic  matter 
is  important  for  several  reasons.  In 
the  first  place,  the  tilth  of  the  soil 
is  related  directly  to  the  amount  and 
kind  of  organic  substances  that  are  sup- 
plied. Second,  plant  nutrients  are  re- 
turned to  the  soil  and,  if  the  crop  is 
a  nodulated  legume,  nitrogen  may  also  be 
added.  Third,  the  availability  of  nu- 
trients already  present  in  the  soil  may 
be  increased  or  decreased,  depending  on 
the  nature  of  the  organic  matter  that  is 
added. 

All  of  these  results  are  affected  by  mi- 
crobial activity  in  the  soil,  and  micro- 
bial activity  is  in  turn  affected  by 
both  amount  and  kind  of  organic  material. 
Within  certain  limits,  the  greater  the 
amount  of  organic  matter,  the  greater  the 
microbial  activity.  Even  more  important, 
however,  is  the  nitrogen  content  of  the 
organic  materials  that  are  added. 


This  experiment  was  conducted  in  the 
laboratory  under  conditions  favorable 
for  nitrate  formation.  These  exact  fig- 
ures will  not  apply  to  field  soils,  but 
the  principles  are  the  same. 

The  significant  point  here  is  the  amount 
of  nitrogen  supplied  in  the  organic  mat- 
ter, and  not  the  sources  from  which  it 
comes,  because  they  were  selected  for 
their  nitrogen  content.  In  providing 
nitrogen,  the  stage  of  growth  of  the 
plant  may  be  more  important  than  the 
kind  of  plant  that  is  used.  In  general, 
mature  residues,  both  leguminous  and 
nonleguminous,  are  lower  in  nitrogen  than 
are  young  succulent  materials.  Thus  it 
is  possible  for  very  young  bluegrass  to 
have  a  higher  nitrogen  content  than  ma- 
ture leguminous  crops. 

Two  processes  occur  continuously  when 
soil  moisture  and  temperature  are  favor- 
able for  the  activity  of  microorganisms : 


The  following  data  show  how  the  nitrogen 
content  of  organic  matter  supplied  by 
various  green  manures  affects  one  kind 
of  microbial  activity,  nitrate  formation. 
In  general,  the  higher  the  percentage  of 
nitrogen  in  the  added  organic  matter, 
the  greater  the  nitrate  e.ccumulation. 


1.  Nitrogen  is  released  from  both  ap- 
plied and  native  organic  matter. 

2.  Nitrogen  is  assimilated  by  micro- 
organisms and  becomes  a  part  of  their 
protein  and  protein-like  cell  com- 
ponents . 


Effect  of  Nitrogen  Content  of  Green  Manures  on 
Nitrate  Nitrogen  Accumulation 


Green 

Nitrogen 

Nitrate 

nitrogen 

manures 

After  2  weeks 

After  6  weeks 

pet. 

lb. /A 

lb. /A 

None 

•  •  • 

27 

27 

Timothy 

1.1 

6 

19 

Bluegrass 

1.8 

28 

h9 

Oat  hay 

2.2 

50 

75 

Eed  clover 

2.8 

h3 

98 

Sweet  clover 

5.3 

71 

275 

(Continued  on  other  aide) 


(Continued  from  other  aide) 


The  result  of  these  interactlona  may  be 
determined  by  the  accumulation  of  ni- 
trates in  the  soil. 

When  organic  matter  with  a  nitrogen  con- 
tent much  below  2  percent  is  added  to 
the  soil,  the  organisms  use  all  of  the 
nitrogen  and  none  of  it  is  released  to 
form  nitrates.  In  fact,  nitrate  in  the 
soil  itself  is  also  built  into  microbial 
tissue.  The  data  show  that  the  nitrate 
content  of  soil  receiving  organic  mate- 
rial containing  1.1  percent  of  nitrogen 
(timothy)  was  less  than  that  of  soil  to 
which  no  organic  matter  was  applied. 

As  the  nitrogen  content  of  the  added  or- 
ganic matter  increases,  the  accumulation 
of  nitrates  increases. 

It  is  obvious,  then,  that  plowing  under 
organic  matter  with  a  low  nitrogen  con- 
tent will  decrease  the  amount  of  nitro- 
gen available  immediately  to  the  crop. 


This  effect  may  be  desirable  or  undesir- 
able, depending  on  the  objectives  to  be 
attained. 

If  a  nonleguminous  crop  is  to  be  seeded 
soon  after  plowing,  a  nitrogen  deficien- 
cy may  decrease  yields  if  no  nitrogen 
fertilizer  is  applied.  If,  on  the  other 
hand,  no  crop  is  to  be  grown  or  if  a 
leguminous  crop  is  to  be  used,  the  de- 
crease in  nitrates  may  be  desirable. 

The  benefits  derived  from  applied  organic 
matter  depend  largely  on  its  decomposi- 
tion, and  not  merely  on  its  presence  in 
the  soil.  The  most  favorable  over-all 
effects  will  be  secured  when  leguminous 
green  manures,  young  succulent  nonlegu- 
minous crops,  or  supplementary  nitrog- 
enous fertilizers  together  with  residues 
that  are  low  in  nitrogen,  are  added  to 
the  soil. 

0.  H.  Sears 
5-29-5^ 


1 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


5F-24 


SOIL  REACTION  PREFERENCES  OF  CROPS 


Crops  vary  considerably  in  their  ability 
to  produce  satisfactorily  at  different 
soil  reactions.  The  yardstick  used  to 
measure  the  reaction  preferences  of  plants 
is  the  soil  pH.  Active  soil  acidity,  or 
its  concentration  as  indicated  by  pH,  is 
therefore  important  in  determining  the 
ability  of  a  soil  to  produce  any  crop. 

The  hydrogen  ion  itself  is  not  toxic  to 
plants  within  the  normal  pH  range  of 
soils.  Alfalfa,  a  very  acid-sensitive 
crop,  for  example,  will  grow  well  at  pH 
h  in  solution  greenhouse  cultures  pro- 
vided all  the  essential  nutrients  are 
ample.  Yet  this  crop  will  not  grow  on 
soils  at  pH  U.  Differences  in  soil  re- 
action preferences  must  therefore  be  due 
to  variable  plant  tolerance  to  secondary 
factors  induced  at  different  pH  levels. 

The  following  are  the  principal  secondary 
factors  that  might  affect  plant  growth 
at  different  soil  reaction  levels. 

Lov-calcium  and  phosphate  availability 
on  acid  soils.  Crops  vary  in  their  cal- 
cium and  phosphorus  requirements  and  in 
their  ability  to  extract  these  elements 
from  the  available  soil  forms.  The  pH 
of  soils  is  related  to  the  degree  of  base 
saturation  (SF-19).  Calcium  is  usually 
the  dominant  replaceable  basic  cation  in 
soils.  It  follows,  therefore,  that  on 
acid  soils  with  low  degrees  of  sat\iration 
the  quantity  of  available  calcium  also 
decreases,  and  it  becomes  increasingly 
difficult  for  plants  with  high  calcium 
requirements  to  secure  adequate  available 
calcium.  Such  plants  may  therefore  not 
be  well  adapted  for  growth  on  acid  soils. 

The  dominant  native  forms  of  available 
phosphorus  occurring  in  soils  tend  to  be 
related  to  soil  reaction.  Above  pH  6  on 
noncarbonate  soils,  available  phosphorus 
occiors  chiefly  as  an  acid-soluble  form. 
Below  pH  6  adsorbed  phosphorus  becomes 


relatively  abundant,  and  on  some  strong- 
ly acid  soils  it  may  even  be  the  domi- 
nant available  form.  Plants  are  poor 
feeders  on  adsorbed  available  phosphorus 
on  acid  soils;  and  if  adsorbed  phosphorus 
is  the  dominant  available  form,  they  make 
little  growth.  It  is  doubtful,  however, 
if  phosphate  availability  basically  in- 
fluences plant  preferences.  The  data 
cited  in  Table  1  are  for  phosphatedland. 
It  is  evident  that  reaction  preferences 
vary  even  with  phosphate  fertilization. 

Toxic  aluminum  and  manganese  concentra- 
tions on  very  acid  soils.  Aluminum  and 
manganese  become  more  soluble  as  soils 
become  more  acid.  The  tolerance  of  plants 
to  soluble  alumintim  and  manganese  varies. 
Oats  tolerate  high  soil  acidity  for  sev- 
eral reasons.  First,  they  have  a  low 
calcium  requirement  and  can  get  enough 
calciim  even  from  strongly  acid  soils. 
Moreover,  they  have  a  high  tolerance  to 
soluble  aluminum  and  manganese.  This  ex- 
plains why  satisfactory  oat  yields  may 
be  secured  even  on  soils  with  a  pH  of  5 
(Table  l). 

Alfalfa,  on  the  other  hand,  is  very  sen- 
sitive to  soil  acidity.  Maximum  produc- 
tion occurs  at  or  near  neutrality.  Re- 
sults published  by  the  Ohio  Agricultural 
Experiment  Station  (Table  l)  indicate  a 
58  percent  yield  decrease  for  alfalfa 
when  the  soil  pH  drops  from  6.8  to  5.7. 

Alfalfa  has  a  high  calcium  requirement. 
The  low  calcium  content  of  alfalfa  grown 
on  soils  of  even  moderate  acidity  has 
given  rise  to  the  belief  that  alfalfa  is 
acid  sensitive  because  of  inability  to 
secure  sufficient  calcium.  But  evidence 
from  Cornell  indicates  that  the  high 
solubility  of  aluminum  and  manganese  in 
very  acid  soils  interferes  with  normal 
calcium  uptake  by  alfalfa.  The  inability 
of  alfalfa  to  secure  ample  calcium  would 


therefore  appear  to  be  related  to  its 
sensitivity  to  the  soluble  aluminum  and 
manganese  concentrations.  Lime  reduces 
the  aluminum  and  manganese  concentrations 
in  soil  solution  and  thus  removes  the 
block  to  normal  calcium  absorption. 

Minor  element  deficiencies  induced  at 
alkaline  reactions.  With  the  exception 
of  molybdenum,  availability  of  the  minor 
elements,  zinc,  copper,  iron,  manganese, 
and  boron,  decreases  as  soils  approach 
neutral  to  alkaline  reactions.  Border- 
line deficiencies  of  these  elements  at 
acid  soil  reactions  frequently  become 
striking  if  too  much  lime  is  applied. 
This  is  particularly  true  on  the  sandy 
soils  of  the  South.  But  Illinois  soils 
appear  to  be  amply  supplied  with  all  the 
minor  elements  except  boron.  The  possi- 
bility of  creating  minor  element  defi- 
ciencies through  the  use  of  lime  there- 
fore appears  rather  remote. 

Tolerance  of  crops  to  strongly  alkaline 
soil  (pH  7.5-8.0)  varies.  Soybeans  grow- 
ing on  shelly  spots  are  often  severely 
stunted  and  turn  yellow.  In  some  in- 
stances this  condition  may  be  corrected 
by  applying  potash.  In  other  cases  iron 
or  manganese  deficiencies  induced  by  al- 
kaline conditions  may  be  the  cause  of 
poor  grovrth.  Applying  available  iron  or 
manganese  to  the  soil  would  not  correct 
the  deficiency  because  they  would  imme- 
diately precipitate  out  as  unavailable 
forms.  Foliar  sprays  containing  soluble 
iron  and  manganese  would  correct  the 
trouble  if  the  symptoms  were  caused  by  a 
deficiency  of  these  nutrients. 

Effects  of  pH  on  susceptibility  to  soil- 
borne  diseases.  Susceptibility  of  crops 
to  certain  fungus  diseases  may  vary  with 
soil  reactions.  Club  root  of  cabbage 
and  potato  scab  are  the  classic  examples 
usually  cited  to  illustrate  the  role  of 
soil  reaction  in  disease  control.  The 
organism  causing  club  root  of  cabbage  is 
more  tolerant  of  soil  acidity  than  the 
host  plant.  Liming  to  about  neutrality 
makes  the  soil  less  favorable  for  growth 


of  the  fungus  and  thereby  reduces  damage 
from  club  root. 

Potatoes  are  very  acid  tolerant  (Table  2). 
The  fxingus  causing  potato  scab  is  less 
tolerant  of  soil  acidity  than  its  host. 
Potatoes  are  often  grown  on  strongly  acid 
soils  (pH  5»5  or  lower)  primarily  to  avoid 
the  serious  damage  caused  by  scab. 

From  the  discussion  of  factors  affecting 
plant  growth  at  various  soil  reaction 
levels,  it  is  obvious  that  the  question 
of  why  plants  vary  in  their  soil  reac- 
tion preferences  is  not  simple. 

The  pH  ranges  for  satisfactory  growth  of 
a  number  of  crops  are  given  in  Table  2. 
All  plants  have  a  considerable  pH  range 
throughout  which  satisfactory  growth  oc- 
cxirs.  But  it  does  not  necessarily  fol- 
low that  maximum  yields  can  be  secured 
throughout  the  indicated  range.  The  ex- 
tent to  which  production  may  be  sacri- 
ficed in  various  crops  at  various  pH 
levels  is  given  in  Table  1.  Contrast 
the  yield  of  oats  \7ith  alfalfa  at  pH 
levels  ^,0,   5*1}   and  6,8. 

Satisfactory  growth  is  occasionally  re- 
ported at  pH  levels  somewhat  lower  than 
those  indicated  in  Table  2.  Several 
factors  might  be  involved  in  this  con- 
tradictory evidence.  Satisfactory  growth 
is  sometimes  a  matter  of  opinion.  In  Il- 
linois the  agricultixral  lime  is  usually 
coarse.  The  rapidity  with  which  soil  pH 
shifts  occTor  after  liming  depends  on 
fineness  of  the  limestone  and  degree  of 
mixing.  If  an  adequate  amount  of  coarse 
lime  is  applied  and  thoroughly  incorpo- 
rated, crop  roots  may  contact  numerous 
limestone  particles  and  get  ample  avail- 
able calcium.  In  this  case  the  improved 
soil  calcium  status  might  not  be  reflect- 
ed in  marked  neutralization  or  pH  change 
for  some  time.  This  could  lead  to  dif- 
ferent impressions  of  a  plant's  relative 
reaction  preference.  In  general,  how- 
ever, the  data  in  Tables  1  and  2  are  the 
soundest  criteria  for  judging  whether 
growth  will  be  satisfactory. 


A 


There  are  many  soils ^  particularly  in 
northern  Illinois,  where  an  acid  surface 
is  underlain  at  3  to  5  feet  "by  neutral 
or  alkaline  substrata.  A  seeding  of  al- 
falfa at  a  borderline  surface  soil  pE 
level  may  make  excellent  grcirth  once  the 
roots  reach  the  deep-seated  calcixm  sup- 
ply. In  general;  this  applies  chiefly 
to  alfalfa  stands  held  over  for  2  or  more 
years.  Shallower  rooted  annual  crops 
and  alfalfa  stands  held  for  a  single  year 
are  probably  less  capable  of  tapping  deep 
calcium  reserves.  For  such  crops  the 
reaction  preferences  will  tend  to  con- 
form to  those  given  in  Tables  1  and  2. 


Surra ry.  Plants  vary  in  their  soil  reac- 
tion requirements.  Fcrtunatel;^  there  is 
certain  flexibility  in  these  preferences. 
The  limiting  of  gro'vrth  at  a  particular 
range  carir.ot  be  attributed  to  any  single 
uT-favorable  factor.  On  acid  soils  growth 
may  be  limited  by  lack  of  available  cal- 
cium, phosphorus ,  or  the  toxicity  of  solu- 
ble aliiminvr:  cr  manganese.  Poor  grc^rth 
in  the  al'-.alir-e  range  may  be  due  to  the 
low  availability  of  major  or  m.incr  nutri- 
ents. In  other  cases  gro^rth  may  be  im- 
proved by  the  control  of  disease  at  specif- 
ic reaction  levels  that  are  unfavorable 
to  the  pathogen  but  not  to  the  host  plants. 


Table  1.- 

-Relative  Yields 

of  Crops  at  Different  Soil 

Reactions 

=/ 

Percent 

of  maxim\ja  yield 

pH  of 

Alfal 

-  Sweet   Red  Alsike 

y.ejr-^zz'- 

Scy- 

_  !_!Ilw  ~ 

soil 

Corn 

^■•Jheat 

Cats 

Barley 

fa 

clover  clover  clover 

c lover 

ceans 

X/C^^r 

h.7 

3U 

6Q 

77 

0 

2 

0     12     13 

16 

65 

3- 

5.0 

73 

76 

93 

23 

9 

2     21     27 

29 

79 

^1 

5.7 

83 

89 

99 

80 

i+2 

h9          53    72 

80 

66 

6.8 

100 

100 

98 

95 

100 

89    98   100 

100 

100 

100 

7.5 

85 

99 

100 

100 

100 

100   ICO    95 

99 

93 

95 

1/  Ohio  Spec.  Cir.  53;  1938.  Phosphated  land. 


Tacle  2. --The  pH  Ranges  at  VJhich  Satisfactory  Growth  Occurs 


1/ 


vh  rar.se 


Jrcrs 


4.0       k.5       5.0 


;.0       6.5       7.0       7.5 


8.0 


QlAHfS 

Barley 
Euclc^heat 
Corn 
Cats 

^■Theat 


Als-l'ie   clover 
Cri:rscn  clover 
laiiric  clover 
Ke.rrr.c~h  clover 
Red  clover 
Sweet  clover 
vrhite  clover 
Lespedeza 
Soybeans 

GLASSES 

Bluegrass 
Br  cEie  grass 
Fescues 
Orchard  grass 
Redtop 
Timothy 


S2/ 


;iI'T  CROP; 


Asparagxis 

Eeans  ( garden ) 

Beans  (lira) 

Beets  (garden) 

Cabbage 

Lettuce 

Onions 

Feas  (garden)     . 

Potatoes  (white )!/ 

Pumpkin 

Strawberries 

Turnips 

Wateme  lens 


T7  Infoni:ation  from  various  scurces. 
2/  For  other  garden  crops  see  H-U20. 
3/  pE  5.6  -  upper  limit  for  scab  disease  control. 


E.  H.  Tyner 
April  5,   195^ 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


50IL  FERTILITY 

AND  ^. 

TESTING 


AGRONOMY  FACTS 


SF-25 


CORN  iS  A  SOIL  BUILDER 


Corn  is  often  regarded  as  being  hard  on 
the  soil.  For  this  reason  it  has  not 
teen  reccnmended  as  a  crop  to  grow  con- 
tinually on  any  given  area.  In  fact^ 
continuous  corn  production  has  generally 
been  considered  the  worst  treatment  a 
soil  could  have. 

But  today  we  knew  that  it  is  not  the  corn 
crop  itself  that  is  responsible  for  the 
soil  deterioration, but  the  improper  till- 
age and  management  practices  that  are 
used  in  producing  corn.  With  the  use  of 
improved  cultiiral  practices,  corn  could 
actually  become  a  soil-building  crop. 

Row  crops  like  corn  and  soybeans  lend 
themselves  to  excessive  cultivation. 
Generally  overtillage  andunderfertiliza- 
tion,  especially  with  nitrogen,  are  re- 
sponsible .for  the  damage  observed  on  the 
land.  This  damage  is  usually  reflected 
in  the  following  soil  characteristics: 

(1)  Rapid  loss  of  soil  organic  matter 
and  accompanying  loss  of  soil  tilth  re- 
sulting from  use  of  too  little  nitrogen. 

(2)  Excessive  soil  erosion  resiilting 
from  lack  of  soil  cover  under  clean  cul- 
tivation practices,  and  too  fine  a  brealc- 
d.o\m  of  soil  structure  resulting  from 
excessive  tillage. 

(3)  Increased  loss  of  water  due  to  ex- 
cessive evaporation  from  the  bare  soil 
surface,  and  poor  penetration  of  rain 
water  where  desirable  soil  structure  has 
been  destroyed  by  overtillage. 

To  make  corn  a  soil  builder,  tillage  and 
management  practices  must  be  modified  to 
overcome  the  damage  that  present  prac- 
tices are  causing. 

The  first  requisite  in  making  corn  a 
soil  builder  is  to  use  adequate  nitrogen 
fertilizer,  along  with  a  fertilization 


program  that  puts  all  nutrients  into 
positive  balance,  v/hen  corn  is  adequate- 
ly fertilized,  more  plant  food  nutrients 
are  returned  to  the  soil  than  the  corn 
crop  removes,  and  loss  of  soil  organic 
matter  is  reduced  to  a  minimijn.  Main- 
taining soil  organic  matter  depends  on 
returning  adequate  amounts  of  crop  resi- 
dues and  nitrogen  to  the  soil. 

Plowing  doim  a  little  nitrogen  (20  to  3C 
po\inds  an  acre)  with  the  cornstalks  will 
help  to  decompose  them  and  keep  a  supply 
of  active  organic  matter  in  the  soil. 
Cornstalks,  or  any  other  crop  residues 
that  are  low  in  nitrogen,  do  not  make 
good  soil  builders  unless  they  are  sup- 
plemented with  nitrogen.  Supplementing 
lew-nitrogen  residues  with  nitrogen  will, 
in  tiirn,  help  to  maintain  good  soil  tilth. 

A  second  requisite  in  making  corn  a  soil- 
building  crop  is  to  decrease  tillage  op- 
erations as  they  are  now  practiced  and 
provide  a  cover  for  the  soil  during  the 
winter  and  early  spring.  Excessive  till- 
age helps  to  destroy  soil  organic  matter, 
and  consequently  soil  tilth.  Cutting 
doim  the  amount  of  ciiltivation  will  make 
the  soil  more  resistant  to  erosion. 

Scd  crops  tendtc  improve  soil  tilth,  but 
the  excessive  tillage  that  usually  fol- 
lows a  scd  crop  in  preparing  for  the  corn 
crop  often  destroys  much  of  the  advantage 
resulting  from  the  sod  crop.  Sod  seed- 
beds and  mulch  planters  are  being  inves- 
tigated and  recommended  on  a  trial  basis 
because  they  reduce  tillage  operations. 
V/hen  these  practices  are  used,  the  corn 
is  planted  directly  in  the  sod  in  a  sort 
of  once-over  operation.  Then  the  crop  is 
cultivated  only  enough  to  control  weeds. 

The  third  requisite  in  mialsLing  corn  a  soil 
builder  is  to  control  the  erosion  losses 
now  associated  with  clean  cultivation  of 
row  crops.  For  corn,  the  erosion  losses 


can  "be  minimized  "by  seeding  fall  cover 
crops.  When  corn  is  seeded  in  a  sod 
seedbed,  the  soil  has  cover  during  the 
entire  year.  If  the  sod  seedbed  con- 
tains a  living  crop_,  a  living  mulch  sys- 
tem is  established.  This  system  is  very 
effective  in  controlling  erosion,  but 
its  success  depends  on  adequate  nitrogen 
fertilization  and  water. 

If  the  sod  crop  is  destroyed  by  chemical 
sprays  or  by  cutting,  a  dead  (trash) 
mulch  system  is  established.  Both  the 
living  and  trash  mulches  are  effective 
in  controlling  erosion.  They  do,  how- 
ever, require  special  equipment  for  seed- 
ing the  corn.  Under  either  system  only 
a  minimiun  amount  of  cultivation  is  re- 
quired to  control  weeds. 

Fall-seeding  a  grass  or  small  grain  in  the 
corn  to  provide  winter  cover  for  the  soil 
is  recommended  where  corn  is  grown  on 
sloping  land  that  is  subject  to  erosion. 
When  properly  fertilized,  lye  will  usual- 
ly produce  enough  growth  in  the  fall  to 
cut  dc\'m  erosion.  Shredding  the  corn- 
stalks in  the  fall  and  leaving  them  on  the 
land  will  provide  a  mulch  cover  for  the 
soil  and  lessen  dam.age  from  beating  rains. 


Cn  well  fertilized  soil  that  is  properly 
managed,  corn  grown  continuously  can 
well  become  a  soil-building  crop.  When 
yields  are  high,  a  large  amount  of  crop 
residues  is  returned  to  the  soil.  With 
high  nitrogen  fertility,  cornstalks  that 
are  returned  to  the  land  will  contain 
fairly  large  amounts  of  nitrogen  that 
will  cause  them  to  decompose  more  rapid- 
ly and  form  active  soil  organic  matter. 

Because  continuous  corn  will  produce 
more  crop  residues  than  almost  any  crop 
rotation,  corn  can  become  one  of  the  best 
crops  a  farmer  can  groxf  to  build  up  his 
soil. 

Under  improper  cultural  and  management 
practices,  any  crop  can  destroy  the  soil. 
It  is  the  tillage  and  fertilizer  prac- 
tices that  determine  the  amount  of  dam- 
age a  crop  will  do  to  a  soil.  Like  any 
other  crop,  corn  can  be  a  soil  builder 
if  it  is  properly  managed.  Whether  it 
is  grown  continuously  or  in  rotation, 
the  culttiral  practices  should  be  such 
that  they  are  soil  conserving.  This 
means  high  fertility,  minimum  cultiva- 
tion, and  introduction  of  cover  crops  on 
land  that  is  subject  to  erosion. 


S.  W.  Melsted 
5-10-5^^ 


I 


I 


UNIVERSITY  Or 


AGRONOMY  FACTS 


SF-26 


ORGANIC  MATTER  RFPLE  NISHME  NT 


Soil  organic  matter  is  not  being  main- 
tained on  most  farms  in  Illinois  where 
an  intensive  system  of  cropping  is  being 
practiced.  Whether  it  is  essential  to 
maintain  organic  matter  on  all  soils  has 
not  been  established,  but  there  is  a  level 
below  which  maximum  productivity  cannot 
be  expected. 

It  is  necessary  to  replenish  organic  mat- 
ter if  unfavorable  physical,  chemical,  and 
biological  conditions  are  to  be  avoided. 
This  replenishment,  or  recharge,  is  made 
through  the  use  of  farm  manure,  green 
manure  crops,  and  crop  residues,  and  the 
needed  amount  relates  directly  to  the 
management  and  productive  capacity  of  the 
soil.  Land  on  which  large  crops  are 
grown  furnishes  larger  quantities  of  or- 
ganic material  than  soils  that  are  low 
in  productivity  and  therefore  requires 
more  replenishment. 

A  favorable  soil  reaction  and  a  supply 
of  available  phosphorus  and  potassium 
are  prerequisites  in  organic  matter  re- 
plenishment. Because  nitrogen  is  needed 
in  largest  quantities,  and  is  more  gen- 
erally lacking  than  other  plant  foods  in 
soils,  it  is  an  important  key  to  organic 
matter  recharge. 

The  organic  materials  that  are  added  to 
soils  undergo  rapid  changes  as  a  result 
of  microbial  activity.  Much  is  released 
as  carbon  dioxide  and  water,  and  part  is 
synthesized  by  soil  microorganisms.  There 
remains  the  part  of  the  organic  materials 
that  is  resistant  to  decay.  This  resid- 
ual resistant  part,  together  with  the 
microbial  tissues,  is  sometimes  called 
humus . 


As  indicated  previously  (SF  23),  the  rate 
of  decomposition  of  the  added  organic 
material  is  affected  by  its  nitrogen  con- 
tent and  by  the  supply  of  available  ni- 
trogen in  the  soil.  When  the  nitrogen 
content  of  the  residues  is  below  approxi- 
mately 1.75  percent,  rapid  decomposition 
does  not  occur  unless  the  soil  contains 
a  considerable  amount  of  nitrogen  in  an 
available  form. 

The  average  nitrogen  content  of  corn- 
stalks is  about  .85  percent,  or  17  pounds 
per  ton.  If  the  nitrogen  content  were 
1.75  percent,  the  stalks  would  contain 
35  pounds  per  ton.  Thus  the  addition  of 
18  pounds  of  nitrogen  per  ton  of  stalks 
ought  to  be  sufficient  to  insure  decompo- 
sition. However,  this  amount  would  need 
to  be  uniformly  distributed  throughout 
the  added  organic  material,  a  condition 
that  would  not  exist  if  the  needed  nitro- 
gen were  added  to  the  soil  in  the  form 
of  ammonium  sulfate,  ammonium  nitrate, 
or  some  other  nitrogen  carrier.  Thirty- 
five  pounds  of  nitrogen  should  insure 
rapid  decay  of  the  cornstalks  without  a 
drain  on  the  supply  of  available  nitrogen 
furnished  by  the  native  soil  organic  mat- 
ter, or  humus. 

Of  the  constituents  of  organic  materials 
that  are  added  to  soils,  the  proteins  and 
carbohydrates  are  readily  decomposed, 
whereas  the  lignins  and  waxes  are  more 
resistant.  Lignin,  particularly,  is  an 
important  contributor  to  the  hixmus  frac- 
tion of  the  soil,  because  it  decomposes 
so  slowly  and  is  present  in  appreciable 
amounts  in  many  plants. 


(Continued  on  other  side) 


(Continued  from  other  side) 


Crops  differ  considerably  in  the  amount 
of  lignin  they  contain.  In  a  given  plant 
the  proportion  of  lignin  increases  with 
stage  of  maturity.  For  instance,  young 
rye  plants  contain  10  percent  of  lignin 
and  2.5  percent  of  nitrogen,  whereas 
mature  plants  contain  20  percent  of  lig- 
nin and  .5  percent  of  nitrogen. 

Unlike  rye  and  wheat  straw,  many  legume 
crops  are  low  in  lignin.   Soybean  plants 


and  alfalfa  contain  about  half  as  much 
lignin  as  cereal  straws.  Because  of  this 
lower  lignin  content  and  their  higher  ni- 
trogen content,  legume s  may  not ,  in  them- 
selves, be  quite  so  conducive  to  the 
formation  of  humus  as  are  some  of  the 
nonlegume  crops.  On  the  other  hand,  the 
legumes  may  contribute  indirectly  to  humus 
accumulation  by  increasing  the  amounts 
of  residues  that  may  be  added  to  soils 
as  h\xmus-forming  materials. 


0.  H.  Sears 
5-24-54 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


SF-27 


EVALUATION  OF  CATCH  CROPS 


The  term  catch  crop  is  used  here  to  in- 
dicate a  legume  or  a  mixture  of  legumes 
grown  in  a  grain  field  for  the  purpose 
of  improving  the  soil  for  the  following 
crops.  Seeded  in  winter  grain  in  Febru- 
ary or  March  or  in  spring  grain  at  seed- 
ing time,  catch  crops  become  established 
before  harvest  and  usually  cause  little 
or  no  interference  with  the  grain  crop. 


Many  comparisons  of  catch  crops  have 
shown  alfalfa  to  be  almost  as  efficient 
as  sweet  clover,  and  even  superior  to  it 
in  some  cases.  Red  clover  and  mammoth 
clover  are  also  very  effective.  These 
legumes  are  being  used  alone  or  in  mix- 
tures with  sweet  clover  on  many  farms  in 
areas  where  the  sweet  clover  weevil  is  a 
serious  threat. 


With  favorable  season  and  soil  condi- 
tions, catch  crops  make  large  fall  growth 
that  can  be  plowed  under  very  late  in 
the  fall  or  in  April  or  early  May  in 
time  to  prepare  the   seedbed  for  corn. 

Sweet  clover  has  been  very  effective  be- 
cause of  its  rapid,  vigorous  growth. 
Total  root  and  top  weight  of  sweet  clo- 
ver catch  crops  sampled  in  mid-April  of 
the  year  after  seeding  has  ranged  from 
1  l/^  to  2  tons  of  dry  matter  per  acre  con- 
taining 8O-I95  pounds  of  nitrogen  (Bul- 
letin 539) .  The  part  of  this  nitrogen 
that  comes  from  the  air  differs  somewhat 
depending  on  soil  conditions,  but  it  is 
generally  believed  to  be  about  two-thirds 
of  the  total  in  the  crop. 


The  value  of  catch  crops  may  be  estimated 
by  several  yardsticks,  such  as  control  of 
soil  erosion,  depth  of  root  penetration, 
total  top  growth,  and  effect  on  soil 
tilth.  However,  the  most  realistic  test 
is  the  long-time  effect  on  crop  yields. 

Many  field  tests  have  shown  legume  catch 
crops  to  be  most  effective  when  used  in 
combination  with  nonlegume  residues. 
This  is  demonstrated  on  the  experiment 
fields  at  Aledo,  Hartsburg,  McNabb,  and 
Minonk,  where  a  corn,  corn,  oats,  and 
wheat  rotation  has  been  in  use  for  sev- 
eral years.  These  fields  also  have  a 
rotation  of  corn,  corn,  oats,  and  legume 
hay  and  therefore  the  effect  of  catch 
crop  vs.  standover  hay  can  be  compared. 


Results  at  Urbana  on  Flanagan  Silt  Loam 
Rotation:   Corn,  Corn,  Oats  (Catch  Crop),  Wheat  (Catch  Crop)  Since  1937 
Annual  Acre  Yields  and  Values,  Last  Four  Years 


Corn 
1st  year 

Corn 
2nd  year 

Oats 

Wheat 

Acre  values 
all  crops 

Wo  catch  crop 
Catch  crop 
Increase 

bu. 

62 
90 
28 

bu. 

60 
73 
13 

bu. 

^3 
11 

bu. 

28 

3^ 
6 

$69.83 

88.1^ 

$18.31 

Results  at  Urbana  on  Drummer  Clay  Loam 

Rotation:   Corn,  Oats  (Catch  Crop)  Since  1936 

Annual  Acre  Yields  and  Values,  Last  Four  Years 


Corn 

Oats 

Acre  value 

bu. 

bu. 

No  catch  crop 

71 

Uo 

$64.76 

Catch  crop 

9^ 

k2 

81.18 

Increase 

23 

2 

$16.^2 

Results  at  Dixon  on  Muscatine  Silt  Loam 
Rotation:   Corn,  Oats  (Catch  Crop),  Wheat  (Catch  Crop)  Since  I927 
Annual  Acre  Yields  and  Value aS/,  I95O-I953 


Corn 

Oats 

Wheat 

Acre 
value 

Wo  catch  crop 
Catch  crop 
Increase 

bu. 

55 
95 

bu. 

32 

50 
iB 

bu. 
21 

27 
6 

$i+1.32 

75.13 

$33.81 

Results  at  Ewing  on  Cisne  Silt  Loam 
Rotation:  Corn,  Wheat,  Winter  Oats  (Catch  Crop) 
Annual  Acre  Yields  and  Values^/,  1950-1953 


Winter    Acre 
Corn   Wheat  oats     value 


bu .    bu .    bu . 

Wo  catch  crop    38      h  I8     $26. 80 

Catch  crop      58     13     23     ^^.62 
Increase        20      9      5     $17. b2 

a/  From  soil  experiment  field  mimeographs. 

Aledo,  Hartsburg,  McNabb,  Minonk 
Average  Crop  Yields  and  Values^/,  1950-1953 


Corn 

Corn 

Legume 

Acre 

1st  year 

2nd  year   Oats 

Wheat 

hay 

value 

Rotation: 

Corn, 

corn,  oats. 

wheat 

bu. 

bu. 

bu. 

bu. 

tons 

Wo  residues  and 

51 

50 

38 

21 

$57.78 

no  catch  crop 

Residues  and 

catch  crop 

81 

68 

1;!+ 

26 

79.58 

Increase  for 

residues  and 

catch  crop 

30 

18 

6 

5 

$21.80 

Rotation: 

Corn, 

corn,  oats 

,  hay 

No  treatment  81+      77      51  2.1      $85.18 

Advantage  for 

standover  compared 

with  catch  crop        3        9       7  5.60 


a/  From  soil  experiment  field  mimeographs. 


SOIL  EXPERIMENT  FIELD  STAFF 

5-31-5^ 


UNIVERSITY  OF  ILLINOIS  ■  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


V/.-l 


GIANT  FOXTAIL  (Setaria  foberii) 


We  have  four  common  types  of  foxtail 
in  Illinois--giant,  green,  yellow,  and 
sticky.  If  giant  foxtail,  the  most  seri- 
ous of  the  four,  continues  to  spread.  It 
will  be  our  worst  weed.  At  present  it 
is  concentrated  chiefly  in  east-central 
Illinois,  hut  some  can  be  found  in  every 
county  in  the  southern  three-fourths  of 
the  state. 

Giant  foxtail  can  be  distinguished  from 
other  foxtails  by  its  long,  lopping  head 
and  Its  unusual  size.  If  left  undis- 
turbed. It  will  grow  seven  feet  tall. 
Another  distinguishing  feature  is  the 
short  hairs  covering  the  upper  sides  of 
the  leaves. 

The  weed  usually  starts  to  germinate 
about  April  20  in  central  Illinois.  If 
left  undisturbed  in  fencerows  it  will 
produce  seed  by  July  15-  Seed  produc- 
tion usually  continues  until  frost 
through  new  spikes  appearing  from  the 
lower  nodes.  Type  of  ground  cover  does 
not  seem  to  matter,  as  the  seed  can  be 
found  in  legumes,  fencerows,  or  plowed 
fields  at  about  the  same  time  in  the 
spring.  Established  legumes  or  winter 
grains  may  greatly  hinder  its  develop- 
ment, but  it  grows  rapidly  as  soon  as 
the  crop  is  removed. 

Although  giant  foxtail  seed  has  not 
been  tested  for  longevity,  its  viability 
is  probably  good,  as  green  and  yellow 
foxtail  seeds  have  germinated  after  be- 
ing burled  for  20  years. 

Wo  good  cropping  system  has  been  found 
that  will  control  this  weed.  It  sur- 
vives competition  from  cultivated  crops 
as  well  as  from  rotations  that  Include 
small  grains  and  stand-over  legumes. 
The  only  crop  that  offers  possibilities 
for  control  Is  winter  wheat.  Since  the 
wheat  is  well  established  in  early 
spring.   It  competes  well  with  giant 


foxtail  and  is  harvested  before  the  weed 
produces  seed.  Plowing  immediately  after 
wheat  harvest  will  prevent  seed  produc- 
tion, and  later  cultivations  will  reduce 
the  seed  supply. 

Spring  oats  have  not  proved  to  be  a 
good  competitor.  Often  giant  foxtail 
produces  seed  about  the  same  time  as  the 
oats.  In  a  few  instances  when  oats  seed- 
ing has  been  delayed,  the  weed  has  grown 
faster  than  the  oats  and  made  harvest 
Impossible. 

Infestations  in  corn  and  soybeans  may 
or  may  not  be  serious,  depending  on  cul- 
tural practices.  If  cultivations  are 
timely  and  are  not  interrupted  by  rain, 
the  crops  may  be  completely  free  of  fox- 
tail. On  the  other  hand,  rain  combined 
with  untimely  cultivations  usually  means 
heavy  infestations.  Delays  of  a  week  or 
10  days  in  the  first  cultivation  may 
cause  farmers  to  disk  up  corn  and  bean 
fields  and  replant.  Because  the  foxtail 
becomes  so  well  established  that  normal 
row  cultivation  will  not  remove  it. 

Giant  foxtail  will  continue  to  ger- 
minate during  the  s\immer  if  there  is 
moisture, but  summer  germination  is  small 
compared  with  that  at  crop-planting 
time.  Legume  crops  are  one  of  the  worst 
offenders  in  spreading  this  weed.  If 
the  legume  is  cut  for  hay  or  left  for 
seed,  giant  foxtail  produces  abundant 
seed;  but  if  the  legume  is  grazed,  very 
little  foxtail  seed  develops.  Getting 
good  legume  stands  In  Infested  areas  is 
becoming  a  serious  problem. 

After  the  nurse  crop  is  removed,  the 
weed  grows  rapidly,  offering  severe  com- 
petition to  the  seeding.  Three  clip- 
pings during  late  summer  will  prevent  90 
percent,  but  not  all,  normal  seed  pro- 
duction. Few  farmers  are  willing  to 
clip  meadows  three  times.   Grazing  the 


forage  is  therefore  a  better  way  to  pre- 
vent seed  production. 

Use  of  chemicals  for  control  offers 
limited  possibilities.  Pre-emergence 
sprays  are  sometimes  effective  in  corn, 
but  their  success  varies  with  the  weath- 
er. However,  results  have  been  good 
enough  to  recommend  spraying  around  the 
edges  of  fields  where  giant  foxtail 
seems  to  concentrate  in  the  early  stages. 
TCA  has  proved  100  percent  effective, 
but  it  will  also  injure  corn,  small 
grains,  and  soybeans.  It  can  be  used  in 
fencerows  and  in  established  alfalfa 
fields. 

Although  no  control  measures  are  en- 
tirely effective,  the  following  prac- 
tices will  help  to  reduce  giant  foxtail 
infestations: 

1.  Check  corn  instead  of  drilling  or 
hill-dropping.  Cross  cultivation  will 
be  helpful  between  hills. 

2.  Use  clean  crop  seed.  Unless  crop 
seed  has  been  thoroughly  cleaned,  it  may 
be  heavily  infested  with  foxtail  seed. 

3.  Clean  up  harvesting  equipment.  Com- 
bines and  balers  carry  the  weed  to 
many  clean  fields.  Clean  equipment  be- 
fore moving  to  the  next  field. 

k.  Use  2,4-D  as  a  pre-emergence  spray 
around  borders  in  cornfields.  Apply  two 
pounds  of  2,k-'D     ester  per  acre  after 


corn  planting.  If  there  is  enough  mois- 
ture, this  treatment  will  work.  Do  not 
cultivate  border  rows  as  long  as  no  fox- 
tail appears. 

5 .  You  may  use  TCA  in  fencerows  and 
established  alfalfa.  Applying  TCA  at  10 
pounds  per  acre  when  foxtail  is  germinat- 
ing will  eradicate  it.  This  rate  will 
not  harm  established  alfalfa  but  will 
injure  red  clover.  Use  the  same  rate  in 
fencerows  when  the  foxtail  plants  are 
emerging.  There  may  be  seme  later  rein- 
festations  from  late  germination. 

6.  Graze  infested  areas.  Livestock 
will  eat  giant  foxtail  readily  in  the 
vegetative  stages.  Most  seed  produc- 
tion can  be  prevented  by  grazing. 

7.  Remove  scattered  plants  by  hand; 
it  is  the  best  way  to  control  new  in- 
festations. 

8.  If  grazing  is  not  possible,  clip 
to  help  prevent  seed  production.  Clip- 
ping is  not  entirely  effective,  but  it 
reduces  the  amount  of  seed  and  thus 
helps  in  control. 

9.  Grow  winter  wheat  for  three  years, 
and  plow  immediately  after  harvest.  Sum- 
mer cultivation  should  greatly  reduce  the 
seed  population.  Growing  winter  wheat 
every  few  years  in  a  rotation  should  re- 
duce infestations,  but  it  is  not  so  ef- 
fective as  continuous  wheat  for  several 
years. 

F.  W.  Slife 
1/12/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


vy. 


CONT^CLLING  WEEDS  IN  SOYBEANS 


The  best  way  to  control  weeds  in  soybeans 
is  to  use  good  cultural  practices.  The 
most  effective  practice  is  to  prepare 
the  seedbed  early  and  then  wait  several 
weeks  so  that  a  few  crops  of  weeds  can 
be  destroyed  before  the  beans  are  planted. 
Delayed  planting  usually  means  that  the 
soil  will  be  warmer  and  the  beans  will 
germinate  and  develop  more  quickly. 

In  Illinois  soybeans  are  usually  planted 
in  rows  as  a  weed  control  measure.  Row 
planting  permits  cultivation  betv/een  the 
rows  and  helps  to  control  late  germinat- 
ing weeds  by  covering  them  with  dirt 
from  the  cultivator. 

Our  weed  problem  in  soybeans  has  in- 
creased steadily  from  year  to  year.  The 
combine  harvester  has  probably  added  to 
the  problem  by  distributing  the  weed 
seeds  over  the  fields  and  moving  them 
from  farm  to  farm. 

The  number  of  weeds  in  soybeans  will  de- 
pend largely  on  the  weather.  If  the 
cultivations  are  timely  and  not  inter- 
rupted by  rain,  soybeans  are  likely  to 
be  the  cleanest  crop  on  the  farm.  But 
if  the  cultivations  are  interrupted  by 
rains,  soybeans  are  often  the  weediest 
crop  we  have. 

Chemical  control  of  weeds  in  soybeans 
has  developed  slowly  because  the  beans 
are  sensitive  to  most  of .the  chemicals 
that  have  been  tested.  At  present  the 
Illinois  Agricultural  Experiment  Station 
is  recommending  chemical  weed  control  on 
only  a  limited  basis.  Chemicals  should 
be  used  on  soybeans  only  when  in  past 
years  cultural  practices  have  failed  to 
control  weeds  and  yields  have  been  se- 
verely  reduced. 


There  are  several  chemicals  that  do  of- 
fer limited  possibilities  for  control- 
ling weeds  in  soybeans.  These  chemicals 
are  pre-emergence  herbicides,  which  are 
applied  to  the  soil  before  the  weeds  and 
beans  emerge . 

The  effectiveness  of  pre-emergence  treat- 
ments depends  largely  on  the  weather. 
If  a  pre-emergence  chemical  is  applied 
to  a  dry  soil  and  the  soil  remains  dry 
for  two  or  three  weeks,  much  of  the 
chemical  will  be  lost  or  will  decompose. 
Rains  after  that  time  will  cause  many 
weeds  to  grow.  If,  however,  the  treat- 
ment is  applied  to  a  soil  that  has 
enough  moisture  to  insure  prompt  germi- 
nation of  weed  seeds,  the  chemical 
should  be  effective  in  killing  the  weeds. 

The  most  effective  chemical  for  pre- 
emergence  treatment  of  soybeans  has  been 
dinitro -ortho- sec -butyl -phenol  (called 
dinitro).  The  recommended  rate  of  appli- 
cation is  between  6  and  8  pounds  of  acid 
dinitro -phenol  per  acre  as  an  overall 
treatment.  The  6-pound  rate  is  recom- 
mended for  the  lighter  soils  and  the 
8-pound  rate  for  heavy  soils  or  for 
soils  with  a  high  clay  content.  Under 
no  circumstances  is  this  material  recom- 
mended for  sandy  soils. 

Because  the  cost  for  complete  coverage 
is  so  high,  it  seems  best  to  treat  a 
band  about  12  inches  wide  over  the  row. 
For  band  treatment  the  per  acre  cost  is 
$3.00  to  $i4-.00.  As  a  rule  the  treatment 
should  be  applied  immediately  after  plant- 
ing. Delaying  the  application  until  two 
or  three  days  after  planting  will  usual- 
ly increase  control.  But  if  it  should 
rain,  the  application  may  be  prevented 
altogether  because  of  wet  weather. 


The  mcst  efficient  method  of  application 
is  to  apply  at  planting  time  with  a 
sprayer  mounted  on  the  planter  so  that 
the  material  is  applied  behind  the  plant- 
er wheels.  Not  all  types  of  weeds  can 
be  controlled  by  this  chemical.  It  will 
usually  control  annual  broad-leafed  weeds 
but  not  the  annual  grasses.  Giant  fox- 
tail or  wild  millet  cannot  be  successful- 
ly controlled  at  the  6-  to  8-po-and  rate 
of  application.  Ten  pounds  will  control 
giant  foxtail^  but  soybeans  will  not 
tolerate  this  rate.  Perennial  weeds  or 
weeds  coming  up  from  underground  roots 
are  not  materially  affected  by  pre- 
emergence  treatments. 


we  cannot  recommend  it  until  another 
year's  tests  have  been  completed. 

Chloro  IPC  at  6  to  8  pounds  used  as  a 
pre- emergence  spray  on  soybeans  has  been 
slightly  better  than  dinitro  in  control- 
ling grass  weeds.  It  has  been  less  ef- 
fect ive^  however,  against  cocklebur  and 
giant  ragweed.  Smartweeds  seem  to  be 
particularly  sensitive  to  Chloro  IPC, 
and  it  may  be  that  this  chemical  can  be 
used  in  soybean  fields  that  are  infested 
mainly  with  smartweeds.  Because  of  cost 
it  will  have  to  be  applied  as  a  band 
treatment,  and  it  probably  should  be  ap- 
plied imm.ediately  after  planting. 


If  dinitro  has  been  applied  as  a  pre- 
emergence  treatment  and  no  weeds  are 
emerging,  it  is  important  not  to  cover 
the  treated  area  with  dirt  from  the  cul- 
tivator. Dirt  over  the  treated  area 
will  introduce  new  weed  seeds.  This  can 
be  prevented  by  using  fenders  or  by  us- 
ing a  blade  cultivator  that  cuts  the 
weeds  off  and  dees  not  throw  much  dirt. 

Occasionally  dinitro  will  slightly  re- 
duce soybean  stands,  but  in  the  tests  it 
has  never  caused  a  reduction  in  yield. 

Another  chemical  that  holds  some  promise 
as  a  pre-emergence  herbicide  for  soy- 
beans is  Chloro  IPC.  However,  because 
it  has  not  been  tested  thoroughly  enough, 


As  yet  no  chemical  has  been  found  that 
is  effective  in  controlling  weeds  in  soy- 
beans after  the  beans  have  emerged. 

We  are  not  recommending  pre-emergence 
control  of  weeds  in  complete  soybean 
fields  until  some  experience  with  these 
chemicals  has  been  obtained.  By  far 
the  best  plan  now  is  to  treat  several 
rows  across  soybean  fields  or  around  the 
ends  and  compare  the  results  with  those 
in  unsprayed  areas.  IThen  some  experi- 
ence has  been  obtained,  the  decision  on 
whether  to  use  pre-emergence  weed  con- 
trol in  soybeans  will  be  up  to  the  indi- 
vidual farmer. 

F.  W.  Slife 
V13/53 


UNIVERSITY  OF  ILLINOIS  •  COLLEGE  OF  AGRICULTURE 


AGRONOMY  FACTS 


W-3 


BRUSH  CONTROL 


Brush  control  is  a  problem  that  affects 
almost  every  type  of  property.  Undesi- 
rable brush  can  be  found  growing  on  most 
farms ^  along  railways^  highways^  and 
drainage  ditches,  and  around  industrial 
plants.  It  is  true  that  certain  types 
of  brush  provide  food  and  cover  for  wild- 
life or  may  have  other  values.  But 
these  types  are  not  the  ones' that  pre- 
sent a  problem. 

In  the  past  brush  had  to  be  removed  by  me- 
chanical means.  Often  the  cost  was  pro- 
hibitive and  the  brush  was  allowed  to  re- 
main; hence  the  problem  has  increased. 
With  the  introduction  of  2,U-D,  '2,h,'^-T, 
and  other  chemicals,  however,  many  types 
of  brush  can  now  be  eliminated  easily 
and  at  relatively  low  cost. 

There  are  several  older  chemicals  that 
have  been  effective  in  controlling  brush. 
One  of  them,  sodium  arsenite,  has  been 
used  extensively  in  some  areas  to  kill 
large  trees.  It  is  very  effective  for 
this  purpose  and  is  reasonable  in  cost. 
The  usual  method  ia  to  apply  the  chemi- 
cal in  a  frill  around  the  trunk  or  pour 
it  into  holes  bored  in  the  trunk.  Be- 
cause it  is  extremely  poisonous  to  hu- 
mans and  livestock,  however,  it  is  not 
recommended  for  use  by  the  average  farm- 
er. 

Ammate  or  ammonium  sulfamate  is  another 
woody  plant  killer  that  has  been  on  the 
market  for  a  number  of  years.  If  is  ef- 
fective on  certain  types  of  brush,  but 
not  so  effective  on  others.  Because  it 
is  expensive,  It  has  not  been  used  so 
widely  as  2,1|-D  and  2,U,5-T.  It  will 
also  corrode  equipment  unless  it  is 
thoroughly  cleaned  after  use. 


Although  -ammate  ia  irritating  to  humans, 
it  is  not  poisonous.  It  can  be  used  as 
a  foliage  spray,  as  a  frill  treatment, 
or  as-  a,  stump  treatment  to  prevent  re- 
sprouting. 

2,U-D  and  2,U,5-T  are  the  latest  chemi- 
cals to  be  used  in  controlling  brush. 
They  are  noncorrosive,  nonpoisonous  to 
humans  and  animals,  and  reasonably  cheap. 
If  used  correctly  they  are  effective  in 
eliminating  many  of  our  serious  brush 
problems.  One  hundred  percent  control 
is  seldom  achieved  with  one  application, 
however;  at  least  two  applications  are 
needed  to  do  a  complete  Job. 

These  two  chemicals  can  be  used  in  sev- 
eral ways  to  eliminate  brush.  Among 
them  are  foliage  sprays,  basal  bark 
treatment,  and  stump  treatment. 

Foliage  sprays.  Types  of  brush  vary  in 
their  susceptibility  to  these  chemicals. 
Most  species  are  more  susceptible  to 
2,^,5-T  than  to  2,i|-D,  although  at  least 
one  is  affected  more  readily  by  2,U-D. 
Some  others  are  equally  susceptible  to 
either  one. 

For  spraying  mixed  types  of  brush,  it  is 
best  to  use  a  combination  of  2,1+-D  and 
2,ij-,5-T.  The  mixture  costs  less  than 
2,1|,5-T  alone  and  yet  gives  as  good  re- 
sults. The  only  exception  is  buckbruah, 
which  is  most  susceptible  to  2,h-'D. 

Application  rates  are  given  on  the  con- 
tainer, but  the  best  rate  seems  to  be  k 
pounds  of  acid  in  100  gallons  of  water. 
There  is  no  advantage  to  using  oil  in- 
stead of  water  as  a  carrier.  A  heavier 
rate  will  kill  the  top  growth  too  fast 
and  will  not  allow  the  chemical  to  pene- 
trate the  root  system. 


-2- 


Foliage  ■  sprays  can  "be  applied  at  any- 
time after  the  leaves  are  fully  devel- 
oped  in  the  spring.  They  do,  however, 
have  the  following  limitations  that 
should  be  considered  before  a  spraying 
program  is  started: 

1.  Foliage  sprays  are  most  effective 
against  small  brush  or  regrowth  up 
to  15  feet  tall.  It  is  not  practi- 
cal to  try  to  kill  tall  trees  by  this 
method. 

2.  Several  species  are  almost  resistant 
to  foliage  sprays.  Oaks,  maple, 
hickory,  and  ash  can  not  usually  be 
controlled  by  this  method. 

5.  Drift  from  foliage  sprays  can  cause 
serious  injury  to  nearby  susceptible 
crops . 

Basal  bark  treatment  consists  of  paint- 
ing the  lower  part  of  the  trunk  with 
2,i|,5-T  in  oil  at  the  rate  of  I6  pounds 
of  acid  per  100  gallons  of  oil.  Mixing 
in  an  oil- soluble  dye  or  a  small  amount 
of  paint  will  help  to  mark  treated  areas. 
It  is  important  to  completely  encircle 
the  trunk  and  to  cover  it  thoroughly 
from  the  ground  line  up  to  15  inches 
above  the  ground  level.  The  mixture 
should  be  applied  to  the  point  of  runoff, 
and  the  ground  line  should  be  thoroughly 
soaked. 

Basal  bark  treatment  has  the  following 
advantages  over  foliage  sprays: 

1.  It  can  be  used  on  taller  trees. 
Although  there  seems  to  be  no  height 
limit,  on  trees  more  than  8  inches 
in  diameter,  it  may  be  more  economi- 
cal to  frill. 

2.  The  basal  bark  treatment  can  be  ap- 
plied during  the  winter  whenever  the 
weather  permits,  although  it  seems 


5- 


to  be  effective  at  any  time  during 
the  year. 

There  is  no  danger  of  drift  from  the 
basal  bark  treatment  if  it  is  applied 
during  the  winter.  ^ 

No  special  equipment  is  required.  An 
ordinary  5-salloi^  knapsack  spray 
seems  to  be  best. 

The  treatment  is  effective  against 
species  that  are  not  easily  con- 
trolled with  2,U-D. 


Stump  treatment.  When  growing  brush  is 
cut  down,  it  is  advisable  to  treat  the 
stumps  to  prevent  regrowth.  The  recom- 
mended mixture  is  I6  pounds  of  2,l4-,5-T 
acid  in  100  gallons  of  oil.  The  top  and 
sides  of  the  stump  should  be  treated  to 
the  point  of  runoff.  Application  should 
be  made  soon  after  cutting. 

Only  the  ester  forms  of  2,1|-D  and  2,ij.,5-T 
should  be  used  to  control  brush  because 
they  are  more  effective  than  the  amines. 
The  low-volatile  esters  seem  to  have  an 
advantage  over  the  normal  esters  because 
they  produce  less  gas. 

The  best  method  of  controlling  brush  de- 
pends on  individual  circumstances.  If 
it  must  be  removed  at  once,  it  may  be 
better  to  use  a  bulldozer  or  other  im- 
plement than  a  chemical.  If  the  top 
growth  must  be  removed  quickly,  it  would 
be  best  to  cut  the  brush  green  and  then 
treat  the  stumps  to  prevent  regrowth. 

Foliage  sprays  and  basal  bark  treatment 
can  be  used  to  best  advantage  in  fence- 
rows  and  drainage  ditches  and  on  scat- 
tered brush  in  pastures.  A  year  or  so 
after  chemical  treatment,  the  dead  brush 
can  be  removed  by  hand  or  with  a  tractor. 

F.  W.  Slife 
11-16-53 


8/4/2010 
T  205645    3  152  00 


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