Table Of ContentPURDUE UNIVERSITY
THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION
BY Awadh Behari Saran Verma
ENTITLED THE EFFECTS OF CROP RESIDUES ON SOIL CONDITIONS
IN CARRINGTON LOAM__________________________________________
COMPLIES WITH THE UNIVERSITY REGULATIONS ON GRADUATION THESES
AND IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS
FOR THE DEGREE OF
Doctor of Philosophy
Professob in Charge of Thesis
:ead of School or Department
February 19 50
TO THE LIBRARIAN:--
__
THIS THESIS IS NOT TO BE REGARDED AS CONFIDENTIAL
jf.
FBOFESSOH nr CHARGE
GBAD. SCHOOL FORM 0—3.48—1M
THE EFFECTS OF CROP RESIDUES ON SOIL CONDITIONS
IN CARRINGTON LOAM
A Thesis
Submitted to the Faculty
of
Purdue University
by
Awadh Behari Saran Verma
in partial fulfillment of the
requirements for the Degree
of
Doctor of Philosophy
February, 1950
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ABSTRACT
Verma> A.B.S. The Effects of Crop Residues on Soil Condi
tions in Carrington Loam.
Wheat straw was applied at the rate of 1.5 tons per acre in
small plots from which the soil was dug out and replaced after sieving
and mixing. The straw was placed on the surface, and under 7" of soil
and mixed with and 0"-7M of soil. There was no crop, and no weed
was allowed to grow on the plots.
In another set of experiments, wheat straw, corn stover, and
glass wool were applied at the rate of 1.5 tons per acre to soybeans.
In the third set of experiments, residues from a meadow crop
of timothy, alfalfa, and red clover were applied to the corn crop in
four different methods of handling, using different tillage implements -
1. Residues left on the surface, tilled 3n with shallow
sweeps.
2. Residues mixed with and tilled with T.N.T. spe
cial plow.
3. Residues mixed with 0"-7" and tilled with deep disk.
4. Residues under ?" and tilled with conventional plow.
A total of 70 pounds of nitrogen was applied in three applications in
fall, spring, and at planting time. All plots were subsequently culti
vated.
Studies on soil organic matter, nitrate nitrogen, ammoniacal
nitrogen, soil reaction, soil moisture relationships, and soil tempera
ture were made. The yields of soybeans and corn were compared.
The increase in yield of soybeans was found to be from 4 to
6 bushels per acre in the mulched plots against the no-mulch plots*
When the meadow residue was mixed with 0"—7" soil and worked
with a deep disk, the increase in the yield of corn was 24 bushels per
acre over the plot where the residue was left on the surface and tilled
with a shallow disk. The increase was 13 bushels per acre in case of
residues mixed in 0*-3” and placed under 7” of soil.
The increase in yield of soybeans and corn was found corre
lated to the soil moisture and soil temperature.
The soil organic matter is found to increase with the appli
cations of crop residues.
The accumulation of nitrate nitrogen was found to be low
where large quantities of undecomposed residues were present. Larg
er concentration of nitrate nitrogen was found in the dry periods
on account of the rise of nitrates with the capillary water. After
showers of rain, the nitrates were found to have moved down or dis
appeared. When nitrogenous fertilizers were applied, the accumula
tion of nitrates was not lowered by the presence of undecomposed or
ganic matter.
The concentration of ammonia was found to be very low in
all treatments.
The effect of crop residues on soil reaction was not pro
nounced.
When the residues were placed on the surface, the increase
in soil moisture has been about 6 per cent in the surface soil and
about 3 per cent in the subsurface soil. The soil moisture during
dry periods has been very close to the wilting point in the no-mulch
soybean plots. The incorporation of residues by different tillage im
plements raised the total porosity of the surface soil by about 4 per
cent as against the subsurface soil. However, the mulch materials
which remained on the surface for four months did not show any effect
on soil porosity.
In summer between July and September the weekly mean soil
temperature was found to be lower by 6° to 20° F. by surface applica
tion of straw. The mulches had a moderating influence on the soil
temperature and reduced its wide fluctuations in the diurnal varia
tions.
The residues maintained loose structure of the surface soil
and reduced surface flow and run-off.
The data thus indicate that crop residues improved moisture
content, moderated soil temperature, and maintained a favourable phy
sical condition of soil which gave higher yields of soybeans and corn.
ACKNOWLEDd/IENTS
The author is deeply indebted to Dr. Helmut Eohnke for his
valuable guidance and helpful advice given throughout the course of
this research.
Sincere thanks and appreciation are due to Mr. R* B. Hickok
for giving me permission to carry on my research at the Throckmorton
Farm. Thanks are also due to Mr. Evan R* Baugh for his sincere help
and cooperation in carrying out many difficult operations on the farm.
The author extends warm, thanks to Dr. N. J. Volk, Associate
Director, Agricultural Experiment Station, and Dr. J. B. Peterson,
Head of the Agronomy Department, for providing facilities to carry
out the research at the Agricultural Experiment Station.
Dr. B. R. Bert ramson and Dr. J. L. White have also been help
ful in giving advice and suggestions on some analytical methods, for
which sincere thanks are expressed.
The author is also thankful to Dr. G. A. Dries, Agricultural
Botany Department, Dr. N. K. Ellis, Horticultural Department, and Dr.
G-, 0. Mott, Crops Section, Agronomy Department, for their sincere en
couragement and warm good will which were so vital to the success of
this research.
He is also grateful to the Government of Central Provinces
and Berar, India, for the grant of an overseas scholarship which made
this undertaking possible.
There are a number of other friends and colleagues who de
serve appreciation for their timely help.
TABLE OF CONTENTS
Page
INTRODUCTION................................................... 1
Objectives ............................................ 5
REVIEW OF LITERATURE........................................ 4
EXPERIMENTAL ................................................... 16
Mulch Placement Experiments................................ 16
Field Technique..................................... 16
Treatments................................. 17
Mulch Material Experiments................................. 19
Field Technique........................................ 19
Treatments ........................ 19
Layout................................. 20
Replication ....................... 20
Location ...................... 20
Crop ............................................. 20
Time of Application.................................... 20
Size of Plots.................................... 20
Sampling.................................. 22
Previous History of Plots.............................. 22
Mulch Tillage Experiments ......................... 23
Treatments ................................... 23
Replications........».............................. 24
Layout ................................................ 24
Size of Plots............................. 24
Location .......................... 24
Fertilizer Used......................... 24
Cultivation Given................................... 26
Previous History of Plots.............................. 26
Sampling.................................. 26
Measurement of Soil Temperature............................ 27
Laboratory Techniques ................................... 30
Organic Matter Determination ....................... 30
Nitrate-Nitrogen Determination ............... 30
Ammoniacal Nitrogen Determination...................... 30
Moisture Determinations...................... 30
Soil Reaction Determination............................ 31
PRESENTATION OF DATA AND DISCUSSION............................ 32
Rainfall and Season.............................. gg
TABLE OF CONTENTS ( Cont» d)
Page
Effect of Crop Residues on Yield of Crops ............. 37
Yield of Soybeans.........................*........ 57
Yield of Corn.............................. 41
Effect of Crop Residues on Soil Organic Matter ........ 45
Effect of Mulch Placement on Soil Organic Matter 45
Effect of Mulch Materials on Soil Organic Matter 48
Effect of Mulch Tillage on Soil Organic Matter...... 48
Effect of Crop Residues on NO3-N of Soil................ 53
Effect of Mulch Placement on NO3- N ........... 53
Effects of Mulch Materials on NO3- N ....... » • 60
Effect of Mulch Tillage on NOg-N ........... 60
Effect of Crop Residues on NH^-N of Soil ...... 67
Effect of Mulch Placement on ÎE4- N .................. 67
Effect of Mulch Materials on NH4- N .................. 67
Effect of Mulch Tillage on NH4- N .................... 67
Effect of Crop Residues on Soil Reaction................ 74
Effect of Mulch Placement on Soil pH ........... 74
Effect of Mulch Materials on Soil p H ............... 74
Effect of Mulch Tillage on Soil pH ................ 74
Effect of Crop Residues on Soil Moisture................ 79
Effect of Mulch Placement on Soil Moisture......... 79
Effect of Mulch Materials on Soil Moisture........ 79
Effect of Mulch Tillage on Soil Moisture............ 84
Effect of Crop Residues on the Energy Relationships of Soil
Moi sture......... 87
Effect of Mulch Placement on the pF Curve............ 87
Effect of Mulch Materials on Soil p F ................ 87
Effect of Mulch Tillage on Soil p F .... ...... 92
Effects of Crop Residues on Porosity and SoilS tructure .. 92
Porosity of Soil.......... 92
Condition of Surface Soil......... 94
Effect of Crop Residues on Soil Temperature............. 98
Effect of Placement of Straw on Seasonal Variations
of Soil Temperature ............................ 98
Effect of Placement of Straw on Diurnal Variations
of Soil Temperature..................... 103
Effect of Mulch Materials on Soil Temperature ........ 105
