improving nitrogen management with the anaerobic potentially mineralizable nitrogen test a

200 Pages·2017·2.43 MB·English

by  Jason D Clark

IMPROVING NITROGEN MANAGEMENT WITH THE ANAEROBIC
POTENTIALLY MINERALIZABLE NITROGEN TEST

A DISSERTATION
SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL
OF THE UNIVERSITY OF MINNESOTA
BY

Jason Daniel Clark

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

Major Professor: Fabián Fernández

May 2018

University of Minnesota

St. Paul, Minnesota
© Jason Daniel Clark 2018
ACKNOWLEDGEMENTS
I would like to thank Dr. Fabián Fernández for giving me the opportunity to be
part of his corn N management program here at the University of Minnesota and for his
support and guidance through my degree program. I would also like to thank my
committee members, Drs. Carl Rosen, Dan Kaiser, and Dave Franzen for their time,
direction, and advice they have given me in the pursuit of my research and educational
goals.
I would like to thank the other supporting scientists working on this project from
DuPont Pioneer and the seven other universities (Newell Kitchen, John Shanahan, James
Camberato, Paul Carter, Richard Ferguson, Carrie Laboski, Emerson Nafziger, John
Sawyer, and Matt Yost) for their help and guidance as I have collected data, solved
problems, and improved manuscripts and presentations. I would also like to thank the
four other graduate students on this project that have helped collect samples and analyze
data (Curtis Ransom, Christopher Bandura, Mac Bean, and Matt Shafer). In addition, I
would like to give a special thanks to Kristen Veum from the University of Missouri for
letting me come to her lab for a week and learn how to perform the anaerobic potentially
mineralizable N test.
I am also grateful for the help and friendship of my fellow graduate students and
undergraduate student workers who have helped me in collecting and analyzing data. I
thank all the personnel at the University of Minnesota research and outreach centers and
the farmer cooperators who allowed me to use their farms and equipment to conduct my
research. I would also like to thank the supporting scientists and field technicians from
each university and DuPont Pioneer for their help on this project (Dan Barker, Lakesh
Sharma, Amitava Chatterjee, Norm Cattanach, Todd Andraski, Tim Hart, Matt
Volkmann, Jason Niekamp, Joshua Vonk, Glen Slater, Andrew Scobbie, Thor Sellie,
Nicholas Severson, Darby Martin, and Erik Joerres). In addition, I would like to thank
DuPont Pioneer for the financial support given for this research.
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I am also grateful for the love and support of my parents Brent and Cindy Clark,
immediate and extended family, and many friends who have been there cheering me on
as I have pursued my educational goals. Most importantly, I am very thankful for the
loving support of my wife Lacee and my son Joshua and daughter Emma for all their
encouragement, love, and patience they have given me as I have worked many long days
and late nights finishing fieldwork and writing the many drafts of this paper.

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ABSTRACT
Clark, Jason Daniel. Ph.D., University of Minnesota, May 2018. Improving Nitrogen
Management with the Anaerobic Potentially Mineralizable Nitrogen Test. Major
Professor: Fabián Fernández

The anaerobic potentially mineralizable N (PMN ) test alone or combined with
an
the pre-plant (PPNT) and pre-sidedress (PSNT) nitrate tests may improve predictability
of corn (Zea may L.) N needs. Forty-nine N response studies were conducted from 2014-
2016 across various soil and weather conditions in the US Midwest to 1), evaluate the
influence of soil and weather conditions on PMN from different soil sampling timings
an
(pre-plant vs. V5 corn development stage), N rates (0- and 180-kg-N ha-1 applied at
planting) and incubation lengths (7-, 14-, and 28-d); and 2), evaluate the predictability of
grain yield, relative yield, N uptake, and economic optimal N rate (EONR) of corn with
PMN , PPNT, and PSNT alone and combined. The top 30-cm of soil was sampled for
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PMN analysis before planting and N fertilization and at V5 in the 0- and 180-kg-N ha-1
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treatments. Soil was sampled for the PPNT before planting (0-90 cm) and for the PSNT
at V5 (0-60 cm) in 30-cm increments. Soil parameters measuring or associated with
greater organic matter increased PMN along with evenly distributed rainfall while
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increasing temperatures decreased PMN . Soil parameters followed by precipitation and
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air temperature had the best relationships with PMN . Differences in PMN due to
an an
sampling time, N rate, and incubation length were best explained by soil parameters. Soil
and weather variables alone (R2 ≤ 0.41) or combined (R2 ≤ 0.60) did not predict PMN
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well enough to estimate PMN reliably. Including PMN with PPNT or PSNT as
an an
separate variables with the initial amount of NH + from the PMN test improved
4 an
predictability of grain yield and EONR. The PMN timing and N rate used varied by soil
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texture or growing degree-day (GDD) category evaluated. Regardless of the
improvements in predictability of crop responses from including PMN with PPNT or
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PSNT in addition to other modifiers (separating sites by texture or GDDs, using deeper
soil NO --N sampling depths, delaying soil NO --N sampling from pre-plant to V5, or
3 3
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including initial NH +), the predictability of crop responses after N fertilization (a
4
common practice in commercial fields) was not substantial enough (R2 ≤ 0.41) for using
these soil tests alone to predict corn N needs.

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TABLE OF CONTENTS
Abstract .............................................................................................................................. iii
List of Tables .................................................................................................................... vii
List of Figures .................................................................................................................... xi
Chapter 1. Summary ........................................................................................................... 1
Chapter 2. US Midwest Soil and Weather Conditions Influence Anaerobic Potentially
Mineralizable Nitrogen ....................................................................................................... 5
2.1. Synopsis ................................................................................................................... 5
2.2. Introduction ............................................................................................................. 6
2.3. Materials and Methods ............................................................................................ 9
2.3.1. Experimental Design ......................................................................................... 9
2.3.2. Soil Sampling .................................................................................................. 10
2.3.3. Weather ........................................................................................................... 11
2.3.4. Statistical Analysis .......................................................................................... 12
2.4. Results and Discussion .......................................................................................... 14
2.4.1. Relationship Between PMNan and Soil Parameters ........................................ 15
2.4.2. Relationship Between PMNan and Weather .................................................... 18
2.4.3. PMNan Prediction ............................................................................................ 19
2.4.4. PMNan Treatment Differences ........................................................................ 22
2.5. Conclusions ........................................................................................................... 26
2.6. References ............................................................................................................. 28
2.7. Tables .................................................................................................................... 36
Chapter 3. Predicting Economic Optimal Nitrogen Rate with the Anaerobically
Potenially Mineralizable Nitrogen Test ............................................................................ 51
3.1. Synopsis ................................................................................................................. 51
3.2. Introduction ........................................................................................................... 53
3.3. Materials and Methods .......................................................................................... 57
3.3.1. Experimental Design ....................................................................................... 57
3.3.2. Soil Sampling .................................................................................................. 57
3.3.3. Plant Sampling ................................................................................................ 58
3.3.4. Statistical Analysis .......................................................................................... 59
3.4. Results and Discussion .......................................................................................... 60
3.4.1. Predicting EONRs with PMNan ...................................................................... 61
3.4.2. Predicting EONRs with PMNan and Initial NH4+ ........................................... 63
3.5. Conclusions ........................................................................................................... 67
3.6. References ............................................................................................................. 68
3.7. Tables .................................................................................................................... 77
Chapter 4. Can the Anaerobic Potentially Mineralizable Nitrogen Test Improve Pre-
plant and Pre-sidedress Nitrate Tests? .............................................................................. 85
4.1. Synopsis ................................................................................................................. 85
4.2. Introduction ........................................................................................................... 87
4.3. Materials and Methods .......................................................................................... 91
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4.3.1. Experimental Design ....................................................................................... 91
4.3.2. Soil Sampling .................................................................................................. 91
4.3.3. Plant Sampling ................................................................................................ 93
4.3.4. Weather ........................................................................................................... 93
4.3.5. Statistical Analysis .......................................................................................... 94
4.4. Results and Discussion .......................................................................................... 96
4.4.1. Nitrogen Sufficiency Using Soil Available N................................................. 98
4.4.2. Critical Soil Nitrate Content ......................................................................... 105
4.5. Conclusions ......................................................................................................... 107
4.6. References ........................................................................................................... 108
4.7. Figures ................................................................................................................. 117
4.8. Tables .................................................................................................................. 119
Chapter 5. Corn Nitrogen Management Using Soil Nitrate Tests Adjusted by the
Anaerobic Potentially Mineralizable-Nitrogen Test and Field Conditions .................... 125
5.1. Synopsis ............................................................................................................... 125
5.2. Introduction ......................................................................................................... 127
5.3. Materials and Methods ........................................................................................ 130
5.3.1. Experimental Design ..................................................................................... 130
5.3.2. Soil Sampling ................................................................................................ 131
5.3.3. Plant Sampling .............................................................................................. 132
5.3.4. Weather ......................................................................................................... 133
5.3.5. Statistical Analysis ........................................................................................ 133
5.4. Results and Discussion ........................................................................................ 135
5.4.1. Soil Nitrate Sampling Depth ......................................................................... 136
5.4.2. Grain Yield .................................................................................................... 137
5.4.3. Nitrogen Uptake ............................................................................................ 144
5.4.4. EONR ............................................................................................................ 145
5.5. Conclusions ......................................................................................................... 147
5.6. References ........................................................................................................... 149
5.7. Tables .................................................................................................................. 157
Chapter 6. General Discussion ........................................................................................ 165
6.1. Advantages and Limitations ................................................................................ 165
6.2. Conclusions ......................................................................................................... 167
6.3. Future Research ................................................................................................... 171
Bibliography ................................................................................................................... 173

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LIST OF TABLES
Table Page
Table 2.1. Minimum, maximum, mean, standard deviation, and coefficient of
variation of anaerobic potentially mineralizable N (PMNan) and soil parameters
across 32 site-years. .................................................................................................... 36
Table 2.2. Minimum, maximum, mean, standard deviation, and coefficient of
variation of precipitation and temperature conditions for the period of first
growing degree-day (GDD) of the year to the V5 corn development stage (V5)
and from the pre-plant (PP) soil sampling time to V5 across 32 site-years. ............... 37
Table 2.3. Weather variables used and their calculations. The time intervals evaluated
for anaerobic potentially mineralizable N (PMN ) from the pre-plant soil
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sampling timing (PP ) were first growing degree-day (GDD) of the year to pre-
0N
plant soil sampling (PP) and 30-d before PP. For PMN from the V5 corn
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development stage (V5) soil sampling where 0 kg-N ha-1 (V5 ) and 180 kg-N ha-
0N
1 was applied at planting (V5 ), the time intervals evaluated were first-GDD of
180N
the year to V5, 30-d before PP to V5, PP to V5, and 30-d before V5. ....................... 38
Table 2.4. Type of model (M) and coefficient of determination of the anaerobic
potentially mineralizable N soil test (PMN ) from soil samples obtained before
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planting and N fertilizer application (PP ) and at the V5 development stage
0N
where zero (V5 ) or 180 kg-N ha-1 (V5 ) was applied at planting and
0N 180N
incubated for 7-, 14-, and 28-d as a function of soil parameters, precipitation, and
temperature variables across 32 site-years. ................................................................. 39
Table 2.5. Pearson correlation coefficients of soil parameters. ........................................ 41
Table 2.6. Pearson correlation coefficients of soil N measurements. ............................... 42
Table 2.7. Pearson correlation coefficients of precipitation variables of two-time
intervals: First growing degree-day (GDD) to pre-plant sampling timing (above
line) and pre-plant to V5 corn development stage (below line).................................. 43
Table 2.8. Pearson correlation coefficients of temperature variables of two-time
intervals: First growing-degree-day (GDD) to pre-plant sampling timing (above
line) and pre-plant to V5 corn development stage (below line).................................. 44
Table 2.9. Average percent use of soil parameters, precipitation, and temperature
variables from 32 sites by four automatic variable selection methods (Stepwise,
Forward, Backward, Lowest CP) and their average total R2 when predicting
anaerobic potentially mineralizable N (PMN ) from soil samples obtained before
an
planting and N fertilizer application (PP ) and at the V5 development stage
0N
where zero (V5 ) or 180 kg-N ha-1 (V5 ) was applied at planting and
0N 180N
incubated for 7-, 14-, and 28-d along with their average partial R2 when the given
variable was selected by the Stepwise variable selection procedure. ......................... 45
Table 2.10. Statistical analysis of fixed and random effects and their interactions for
anaerobic potentially mineralizable N across 32 site-years. ....................................... 46
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Table 2.11. Mean comparisons of anaerobic potentially mineralizable N (PMN )
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affected by soil sampling timing and N rate (STNR) and incubation length (Inc.)
for 32 site-years........................................................................................................... 47
Table 2.12. Comparison of the effect of soil and weather variables across 32 site-
years on the intercept and slope coefficients for anaerobic potentially
mineralizable N (PMN ) from when soil samples were obtained before planting
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and N fertilizer application (PP ) and at the V5 development stage where zero
0N
(V5 ) or 180 kg-N ha-1 (V5 ) was applied at planting with incubation lengths
0N 180N
(Inc.) of 7-, 14-, and 28-d. Only those soil and weather variables that had a
significant interaction (P ≤ 0.1) with STNR or IL were included. ............................. 48
Table 2.13. Comparison of the random effects on anaerobic potentially mineralizable
N (PMN ) and their significance level when site and its interactions were
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evaluated as random effects and their change when soil parameters, precipitation,
and temperature variables were added as individual fixed effects. Only those soil
and weather variables that had a significant interaction (P ≤ 0.1) with sampling
timing and N rate (STNR) or incubation length (Inc.) were included. ....................... 50
Table 3.1. Economical optimum N rate (EONR) for single (EONR ) and split N
single
applications (EONR ) and soil characteristics across 32 site-years (All) or
split
partitioned by soil texture (coarse, medium, and fine). Mean values ± standard
deviation. ..................................................................................................................... 77
Table 3.2. Anaerobic potentially mineralizable N (PMN ) from different sampling
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timings and N rate treatments (PP , V5 , and V5 ) that were incubated for 7-,
0N 0N 180N
14-, and 28-d with the amount of initial ammonium-N (NH +-N) at each sampling
4
before incubation. Mean values ± standard deviation. ............................................... 78
Table 3.3. Coefficient of determination (R2) and root mean square error (RMSE)
averaged across all sites for regression of economical optimum N rate (EONR) of
single- and split-N applications and the anaerobic potentially mineralizable N test
(PMN ), PMN combined with initial NH + (PMN +NH +), and PMN and
an an 4 an 4 an
initial NH + as separate explanatory variables (PMN and NH +) at different soil
4 an 4
sampling timings and N rate treatments (PP , V5 , and V5 ) and three
0N 0N 180N
incubation lengths (7-, 14-, and 28-d). ........................................................................ 79
Table 3.4. Coefficient of determination (R2) and root mean square error (RMSE) for
coarse-textured soils for regression of economical optimum N rate (EONR) of
single and split N applications and the anaerobic potentially mineralizable N test
(PMN ), PMN combined with initial NH + (PMN +NH +), and PMN and
an an 4 an 4 an
initial NH + as separate explanatory variables (PMN and NH +) at different soil
4 an 4
sampling timings and N rate treatments (PP , V5 , and V5 ) and three
0N 0N 180N
incubation lengths (7-, 14-, and 28-d). ........................................................................ 80

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