Previous Crop and Cover Crop Effects on Corn
Nitrogen Response
1Department of Soil, Water, & Climate, 2Southern Research and Outreach Center
MVTL Agronomy Update Meeting
January 30, 2020
New Ulm, MN
Carl Rosen1
Vince Fritz2
Charlie Rohwer2
James Crants1
Matt McNearney1
Background and Topics Covered
• Benefits and risks of a rye cover crop
• Sweet corn N rate, timing, and source study
– motivation for previous crop study
• Previous crop establishment to determine N credits
• Field corn N response following various previous crops
Why Plant Cover Crops?• Provides soil cover for extended period in the fall and spring
• Reduces runoff and wind erosion
• Captures residual nutrients (esp. N) to prevent leaching
• Outcompetes/controls weeds
• Potentially suppresses some insects and diseases
• Adds biomass and carbon (& nitrogen if a legume)
• Stimulates soil microbial activity
• Over time can improve soil aggregation
• Of the non-legume cover crops available, cereal rye is the easiest to establish and grow under Minnesota conditions
https://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition/Text-Version/Nonlegume-Cover-Crops/Cereal-Rye
Cover Crop (Rye) Challenges for Corn
• Short time for seeding and stand establishment
– Seed into corn or soybeans before harvest (timely rain needed)
• Sometimes more diseases and pests
• Poor corn stand; Allelopathy? Lots of debate
– Chemical, physical or biological?
• Yield drag
– Termination date
– C/N ratio
– Environmental conditions
https://agfuse.com/article/how-to-protect-corn-yields-following-cereal-rye
Yield Advantage of Corn Following CC vs. No CC
https://www.iasoybeans.com/upl/downloads/publications/long-term-cover-crop-trials.pdf
15 Sites in Iowa in 2017 and 2018
Termination Date is Important – Illinois Study
https://www.dekalbasgrowdeltapine.com/en-us/agronomy/influence-of-the-timing-of-cereal-rye-cover-crop-termination-on-corn-yield.html
-26 -15 0 +7 Photos taken 6/11
Overall Assessment of a Rye CC for Corn
• Use of a winter rye CC can result in reduced or increased corn yields
• Management is important to maintain yields
• Late termination tends to result in lower yields
– Germination effects
– N effects
– Diseases
– Allelopathy
https://agfuse.com/article/how-to-protect-corn-yields-following-cereal-rye
What About CCs Following Sweet Corn?
• About 120,000 acres grown in MN for processing
• In rotation with soybeans and field corn
• Harvest starts early August until mid-late September
• Time and opportunity to establish a cover crop
https://agfuse.com/article/how-to-protect-corn-yields-following-cereal-rye
Previous N Rate Sweet Corn Study - SROC
• Three hybrids– GSS 1477
– DMC 21-84
– GM Code 646
• Two plant populations– 22,000 plants/A
– 28,000 plants/A
• Two planting dates– May
– June
• Six nitrogen treatments
1. 0 (no N applied),
2. 60 lb N/A applied preplant as urea,
3. 120 lb N/A applied preplant as urea,
4. 180 lb N/A applied preplant as urea,
5. 120 lb N/A applied preplant as ESN
(Environmentally Smart Nitrogen,
Agrium Inc.),
6. 120 lb N/A as urea with 60 lb N/A
applied preplant and 60 lb N/A applied
at V6-8.
Green Yield as Affected by N Treatment
and Plant Population Yield increased with
increasing N rate at both
populations;
An N rate between 120 and
180 lb N/A was required
Adequate N is necessary to
support yields at the higher
plant population
No difference in yield due to
N timing or N source
N Uptake as Affected by N Treatment and
Plant PopulationN uptake increased with
increasing N rate at both
populations;
N uptake was greater at the
higher plant population
No difference in N uptake
due to N timing or N source
50
55
60
65
0 50 100 150 200
Pe
rce
nt
of
N u
pta
ke in
sto
ver
N applied (lbs/ac)
Urea
ESN
Split
a
b bc bcd
cd d
Proportion of N in Stover as Affected
by N Treatment
At optimum N rates,
57% to 59% of the
N taken up remains
in the stover
C:N ratio of ~ 32
Overall Summary from Sweet Corn N Study
• Optimal N rate for sweet corn following soybeans in a dryland high OM
soil was between 120 -180 lbs N/A; this is higher than current N
recommendations of 110 lbs N/A
• Split N applications and use of coated urea resulted in similar yields
compared to preplant applied urea
• About 58% of the N taken up by sweet corn was still in the stover at
harvest = 60-70 lbs N/A; C:N ratio ~ 30-40
• Can N rates be lowered in a subsequent corn crop?
Nitrogen Credit Study for Field Corn
• Objectives: – To assess the effect of sweet corn as a previous crop, relative to field
corn and soybean on field corn N response
– To determine the effect of a rye cover following sweet corn on field corn N response
• Can N rates be lowered for field corn if sweet corn is the previous crop? – Currently no N credit given for sweet corn
• First step was to establish the previous crops (and rye cover)
Methods
• Rotation crops established in 2017 & 2018
• Field corn N response was evaluated in 2018 & 2019
• Southern Research and Outreach Center (Waseca);
rainfed conditions
Previous Crops – 2017 and 2018
• Sweet Corn, Syngenta GSS1477– 140 lbs N/A
• Sweet Corn, Syngenta GSS1477 + rye cover crop– 140 lbs N/A
• Field corn, Nutech 5F-503AM (2017); 5F-196AM (2018)– 170 lbs N/A
• Soybean, Asgrow AG1733 (2017); Pioneer P15T46R2 (2018)– 0 lbs N/A
• 4 previous crops x 6 N treatments x 4 replications = 96 plots
101 201 301
0 #N 200 #N 100 #N
102 202 302
150 #N 250 #N 50 #N
103 203 303
100 #N 150 #N 200 #N
104 204 304
50 #N 0 #N 250 #N
105 205 305
100 #N 200 #N 0 #N
106 206 306
150 #N 50 #N 250 #N
107 207 307
150 #N 200 #N 0 #N
108 208 308
100 #N 250 #N 50 #N
109 209 309
0 #N 100 #N 150 #N
110 210 310
50 #N 250 #N 200 #N
111 211 311
150 #N 0 #N 200 #N
112 212 312
250 #N 100 #N 50 #N
113 213 313
150 #N 200 #N 100 #N
114 214 314
250 #N 50 #N 0 #N
115 215 315
100 #N 0 #N 150 #N
116 216 316
200 #N 250 #N 50 #N
117 217 317
250 #N 50 #N 0 #N
118 218 318
150 #N 200 #N 100 #N
119 219 319
50 #N 0 #N 250 #N
120 220 320
150 #N 100 #N 200 #N
121 221 321
150 #N 200 #N 100 #N
122 222 322
50 #N 250 #N 0 #N
123 223 323
0 #N 50 #N 150 #N
124 224 324
100 #N 250 #N 200 #N
125 225 325
0 #N 200 #N 250 #N
126 226 326
100 #N 50 #N 150 #N
127 227 327
250 #N 200 #N 100 #N
128 228 328
0 #N 150 #N 50 #N
129 229 329
200 #N 150 #N 50 #N
130 230 330
250 #N 0 #N 100 #N
131 231 331
200 #N 250 #N 50 #N
132 232 332
150 #N 0 #N 100 #N
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Precipitation and Temperature
Previous Crop Data Results - 2017
Crop Harvest yield Residue dry
yield (T/ac)
Residue N
uptake (lbs/ac;
left in field)
Residue C:N
Field corn 157 ± 16 bu/ac 5.1 ± 0.4 66.9 ±5.7 70.1 ± 4.2
Soybeans 48.2 ± 6.8 bu/ac 2.1 ± 0.1 50.0 ± 3.5 40.3 ± 2.1
Sweet corn 4.5 ± 1.2 T/ac 1.7 ± 0.1 59.7 ± 4.8 25.7 ± 2.5
Previous Crop Data Results - 2018
Crop Harvest yield Residue dry
yield (T/ac)
Residue N
uptake (lbs/ac;
left in field)
Residue C:N
Field corn 183 ± 19 bu/ac 3.7 ± 0.1 44.9 ± 1.6 76.8 ± 4.9
Soybeans 62.7 ± 2.7 bu/ac 2.0 ± 0.1 34.4 ± 4.2 58.8 ± 6.2
Sweet corn 6.2 ± 0.4 T/ac 2.4 ± 0.3 56.1 ± 18.4 40.4 ± 7.7
Rye Cover Crop Establishment & Management
• Sweet corn harvested August 15, 2017 & August 15, 2018
• Rye planted August 30, 2017 & September 11, 2018
• Sprayed with Roundup on May 10, 2018 & May 7, 2019
• Disked in 3 days later
Aug. 15, 2017
No-till grain drill
Sept. 7, 2017
Oct. 10, 2017
April 10, 2018
April 25, 2018
May 10, 2018
May 18, 2018
May 7, 2019
Results: Soil Nitrate-N (0-2 ft)
Fall 2017 & Spring 2018
CropFall 2017 nitrate-N
(ppm)
Spring 2018 nitrate-N
(ppm)
Field corn 2.8 ± 1.1 3.9 ± 0.6
Soybeans 3.8 ± 0.3 6.5 ± 2.8
Sweet corn 7.5 ± 0.9 6.4 ± 2.0
Sweet corn + rye 2.2 ± 0.4 3.1 ± 0.9
Soil Nitrate-N (0-2 ft)
Fall 2018 & Spring 2019
CropFall 2018 nitrate-N
(ppm)
Spring 2019 nitrate-N
(ppm)
Field corn 7.1 ± 1.0 8.7 ± 1.5
Soybeans 6.9 ± 1.2 8.1 ± 1.1
Sweet corn 5.8 ± 1.4 7.9 ± 1.9
Sweet corn + rye 6.9 ± 1.1 6.2 ± 1.2
Rye Dry Biomass and N Uptake (May 8, 2018)
1618+372 lbs/A
51+7 lbs N/A
C/N = 14
Rye Dry Biomass and N Uptake (May 7, 2019)
1887+779 lbs/A
56+21 lbs N/A
C/N = 14
N Treatments in 2018 & 20191. 0 lb N/A
2. 50 lb N/A
3. 100 lb N/A
4. 150 lb N/A
5. 200 lb N/A
6. 250 lb N/A• P, K, S all applied preplant and
incorporated with the N
Field corn planted:May 18, 2018 and May 15, 2019
101 201 301
0 #N 200 #N 100 #N
102 202 302
150 #N 250 #N 50 #N
103 203 303
100 #N 150 #N 200 #N
104 204 304
50 #N 0 #N 250 #N
105 205 305
100 #N 200 #N 0 #N
106 206 306
150 #N 50 #N 250 #N
107 207 307
150 #N 200 #N 0 #N
108 208 308
100 #N 250 #N 50 #N
fiel
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June 28, 2019
Previous crop - Field Corn Previous crop Sweet Corn
Field Corn N Response 2018 –
Previous Crop Effects on EONR
Rotation cropYield peak
(bu/ac)
EONR
(lbs/ac)
Field corn 185 252
Soybean 202 160
Sweet corn 207 180
Sweet corn + rye 205 161
N application rate (lbs/ac)
250
Field Corn N Response 2019 –
Previous Crop Effects on EONR
Rotation cropYield peak
(bu/ac)
EONR
(lbs/ac)
Field corn 191 256
Soybean 215 170
Sweet corn 219 166
Sweet corn + rye 225 191
250 188
Conclusions
• An N credit can be given when sweet corn is the previous
crop; possibly similar to or slightly less than soybean
• Adding a rye cover crop after sweet corn results in similar
or slightly less N credit than sweet corn or soybean
• N required for field corn following field corn was much
higher than expected
Next Steps• Data on field corn N uptake
from 2019 still to be analyzed
• Rotation crops & rye were grown for a study in 2020
• Plan is to repeat this study if funding is available
October 2019
Thank You & Questions?
Research Funding AcknowledgmentsMidwest Food Products Association
MN Agricultural Fertilizer Research and Education Council
Field Corn N Response 2018 –
Previous Crop Effects on EONR
Rotation cropYield plateau
(bu/ac)
EONR
(lbs/ac N)
Field corn 183 249
Soybean 198 144
Sweet corn 205 149
Sweet corn + rye 198 82
Field Corn N Response 2019 –
Previous Crop Effects on EONR
Rotation cropYield plateau
(bu/ac)
EONR
(lbs/ac)
Field corn 192 257
Soybean 211 126
Sweet corn 211 146
Sweet corn + rye 224 188