1. Strategies for Split N Applications for Corn
Gyles Randall
Soil Scientist and Professor
Univ. of Minnesota, SROC, Waseca
11/8/2018

2. What do 67 site-years of split-N research in Southern Minnesota tell us?
11/8/2018

3. Preplant vs. Split Application 1989–1992
Conditions
32 sites including coarse-textured outwash, medium-textured loess, and fine-textured glacial till soils
Growing season rainfall ranged from 36% below normal to 59% above normal
Previous crop = soybean, corn, oat, and rye
11/8/2018

4. Preplant vs. Split Application 1989–1992
Procedures
Preplant N rates = 0, 30, 60, 90, 120, 150, and 180 lb N/A as broadcast incorporated urea
Split rates = 60 and 30 lb N/A as PP urea in 1989–90 and 1991–92, respectively, PLUS 30, 60, and 90 lb N/A as urea knifed in 4” deep at V5 to V6
11/8/2018

5. Preplant vs. Split, 1989–92 Corn Grain Yield Summary
Sites
Total
Till
Loess
Outwash
Number 32 14 11 7
N responsive 28 9 5
Preplant = split 16 2
Preplant < split 8 4 1 3
Preplant > split
11/8/2018

6. Preplant vs. Split, 1989–92 Conclusions:
Grain yield responded to N at 88% of the sites.
Preplant application was equal to split application at 16 of the 28 responding sites (58%).
Split application was superior to PP application at 8 sites (28%).
Excessive rainfall and/or sandy soils.
Preplant application was superior to split application at 4 sites (14%).
Below-normal or above-normal rainfall and insufficient N rate applied early.
Split application of N out performed PP application at 3 of 5 sandy sites, 1 of 9 loess sites, and 4 of 14 till sites and only in wetter-than-normal years.

7. Corn yield as affected by split-N application and precipitation.
Time of N Application
Year (precip. departure)
Preplant
12” Corn
1991 (+56%)
1992 (+16%)
- N rate (lb N/A) -
- - Yield (bu/A) - - 84
107 60
143
144 30
161
141 90
158
156
157
137
120
165
164
182
153
Advantage for split =
+11
-11
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8. Continuous Corn, 1992–97 Olmsted Co. Port Byron silt loam (loess)
Chisel plow
N Source = anhydrous ammonia (AA)
11/8/2018

9. Continuous Corn, 1992–97 N Treatment 7-Year Rate Time Average Yield
lb/A
bu/A -- 63 90 PP
129
⅔ PP+ ⅓ SD (V6-7)
134
Sidedress (V6-7)
127
120
135
½ PP + ½ SD (V6-7)
137
LSD (0.10) 3
11/8/2018

10. Continuous Corn, 1992–97 Conclusions:
Grain yield was 2 – 5 bu/A higher with split applications of N in these wetter years.
Delaying a single sidedress application to the V6-7 stage can reduce grain yield and profitability.
11/8/2018

11. Corn-Soybeans, 1987–93 Waseca Co. Canisteo clay loam (glacial till)
pH = 7.6
One-pass (field cultivation) tillage
N rate = 135 lb N/A as AA
Tile drainage study
11/8/2018

12. Corn-Soybeans, 1987–93 Application Time N-Serve 7-yr Avg. Yield
N Recovery
bu/A %
0-lb Check -- 95
Fall (late Oct.) No
131 31 “
Yes
139 37
Spring PP 40
40% PP+60% SD V8
145 44
LSD (0.10): 4
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13. 11/8/2018

14. Study A, Waseca, MN Continuous Corn, 2003
Treatments
Yield (bu/A)
Check, no N 67
160 lb N/A, spring urea
169
5000 gal hog manure/A,
fall (270 lb “avail.” N/A)
180
11/8/2018

15. Growth Stage, NDVI (red)
Correlation matrix between remote sensing and corn production parameters, Study A.
Growth Stage, NDVI (red)
Parameter
Stat V6 V7 V9
V11
V14
Relative R
.88
.96
.82
.94
.27
Chlorophyll P **
*** NS
Grain
.90
.81
.31
Yield
Total N
.29
Uptake
11/8/2018

16. Interpretation, Study A
Correlations between GreenSeeker (red) NDVI and relative chlorophyll, grain yield, or total N uptake were significant between the V6 and V11 stages with highest correlation at the V7 and V11 stages.
11/8/2018

17. Study B, Waseca, MN Corn after Soybean, 2003
Treatments
Yield (bu/A)
0 lb N/A
131
80 lb N/A, fall + N-Serve
160
120 lb N/A, fall + N-Serve
184
160 lb N/A, fall + N-Serve
185
120 lb N/A, spring + N-Serve
189
11/8/2018

18. Growth Stage, NDVI (red)
Correlation matrix between remote sensing and corn production parameters, Study B.
Growth Stage, NDVI (red)
Parameter
Stat V5 V7 V8
V10
V12
Relative R
.31
.32
.52
.56
.81
Chlorophyll P NS **
***
Grain
.36
.57
.44
.76
Yield *
Total N
.30
.37
.51
.74
Uptake
11/8/2018

19. Interpretation, Study B
GreenSeeker (red) optical sensing did not distinguish between corn receiving N vs. no N until the V8 stage.
Highest correlations for relative chlorophyll, grain yield, or total N uptake with GreenSeeker (red) NDVI were measured at the V12 stage.
11/8/2018

20. Southern Research and Outreach Center
THANK YOU
Gyles Randall
Univ. of Minnesota,
Southern Research and Outreach Center
11/8/2018