1. Experiences with Remote Sensing for Preplant and Split Applications of N for Corn
Gyles Randall and Jeff Vetsch
University of Minnesota
Southern Research and Outreach Center
1/17/2019

2. Purpose
To evaluate the GreenSeeker and SPAD meter as diagnostic tools for making in-season N applications to corn.
1/17/2019

3. Procedures Previous crop: Corn removed for silage
Tillage: Chisel plow + spring field cultivate
Soil: Nicollet-Webster complex
Hybrid & date: DKC at 33,000
plants/A planted on May 1.
N applied: 4/30 (PP), 6/28 (V8), 7/13 (V12)
Sensing dates: 6/23 (V7), 6/28 (V8), 7/7
(V10), 7/12 (V12), and 7/26 (R1).
1/17/2019

4. Precipitation Month 2004 30-yr normal ----- inches ----- May 5.61 3.96
June
6.42
4.22
July
7.08
4.47
August
5.73
4.58
Sept.
6.92
3.19
5-mo. Total
31.76
20.42
1/17/2019

5. Treatments Time and Rate of N Application # Total N Rate Preplant 1/V8
V12
lb N/A 1 2 40 3 80 4
120 5
160 6
200
1/ Urea PPI
1/17/2019

6. Treatments cont. Time and Rate of N Application # Total N Rate
Preplant 1/
V8 2/
V12
lb N/A 7 80 40 8
120 9
160 10 11 12
1/ Urea PPI
2/ UAN injected between rows
1/17/2019

7. Treatments cont. Time and Rate of N Application # Total N Rate
Preplant 1/ V8
V12 2/
lb N/A 13 80 40 14
120 15
160 16 17 18
1/ Urea PPI
2/ Urea + Agrotain dribbled near the row
1/17/2019

8. ------------------- lb N/A -------------------
Corn grain yield and N uptake as affected by rate and time of N application.
Total
Application Time
Corn Grain
N Rate PP V8
V12
Yield
N Uptake
lb N/A
bu/A
lb/A 92 40
146 68 80
176
120
177 99
160
190
117
200
188
164 88
113
114
166 84
185
105
186
109

9. ------------------- lb N/A -------------------
Relative chlorophyll (SPAD) as affected by rate and time of N application.
Total
Application Time
Corn Grain
N Rate PP V8
V12 R1
lb N/A % 78 70 40 91 87 80 96 92
120 97 94
160 98
200 93 95 84 90

10. Correlation between in-season corn growth parameters and grain yield and N uptake.
Corn Grain
Parameter
Yield
N Uptake
r value 1/
Plant height, V8
0.59
0.42
Plant height, V10
0.87
0.76
Plant height, V12
0.90
0.80
Total DM, V8
0.57
0.40
Total DM, V12
0.88
0.77
Total N uptake, V8
0.82
0.70
Total N uptake, V12
0.95
0.93
1/ Statistically significant when r > (0.05) and r > 0.515
(0.01), df=22.
1/17/2019

11. Correlation between in-season diagnostic parameters and grain yield and N uptake.
Corn Grain
Parameter
Yield
N Uptake
r value 1/
INSEY (53), V7
0.56
0.41
INSEY (58), V8
0.72
INSEY (67), V10
0.62
0.64
INSEY (72), V12
0.74
SPAD, V8
0.85
0.75
SPAD, V10
0.83
0.77
SPAD, V12
0.95
0.89
SPAD, R1
0.96
0.93
1/ Statistically significant when r > (0.05) and r > 0.515
(0.01), df=22.
1/17/2019

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19. Conclusions
Although statistical differences were not found among the PP, V8, and V12 N application times, grain yield was 10 to 12 bu/A greater when the 80-lb N rate was applied PP compared to split between 40 lb/A PP and 40 lb/A either at V8 or V12 in this wet year.
Relative leaf chlorophyll at the R1 growth stage was considerably less for the PP+V12 split application compared to the single PP or split (PP+V8) applications.
Grain yield was correlated better with relative chlorophyll at all growth stages (V8, V10, V12) than with INSEY.
1/17/2019

20. Conclusions cont.
INSEY was minimally affected by PP N rates between 40 and 200 lb/A, suggesting that this diagnostic criteria may have limited value if some N has been applied preplant for corn after corn.
If no N was preplant applied and the initial application was made at V8, corn yields would likely be reduced significantly.
1/17/2019

21. THANKS Gyles Randall Soil Scientist and Professor
Southern Research and Outreach Center
1/17/2019