1. Developing an N Algorithm for Northern Corn Belt Rainfed Conditions: Minnesota Experience
Jeff Vetsch and Gyles Randall
University of Minnesota
Southern Research and Outreach Center
7/24/2019

2. Developing a MN N Algorithm: Objective
To develop an algorithm (nitrogen recommendation) for sidedress application that would:
Maximize economic return to nitrogen
Increase fertilizer use efficiency, and
Incorporate some recently proposed and refined N recommendations, based on a regional database project.
7/24/2019

3. 7/24/2019

4. 2004 remote sensing for N on corn
Previous crop: Corn removed for silage
Soil: Nicollet-Webster complex
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).
7/24/2019

5. ------------------- 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

6. Nebraska Approach
7/24/2019

7. Corn grain yield vs relative chlorophyll
7/24/2019

8. Relative chlorophyll vs N rate at V8
7/24/2019

9. Relative chlorophyll vs N rate at V10
7/24/2019

10. Relative chlorophyll vs N rate at V12
7/24/2019

11. Relative chlorophyll vs N rate at R1
7/24/2019

12. Relative chlorophyll vs N rate at R1
7/24/2019

13. Predicted values based MN algorithm
N Rate V8
V10
V12 R1
lb/A
relative chlorophyll, %
80.7
80.5
79.4
70.9 10
86.2
85.0
82.9
75.2 20
90.6
88.9
86.0
79.1 30
93.9
92.0
88.8
82.6 40
96.1
94.4
91.3
85.8 50
97.2
93.4
88.6 60
97.4
97.1
95.1
91.0 70
97.3
96.5
93.0 80
97.5
94.6 90
98.2
95.9
100
98.6
96.7
110
120
130
140
150

14. Sidedress N rates: MN algorithm
1201 – N rate credit2 = sidedress rate
Based on 2004 yield data, where a total of 120 lb N/A split applied yielded as well as 160 lb applied PP.
Based on relative chlorophyll content and response curve at respective growth stage.

15. Application rates for the 2005 regional N project Minnesota Treatments (V12 sensing, July 7)
Chlorophyll
MN Algorithm N Rate
Plot
Trt
N rate
SPAD
Rel.1
Credit
Applied #
lb/A %
lb N/A
104 11
39.0
0.82 5
115
204
38.4
0.83 10
110
303
41.0
0.84 15
105
411
39.9
0.86 20
100 12 40
46.8
0.98 90 30
208
44.8
0.97 70 50
313
45.8
0.94
412
44.9
0.96
1 Relative calculated using 200 lb rate as reference (non limiting).

16. Growing season precipitation at Waseca in 2005

17. MN “Norwegian” algorithm: First-year experiences
Advantages
Simple intuitive / similar to Nebraska approach
SPAD very good predictor of grain yield at V10-12
Fits well with our new approach to N recommendations.
Disadvantages / concerns
Algorithm based on ONE YEAR OF DATA (2004)
Need to adapt it to on-the-go sensing / application
Not sure if it will work for other soils / crop rotations
Still need a timely rain – cooperative weather
Need more out of range plots
Is 120 lb N/A needed at sidedress or has yield potential already been lost and cannot be attained, and how does growth stage affect recs.

18. Southern Research and Outreach Center
THANKS
Jeff Vetsch
Assistant Scientist
Southern Research and Outreach Center
7/24/2019

19. ---------- inches ----------
Precipitation
Month
2004
2005
30-yr norm.
inches
May
5.61
5.96
3.96
June
6.42
5.71
4.22
July
7.08
3.09
4.47
August
5.73 --
4.58
Sept.
6.92
3.19
Total
31.76
20.42
7/24/2019

20. Application rates for the 2005 regional N project Minnesota treatments (est., V10 sensing, July 2)
Chlorophyll
MN Algorithm N Rate
Plot
Trt
N rate
SPAD
Rel.1
Predicted
Applied #
lb/A %
lb N/A
104 11
40.2
0.82 5
115
204
40.9
0.86 15
105
303
43.6
411
41.5
086 10
110 12 40
45.3
0.93 35 85
208
46.1
0.97 60
313
45.6
0.90 25 95
412
47.1
0.98 65 55
1 Relative calculated using 200 lb rate as reference (non limiting).

21. Application rates for the 2005 regional N project Nebraska treatments (V10 sensing, July 2)
Chlorophyll
MN Algorithm N Rate
Plot
Trt
N rate
SPAD
Rel.1
Predicted
Applied #
lb/A %
lb N/A
103 7
45.8
0.94 90 75
214
46.5
0.98
140 25
308
46.8
0.93 77 88
409
47.0
0.97
130 35
113 8 40
45.2 80 85
202
0.99
180
312
47.4
410
46.7
120 45
Relative calculated using 200 lb rate as reference (non limiting).