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 http://sroc.coafes.umn.edu/ 1/17/2019
Purpose To evaluate the GreenSeeker and SPAD meter as diagnostic tools for making in-season N applications to corn. 1/17/2019
Procedures Previous crop: Corn removed for silage Tillage: Chisel plow + spring field cultivate Soil: Nicollet-Webster complex Hybrid & date: DKC 51-41 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
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
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
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
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
------------------- 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
------------------- 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
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 > 0.404 (0.05) and r > 0.515 (0.01), df=22. 1/17/2019
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 > 0.404 (0.05) and r > 0.515 (0.01), df=22. 1/17/2019
1/17/2019
1/17/2019
1/17/2019
1/17/2019
1/17/2019
1/17/2019
1/17/2019
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
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
THANKS Gyles Randall Soil Scientist and Professor Southern Research and Outreach Center grandall@umn.edu http://sroc.coafes.umn.edu/ 1/17/2019