Validating Weather and Sensor-based N Prediction Models for Michigan Corn Production


02 Jun 2018

2017 Annual Interpretive Summary

Differences in weather, particularly the timing and amount of rain, cause variability in corn response to nitrogen (N) fertilizer from one year to another. The regional Maximum Return to Nitrogen (MRTN) approach used in seven midwestern states provides recommendations based on documented yield responses to N, and allows for economic optimization, but does not adjust for year-specific weather events. This trial compared two year-specific approaches as alternatives to MRTN. One was the use of a deterministic daily weather-based crop and soil model (Adapt-N®), and the other was a crop canopy sensor (Greenseeker®) using an algorithm developed in Minnesota. The trial was implemented at the Michigan State University research station near Lansing, Michigan in 2015 and 2016. Nitrogen fertilizer rates, ranging from 33 to 167% of the MRTN rate, were applied with 40 to 46 lb N/A as starter and the remainder as sidedress urea-ammonium nitrate (UAN) injected into the soil at the V4 growth stage. In comparison, the weather-based rates were determined just before the V8 growth stage, and applied at V8 using a surface band of UAN with urease inhibitor.

In 2015, a year wetter than normal in the first half of the growing season, the optimum N rate of 173 lb/A produced a corn yield of 165 bu/A. The MRTN rate was 140 lb/A, producing a yield of 150 bu/A. The Adapt-N model recommended a higher rate of 171 lb/A producing a yield of 154 bu/A, similar to but slightly below the yield expectation from the N response curve derived from V4 application timing. The crop canopy sensor recommended a rate of only 121 lb/A, resulting in a much lower yield of 138 bu/A.

In 2016, a year drier than normal in the first half of the growing season, the optimum N rate of 123 lb/A produced a corn yield of 208 bu/A. Owing to lower fertilizer prices, the MRTN rate was slightly higher than in 2015, and the Adapt-N model rate was lower. For both, 150 lb/A of N was recommended and this rate produced corn yields identical to those achieved at the optimum rate. The sensor-based N rate of 161 lb/A also produced the same yield.

The results from these two years demonstrated potential for a weather-based approach, and have been published in the Journal of Crop Improvement. DOI:10.1080/15427528.2017.1359715.