Prediction of Maize Grain N Concentration across the US Corn Belt.

Maintaining high yields while minimizing negative environmental impact is a critical challenge for agricultural productivity because N application in excess of crop demand can pollute water resources and contribute to global warming, while N applications less than demand reduces crop biomass and yield. The N balance approach, which monitors N inputs from all sources in relation to N removal with harvest, provides a measure of the degree of congruence between N supply and crop N demand. For cereal crops, grain N concentration has a large influence on N removal, but it varies considerably due to management practices, environmental factors, and their interactions. To evaluate variability in maize grain N, we collected data from field studies conducted from 1999 to 2016 across the Corn Belt. Collected data included location of field study, grain N concentration, grain yield, management practices (N fertilizer rate, irrigated or rainfed), and environmental factors, including weather data during the growing season, soil texture and root zone water holding capacity, and field topography. In total, statistical analysis utilized 10,860 observations, from 103 locations in nine Corn Belt states. Preliminary analyses revealed strong positive correlations between grain N concentration and grain yield, N fertilizer rate, number of days with maximum temperature ≥32ºC in July and August, number of days with minimum temperature ≥ 22ºC in August, and mean temperature in July. We further analyze these data to determine the most important factors affecting grain N variation with multiple linear regression analysis, regression trees, and path analysis and results will be presented at the meeting. We believe this information will help to improve estimates of N balance for a given region for a given year as a tool to improve N management to optimize yield and profit while minimizing environmental impact.