Midseason Nitrogen Fertility Management for Corn Based on Weather and Yield Prediction

Abstract

Nitrogen fertilizer applications for irrigated corn (Zea mays L.) based on yield goals established before planting may result in under- or overapplication of N because of weather-induced variations in yield potential from year to year. This study was conducted to develop and evaluate a regression model to predict corn grain yield at a midpoint in the growing season based on the current year's cumulative thermal factors and N fertility levels. The relationship among early-season growing conditions, N fertility, and corn grain yield under continuous corn production and sprinkler irrigation was investigated from 1990–1995 in southeastern North Dakota. Fertility levels on small plots ranged from 0 to 224 kg ha−1 applied N. There was a wide range of cumulative growing degree days (GDD) and evapotranspiration (ET) during the study period. Least-squares regression was used to develop equations to predict, on 10 July, grain yield based on cumulative ET or GDD from 1 May to 10 July and soil N plus applied N. Yields predicted on 10 July corresponded well to individual observed yields (r2 = 0.80), and predicted optimum yield (YOPT) was highly correlated to observed YOPT (r2 = 0.885). The model could provide a season-specific yield potential used to modify N application during the growing season, resulting in fertilizer savings in the extreme years when cool early-season weather limited yield potential or fertilizer increases to take advantage of optimum growing conditions and increase yields. Including meteorological measurements can improve fertilizer management decisions by providing midseason adjustments to fertilizer recommendations.