Corn Response to Nitrogen Fertilizer as Affected by Planting Date and Hybrid

Abstract

Producers of the eastern Corn Belt are often forced to either delay corn (Zea mays, L.) planting or replant due to unfavorable early season growing conditions. In these situations producers may decrease N rates due to decreased yield potential or switch to short season hybrids to reduce the risk of frost injury prior to maturity. Hybrids with differing yield potential may have different N requirements, but definitive research to determine the impact of hybrid selection on N response is lacking. Field experiments were conducted in Ohio during 2006 and 2007 to evaluate if corn grain yield and stalk lodging attributed to N fertilizer is affected by hybrid or planting date. This experiment evaluated two planting dates (late April/early May and early/mid-June), with subplots comparing N fertilizer rates (0, 60, 120, and 180 lb N/acre), and sub-subplots containing corn hybrids of differing maturities (104, 108, 109, and two 113 days relative maturity). In 2006, planting date did not affect the economically optimum N fertilizer rate (EONR), although late planted corn did produce lower grain yields. In 2007, late-planted corn was less responsive to N with the optimum N rate being 38 lb N/acre less than early-planted corn. Differences in N response between hybrids were noted, but optimum N rates were not markedly different.