Late-season nitrogen application for corn

Providing sufficient but not excessive nitrogen (N) to corn is difficult especially with fall and early spring fertilizer applications where N loss can vary substantially with the timing of the application relative to the occurrence of warm soil and excessive rainfall. Nitrogen deficiency occurs most growing seasons and often leads to an interest in applying N fertilizer beyond the growth stage and height where standard N application equipment can be used. Nitrogen applied up to 2-3 weeks after silking to N deficient but otherwise healthy corn can result in increased grain yield. The greater the N deficiency and the earlier the N application the larger the yield increase. An irrigated 2-year study conducted in Nebraska illustrates this point well.1 Rates of N were applied from 0 to 300 lb N/ac at planting to establish different levels of N sufficiency. Nitrogen sufficiency (SI) was quantified with a SPAD chlorophyll meter by measuring greenness of the most recently collared leaf in sub-optimal N rates compared t