Factors Influencing The Preplant Fertilizer Nitrogen Uptake Efficiency Of Furrow-Irrigated Corn.

Corn (Zea mays L.) is becoming an increasingly important row-crop in the Mid-south and irrigation is required to produce optimal yields. Nitrogen fertilizer is the largest line-item input cost for most producers and can represent as much as 28% of total operating costs. Current recommendations suggest that 1/3 of the N be applied preplant with the remainder applied prior to the V8 growth stage. Previous research indicates ~ 8% of the total plant N is taken up by the corn plant prior to the V6 growth stage. The objective of this research is to investigate the influence of preplant N rate and application strategy on Fertilizer N Uptake Efficiency (FNUE) in a furrow-irrigated corn production system. Preplant N rates ranged from 0 to100 kg N/ha and were applied using common application strategies including: preplant N incorporation, broadcast over the surface, and in-furrow application. All N fertilizer was applied immediately prior to planting using NBPT treated ¹⁵N-labeled urea. There was a significant two-way interaction involving preplant N rate by N application strategy (P=0.0009). Preplant FNUE for all treatments ranged from 1.6 to 13.3% with maximum FNUE being achieved when 67 kg N/ha was applied preplant N and incorporated into the bed. The broadcast N application displayed a linear increase in N uptake as N rate increased indicating that it was limited by N fertilizer placement. The in-furrow application strategy slightly increased in fertilizer N uptake as N rate increased, only reaching 1/3 the maximum amount of N taken up by the most efficient treatment, with a FNUE of only ~ 2.4%. Results of this research suggest that corn producers should incorporate their preplant N into the bed and only apply up to 67 kg N/ha in order to maximize preplant FNUE.