Alternative N Fertilizer Management Strategies Effects on Subsurface Drain Effluent and N Uptake

Demonstrating positive environmental benefits of alternative N fertilizer management strategies, withoutadversely affecting crop growth or yield, was a major goal for the Midwest Management Systems Evaluation Areas(MSEA) program. Our project objectives within this program were to quantify the effects of split- and single-Nfertilization strategies on NO3-N concentration and loss in subsurface drain effluent and N accumulation and yield ofcorn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. The study was conducted on glacial till derived soils innortheast Iowa from 1993 through 1995 using no-till and chisel plow tillage treatments. One-third of the 2,611 effluentsamples had NO3-N concentrations greater than 10 mg L1. Split applying fertilizer N based on pre-sidedress soil nitratetest (PSNT) results significantly increased corn yield for both tillage treatments in the extremely wet 1993 withoutincreasing NO3-N loss in drain effluent. Increased grain yield also resulted in significantly more N removal. Whenfertilizer N was applied based on the PSNT, no-till and chisel treatments had similar NO3-N losses and concentrations.Average flow-weighted NO3-N concentrations in drain effluent were not increased when larger amounts of fertilizer wereapplied based on PSNT. However, prior crop and tillage practices and differences in drain flow volume caused significantdifferences in NO3-N losses and concentrations. These results suggest that spatial differences in flow volume are a majorfactor determining NO3-N loss in drainage effluent. Significant differences suggest that combining no-tillage practiceswith split N fertilizer management strategies can have positive environmental benefits without reducing corn yield.