Assessing Nitrogen Use Efficiency of Maize Grown On Highly Productive Irrigated Sandy Soils.

The Minnesota irrigated soils account for only 500,000 acres, but these acres are some of the most productive and environmentally sensitive areas in Minnesota.  Ground water is the major source of drinking water in the sandy areas of the state, so obtaining information on nitrogen use efficiency is critical for maize grown on these soils. Corn (Zea maize L.) was grown at two locations on sandy soils in Minnesota. Nitrogen was broadcast as split applications of urea at rates of 0, 40, 80, 120, 160, 200, 240, and 280 lbs. /acre.  The first application was done at planting and the second at the V3 growth stage. Two additional commercial nitrogen products, Super U (Koch Fertilizer LLC) and ESN (Agrium Advanced Technologies, Inc.), were applied at planting at rates of 160 lbs. /acre, and ESN was also applied at a rate of 200 lbs. /acre. A randomized complete block with four replications was used at both field sites. In- season measurements of NDVI and leaf chlorophyll were taken at the V8 and V12 growth stages. Plant masses and tissue analysis for nitrogen was also done at the V8 and V12 growth stages. Results showed increases in plant mass, NDVI, and leaf chlorophyll with increased nitrogen rates. Response to nitrogen was similar within the same nitrogen rates regardless of product. Benefits of applying additional nitrogen diminished between the 200 and 240 lb. /acre rates.