Corn response to nitrogen rate, row spacing, and plant density in eastern Nebraska

Efficient use of N by corn (Zea mays L.) is financially and environmentally important, and may be improved with higher plant density and reduced row spacing. Hypotheses were tested that irrigated corn yield in northeast Nebraska is increased by reducing row spacing from 0.76 in and increasing plant density above 61800 plants ha(-1), and that grain yield response to applied N is greater with reduced row spacing and increased plant density. Field experiments were conducted for 3 yr comparing the effects 0.76- vs. 0.51-m row spacing, three plant densities, and four N rates on crop performance. The soil was a silty clay loam (mesic Cumnlic Haplustoll). Nitrogen rates ranged from 0 to 252 kg N ha(-1). Plant N concentration and biomass and grain yield were not affected by plant density. Decreasing row spacing from 0.76 to 0.51 in resulted in 4% more grain yield. Grain yield response to applied N and N rates for optimum yield were not affected by row spacing. Nitrogen application resulted in mean increases of 22% more biomass production and 24% more grain yield. The N response function was linear in 1996, quadratic in 1997, and quadratic with decreased yields at the high N rate (252 kg N ha(-1)) in 1998. Grain yield was not affected by increasing plant density above 61800 plants ha(-1) but was greater with narrow row spacing. Yield response to applied N was similar for all planting arrangements. Optimal N rate cannot be better predicted by considering plant density and row spacing.