Nitrogen Management for High Population Corn Production in Wide and Narrow Rows

Recent trends of planting corn (Zea mays L.) at higher populations and in narrower rows could influence optimum N management. This study investigates the effects of N rates (0–224 kg ha–1 N plus a low rate of uniformly applied starter) and timing (at planting, V5–V7 sidedress) on corn in wide and narrow rows (76–102 cm vs. 38–51 cm) at 13 sites over 3 yr in North Carolina. Early season N uptake, grain yield, and yield components were measured. Delaying N until sidedress increased yields, but there was an interaction effect with row spacing. Yields were greater with narrow rows and sidedress N (11.7 Mg ha–1) than with narrow rows and all N at planting (11.0 Mg ha–1) or with wide rows fertilized at either time (11.0 Mg ha–1), when averaged across N rates. Three ear yield components increased in response to N fertilization, leading to a 35% yield increase. Rows per ear increased from 15.5 to 15.9 ear–1, kernels per row increased from 27 to 32 row–1, and individual kernel mass increased from 226 to 253 mg. Aboveground plant N uptake by the V5 to V7 growth stage was only 9 kg ha–1, with very little additional N uptake in response to higher N rates. Sidedress N application at V5 to V7 maximized the formation of the ear yield components and grain yield for high population corn in narrow rows, but N timing did not affect yield or ear yield components of wide‐row corn.