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.