Potato yield response and nitrate leaching as influenced by nitrogen management

Nitrogen management for irrigated potato (Solanum tuberosum L.) is important from both a production and environmental stand-point. Nitrogen deficiency can limit yield, while excessive N cab leach to groundwater. The objective of this study was to investigate the effects of early-season N management on irrigated 'Russet Burbank' potato yield, N recovery, and NO₃-N leaching. A 2-yr experiment was conducted on a Hubbard loamy sand (Udorthentic Haploborolls), using four N treatments and a 0 N control. Total N applied was 270 kg N ha^-1; the portion applied at planting was 0, 45, 90, and 135 kg N ha^-1, with the remainder applied in equal quantifies at emergence and hilling. In 1991, increasing the amount of N applied at planting did not affect total yield, but significantly increased the yield of nonmarketable tubers. In 1992, total yield again was not affected, but the yield of smaller tubers significantly increased and the yield of larger tubers decreased as the proportion of N applied at planting increased. During 1991, when heavy leaching occurred, an average of only 33% of applied N was recovered by the crop. In contrast, during 1992, when fewer leaching events occurred, recovery of N averaged 56%. In both growing seasons, the amount of NO₃-N leached increased linearly as the proportion of N applied at planting increased. The strategy of reducing N application at planting for irrigated Russet Burbank potato can reduce the potential for NO₃-N leaching, increase N uptake, and improve marketable yield.