Hilling

Abstract: Nitrogen management for irrigated potato (Solanum tuberosum L.)is important from both a production and environmental standpoint. Nitrogen deficiency can limit yield, while excessive N can 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 NO 3 -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 quantities 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 non-marketable 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 NO 3 -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.