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 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 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 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.

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An important aspect of establishing critical sap nutrient concentrations for diagnostic purposes is to determine the accuracy of the analytical method used. We compared a Cardy flat membrane NO3 electrode, a Hach portable NO3 electrode, and a Wescan N analyzer for their ability to determine NO3 concentrations in sap of potato (Solanum tuberosum L.) petioles. The Hach and Wescan instruments require diluted sap, while nondiluted sap can be used with the Cardy. Nitrate-N concentrations in nondiluted petiole sap measured with the Cardy electrode were 90 to 120 mg·L–1 higher than the other two methods. Using sap diluted with 0.075 m aluminum sulfate tended to lower Cardy NO3 readings to concentrations closer to the other methods, but made the procedure more complicated for practical use. We also compared a Cardy K electrode with flame emission spectroscopy for determining K concentrations in sap. Using nondiluted sap with the Cardy procedure resulted in K concentrations 200 to 2500 mg·L–1 lower than those determined by flame emission, depending on K concentration of the sap. Diluting sap with 0.075 m aluminum sulfate or deionized water for use with the Cardy electrode resulted in K concentrations similar to those determined by flame emission.