Yield response curves were developed for potatoes (Solanum tuberosum cv. Russet Burbank) with sprinkler-applied N fertilizer on a high-frequency schedule. The potatoes were grown on a Quincy sand to loamy sand (mixed, mesic, Xeric Torripsamments) typical of sandy-textured soils of the center-pivot irrigated areas of the Columbia River Basin of Oregon and Washington. These soils require daily irrigation at peak evapotranspiration because of low water-holding capacity. Yields were measured for total quantities of N, ranging from 100 to 665 kg N/ha, applied in small frequent increments as a urea-NH4NO3 solution. Maximum tuber yields ranged from 67 to 85 Mg/ha in 6 experiments over a period of 6 years. Economically optimum yields were obtained at fertilizer rates between 300 and 400 kg N/ha depending on cost-price ratio of N fertilizer and potatoes. Fertilization in this range should optimize tuber yield and quality with fertilizer N efficiency and economic return on fertilizer investment.