Applied the Right Rate and Right Source of Nitrogen Fertilizers Under Potato Prodcution.

Nitrogen (N) management strategies to reduce N losses to the environment from potato (Solanum tuberosum L.) production while maintaining tuber yields and quality is dependent on selecting the right N source and rate. A 5-yr (2008-2012) field experiment was conducted on irrigated sandy soils in Quebec, Canada, to examine the effect of N fertilizer source and rate on potato total (TY) and marketable tuber yield (MY), denitrification, in-season N leaching and residual soil nitrate. The treatments included an unfertilized control, and three N sources [ammonium nitrate (AN), ammonium sulphate (AS) and a polymer-coated urea (PCU)] applied at four N rates (60, 120, 200, and 280 kg N ha^-1). The PCU was applied 100% at planting and the AN and AS were applied 40% at-planting and 60% at hilling. On average across the five growing seasons, TY and MY increased with N fertilizer rate up to 200 kg N ha^-1, but were similar among the N sources. In general, in-season N leaching with PCU was lower than AS and AN at the beginning of the season. Residual soil nitrate was generally higher at the end of the season with PCU than AS and AN. Denitrification was significantly influenced by N fertilizer rate only in 2011, but the response was dependent on growing season climatic conditions. Overall, our results suggest that, under humid conditions with supplemental irrigation, a one-time application of PCU can be used as an alternative N management strategy to split N applications with conventional N fertilizers to minimize the risk of N losses to the environment, without reducing tuber yield and quality.