Potato response to nitrogen sources and rates in an irrigated sandy soil

Management strategies to reduce N losses to the environment from potato (Solanum tuberosum L.) production while maintaining yields depend on selecting the right N source and rate. A 5-yr (2008-2012) fi eld experiment was conducted on an irrigated sandy soil in Quebec, Canada, to examine the effect of N fertilizer source and rate on total (TY) and marketable tuber yield (MY), total plant N accumulation (vines + tubers), specific gravity, culls (unmarketable tubers), and apparent fertilizer N recovery (ANR). The treatments included an unfertilized control, and three N sources [ammonium nitrate (AN), ammonium sulfate (AS), and polymer-coated urea (PCU)] applied at four 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. The TY and MY increased with N rate up to 200 kg N ha–1, but were similar among the N sources. On average, total plant N accumulation and ANR were greater for AN and PCU than AS. However in 2008, when there was a greater risk of N loss due to high rainfall, total plant N accumulation and ANR were greater for PCU than AN and AS. Tuber specific gravity and culls were influenced by N rate, but the response was dependent on soil and climatic conditions. Results suggest that, under humid conditions with irrigation, a one-time application of PCU in potato production can minimize the risk of N loss without reducing tuber yield and quality.