Utilizing Fertilizer Technologies in Potato Production to Reduce Nitrogen Leaching in Sandy Soils.

Leaching of nitrate into the groundwater has been a continuing – and extensively researched – problem in the sandy soils of Wisconsin. However, no proven solution has been identified yet. The objective of this study was to evaluate performance of conventional fertilizer, slow-release fertilizer and enzyme inhibitors on potato yield and nitrate leaching losses. The five treatments include: (1) a conventional application (split application of ammonium sulfate and ammonium nitrate); (2) single application of poly-coated urea (ESN^®, Agrium, Inc.); (3) split application of urea with a urease inhibitor (Agrotain^®, Agrotain, Inc); (4) split application of urea with a urease and nitrification inhibitor (SuperU^®, Agrotain, Inc.) and (5) a control treatment without N fertilizer.  All fertilizer was applied at a rate of 280 kg ha^-1 of N. Porous stainless steel pan lysimeters installed at the depth of 75 cm under potato hill were used to collect leachate samples during the 2009 and 2010 growing seasons. These samples were used to measure nitrate-N (NO₃-N) concentrations, quantify drainage, and calculate evapotranspiration (ET). Although not always statistically significant, ESN produced the highest yields (83 Mg ha^-1), compared to 76 Mg ha^-1 produced by the ammonium sulfate/ammonium nitrate treatment, and 66 Mg ha^-1 produced by the unfertilized control treatment in the first year. ESN also produced the lowest NO₃-N leachate concentrations during the first half of the growing season. First year NO₃-N cumulative loading on the ESN treatment was the second lowest after the unfertilized control treatment.