Controlled release fertilizers and split fertilizer N applications are expected to provide plant-available nitrogen (N) in synchrony with crop requirements, which should mitigate nitrous oxide (N 2O) emissions from agricultural soils. This study compared a polymer coated urea (PCU) controlled release N fertilizer (Environmentally Smart Nitrogen), split fertilizer N application and conventional fertilizer N management on the crop response and growing season N 2O emissions from rain-fed potato ( Solanum tuberosum L.) production on a medium-textured soil in Atlantic Canada from 2008 to 2010. Fertilizer were applied at the recommended rate (193 kg N ha -1) and treatments included the PCU product banded at planting, conventional fertilizer in a split application (60% as diammonium phosphate plus ammonium nitrate at planting plus 40% as ammonium nitrate at final hilling), conventional fertilizer (diammonium phosphate plus ammonium nitrate) banded at planting, and an unfertilized control. Within each year, cumulative growing season N 2O emissions were closely related to soil nitrate availability as measured by nitrate exposure (sum of daily nitrate concentration in the surface soil). Split N application had no effect on crop response, and significantly reduced nitrate exposure, but did not reduce N 2O emissions. With the PCU, there was evidence of increased plant N availability and greater N 2O emissions. In situations where the risk of nitrate leaching is limited, substitution of a PCU product for conventional fertilizer at the same N application rate will not necessarily reduce growing season N 2O emissions and may in some cases increase the risk of N 2O emissions. Further research is required to determine if lowering N rates with PCU products will be effective agronomically and environmentally.
