Polymer‐Coated Urea Maintains Potato Yields and Reduces Nitrous Oxide Emissions in a Minnesota Loamy Sand

Irrigated potato (Solanum tuberosum L.) production requires large inputs of N, and therefore has high potential for N loss including emissions of N2O. Two strategies for reducing N loss include split applications of conventional fertilizers, and single applications of polymer‐coated urea (PCU), both of which aim to better match the timing of N availability with plant demand. The objective of this 3‐yr study was to compare N2O emissions and potato yields following a conventional split application (CSA) using multiple additions of soluble fertilizers with single preplant applications of two different PCUs (PCU‐1 and PCU‐2) in a loamy sand in Minnesota. Each treatment received 270 kg of fertilizer N ha−1 per season. An unfertilized control treatment was included in 2 of 3 yr. Tuber yields did not vary among fertilizer treatments, but N2O emissions were significantly higher with CSA than PCU‐1. During 3 consecutive yr, mean growing season emissions were 1.36, 0.83, and 1.13 kg N2O‐N ha−1 with CSA, PCU‐1, and PCU‐2, respectively, compared with emissions of 0.79 and 0.42 kg N2O‐N ha−1 in the control. The PCU‐1 released N more slowly during in situ incubation than PCU‐2, although differences in N2O emitted by the two PCUs were not generally significant. Fertilizer‐induced emissions were relatively low, ranging from 0.10 to 0.15% of applied N with PCU‐1 up to 0.25 to 0.49% with CSA. These results show that N application strategies utilizing PCUs can maintain yields, reduce costs associated with split applications, and also reduce N2O emissions.