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 [N.sub.2]O. 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 [N.sub.2]O 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.sup.-1] per season. An unfertilized control treatment was included in 2 of 3 yr. Tuber yields did not vary among fertilizer treatments, but [N.sub.2]O 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 [N.sub.2]O-N [ha.sup.-1] with CSA, PCU-1, and PCU-2, respectively, compared with emissions of 0.79 and 0.42 kg [N.sub.2]O-N [ha.sup.-1] in the control. The PCU-1 released N more slowly during in situ incubation than PCU-2, although differences in [N.sub.2]O 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 [N.sub.2]O emissions. Abbreviations: AN, ammonium nitrate; BMP, best management practice; CSA, conventional split application; PCU, polymer-coated urea. doi:10.2136/sssaj2009.0126