Oil-based polyurethane-coated urea reduces nitrous oxide emissions in a corn field in a Maryland loamy sand soil

Urea is the most widely used N fertilizer due to its high N concentration (46%), cost effectiveness and ease of handling. However, urea is susceptible to loss as N2O, a greenhouse gas and catalyst of stratospheric ozone decline. Polymer-coated fertilizers may be effective in reducing such losses but the appropriate coating thickness for effective field performance is unknown. We prepared urea granules with polyurethane coating (PCU) based on castor oil at 2%–8% by weight. We tested the fertilizer value of these materials for maize (Zea mays L.) and measured field loss of N2O. Maize grain yield and N uptake were similar in treatments fertilized with urea (uncoated) and each of the coated materials. Cumulative N2O–N per unit of grain yield, however, was reduced by 80% with PCU8% compared with uncoated urea. Results indicate that polyurethane-coated urea performs similarly to uncoated urea for maize production while reducing soil N2O emissions up to 60–80%, with an efficiency factor twice as high as that suggested by the Intergovernmental Panel on Climate Change (IPCC) for N fertilizers. Our results indicate that urea with a polyurethane coating of 8% (PCU8%) had the best combined agronomic and environmental performance in a field study.