Reduction in nitrogen fertilizer applications by the use of polymer‐coated urea: effect on maize yields and environmental impacts of nitrogen losses

BACKGROUND Urea is commonly over‐applied as a nitrogen (N) fertilizer to crops in southern China and has a low utilization efficiency as a result of the high precipitation and high temperatures in this region. This has led to a need to optimize the management of N fertilizer use in maize crops on the subtropical hilly uplands of southern China. RESULTS We investigated the effects of applying different amounts of N in the form of polymer‐coated urea (PCU) on the yield of maize and gaseous losses of N from soils in the form of NH 3 and N 2 O. The field plots used in this trial had zero‐added N (0 kg N ha −1 ), the addition of urea (240 kg N ha −1 ) and four levels of fertilization with PCU (1 PCU, 0.9 PCU, 0.8 PCU and 0.7 PCU), which represented a 0%, 10%, 20% and 30% reduction, respectively, in the application of PCU‐N relative to the urea plot. Compared to the urea plot, there was little variation in the yield of maize for all the PCU‐N treatments, with a significant improvement in the utilization efficiency of N (up to 46.0–51.2%) with a 0–30% reduction in the application of PCU‐N. Significant effects in the mitigation of the N 2 O emission flux and the accumulation of N 2 O‐N were observed in the 0.8 PCU and 0.7 PCU plots. The application of PCU‐N significantly reduced the flux and total amount of NH 3 ‐N lost to the environment: as the application rate for N decreased by 0–30%, the NH 3 loss was significantly reduced by 12.7–36.1%. CONCLUSION The findings of the present study suggest that the use of PCU could allow a reduction in the application of N of 20–30% compared to traditional agricultural practices in this area with the same yield of maize, although with significantly decreased NH 3 and N 2 O losses and the increased utilization of N. © 2018 Society of Chemical Industry