Nitrous Oxide and Methane Emissions in Spring Maize Field in the Semi-Arid Regions of Loess Plateau

A 2-year field study was conducted to measure nitrous oxide (N2O) and methane (CH4) in a rain-fed spring maize cropland in the Loess Plateau, P. R. China, and to determine the effects of optimized nitrogen (N) fertilization practices on urea-derived N2O emission factor (EF), grain yield, net greenhouse gas (NGHG) emission, and net greenhouse gas intensity (NGHGI). Five treatments were considered, including control (CK), conventional N fertilization (Con), optimal N fertilization (Opt), optimal N fertilization plus nitrification inhibitor (Opt+DCD), and optimal N fertilization with slow release urea (Opt+SR). Soil acted as a small sink for atmospheric CH4. Nitrogen fertilization and heavy rainfall events (>40mm) were the main factors controlling N2O emissions. The annual mean EF ranged from 0.12 to 0.55%. Compared to conventional N fertilizer, nitrification inhibitor decreased the annual cumulative N2O, NGHG, and NGHGI emissions by 45, 52, and 48%, respectively, without decreasing grain yield. In conclusion, nitrification inhibitor addition was the most effective practice to reduce N2O emissions in the rain-fed regions of Loess Plateau