Nitrogen application at a lower rate reduce net field global warming potential and greenhouse gas intensity in winter wheat grown in semi-arid region of the Loess Plateau

With the intensification of crop production pressure and the urgency of mitigating greenhouse gas emissions, semi-arid regions have increasingly become one of the key areas of research. However, due to the relatively low indigenous soil organic matter (SOM), it is worth pondering whether the long-term introduction of cropland management measures will affect the soil organic carbon (SOC), greenhouse gases (GHGs) and global warming potential (GWP) in the semi-arid areas. This long-term fertilization experiment was conducted for four years during 2017–2021 to assess fertilization impacts on net global warming potential (NGWP) including estimation of SOC change, N₂O and CH₄ emissions and indirect emissions (IE), and the greenhouse gas intensity (GHGI) on the winter wheat in a semi-arid region of China. The treatments included five levels of N application including non-N-fertilized control (N0), 75 kg N·ha⁻¹ (N75), 150 kg N·ha⁻¹ (N150), 225 kg N·ha⁻¹ (N225) and a traditional N application rate, 300 kg N·ha⁻¹ (N300). In comparison with N300, N225 caused a significant increase in SOC content and SOC sequestration rates and reduced the N₂O and CH₄ emissions and N₂O emission factor (EF_N2O) followed by N150, N75 and N0. Indirect emissions from farm inputs were highest in the N300 treatment due to excessive N application. The higher grain yield, during all study years, was recorded in N225 treatment and there was no significant difference between N150 and N300 treatments. However, the lowest grain yield was recorded from N0, followed by N75. The lowest mean NGWP and net greenhouse gas intensity (NGHGI) were recorded from the N150 and N225 treatments than all other treatments. The results of this study suggested that N application at 150–225 kg·ha⁻¹ is an effective method to enhance SOC sequestration and grain yield and to reduce the GHGI.