Integrated impacts of irrigation and nitrogen management for balancing winter wheat yield and greenhouse gas emissions

Irrigation and nitrogen (N) input are effective methods of balancing crop yields and greenhouse gas (GHG) emissions. However, the effects of irrigation and N management on the GHG emission of winter wheat production systems have not yet been well documented. Therefore, we conducted 2-year field experiments on winter wheat and studied the effects of irrigation and N reduction/replacement on GHG emissions, grain yield, global warming potential (GWP), and GHG emission intensity (GHGI). The winter wheat was irrigated once or twice with 60 or 90 mm each time. Five N reduction/replacement treatments were no N application (CK), 25% traditional urea (U) reduction (75%U), traditional U (U), 25% reduction in polymer-coated U (PCU), and 25% reduction in traditional U combined with organic fertilizers (U + OM). The results indicated that N reduction/replacement significantly reduced N2O emissions, but had no significant effect on CH4 emissions. Soil water-filled pore space was the same key factor affecting the emission fluxes of N2O and CH4. Soil temperature significantly affected the fluxes of CH4 (P < 0.001). Irrigation treatment did not exhibit a significant effect on grain yield, but high irrigation input increased the GWP and GHGI. Compared with U, the grain yield of CK, 75%U, PCU, and U + OM increased by -46%, -9.2%, -1.8%, and 5.4%, respectively; GWP decreased by 35.9%, 11.6%, 7.3%, and 2.7%, respectively; and GHGI decreased by -22.1%, 3.1%, 6.0%, and 8.0%, respectively. Therefore, sustainable production goals of increasing grain yield and reducing GHG emissions were achieved with N reduction/replacement using U + OM and low irrigation input of 60 mm.