Assessing resource utilization, food production and ecosystem service value from spring wheat farmland under reduced irrigation and N fertilization management using a process simulation-based framework

Excessive irrigation and nitrogen (N) fertilization have caused severe reductions in farmland water and N pro-ductivity, and functional degradation of agroecosystems in arid to semi-arid regions. Thus, a process simulation -based framework for resource, food, and ecology (RFE) trade-offs was used to optimize the irrigation and N fertilization strategy (IRNF). A scenario study was conducted based on the framework that was developed in our previous companion study in the arid to semi-arid regions of Northwest China. Based on the local IRNF (i.e., 450 mm irrigation and 340 kg ha-1 N fertilization), reduced irrigation and N fertilization management scenarios were proposed considering eleven irrigation depth reduction cases and ten N fertilization reduction cases in three hydrological years (wet, normal, and dry). The integrated responses of spring wheat yield, water and N pro-ductivity, and ecosystem service value (ESV) to various IRNFs were quantified and assessed. The results showed that the local IRNF obtained higher yields and positive ESVs, but was also produced higher greenhouse gas (GHG) emissions, N losses, and water consumption, thus resulting in lower water and N productivity and higher negative ESVs. Among the negative ESVs, GHG emission value accounted for the largest proportion of the total negative ESV (75-80 %), followed by water consumption and fertilizer loss values. Compared with the local IRNF, the scenarios with 210 mm irrigation and 240 kg ha-1 N fertilization in wet years, 240 mm irrigation and 200 kg ha-1 N fertilization in normal years, and 300 mm irrigation and 200 kg ha-1 N fertilization in dry years could not only reduce negative ESVs, improve water and N productivity, and save water and fertilizer resources, but also maintain acceptable yields and positive ESVs. These recommendations reduced the total negative ESV by 4.8-7.7 %, increased water and N productivity by 4.0-8.9 % and 44-69 %, and saved irrigation water and N fertilizer resources by 33.3-53.3 % and 29.4-41.2 % in three hydrological years in relation to the local IRNF, respectively. This study indicates that the framework is a reliable tool for achieving farmland RFE trade-offs and generating appropriate IRNFs for different hydrological years in arid to semi-arid regions. Therefore, sustainable development goals in RFE systems may be achieved by optimizing irrigation and fertilization management.