Optimizing tillage method and irrigation schedule for greenhouse gas mitigation, yield improvement, and water conservation in wheat–maize cropping systems

Excessive agricultural inputs meet food demand only at a huge environmental cost, and optimized management strategies are needed to promote the balanced development of food security, water conservation, and environmental sustainability. Here, we conducted a two-year field experiment to investigate annual greenhouse gas (GHG) emission, yield, water use efficiency (WUE), global warming potential (GWP), and greenhouse gas intensity (GHGI) from 2016 to 2018 in a typical wheat–maize cropping system in the North China Plain. Two tillage methods (T1, rotary tillage; T2, subsoiling) and four irrigation schedules (W1, pre-planting irrigation; W2, pre-planting + jointing irrigation; W3, pre-planting + anthesis irrigation; W4, pre-planting + jointing + anthesis irrigation) were used for winter wheat, and conventional practices were adopted for summer maize. In the winter wheat–summer maize season, the soil acted as a net sink for CH₄ but as a source for CO₂ and N₂O in all treatments, and CO₂ accounted for the highest proportion of the GWP. The inappropriate irrigation period in the W3 treatment caused greater GHG release and reduced crop yield, whereas the excessive irrigation in the W4 treatment led to low water productivity. Although the use of irrigation water increased annual GHG emissions, an appropriate irrigation schedule could significantly mitigate the GHGI. Compared with the W3 and W4 treatments, the W2 treatment increased yield by an average of 7.56–10.58% and 2.06–2.68%, improved WUE by 9.95–17.83% and 11.29–22.84%, reduced GWP by 3.70–5.10% and 0.65–2.25%, and decreased GHGI by 10.66–14.26% and 3.05–4.86%, respectively. The T2 treatment resulted in high GHG emissions and was accompanied by low yield and water productivity. Relative to the T2 treatment, the annual yield and WUE in the T1 treatment increased by an average of 4.41–15.15% and 8.12–12.76%, and the annual GWP and GHGI decreased by 3.97–4.62% and 8.80–16.93%. Therefore, rotary tillage combined with supplementary irrigation at the jointing stage can mitigate GHG emissions and improve yield and water productivity, making it an environmentally friendly agricultural practice.