Impact of plastic mulching and residue return on maize yield and soil organic carbon storage in irrigated dryland areas under climate change

The widespread adoption of returning crop residue to regulate soil properties and improve yields has been well-established. However, the long-term effects of residue return on soil organic carbon (SOC) and yield in film-mulched farmland, especially under future climate conditions, are still unclear. To address this issue, we utilized the SPACSYS model, which was calibrated with 5-year (2016–2020) field experiment data from various mulching and fertilization treatments in the Hetao irrigation district in northwest China. Furthermore, we investigated the impacts of climate change on SOC storage in 20 cm and maize yield with calibrated SPACSYS model driven by 27 global climate models under two climate scenarios (SSP245 and SSP585) from CMIP6. We considered multiple combinations of agronomic options: five residue return levels (R1: 20%; R2: 40%; R3: 60%; R4: 80%; R5: 100%) and three return depths (D1: surface applied; D2: 10 cm; D3: 20 cm) to evaluate the effects of residue return on SOC storage and yield. We found that yield at a high fertilization rate with transparent film mulching (HT) would increase by 10.1% under SSP245, 15.3% under SSP585 in 2021–2060 compared to the baseline (1981–2020). By contrast, the yield would decrease by 5.8% under SSP245, 21.7% under SSP585 in 2061–2100. SOC storage under HT would decrease by 9.4–12.7% and 18.4–41.4% in 2021–2060 and 2061–2100, respectively. We determined that the optimal treatment involves returning 100% of residue to a depth of 20 cm (R5D3). Under R5D3, yield showed an increasing trend in both two future periods; the SOC storage decreased by 4.8–6.8% in 2021–2060 and increased by 3.9–16.1% in 2061–2100 compared to the baseline under HT. Our results highlight the potential of residue return to increase yield while maintaining soil health when film mulching is adopted.