Film mulching can alleviate soil quality decrease and produce high maize yield under different irrigation strategies

Plastic film mulching (PM) combined with irrigation is widely adopted to improve crop yields, water and nitrogen efficiency, especially in arid farming areas. Despite its benefits, the effects of this method on soil quality and its subsequent impact on crop productivity and resource efficiency have not been thoroughly investigated. In this study, we formulated a soil quality indicator (SQI) from five years of field experiments in the Hetao Irrigation District (HID) of Northwestern China. The treatments included border irrigation as the control treatment (CK), CK combined with PM (BI_PM), and three water level drip irrigation treatments combined with PM. Three threshold values of soil matric potential for drip irrigation were −10 kPa (HDI_PM), −30 kPa (MDI_PM), and −50 kPa (LDI_PM). We then examined the SQI changes based on measured multiple soil properties and assessed their implications for maize yield, irrigation water productivity (IWP), and partial factor productivity of nitrogen (PFPN). We found: (1) from 2016 to 2020, HDI_PM achieved the highest average yield (15.77 t ha^–1), IWP (3.73 kg m^–3), and PFPN (63.18 kg kg^–1), showing increases of 54.77 %, 84.90 %, and 96.93 % over the control treatment, respectively; (2) no significant variations in the SQI were observed for HDI_PM in 2020 in the topsoil (0–30 cm) and subsoil (30–60 cm) compared to the initial condition. However, CK, BI_PM, MDI_PM, and LDI_PM showed reductions in SQI in both soil layers, primarily due to decreased soil organic carbon (SOC) and structural stability, along with increased sand content and soil salinity; (3) according to the linear mixed-effects model, a low SQI (< 0.43), elevated temperatures, and drought indices negatively impact yield. Hence, we advocate for HDI_PM to maximize yield and PFPN. To enhance soil quality, identifying agronomic practices that increase SOC and reduce soil salinity in the HID is crucial.