Enhancing soil water stability and retention through plastic mulching under atypical climatic conditions on the Chinese loess plateau

Mulching is an agricultural practice that is extensively implemented worldwide to conserve water in soil to enhance agricultural production，and especially in the temperate continental monsoon climate regions. However, the mechanism controlling soil moisture evaporation, infiltration, and retention by mulching is unclear. We assess the impact of various mulching regimes on the soil–water equilibrium in the root zone of corn fields under atypical climate conditions(Excessive Precipitation) from 2020–2021 in five treatments: (1) ridges mulched with plastic film and furrows without mulching (RF), (2) conventional flat planting with full plastic mulching (FPM), (3) conventional flat planting with straw mulching (SM), (4) conventional flat planting with partial plastic mulching (PPM), and (5) conventional (control) flat planting with no mulching (CK). The HYDRUS-2D model was calibrated and validated using experimental data, to assess soil water content, water flux, and soil water balance within a two-dimensional soil profile. This model accurately replicated the root zone within the soil profile under all mulching scenarios, with numerical simulation outcomes closely aligning with observed measurements. Average R² values for FPM, PPM, RF, SM, and CK scenarios were 0.76, 0.75, 0.86, 0.85, and 0.77, respectively. During the 2020 and 2021 growing seasons, characterized by increased rainfall, plastic-covered treatments (FPM, PPM, RF) more efficiently reduced soil evaporation and enhanced soil-water retention. The combined soil drainage and storage changes for FPM, PPM, RF, and SM treatments exceeded those of CK by an average of 114.57, 64.93, 77.38, and 6.74 mm, respectively. FPM, PPM, and RF treatments had substantial water-retention capabilities during years of atypical climate. Notably, FPM ensured adequate water supply, facilitated deep soil water replenishment, and more effectively maintained soil water stability and retention. This underscores the pivotal regulatory function of mulching in mitigating the impacts of consecutive years of unusual climatic conditions.