Effects of Biodegradable Mulching and Water‐Saving Irrigation on Soil Stability and Aggregates Carbon and Nitrogen Storage in Black Soil Region

To investigate how water‐saving methods with film mulching affect soil stability and the storage of organic carbon (SOC) and total nitrogen (TN) in paddy fields of the black soil region, the combination of black biodegradable plastic film covering and two water‐saving irrigation methods (ridge irrigation and controlled irrigation) was used. Soil aggregate size distribution, SOC and TN contents in the 0–60 cm layer were analysed. Additionally, soil carbon sequestration potential was assessed using the contribution rate of aggregate SOC. Soil stability was evaluated using the mean weight diameter (MWD), geometric mean diameter (GMD), the proportion of > 0.25 mm water‐stable aggregates (WR) and the erodibility factor (K). Water‐saving mulching significantly improved macro‐aggregates (> 0.25 mm) in the 0–60 cm soil layer (1.012%–25.278% increase), enhanced the potential of soil carbon sequestration (6.759%–31.896% increase), thereby stabilising the soil structure and facilitating the soil SOC and TN storage in the 0–40 cm soil layer. The increase of SOC and TN content of larger aggregates in the 20–40 cm soil layer had the strongest influence on soil structural stability (with the highest determination coefficients and the largest slope absolute values of the fitting functions, between 0.61–0.83 and 0.003–0.68, respectively). The combination of black biodegradable film mulching and ridge irrigation significantly improved soil carbon/nitrogen storage and structural stability, indicating high practical application potential.