Ecological Trade-Offs of Plastic Film and Straw Mulching: Mechanistic Insights from Soil Structure and Carbon–Nitrogen

Mulching practices are key technologies for addressing soil degradation and increasing crop yields in the dryland farming regions of the Loess Plateau. However, it remains unclear how they synergistically influence soil health and sustainability by regulating soil physical, moisture, and nutrient processes while ensuring yield improvement. In particular, the ecological trade-off effects between crop yield enhancement and soil fertility improvement under different mulching measures still require further research. This study was conducted in 2022 at the Dryland Agriculture Experimental Station of Gansu Academy of Agricultural Sciences to evaluate the effect of straw strip mulching (TSM), straw crushed mulching (TSR), and plastic film mulching (TPM), with flat planting without mulching (TCK) as the control. The investigation focuses on soil moisture distribution, aggregate composition, soil carbon and nitrogen contents, and yield components in maize fields. The sStudy results showed that all mulching treatments reduced soil bulk density, increased soil porosity, and enhanced soil water content and water storage while reducing evapotranspiration. TSM most effectively increased soil organic carbon and total nitrogen contents. All mulching treatments improved soil aggregate stability, with TSM achieving the most significant reduction in soil erodibility by 40%. Compared with TCK, TPM, TSR, and TSM increased maize grain yield by 71.26%, 44.67%, and 38.04%, respectively. The most influential factors contributing to maize yield are soil water content, soil erodibility, mechanically stable micro-aggregates, and water-stable macro-aggregates. Analysis of the fitting relationship between key influencing factors and yield indicates that soil erodibility demonstrates the optimal fit with yield (R2 = 0.73), followed by the fit between soil water content and yield (R2 = 0.69). Overall, plastic film mulching primarily enhances short-term yield, while straw strip mulching ensures stable maize production and promotes soil health and sustainable development in dryland farming systems of the Loess Plateau, thus providing a clear theoretical basis for selecting mulching practices based on ecological trade-offs in the Loess Plateau region.