The effectiveness of mulching practices on water erosion control: A global meta-analysis

Mulching is widely recognized as an effective soil and water conservation measure all over the world. Nevertheless, a comprehensive evaluation of mulching's effectiveness in controlling soil erosion and the influencing factors is still lacking. A global meta-analysis based on 421 runoff and 512 soil loss observations from 90 publications was conducted to evaluate the effectiveness of mulching in reducing runoff and soil loss across a variety of variables (i.e. mulch type, mulch coverage and application rates, rainfall intensity, land use, soil texture, slope gradient, and slope length). Our meta-analysis shows that overall, mulching significantly reduced runoff and soil loss by 47.4% and 76.2%, respectively. Straw mulch and wood-based mulch are generally more effective in reducing runoff and soil loss than rock fragments, highlighting the effectiveness of organic materials in controlling water erosion. In general, increasing mulch coverage and application rates resulted in a significant reduction in runoff and soil loss. It is recommended, however, that mulch coverage should be at least 60% based on the trade-off between economic costs and ecological benefits, which can reduce runoff and soil loss by approximately 50% and 80%, respectively. An application rate of 0.3–0.4 kg m−2 for straw and 0.6–0.8 kg m−2 for wood-based mulch should be sufficient to effectively control soil erosion. The study also found that mulching is more effective in post-fire forests on medium-textured soils and less effective on steep slopes (>60%) and under both natural and simulated extremely heavy rainfall conditions (>90 mm/h). Overall, this study provides further insights into the impact of mulching on water erosion globally and proposes an overall framework for a precision mulching strategy (P-M-S) to guide the implementation of mulching in soil erosion control.