No-tillage controls on runoff: A meta-analysis

• NT can significantly reduce runoff compared to both RT and MP.
• The effectiveness of NT varied with rainfall types and slope gradients.
• Soil clay content and residue management affected the effectiveness of NT.
• The effectiveness of NT in reducing runoff decreased over time relative to MP.
• No significant temporal trend was found in the effectiveness of NT relative to RT.

Runoff from farmland is of great importance to both agricultural and environmental sustainability. In the present study, a meta-analysis was conducted to quantify the effectiveness of no-tillage (NT) in reducing surface runoff and to explore the factors controlling the effectiveness. Results showed that overall, NT significantly reduced runoff by 21.9% and 27.2% compared to reduced tillage (RT) and conventional moldboard plow (MP), respectively. The effectiveness of NT in reducing runoff was higher under simulated than natural rainfall, particularly as compared to MP. The reduction in runoff under NT was significant and greatest for moderate slope gradients (5–10%) relative to both RT and MP, but without statistical significance for both gentle (<5%) and steep (>10%) slope gradients. As compared to MP, the effectiveness of NT in reducing runoff decreased over time, whereas no such trend was found relative to RT. Compared to RT, NT significantly reduced runoff in soils with low clay content (<33% clay), while resulting in a slight but non-significant increase in runoff in soils with high clay content (≥33% clay). The effectiveness of NT in reducing runoff compared to RT did not vary with tillage direction. Runoff was significantly reduced by NT with crop residue retention relative to RT, but not with residue removal. Our results conclude that NT needs to be adapted to specific environmental conditions and management practices for improved controls on runoff.