The role of conservation agriculture practices in mitigating N2O emissions: A meta-analysis
Yue Li, Ji Chen, C. F. Drury, Mark A. Liebig, Jane M. F. Johnson, Zhaozhi Wang, Hao Feng, Diego Ábalos
Abstract
Abstract Conservation agriculture is often assumed to reduce soil N 2 O emissions. Yet, studies analyzing the specific effect of conservation agriculture practices on N 2 O emissions give contradictory results. Herein, we synthesized a comprehensive database on the three main conservation agriculture practices (cover crops, diversified crop rotations, and no-till and/or reduced tillage (NT/RT)) to elucidate the role of conservation practices on N 2 O emissions. Further, we used a random meta-forest approach to identify the most important predictors of the effects of these practices on soil N 2 O emissions. Averaged across all comparisons, NT/RT significantly decreased soil N 2 O emissions by 11% (95% CI: –19 to –1%) compared to conventional tillage. The reductions due to NT/RT were more commonly observed in humid climates and in soils with an initial carbon content < 20 g kg –1 . The implementation of cover crops and diversified crop rotations led to variable effects on soil N 2 O emissions. Cover crops were more likely to reduce soil N 2 O emissions at neutral soil pH, and in soils with intermediate carbon (~20 g kg –1 ) and nitrogen (~3 g kg –1 ) contents. Diversified crop rotations tended to increase soil N 2 O emissions in temperate regions and neutral to alkaline soils. Our results provide a comprehensive predictive framework to understand the conditions in which the adoption of various conservation agriculture practices can contribute to climate change mitigation. Combining these results with a similar mechanistic understanding of conservation agriculture impacts on ecosystem services and crop production will pave the way for a wider adoption globally of these management practices.