Effects of conservation agriculture on carbon dynamics across eroded slopes: A global synthesis

Conservation agriculture represents an essential management for sustainable development of croplands, and a number of syntheses have been published to investigate its benefits in terms of erosion control and carbon sequestration. However, previous studies usually investigated the two benefits separately, and it currently lacks a comprehensive evaluation of how the application of conservation agriculture impacts on the carbon cycling in the background of erosion. In this study, we systematically investigated the erosion processes and carbon dynamics across eroded slopes after adopting various conservation practices based on the data obtained from field experiments across the globe. The results showed that, compared to conventional tillage, adopting conservation agriculture did not significantly reduce runoff on average (-8.8 %), but it led to a significant reduction of sediment loss (-34.2 %). The application of conservation agriculture resulted in a significant increase of soil organic carbon accumulation in the top layer of 10 cm (+27.7 %), and single erosion event was not able to change the soil organic carbon content in the surface 5 cm. The loss of soil organic carbon was significantly reduced (-31.2 %) under conservation measures, but the soil organic carbon concentration in sediment was significantly increased (+15.2 %). The enrichment ratio of soil organic carbon in sediment did not increase significantly compared to that of conventional tillage (+1.4 %). The impact of conservation agriculture on carbon mineralization was minimal in the soil surface (-0.1 %), but it significantly increased the mineralization rate of carbon in runoff and sediment (+63.7 %), indicating a higher mineralization potential of eroded carbon under conservation agriculture. The results further highlighted the critical contribution of straw mulching in erosion control, soil organic carbon loss reduction, and soil organic carbon accumulation, while reduced tillage represents the least effective measure. Overall, this study quantitively summarizes the basic carbon dynamics across eroded slopes under conservation agriculture, and may provide important evidence for comprehensively understanding the mechanisms of how conservation agriculture influences on carbon accumulation, erosion, and mineralization under the background of erosion from a new perspective.