Synergistic Effects of Soil and Water Conservation Practices on Soil Organic Carbon Dynamics in Watershed Environments: A Review

Abstract

Soil Organic Carbon (SOC) serves as a vital indicator of soil health, ecosystem performance, and climate-change mitigation efforts. Soil erosion leads to the loss and redistribution of SOC by stripping away carbon-rich topsoil. This review explores the relationships among soil erosion, SOC dynamics, methods for estimating SOC, and Soil and Water Conservation (SWC) practices across various geographical areas, land uses, soil depths, and landscape positions. The results reveal that erosion typically diminishes SOC levels, while techniques such as contour bunds, contour trenches, vegetative barriers, terraces, conservation tillage, mulching, and integrated watershed management can significantly increase SOC storage. For instance, a 17-year study conducted in southern China found an increase in SOC ranging from 8% to 57% due to practices such as straw mulching, contour ridge cultivation, and downslope cultivation, with straw mulching and contour ridge cultivation yielding the most significant improvements. Additional studies have also indicated increased SOC levels associated with different SWC practices, with variations depending on soil type, climate, land use, soil depth, landscape position, and duration of implementation. This review also provides a summary of different SOC estimation methods, including traditional laboratory-based techniques as well as more advanced methods such as spectroscopy, remote sensing, proximal sensing, and modelling. Nonetheless, gaps remain in understanding the combined impacts of erosion and SWC on SOC storage, especially in tropical and semi-arid regions such as India. Future research should prioritise integrated assessments of erosion, SWC, and SOC, long-term studies, and tailored conservation strategies. This review concludes that integrated SWC strategies not only mitigate soil erosion but also foster SOC accumulation and stabilisation, thereby supporting sustainable land management, enhancing soil health, and aiding climate-change mitigation.