Straw Versus Manure in Soil Organic Carbon Sequestration: Mechanisms, Efficiency and Synergies for Sustainable Agriculture: A Review

Abstract

Soil organic carbon (SOC) sequestration is a key strategy for mitigating climate change and enhancing agricultural sustainability. This review carefully compares straw and manure, which are both commonly used to increase SOC levels, by explaining how they work differently, their effectiveness, and their real-world effects. Although both manure and straw enhance SOC, the latter is more efficacious due to its robust constituents (such as lignin) and nutrient density, which foster enduring humus development and microbial activity, resulting in a 32–50% augmentation of SOC stocks. Straw breaks down quickly and has a high carbon-to-nitrogen (C:N) ratio, which helps soil clump together; however, it needs to be used for a long time (more than 20 years) and managed carefully (like being buried deep at 35 cm) to noticeably increase SOC levels by about 16%. Significant differences in decomposition dynamics indicate that manure retains 45–58% of its carbon after one year, but straw retains just 27–48% due to accelerated mineralization rates. The amalgamation of manure and straw has synergistic effects that enhance carbon sequestration efficacy by 39.9%, prolong the carbon residence time below the surface by 20–30 days, and elevate crop yields by as much as 70.4% compared to individual applications. Although manure entails elevated handling expenses, it provides superior nutrient recycling and enhances soil health. Straw, on the other hand, has lower initial costs but, for practical and financial reasons, comes with the risk of long-term nutrient depletion. Case studies show that using combined methods works well, especially in dry and salty soils, where these methods can improve crop yields by 10–44%. Future work should focus on long-term field studies, understanding how microbes interact, and creating specific strategies for different regions to make the best use of modification techniques. This review advocates for the tailored incorporation of straw and manure into climate-smart agriculture models to improve SOC storage, resilience, and food security.