Effect of Cover Crops on Soil Carbon Sequestration in Agroecosystems

Thesis Abstract

Soil carbon sequestration is a vital component of sustainable agriculture and climate change mitigation, yet its enhancement through practical soil management practices remains inadequately documented in agroecosystems, particularly in regions heavily reliant on conventional cropping systems. This study investigates the effect of cover crops on soil organic carbon (SOC) accumulation, aiming to provide empirical evidence for optimizing soil carbon storage strategies under diverse agroecological conditions. The specific objectives are to evaluate the impact of different cover crop species on soil carbon levels, determine temporal variations in SOC under cover cropping systems, and identify the key soil and crop management factors influencing carbon sequestration potential. Employing a field-based, quasi-experimental research design, the study was conducted across three distinct agricultural zones characterized by contrasting climate and soil types, with a total population comprising twenty-four farms randomized into four treatment groups legumes, grasses, mixture of legumes and grasses, and uncovered fallow as control. The sample consisted of 96 experimental plots (four per farm) monitored over three cropping seasons (totaling nine months per plot). Data collection involved soil sampling at 0–15 cm and 15–30 cm depths at baseline, six months, and twelve months, followed by laboratory analysis of SOC using dry combustion via a LECO TruNon elemental analyzer to ensure precise quantification. Additional data on crop biomass, residue incorporation, soil pH, moisture content, and temperature were also collected to elucidate influencing factors. Complementing the empirical data, the study utilized quantitative statistical methods, including analysis of variance (ANOVA) to compare SOC changes across treatment groups over time, followed by multiple regression analysis to identify significant predictors of carbon sequestration. Data interpretation was guided by the Carbon Sequestration Potential Model (CSPM) and supported by the Theory of Soil Organic Matter Dynamics, which posits that organic inputs and soil conditions mediate SOC stabilization. Validity and reliability of the laboratory analyses were confirmed through calibration standards and duplicate measurements, and appropriate ethical considerations, such as obtaining consent from participating farmers and adhering to environmental safety standards, were observed. It is anticipated that the findings will demonstrate significant enhancements in SOC levels with cover cropping, notably with leguminous species due to nitrogen fixation and organic matter addition, with the greatest sequestration observed in the initial six months followed by stabilization. The study expects to identify critical soil properties and management practices that facilitate maximum carbon storage, thus contributing empirical evidence to the discourse on climate-smart agriculture. The results are projected to reveal that cover crop diversity and management practices positively influence SOC accrual, with implications for scaling sustainable farming practices. This research makes a substantial contribution to the knowledge base by providing a validated, context-specific understanding of how cover crops influence soil carbon dynamics in diverse agroecosystems and offers practical guidelines for integrating cover cropping into land management to optimize carbon sequestration. Concluding, the study recommends that farmers adopt mixed-species cover cropping strategies tailored to local conditions, alongside improved residue management techniques, to enhance soil carbon storage. Future research directions include long-term monitoring beyond one year and exploring molecular-level mechanisms of carbon stabilization, thus broadening the scope of sustainable soil management solutions.