Weed management and conservation agriculture in cotton-based systems: Implications on soil quality and climate change mitigation

Conservation agriculture (CA), characterized by reduced tillage, continuous soil cover through mulching or cover cropping, and crop rotation, is established as a sustainable approach for enhancing soil health and agricultural resilience, particularly in cotton-based systems. Several studies indicated that CA in cotton systems played a crucial role in climate mitigation by enhancing soil carbon sequestration and mitigating greenhouse gas (GHG) emissions. CA practices reportedly increased soil organic carbon (SOC) levels, which helped stabilize atmospheric CO₂ Additionally, CA minimized energy-intensive inputs by reducing reliance on machinery, thereby further lowering CO₂ emissions. With reduced tillage, weed management became more challenging but remained essential for productivity, soil health, and sustainability. Research showed that weed management practices in CA systems influenced soil physical, chemical, and biological properties. CA was found to improve physical attributes such as bulk density, soil structure, aggregation, and hydraulic conductivity, which enhanced porosity, root growth, and water infiltration. CA-based weed control helped in stabilizing the soil pH, reducing electrical conductivity, increasing cation exchange capacity, and enhancing SOC, thereby improving nutrient retention. Reliance on herbicides in CA-based cotton systems was shown to impact soil microbial diversity and enzyme activity, varying with herbicide type and frequency of application. Some herbicides temporarily inhibit soil microorganisms and enzyme functions (e.g., dehydrogenase, urease, phosphatases). However, mulching and organic residue retention in CA systems demonstrated positive effects on soil microbial biomass carbon (SMBC) and microbial activity. CA practices gradually stored carbon by sequestering CO₂ in SOC, thereby stabilizing carbon and supporting biodiversity.