Role of Legumes in Soil Carbon Sequestration

Abstract

The soil organic carbon (SOC) pool is the key indicator of soil health and quality which in turn plays a vital role to soil sustainability. The continuous uses of unsustainable agricultural approaches have depleted most of the SOC pool of global agricultural lands. Promoting cultivation of leguminous crops, grasses, shrubs, and trees offers multiple advantages, e.g., augmenting crop and soil productivity and adapting to climate change by increasing resilience of agroecosystems. As per model-based prediction by World Bank, the cumulative soil carbon (C) sequestration of pulses in Asia and Africa is expected to be 33.0 and 35.12 Mg ha⁻¹, respectively, by 2030. Legumes have the potential to reduce the CO₂ emitted during the manufacturing of chemical nitrogenous fertilizers through their biological nitrogen fixation (BNF) capacity. Therefore, the main advantage of using legumes is to ensure that the BNF which in turn reduces the amount of nitrogen (N) fertilizer required for the succeeding crop. A meta-analysis study suggested that the legumes have the capacity to store 30% higher soil organic carbon (SOC) when compared to other species; this is because of their N-fixing ability. The leguminous vegetation improves soil health and soil C content as per the nature of the specific crop. The C sequestration potential and the amount of organic C returned by leguminous species to soil depend largely on specific legume species, growth behavior, root morphology and physiology, leaf morphology, climatic conditions, structure and aggregation, prevailing cropping system, and agronomic interventions during crop growth period. The aboveground plant biomass (e.g., plant leaves, branches, stem, foliage, fruits, wood, litter-fall) and the belowground plant biomass (e.g., dead roots, carbonaceous substances from root exudates, rhizospheric deposition, and legume-promoted microbial biomass C) directly contribute to the SOC pool.