A review on carbon pools and sequestration as influenced by long-term management practices in a rice-wheat cropping system

The drastic increase of atmospheric CO2 concentrations and depletion of soil organic carbon (SOC) have prompted interest in exploiting the sink potential of soil to sequester carbon. The role of soils to mitigate climate change by the "4 per 1000" concept to increase global SOC stocks by 0.4% has been acknowledged. However, the potential of soils to sequester C depends on the cropping system, the magnitude of antecedent C depleted from soil, properties of the soil profile, climate and agricultural management practices. To formulate long-term agricultural management practices that lead to C sequestration, it is important to study their effect on SOC pools. Certain labile pools of C are considered sensitive indicators that show quick change after a modification in management practice. In contrast, changes in total SOC are relatively less detectable over the short to medium term. Most SOC pools are interrelated and vary in proportion. Rice-wheat, an intensive and dominant cropping system occupying 24 million hectares of cultivated land globally, significantly contributes to the global warming potential. Therefore, this review aims to identify the best management practices in the rice-wheat system that lead to C sequestration by improving SOC. These include the use of manure, compost, crop residues, balanced fertilization used conjointly with farmyard manure (FYM), mulch farming, conservation tillage, and inclusion of cover crops. The paper provides a comprehensive review of C pools and sequestration as influenced by long-term management practices under a rice-wheat cropping system.