Factors Affecting Carbon Sequestration and Greenhouse Gas Emission in Agroecosystems

Soil organic carbon (SOC) is the most crucial factor in abating and reversing climate change. Researchers, environmentalists, academicians, and global policymakers recognize the importance of SOC in mitigating climate change. Therefore, continuous efforts are being directed toward increasing SOC stock. In this respect, soil carbon sequestration in cropland has received immense focus, instigating a plethora of research work under long-term fertilizer application and tillage trials. Long-term fertilizer trials under different agroecological zones are very important for studying SOC dynamics and carbon stocks and sequestration potential. This is because detectable changes in SOC in response to management practices can be reliably documented over periods of years or decades. Additionally, at most of the sites, SOC has already reached a quasi-equilibrium state, and a rational scenario can be projected for different agroecological zones along with different soil, crop, and climate conditions. Results of long-term fertilizer application have revealed that a balanced use of nutrients is effective in increasing SOC content. Furthermore, integrated nutrient management (INM) has been able to sustain crop productivity, nutrient supplying capacity, and substantially higher SOC stock for a long time. INM has also been reported to increase deep soil carbon sequestration, enrichment of carbon in macroaggregates, and activation energy of SOC, which would act as an energy barrier for SOC decomposition. Furthermore, INM showed the potential of achieving the 4 per 1000 target in the longest running long-term experiments in temperate climate; however, the actual requirement of organic manures/crop residue as carbon inputs to achieve the 4 per 1000 target is quite high.