Global Potential of Soil Carbon Sequestration to Mitigate the Greenhouse Effect

An increase in atmospheric concentration of CO2 from 280 ppmv in 1750 to 367 ppmv in 1999 is attributed to emissions from fossil fuel combustion estimated at 270 ± 30 Pg C and land use change at 136 ± 55 Pg. Of the emissions from land use change, 78 ± 12 Pg is estimated from depletion of soil organic carbon (SOC) pool. Most agricultural soils have lost 50 to 70% of their original SOC pool, and the depletion is exacerbated by further soil degradation and desertification. The restoration of degraded soils, conversion of agriculturally marginal lands to appropriate land use, and the adoption of recommended management practices on agricultural soils can reverse degradative trends and lead to SOC sequestration. Technological options for SOC sequestration on agricultural soils include adoption of conservation tillage, use of manures, and compost as per integrated nutrient management and precision farming strategies, conversion of monoculture to complex diverse cropping systems, meadow-based rotations and winter cover crops, and establishing perennial vegetation on contours and steep slopes. The global potential of SOC sequestration and restoration of degraded/desertified soils is estimated at 0.6 to 1.2 Pg C/y for about 50 years with a cumulative sink capacity of 30 to 60 Pg. The SOC sequestration is a costeffective strategy of mitigating the climate change during the first 2 to 3 decades of the 21st century. While improving soil quality, biomass productivity and enhanced environment quality, the strategy of SOC sequestration also buys us time during which the non-carbon fuel alternatives can take effect.