Soil carbon dynamics under different land-use and management systems

Abstract

Soil organic carbon (SOC) is an important component of soil that maintains soil fertility, productivity, as well as overall sustainability. Low SOC status in tropical soils, particularly those under the influence of arid, semiarid, and subhumid climates, is a major factor contributing to their poor productivity. Land-use change (LUC) is the second most important factor contributing about 20% of global emission after fossil fuel burning. To feed the growing world population, more and more natural or forest area has brought under agricultural uses particularly intensive crop cultivation. Such conversion from natural to agricultural ecosystems has led to an average decrease in C stocks of 25-30%. Soil C pools change rapidly in response to land-use change; intensive cropping/cultivation might disturb soils leading to more oxidative loss of SOC; on the other hand, it leads to huge additions of carbon as crop residue biomass and results in either a net buildup or depletion of SOC stock in soils. Cropping systems, management practices, and soil environment play an important role in C stabilization and maintaining the SOC stock. The cereal-based cropping systems such as double rice as well as forestry (Madhuca longifolia and Diospyros melanoxylon) or horticulture (guava) system conserve organic carbon in soil at a desirable level for performing ecosystem functions that would help to increase food/timber production. Soil C sequestration research has historically focused on the top 0-30 cm of the soil profile, ignoring subsoil horizons that might also respond to management. Despite their low C content, most subsoil horizons contribute to more than half of the total soil C stocks, and therefore, subsoil C may be even more important in terms of source and sink for CO2 than topsoil C. Therefore, the knowledge of SOC distribution and controls on C sequestration within soil profiles are used to predict the effect of land-use changes on C emission. An attempt has been made in this chapter to synthesize the land-use effects on SOC dynamics under different management scenarios.