Soil organic carbon (SOC) is the most important indicator of soil quality and agricultural sustainability. It an important constituent describing soil fertility/soil health and contributes to macro and micronutrients turnover. In arid and semiarid region, there is a rapid decline of soil organic carbon levels with continuous cultivation and less or negligible use of organic manure. Decline of organic carbon stock in the soil affects soil fertility status and climate change regulation capacity. Accordingly, decreasing level of SOC in soil creates widening of nutrient deficiency specially N across the worldwide and other nutrients. Negligible use of organic manures, green manure and extensive tillage usually expose surface soil to water loss; and favour the breakdown of SOC into carbon dioxide. Resultant decline in SOC encourages poor water holdings of soil, encourages nutrient leaching and global warming. All these changes are responsible for decline in the potential productivity of a soil. Soil productivity is closely linked to soil organic matter (SOM) and its primary component soil organic carbon (SOC). To maintain food production for a rapidly growing population, application of mineral fertilizers and the effective recycling of organic amendments such as crop residues and manures are essential especially in the smallholder farming systems that rely predominantly on organic residues to maintain soil fertility.

Keywords: Soil organic carbon; Soil quality; Climate change; Management.