Assessment of Sequestered Organic Carbon and Its Pools Under Different Agricultural Land-Uses in the Semi-Arid Soils of South-Western Punjab, India

This is a study of long-term impact of agricultural land-uses on soil organic carbon (SOC) sequestration, its depth-wise distribution among some selected carbon pools, and their contribution towards loss of C through mineralization as CO2 to understand the present situation as well as to elucidate future strategies. Soil samples from croplands, horticultural lands, and uncultivated lands in semi-arid India (south-western Punjab) were assessed for basic physico-chemical properties, SOC, SOC stock, KMnO4-oxidizable C (KOC), particulate organic C (POC), and C mineralization (CO2-Ccum). Orchards showed highest potential to sequester carbon imparting a trend of horticulture > croplands > uncultivated lands regarding SOC and its pools. Weighted mean values showed the similar trend where croplands and uncultivated lands were mostly at par. Up to 90 cm depth orchards exhibited highest SOC stock (74.89 Mg ha−1) followed by croplands (53.87 Mg ha−1) and uncultivated lands (43.72 Mg ha−1). Decrease in C along the profile was pronounced under croplands. The studied pools were positively correlated with highest magnitude observed in between POC and SOC (r = 0.831, P = 0.01). Least positive linear relation with C mineralization was exhibited by POC particularly under horticulture, and highest C mineralization was recorded in the case of KOC under cultivation. Due to having greater POC contents which is less susceptible to mineralization loss, horticulture exhibited long-term stability of soil C than croplands. Croplands suggest faster loss of soil C for the presence of labile KOC fraction in a comparatively higher extent. Therefore, inclusion of horticultural land-use could be considered as a positive strategy to maintain the future productivity as well as sustainability of the studied area where intensive cultivation is prevailed.