Soil carbon pools under different land uses in Typic Haplustept

Carbon (C) fluxes are largely controlled by the small but highly bio-reactive, labile pools in terrestrial soils, while long-term C storage is determined by the long-lived recalcitrant fractions. This study was conducted to investigate the different organic carbon pools under different land uses at Indian Agricultural Research Institute of New Delhi, India. Land use systems evaluated include: maize-wheat cropping system, rainfed agriculture Aloevera, forestry, agroforestry and rice-wheat cropping system. Surface soil samples were collected from two different depths (0–5 cm and 5–15 cm). Total soil organic carbon was divided into four different pools (pool 1, 2, 3 and 4) using varying strength of sulphuric acid. Labile pool (pool 1 and 2) ranged from 2.6 to 5.3 g C kg^–1 dry soiland recalcitrant pool (pool 3 and 4) ranged from 3.8 to 22.6 g C kg^–1 dry soil in the different land uses. From the view point of different fractions of labile and recalcitrant pools, the performance of land-use systems was in the order of: Forestry > Agro-forestry > Rice-wheat system > Maize-wheat system > rainfed Aloevera. Highest labile as well as recalcitrant pool was observed in 0–5 cm when compared to 5–15 cm depth. Beside, these sulphuricacid oxidizable fractions, other organic C pools, viz. Walkley and Black organic carbon, total carbon and microbial biomass carbon were also determined. These pools also followed the same trendas sulphuric acid oxidizable fractions. Walkley and black organic carbon constituted 31.7 to 37.7% of the total carbon in 0–5 cm depth in different land-uses.