Carbon stocks in major soil types and land use systems in semi arid tropical region of southern India

Abstract

We study here the soil organic and inorganic carbon stock under different land-use systems in semiarid tropical region of India, as carbon storage in the soil profile not only improves fertility but also abates global warming. Soil samples were collected up to 60 cm depth from 51 profiles, one from each Mandal in Warangal District, Andhra Pradesh, representing semiarid tropical region of India. Vertisols and associated soils contained greater C stocks, followed by Inceptisols less than Alfisols. The soil organic carbon (SOC) stocks (CN analyser C-inorganic C) ranged from 22.68 to 94.83 Mg ha–1 with a mean of 52.84 Mg ha–1 in Alfisols; 34.37 to 73.67 Mg ha–1 with a mean of 51.26 Mg ha–1 in Inceptisols, and 27.80 to 74.20 Mg ha–1 with a mean of 49.33 Mg ha–1 in case of Vertisols, whereas soil inorganic carbon (SIC) stock was 12.4 Mg ha–1 in Alfisols, 17.5 Mg ha–1 in Inceptisols and 22.9 Mg ha–1 in Vertisols and associated soils. Among the different land-use systems, total C stock was highest in forest soils followed by fodder system, paddy, maize, cotton, redgram, intercrop, chilli, permanent fallow and lowest in castor system. Soil nitrogen also followed similar trend as SOC stock. A surface map of soil C stock and soil N was prepared for Warangal District using kriging interpolation techniques and total C stock was estimated to 0.088 Pg out of which SOC stock was 77% and SIC stock was 23% for the District. Significant correlation (P < 0.05) was obtained between SOC stock and soil nitrogen with Mandal-wise annual rainfall (r = 0.436 for SOC stock and 0.410 for total soil N). As wet oxidation procedure, i.e. Walkey–Black method is a routine and most popular procedure for estimating SOC, a relationship was developed between Walkley–Black carbon as well as SOC estimated through dry combustion method using CN analyser. It was found that Walkley– Black carbon recovered 90% of SOC for semiarid tropical soils.