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Soil carbon stock (CS), was estimated in the 0-25 and 0-100 cm soil depths of and and semi-arid regions of Rajasthan. Carbon stock was 2.13 Pg in the 0-100cm soil depth, of which 1.23 Pg was soil organic carbon and 0.90 Pg was soil inorganic carbon. The surface horizon (0-25 cm) stored 31% of the soil carbon stock. Soil carbon stocks were higher in Entisols (0.72 Pg or 33.6% of CS on 43.6% of the land area) and Aridisols (0.70Pg or 32.7% of CS on 28.9% of the land area) than in Inceptisols(0.61 Pg or 28.6% of CS on 24.01% of the land area), Alfisols (0.015 Pg or 0.007% of CS on 0.76% of the land area) and Verisols (0.105 Pg or 0.005% of the CS on the 3.2% of the land area). Torripsamments, Haplocambids and Haplustepts together held 80% of CS and 86.9% of soil organic carbon stock, whereas Haplocambids, Petrocalcids and Haplustepts comprised 72% inorganic carbon stock. Soil organic carbon density (SOC) ranged from 4000 to 7000 kg/km(2) in Haplustalfs, Haplusterts, Haplustepts and Torripsamments, while its inorganic counterpart 4200-4600 kg/km(2)/year SOC could be sequestered in untilled soils of the and region, which have year-round canopy cover. (c) 2006 Elsevier Ltd. All rights reserved.