Organic matter asserts an abiding influence on soil fertility. Maintenance of soil organic matter is a problem because its native or added forms are highly unstable. The breakdown products of organic matter accumulate as humus and disappear as CO2.Tropical soils particularly those under the influence of arid and semiarid climate are rarely able to build up organic carbon exceeding 0.6 per cent. Abandoning organic manures in favor of chemical fertilizers is an important factor promoting deficiencies of those nutrients which are not supplied through chemical fertilizers. Keeping these in view, to study the dynamics of soil carbon mineralization, field trials were conducted for a period of five years (2001-2005) with cotton-maize-sunflower cropping sequence in a black sandy clay loam soil belonging to montmorillionitic, isohypothermic, Vertic Ustropept. The experimental soil was low in soil fertility. From the soil test, the nutrient requirement (NR) of the crops in the cropping sequence was computed. The nutrients required by the crop was supplied through inorganic fertilizers (Urea, Single Super Phosphate, Muriate of Potash), organics (crop residues, composted poultry manure) and also through the integrated use of inorganics and organics. The treatments were: T1-100% NR through inorganics T2: 100% NR through incorporation of crop residues T3: 100% NR through incorporation of composted poultry manure T4: 50% NR through inorganics +50% NR through incorporation of crop residues T5: 50% NR through inorganics +50% NR through incorporation of composted poultry manure The mineralization patter of nutrients added through organics was assessed. Evolution of CO2-C and microbial biomass carbon were determined. The organic carbon build up in soil under intensive cropping system over a period of five years was evaluated. The partial nutrient balance at the end of five years crop rotation was computed. From the study, it could be inferred that the CO2-C evolved during the decomposition of crop residues was higher and faster and hence soil carbon depletion was more in the plots incorporated with crop residues. Incorporation of composted poultry manure recorded the maximum soil carbon build up and microbial biomass.