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Not AvailableClayey and smectitic associated red and black Benchmark soils covering 15 m ha area in semi-arid tropics (SAT) were studied in different land use systems (LUSs) viz. agricultural (cereals, soybeans, cotton), horticultural (mandarins), forest (teak and sal) and wasteland to identify LUSs for carbon sequestration. Under each LUS, under two managements (HM:high management; LM: low management) soils under HM contain more soil organic carbon (SOC) and are darker in colour and their consistence was controlled by slickensides, CaCO3 , zeolites and gypsum content. Roots are found to be concentrated in those soil layers containing low CaCO3. Depth of occurrence of slickensides is related to the level of management and climate. Management interventions (including irrigation in drier tracts) push the slickensides further down the depth. Total SOC, SIC and TC (total carbon) stocks estimated for these soils helped to identify 22 systems as viable under the present level of management systems on the basis of minimum and maximum threshold limits of SOC and BD values. The level of management in black soils for the last 25 years helped these soils to reach a relatively higher SOC quasi-equilibrium value. This indicates that these shrink-swell soils under semi-arid and arid bioclimatic systems respond to controlled management level. The results on the effects of various production systems in SAT, with emphasis on rice vs. other arable cropping, showed that soil samples from sites under natural vegetation had the highest contents of organic C and total N, followed by those under lowland rice (anaerobic) cultivation and other arable (aerobic) crop production systems. Thus the sites under continuous wetland rice cropping accumulate organic matter and contain higher soil organic matter compared to the sites under other arable systems. The present study developed the datasets and the techniques to find out threshold limits of SOC and BD in identifying systems for better carbon sequestration and increased productivity. This will not only help the modellers engaged in SOC enhancement but also serve as database for periodic monitoring of soil health.Not Availabl