Impact of cropping systems on soil organic carbon (SOC) dynamics in relation to soils' antecedent C level has not been well addressed, which is important for prioritization of areas for soil C sequestration. We investigated the effect of maize-wheat and soybean-wheat cropping and continuous-fallow on total organic C (TOC) and labile SOC pools in four identical alluvial soils of same type and texture, but different antecedent TOC level: a low-C soil (Soil 1, 5.6 g kg(-1)), two medium-C soils (Soil 2 and Soil 3, 9.0 and 9.6 g kg(-1)), and a high-C soil (Soil 4, 12.9 g kg(-1)), all under semi-arid subtropical climate. After 3 years, maize-wheat and soybean-wheat resulted significant rise in TOC in Soil 1 but decline in Soil 4 compared to the antecedent levels; in Soil 2 and Soil 3, such changes were not considerable. Under the cropping systems, the labile SOC pools, viz. water-soluble, hot water-soluble, permanganate oxidisable, very labile, and mineralizable pool, were significantly higher in Soil 1 (by 23-106%) but lower in the other soils (by 16-49%) compared to the continuous-fallow. Antecedent C of 36 Mg ha(-1) was the critical level; below which cropping gained TOC but above which cropping lost TOC. Cropping effects on the magnitude and direction of changes in SOC depended on soils' antecedent C status. In view of prioritizing areas for C sequestration in soils of north-west India, maize-wheat and soybean-wheat systems can be promoted in soils with < 36 Mg ha(-1) antecedent C level.