Soil aggregate-associated carbon and organic carbon pools as affected by conversion of forest lands to agriculture in an acid soil of India

Aggregate-associated soil organic carbon (SOC) controls organic carbon stabilization. The research question of this paper was: what were the effects of conversion of forest land uses to agriculture at Ranchi, India on SOC pools, soil aggregation and aggregate-associated C? The samples were taken from six different land uses viz. native forest (NF), agri-horticulture (AH), native grass land (NG), rice-wheat (RW), rice- vegetable (RV) and maize-wheat (MW) from three soil depths (0–15, 15–30 and 30–45 cm). Soil aggregation, SOC pools and aggregate-associated C were determined. Results revealed that SOC concentration in NF was 36%, 67% and 127% higher than RW, RV and MW land uses, respectively, at 0–15 cm depth. The microbial biomass carbon (MBC) was higher in NF land uses than rice-based systems in the soil surface (0–15 cm) due to less disturbance. In surface soils (0–15 cm depth) under NF, the large macroaggregates had 21% and 40% higher SOC concentration than RW and RV, respectively. Similarly, NF soil had larger small macroaggregate-associated C than RW, RV and MW systems in the 0–15 and 15–30 cm layers. This result supports that tillage and regular crop removal under arable (MW, RW and RV) systems adversely affect loss of SOC contents in the surface layers and C storage inside aggregates, both in the 0–15 and 15–30 cm soil layers at Ranchi, India.