Stability of organic carbon pools and sequestration potential as affected under different agroforestry systems

There are few data on the possibility of soil organic carbon sequestration for agroforestry systems (AFSs). Rarely are the effects of AFSs established for the regeneration of carbon in degraded soils of the Indian North Eastern Himalayas (susceptible to soil erosion, carbon and nutrient loss) examined. The effects of five different AFSs on the stability of organic carbon pools and sequestration potential were evaluated at the ICAR-Sikkim Centre. Black gram + mandarin + Alnus nepalensis had the lowest bulk density at all depths. The highest oxidizable carbon was observed in the black gram + mandarin + Alnus nepalensis system, followed by soybean + Ficus hookerii + guava, maize + Schima wallichii, and soybean + Ficus hookerii + guava, followed by Napier. Regardless of soil depth, the buckwheat + mandarin system had a noticeably lower SOC than the other systems. The total soil organic carbon gradually decreased with increasing depth of the soil profile. According to the results, there was little difference in the total active carbon pool in the 0-90 cm depth among the various systems; however, when compared with Buckwheat + Mandarin, it varied significantly (P ≤ 0.05). The mean passive carbon pool in soils ranged from 22.4 to 25.1 Mg ha^-1 across the land use in the 0-90 cm depth. The least soil microbial biomass carbon (MBC) was observed during the winter season in all systems at different soil depths. The maximum MBC was recorded at 0 to 15 cm depth (476.2 - 302.5 µg dry soil^-1). By simultaneously cultivating kinds of trees with several uses and agri-horticultural crops, a large-scale adoption of AFSs may replace carbon lost via the development of the crop in degraded soils and offer a viable choice for livelihood.