Soil organic carbon status and sustainability of slash-and-burn cultivation in India

The study was carried out (a) to identify the changes in the soil organic carbon (SOC) content during the different phases of slash-and-burn cultivation-i.e., before slash-and-burn (Phase 1), after slash-and-burn (Phase 2), and after harvest (Phase 3); and (b) to determine the status of soil organic carbon content in the primary undisturbed forest (Site 1) and in the secondary forests, where slash-and-burn cultivation was taken up similar to 25 yr (Site 2), 15 yr (Site 3), and 5 yr back (Site 4). The undisturbed forest holds the largest amount of SOC % (5.25) followed by 25 yr (3.07), 5 yr (2.86), and 15 yr (2.27) fallow. The mean percentages of SOC in the 0- to 15-cm layer fell from 3.07 in Phase 1 to 2.53 and 2.37, respectively, in Phases 2 and 3; in the subsurface 15- to 30-cmlayer, they fell from 1.95 to 1.62 and 1.63, respectively. Although, the SOC in Phase 3 still seems sufficient to support another round of cultivation, further studies are needed to examine crop yields in successive cultivation cycles, suitability of other rice varieties, and weed and pest types and rates of invasion. Tribal population dynamics is another major concern, which needs assessment for monitoring future land requirements.