Impact of shifting cultivation on soil organic carbon in tropical hilly terrain of Mizoram, India


Shifting cultivation is one of the main forms of crop husbandry in the hilly northeast India and is known to change the physico-chemical properties of soil. Data of soil organic carbon (SOC) in relation to shifting cultivation is not available in Mizoram. The study was conducted in an experimental plot of 1-acre area in the natural forest at Khawrihnim village located about 50 km south-west of Aizawl, Mizoram. Five random soil samples each were collected from shifting cultivation (experimental EXPTL) and natural forest (control CTRL) sites at monthly intervals between 2013 and 2015 at three different soil strata (i.e. 0-10 cm, 10-20 cm and 20-30 cm). SOC was estimated in percent by rapid dichromate oxidation method. Shifting cultivation has positive significant effect on SOC content. Compare to pre- and post-Jhum cultivation, the Two-Way ANOVA indicates significant increased of SOC (p<0.05) in the jhum cultivation year, which may be due to burning effect and the weeding practice that coincides with the onset of monsoon rains. The onset of monsoon after the burning of slashed vegetation and the first weeding accelerate the decomposition rate and soil microbial activity. The average of SOC in the surface layer increased from first year to third year by 1.34%. However, significant decreased of SOC content with increased in soil depth (p<0.001) was also recorded in both EXPTL and CTRL sites.

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