Influence of Fallow Length and Land Use Practices on Soil Microbial Properties in Shifting Cultivation Landscapes of Manipur, India

Abstract

This study evaluates the influence of fallow length—ranging from very short (0–1 years) to ecologically optimal periods (12 years)—and alternative land-use systems (intermittent agriculture, agroforestry, and abandoned jhum fields) on soil microbial properties in shifting cultivation areas of Chandel district, Manipur, India. Soil microbial biomass carbon (SMBC), dehydrogenase activity (DHA), and basal respiration (BR) were assessed to quantify biological recovery following slash-and-burn cycles. Short fallow cycles (3–4 years) caused substantial declines in SMBC, DHA, and BR across all land uses, indicating inadequate time for organic matter regeneration and microbial re-establishment. Recovery improved markedly in systems with ≥5–7 years of fallow, although intermittent agriculture showed limited gains due to irregular rotations. Abandoned jhum lands (>5 years) and 8–10-year-old agroforestry systems exhibited the highest restoration of microbial activity, surpassing even 25-year-old Pinus kesiya secondary forests. Overall, the findings highlight that extending fallow duration and adopting diversified, nitrogen-fixing agroforestry systems are key to restoring soil biological functioning, enhancing soil carbon dynamics, and ensuring sustainable productivity in degraded jhum landscapes of the North Eastern Hill region.