The comparative soil fertility in traditional and alder-based shifting cultivation of varied fallow lengths in Eastern Indian Himalayas

Abstract

ABSTRACT Shifting cultivation or Jhum, a form of traditional agroforestry system, constitutes the basic subsistence of livelihood among ethnic tribes throughout the Eastern Indian Himalayas. Shortening of fallow phase length in Jhum cycle to fulfill recent inclining population is one of the challenges concerned for co-existence between agriculture and hill forest-ecosystem. The present investigation is focused on comparative analysis of soil fertility at different fallow lengths, viz. 2, 4, and 8-years for both traditional (T-JF) and alder-Based (Alnus nepalensis D. Don) Jhum (AB-JF) with reference site (Natural forest) in Kohima, Nagaland, India. Soil pH, electrical conductivity (EC), soil organic carbon (SOC), available nitrogen (Avl-N), available phosphorus (Avl-P), exchangeable potassium (Avl-K), microbial biomass carbon (MBC), acid-phosphomonoesterase activity (PHA), dehydrogenase activity (DHA), and potential mineralizable nitrogen (PMN) were analyzed for the comparison between different Jhum systems. All soil parameters in AB-JF system showed a significant difference at P < 0.05 over T-JF (non-alder) except soil pH. This shows the superiority of AB-JF system over T-JF. The findings signify the importance of systematically managed alder trees in the Jhum cultivation system. The impact of fallow length on all soil parameter values was in the order 2 < 4 < 8 years old regardless of AB-JF and T-JF system. The values of SOC, Avl-N, PMN, MBC, PHA, and DHA decreased, while pH, EC, Avl-P, and Avl-K increased in respective fallow length of both Jhum systems after burning of biomass. In conclusion, AB-JF system has specific advantages over T-JF system in terms of improved soil fertility and nutrient cycling potentials.