Understanding the effect of shifting cultivation practice (slash-burn-cultivation-abandonment) on soil physicochemical properties in the North-eastern Himalayan region

Abstract

Shifting cultivation (jhum cultivation), a common practice of converting forest land into agricultural land by slash and burn is threatening the ecosystem. This study assesses the effect of shifting cultivation cycles on soil quality in the North-eastern Himalayan region using a minimum of soil properties. To achieve this goal, a soil quality index (SQI) approach and multivariate techniques were used for surface (0-30 cm) and subsurface (30-70 cm) layers of soils in the forest, jhum land, and jhum fallow areas. The highest variability among land uses was found for clay content, SOC (soil organic carbon), exchangeable Mg and K, CEC (cation exchange capacity), and the Ca/Mg relationship. On the contrary, the lowest variation was recorded in bulk density (BD), porosity, and pH. The results of the principal component analysis (PCA) show BD, soil texture, available nitrogen (Nav), available phosphorus (Pav), available potassium (Kav), calcium (Ca) and sodium (Na) as the major indicators of soil quality. The study indicated that surface layers of forest soils have a lower soil quality when compared to jhum lands. Although jhum lands show a better soil quality compared to forests, their continued cultivation without any fertilisation and subsequent depletion of the soil nutrients can cause a degradation of soil quality as observed in jhum fallow lands. The use of these selected indicators for soil quality assessment was useful in terms of saving time and costs.