Capability and quality assessment of rice growing hydric soils in Majuli river Island, Assam, India

Abstract

The wetland soils in Majuli Island is a unique ecosystem in maintaining rice ecology and geoenvironment in Brahmaputra valley of Assam due to increasing rate of bankline erosion in southern bank and expansion of channel bars on northern banks. These hydric soils in the orders of Entisols and Inceptisols are saturated throughout year as assessed from depleted matrix with hue 10YR, 2.5Y and 5Y, chroma less than 2, stratified textures, neutral to slightly alkaline reaction, low cation exchange capacity and poor exchangeable base status. The assessment of land capability and soil quality for rice production in hydric soils were conducted on twenty five soil mapping units derived from reconnaissance soil survey done on 1:50000 scale. As per land capability assessment, these soils are good (class II) to fairly good (IV) for arable use with limitations of low fertility status, moderate to severe wetness and moderate to rapid permeability. The soil quality rating with multiple variable indicator transform (MVIT) technique of twenty five hydric soil units in active and old floodplains was medium (35% to 65%) with six indicators (pH, organic carbon, base saturation, effective rooting depth, structure and texture) meeting the threshold value above 65 per cent. Thirty five per cent of the total area is suitable for rice cultivation as against the current cropped area of 7.2 % with potassium and zinc deficiencies. The determination of soil quality in relation to land capability was found useful to design best management practices for wetlands in the region to ensure sustainable land use.