Hydromorphic Soils of Tripura: Their Pedogenesis and Characteristics

Hydromorphic soils that have developed on gently to very gently sloping flood plain areas of Tripura, North East India under humid tropical climate, were studied for characterization with reference to the degree of hydromorphism. The soils are characterized by the redoximorphic features, viz. mottling, gley with chroma 2 or less, and have a typical gley colour from the surface to subsoil, mostly influenced by the high groundwater level. These soils support the granary of the state. The degree of hydromorphism in these soils has been determined by the extent and distribution of mottles and gley in the profiles, which reflects the effect of the fluctuating groundwater table and depth of the permanent water table. The soils are deep to very deep with varying texture and drainage classes and have some common characters during pedogenesis under impeded drainage condition. Soils are acidic, medium to high in organic carbon, low in cation exchange capacity (CEC) and medium to high in base status. The low value of 1N KCl extractable Al⁺³ corroborates relatively high proportion of hydroxyinterlayered vermiculitic clay mineral present in the soil. Soil texture is found to be the key factor in developing hydromorphism as well as soil organic carbon stock in the hydromorphic soils of Tripura. Translocation of clay and free iron oxide (Fe_d) is generally prominent in the soils with medium to coarse texture. Based on the physical and chemical properties and the hydromorphic index, the soils can be arranged as Nayanpur > Dukli II > Dharaichherra > Dukli I > Goachand to indicate the degrees of hydromorphism.