Soil survey and soil classification of the Koupendri catchment in Benin, West Africa

Abstract

Lack of detailed soil data has been a major constraint to hydrological modeling and making of agronomic decisions in the Koupendri Catchment. A soil survey was carried out to characterize and classify the soils of the 11.8 km2 catchment using Soil and Terrain (SOTER) approach. The soils were classified using the soil taxonomy (USDA) and the world reference base for soil resources (WRB) classification systems. The soil map produced at a scale of 1:25000 using FAO/UNESCO legend showed five distinct soil types. The dominant soil type - Dystric Plinthosols - covered about 55% of the area and supports few crop productions but make plantation agriculture almost impossible. The soils are slightly acidic to alkaline, predominantly silty to clayey in texture with good to imperfect drainage, low permeability and high bulk density that impedes root growth.  The poor soil organic carbon content, total nitrogen, available phosphorus, cation exchange capacity, base saturation and other basic exchangeable cations with moderately leached horizons indicated low-moderate fertility status of less weathered soils. The soils belong to three major soil orders: Ultisols, Inceptisols and Alfisols (USDA), and reference soil groups: Plinthosols, Cambisols, Luvisols and Gleysols (WRB). The WRB gave a better and detailed soil classification compared to USDA, and thus should be used in subsequent classification of soils in the region.   Key words: Soil and terrain (SOTER), ultisols, alfisols, inceptisols, plinthosols, cambisols, luvisols, gleysols.