PROPERTIES AND CLASSIFICATION OF FTVE SOILS ON ALLUVIAL LANDFORMS IN CENTRAL NIGERIA

Abstract

Five soils formed in alluvium in central Nigeria are described, characterized and classified. One soil is on the present floodplain of the River Benue, while the others are on terraces of both the River Niger and the River Benue and their tributaries. Soils have a preponderance of mottles, sesquioxidic nodules and/or concretions and grayer colors of low chromas. Particle size distribution on a clay-free basis was used in addition to morphology and organic carbon distribution to determine the homogeneity of parent materials. The soil on the floodplain and two others on terraces are all formed in two different parent materials. Two other soils on terraces are formed in homogeneous parent materials. Most soils have a generally low effective cation exchange capacity, but higher values are found in neutral to moderately alkaline profiles containing smectite. The clay fractions are a mixture of kaolinite, smectite and some hydrous mica. Two soils are classified as Ustifluvents. The others are Tropaquepts, Plinthaquults and Argiaquolls. Equivalent FAO/UNESCO classifications are Dystric Fluvisols, Dystric Gleysols, Eutric Planosols, Plinthic Gleysols and Mollic Gleysols. Key words: Alluvium, hydromorphic, Nigeria, mixed clay mineralogy, classification