Soil Morphology, Physico - Chemical Properties and Classification of Typical Soils of Mwala District, Kenya

A soil profile representative of typical soils of Mwala District, Kenya, was dug to study its morphology, soil physico-chemical characteristics and to classify it using two internationally known soil classification systems. Disturbed and undisturbed soil samples were taken from designated pedogenic horizons for physical and chemical analysis in the laboratory. Soil morphological observations revealed that the pedon is well drained and very deep with dark brown to dark yellowish brown topsoil overlying brown to strong brown sandy clay loam to sandy clay subsoil. Clay eluviations - illuviation is a dominant process influencing soil formation in the study area as indicated by the clay gradient between the eluvial and illuvial horizons and the presence of clay cutans in the subsoil. The soil is characterized by weak fine subangular blocky throughout its pedon depth. Laboratory analysis indicates that the soil is very strongly acid (pH 4.6–5.0) throughout the profile, has very low N (<0.1%) and low OC (0.6-1.25%). The pedon has low CEC (6.0-12.0 cmol (+) kg-1) and low base saturation (<50%). Available P is rated as high (>20mg kg-1) in the topsoil while it is low (7-20mg kg-1) in the major part of the subsoil. Using field and laboratory analytical data, the representative pedon was classified to the subgroup level of the USDA Soil Taxonomy as Typic Haplustults and to Tier-2 of WRB as Haplic Cutanic Acrisols (Humic, Hyperdystric, Endosiltic). The general fertility of the soils of the area is discussed highlighting their potentials and constraints.