Abstract

This study was undertaken to characterize and classify Tsukundi fadama soils in Wukari LGA of Taraba state, Nigeria. The geomorphic units were delineated into mapping units based on their physiographic positions (upper slope, mid-slope and valley bottom) and degree of submergence along transect spaced at 300 m across the slope. Sampling was based on genetic horizon differentiation. The soil depth at these mapping units (MUs) is deep < 120 cm indicating a moderate profile and a slope gradient of < 2%. The MUs has restriction zone of hardpan or sesquioxides/ plinthic horizons. The colour matrix of dark yellowish brown, strong brown and reddish yellow are associated with minerals such as goethite (FeOOH) and hematite (Fe2O3) and gibbsite [Al(OH3)]. Dark red (10YR3/6) to reddish yellow (7.5YR6/6) are indication that the soils were either imperfectly drained or poorly drained during rainy season. Soil colours ranged from Black (7.5YR 2.5/1) in Ap horizon to reddish yellow (7.5YR 6/6) to strong brown (7.5YR 5/6) to gray (5YR 5/1) to light gray (5YR 7/1) in Bt1, Bt2 and Bt3 horizon respectively. The percentage sand averages were 804.1 g/kg, 680 g/kg and 788 k/kg in pedon SSS, MSS and LSS respectively. The clay contents of the soils increased with depth generally indicating the illuviation (translocation movement) soil finer particles down the profile and SCR was indicative of a young soil with weatherable mineral reserves. The delta pH (∆pH) of the soils showed all negative values; this indicates that the soil colloids contained appreciable silicate clay minerals with relatively constant surface charge while the CN ratio ranged from 7.68 – 30.0. The percentage base saturation (B-sat) was largely dominated by exchangeable cations in moderately to very high rating and their mean values are 77%, 68% and 80% for MUs SSS, MSS and LSS respectively. TN had highly significant positive correlation with sand (0.61**), SCR (0.55**), BD (0.46**) while significant negative relationship clay (-0.75**), Po (-0.49**). The soils were classified as Alfisols/Entisols mix (USDA) and correlates to Eutric Arenic Fluvisols/ Luvisols (WRB).