Toposequence Study of Soils along Donga River in Manya, Takum Local Government Area Taraba State, Northeast Nigeria

A toposequence soils study was undertaken along Donga River in Manya, Takum LGA Northeast Nigeria. Three (3) profile pits were sunk using physiographic positions (upper slope, mid-slope and valley bottom) and the soil samples were collected based on genetic horizon differentiation, the samples were subjected to routine laboratory analysis. Data generated was analyzed statistically using coefficient of variance and weighted mean. All profile pits were geo-referenced using hand held GPS receiver. Soil colour ranged from dark brown (7.5YR 3/2) in the Ap horizons to strong brown (7.5YR 5/8) in the Bt horizons. Sand and silt dominated the fractions (sand mean content 43.00 g/kg1 , 71.47 g/kg1 and 39.64 for Pedons 1, 2 and 3 respectively and silt mean at Bt2 had 558 g/kg1 , 366 g/kg1 and 680 g/kg1 for Pedons 1, 2 and 3 respectively). The bulk density was higher in the top soils than in the sub soils, the highest mean was recorded in pedon 3 (1.57 g/cm3 ). The silt clay ratio (SCR) was indicative of soils with weatherable minerals. The soil pH ranged from moderately acid to slightly acid (6.48, 5.80, 5.95) in pedons 1, 2 and 3 respectively. The negative ∆pH values obtained are indicative that the colloidal fraction had exchangeable capacity. The total nitrogen was rated low while available phosphorus was rated very high to high. The percentage base saturation had mean from 96.72%, 97.12% and 95.79% in pedons 1,2 and 3 respectively, suggestive of Alfisols -Entisols mix. There were varied results for coefficient of variation (CV) in soil properties among the different positions on the toposequence. Therefore, the soils were classified as Typic Isohyperthermic Haplustalfs in pedons 2 and 3 with fluvic characters in pedon 1 (USDA) which corresponded to Arenic Luvisols (WRB).