Characterization and Classification of Soils along Toposequence of False Bedded Parent Material in Okigwe, Imo State, Southeastern Nigeria

ABSTRACT

This study was carried out on two a toposequence with false bedded sandstone lithologic materials in Imo state, Southeastern Nigeria. Transect survey technique was employed in aligning soil profile pits along the toposequence. Profile pits were sited according to selected physiographic band units on the toposequence, a total of six profile pits were dug, three on toposequence and physiographic land units (toeslope, midslope, summit) with distance of about 100m. Soil data were analyzed statistically using coefficients of variation. Result showed that percent organic matter (OM) content of the false bedded sandstones differed significantly at the summit and toeslope differed significantly at . The coefficient of variation (CV) showed that pH (H₂O) and sand had low variation in OM, Efficient Cation Exchange Capacity (ECEC), Clay and Base saturation. The results of the physical and chemical properties of the different toposequences varied with both depth and physiographic position. The clay content of Umulolo is pronounced which can be as a result of the parent material. The particle size distribution recorded that sand-sized particles dominate other fractions of the fine earth materials. The dominating textural class was sandy clay and loam while sandy loam and sandy clay are more pronounced at the Umulolotoposequence. Silt clay ratio was generally low in all the physiographic positions across the toposequence, which indicates advanced stage of weathering. Bulk density was less than the critical level 1.70 g/cm³ in all the pedons examined on the toposequence. While the variability of soil properties such as percent sand, pH in H₂O and bulk density was generally low ( ).  Also the soil of false bedded sandstone was classified as ArenicKandiudalfs (ArenicLuxisols) at the summit, Typic Hapludults (Haplic Alisols) at the midslope and ArenicHapludults (Arsenic Luvisols) at the toeslope. The Umulolo soil has the mean highest percentage recorded at toeslope (70.47%). The mean distribution of percent silt showed that the midslope (9.90%) recorded the highest value for the toposequences.