Pedogenesis of two lithologically similar soils under vegetation of contrasting features in Ohaji, south-eastern Nigeria

Abstract

Knowledge of pedogenic processes in soils is vital in deepening our understanding of soil development. A pedogenic study was carried on two pedons underlain by similar lithologic material, one located under a seven-year-old vegetation and the other under a twenty-three-year-old vegetation. The two contrasting vegetation ages were randomly selected. Samples were taken from the two pedons and subjected to laboratory analyses. The results were then subjected to statistical analysis using the Statistical Analytical System. The results showed that soil profiles were deep (200 cm) and well drained. The soils were darker and browner in the epipedon and redder down the profile in all the pedons. The soil formed under the 23-year-old vegetation had a thick (18 cm) O horizon with Oe and Oa components. There was no O horizon found in the soil formed under the 7-year-old vegetation. The dominant pedogenic processes in the two soil groups were littering, melanization, illuviation, eluviation, leaching, mineralization, and humification. The two soils were preponderantly sand. Sand accumulation was higher (> 80%) in the epipedon when compared to the subsurface horizons (< 70%). All the soils had silt/clay ratios greater than 0.2. Soils were strongly acidic (4.56-5.01), moderate to high in available phosphorus (17.49-21.47 mg kg^-1) and low to moderate in organic carbon (8.78-14.49 g kg^-1.). Because soil survey reports may not give a clear outlook of the important pedogenic characteristics of soils, the research becomes very necessary in many localities of similar need.

Key words: argillation, eluviation, horizon, pedogenesis, vegetation