Characterization And Classification Of Soils Of Dissimilar Topographic Units In Owerri Area, Imo State, Nigeria

ABSTRACT

The soils of Owerri area, Southeastern Nigeria were studied with a view to characterizing and classifying them. Four locations namely Umuhu (control), Amakohia (summit), Akpodim (midslope) and Ife (footslope) were selected in the study area, to assess the impact of topography on soil properties. Three profile pits were dug in each site. 65 soil samples were collected and examined with regards to their morphological, physical and chemical properties. Test for variance was carried out on physical properties of sand (4.8%), silt (11.0%) and clay (13.0%) and they showed low coefficient of variation, while particle density (19.6%) and total porosity (28.0%) recorded medium variability. Chemical properties such as organic matter (35.1%) and total nitrogen (48.2%) showed high variation. The texture of the soils were predominantly sandy clay loam, however, soils in some parts of the foot slope had a sandy loam texture. Soils of the study area showed strong acidic reactions ranging from 4.10-4.40 in 1N KCl and 5.12-5.58 in H2O. Total nitrogen ranged from 0.19-0.60%, indicating a low presence. The physical and chemical properties of soils varied from place to place due to the toposequence with the summit most affected by loss of vital physical and chemical properties that had been washed down slope by erosion. The soils of the study area showed potential desirable physical fertility, but showed deficiency of some chemical parameters, such as low total nitrogen, low organic carbon very low available P and low Na+ cation. Hence, the fertility status of the soils should be improved by adopting integrated soil conservation measures to avoid removal of soil and soil nutrients by erosion, leaching and other topography-induced factors. Crop residue, compost and animal dung should also be incorporated into the soil to improve its texture and structure. In conclusion, according to the USDA Soil Taxonomy, the soils were classified as Typic Kandiudults (Control), Typic Rhodudults (Summit), Typic Histudolls (Midslope) and Typic Dystrudepts (Footslope); while they were classified as Haplic Arenosols (Umuhu and Ife), Haplic Acrisols (Amakohia) and Technosols (Akpodim) based on the World Reference Base system.