International Journal of Soil Science1816-4978xxxx-xxxxAcademic Journals Inc.10.3923/ijss.2006.171.183YaroD .T.KparmwangT. RajiB. A.ChudeV. O.3200613The hardening of plinthite into petroplinthite restricts soil depth. Subsequent exposure of the petroplinthite to the surface through erosion renders the land unusable for agriculture as plant growth is impaired. Topographic survey and soil survey both at a scale of 1:2,000 were carried out in a landscape to determine the extent of plinthite occurrence and to characterize the soils. Four distinct soil units were identified and mapped as soil units A, B, C and D. The soils were characterized in the field and analyzed for their physical and chemical properties in the laboratory and classified. Soil units A, B and C occupying the crystal to lower slope positions in the landscape contained plinthite in the profile, while soil unit D within the valley floor had no plinthite. Soil units A, B and D were deep to very deep (64 to 172 cm deep), while soil unit C ranged from shallow to deep (28 to 145 cm). Plinthite was found at depth range from 68 to 155 cm in soil unit A, 100 to 150 cm in soil unit B and 13 to 43 cm in soil unit C, while soil unit D was almost free of plinthite. The plinthitic soil units (A, B and C) generally had higher gravel and sand, but lower in clay contents than those of non-plinthitic horizons. Soil reaction varied from extremely acid to moderately acid in all soil units . CEC NH4OAc, ECEC and clay) were statistically similar among the soil units. The organic carbon, total N and available phosphorus were lower in the plinthitic horizons than the non-plinthitic horizons. The soil are classified as Typic Plinthustults, Typic Haplustults and Typic Paleustults according to USDA, Soil Taxonomy System and as Plinthic Acrisols, Plinthic Alisols, Haplic Alisols and Haplic Acrisols by the FAO/UNESCO System.]]>Ahmad, N. and R.L. Jones,196933762764Ahmad, N. and R.L. Jones,196933765768Aide, M., Z. Pavich, M.E. Lilly, R. Thornton and W. Kinsley,2004169613623Anderson, J.M. and J. Ingram, 19932nd Edn.,Blume, L.T., H.F. Perkins and R.K. Hubbard,198751774779Bosch, D.D. R.K. Hubbard, L.T. West and R.R. Lawrence,19943717831790Bray, R.H. and L.T. Kurtz,1945593946Carlan, W.L., H.F. Perkins and R.A. Leonard,19851396266Day, P.R.,19651965pp: 545-567pp: 545-567Daniels, R.B., B.F. Hayek and E.E. Gamble,197842944949Dos Anjos, L.H.C., D.P. Franzmeier and D.G. Schultz,199564257279Esu, I.E., I.J. Ibanga and G. Lombin,19875100123FAO/UNESCO,19881988Higgins, G.M.,196141125Ibanga, I.J.,19801980Kowal, J.M. and D.T. Knabe,1972pp: 11pp: 11Kparmwang, T.,19931993Macleod, W.N., D.C. Turner and E.P. Wright,1971161101Maignien, R.,1966pp: 148pp: 148McCurry, P.,19701970McFarlane, M.J.,1976pp: 151pp: 151Mosugu, M.,19891989Murphy, J. and J.P. Riley,1962273136Oikeh, S.O., J.G. Kling, W.J. Horst, V.O. Chude and R.J. Carsky,199962113Olowu, J.,19671967Perkins, H.F. and E. Kaihula,198173671673Pettry, D.E. and J.G. Elder,197021136136Shaw, J.W., L.T. West, C.C. Truman and D.E. Radcliffe,1997162875885Stolt, M.H., J.C. Baker and T.W. Simpson,199357422428Yaro, D.T.,20052005Alexander, L.T. and J.G. Cady,19621962Bremner, J.M.,19651965pp: 1324-1345pp: 1324-1345FAO/UNESCO,19741974FAO.,19791979Nelson, D.W. and L.E. Sommers,19831983pp: 539-579pp: 539-579Soil Survey Staff,19751975Soil Survey Division Staff,19931993Soil Survey Staff,19991999Soil Survey Staff,20039th Edn.,Sombroek, W.G. and I.S. Zonneveld,1971pp: 109pp: 109Theng, B.K.G.,19801980Wright, J.B. and P. McCurry,19701970pp: 5-12pp: 5-12