Classification of soils derived from amphibolite parent material in south-western Nigeria

Abstract

Soils formed from amphibolite parent material in southwestern Nigeria were characterized and classified according to FAOIUNESCO soil map legend and USDA Soil Taxonomy. The soils had characteristically Jaw silt content. Clay and fine sand contents were high. The soils varied from slightly acidic to acidic. Organic carbon, extractable phosphorus and total nitrogen contents decreased with increasing depth. Cation exchange capacity (by NH. OAc) values of the soils ranged from 2.32 to 15.19 cmol(+)/kg soil. Base saturation (on CEC by NH. OAc) basis) values were quite high (35.4-87.7%). According to FAOIUNESCO soil map legend, the soil at the summit was Rhodic Ferralsol while the soil of the upper slope belonged to Ferric Acrisol. Soils of the middle and lower slopes of the toposequence were classified as Rhodic Nitisol and Haplic Lixisol respectively. The valley bottom soil was Gleyie Lixisol. All the soils belonged to Ultisol of Soil Taxonomy except the soil of the summit which was classified as Oxisol