PROPERTIES, CLASSIFICATION AND AGRICULTURAL POTENTIAL OF BASALTIC SOILS IN SEMIARID NIGERIA

Three pedons developed on basaltic parent materials on the Biu Plateau in the semi-arid region of Nigeria were characterized and classified. Soil pH values ranged from 6.0 to 6.6 and increased slightly with inc rease in profile depth. The clay content was generally above 40% and t he slit fraction ranged from 20 to 34 %. Exchangeable bases were high and values for exchangeable acidity did not exceed 0.20 cmol(+) kg(-1) . The NH4OAc-CEC, effective CEC, and base saturation (NH4OAc-CEC) were moderately high, while base saturation by effective CEC method was hi gh with all values above 90%. Organic C content of the surface soils w as medium, but the soils were deficient in N, P and S. The pedons were classified as Typic Haplustalfs (Haplic Alisol and Chromic Luvisol) a nd as Ustic Dystropept (Chromic Cambisol). The agricultural potentials of the soils were considered to be favourable, although constrained b y N, P and S deficiencies. (C) 1998 Academic Press Limited.