Comparative study of three methods of determining cation exchange capacity of three major soils in the rainforest region of Southwestern Nigeria

The cation exchange capacity (CEC) of three benchmark soils in the rain forest region of Southwestern Nigeria, were measured by three standard CEC methods. Results obtained were compared with a view to selecting the best suited CEC method for the soils. The study sites were the Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, and Itagunmodi settlement. Two representative soil profile pits each were established in soils developed in coarse-grained granite and gneiss, fine-grained biotite gneiss and schist, and the amphibolite. The three methods gave different CEC values in the order of CEC-pH 8.2 > CEC-pH 7 > ECEC. There was a significant correlation between soil organic matter (SOM) and the CEC obtained by each of the three methods (P ≤ 0.05), meanwhile, total clay showed no significant correlation. ECEC provided the best estimate of the CEC for the soils and adequate SOM management is crucial to enhance sustainable productivity of the soils.     

Yield improvement in maize for tolerance to low soil nitrogen

Low soil nitrogen limits maize (Zea mays L.) production in the West and Central African subregion. Levels of residual genetic variability were determined in two low‐N populations using selfed progeny evaluations, and results obtained indicate large genotypic and phenotypic variances for grain yield under both low‐ and high‐N environments for effective selection, while heritability estimates were generally low. Ear aspect and stay green were the most important traits contributing to grain yield for both populations. Selection reduced days to flowering, ASI and ear aspect, but increased plant height and yield. Yield gains of more than 25% occurred for the two populations under both low and high N with the most significant change of 42% occurring in one population under high N.