Soil characteristics and constraints to crop production in inland valley bottoms in southwestern Nigeria

The paper reports the soil characteristics and constraints to agricultural production in inland valley bottom wetlands in southwestern Nigeria. The soils have high silt and clay fractions in the surface horizons, and soil texture vary remarkably from sandy to clayey both within and among the bottomlands. Bulk density averaged 0.96 g/cm^3 in the 30 cm topsoil layer and increased substantially to 1.57 g/cm^3 with depth. Non-capillary porosity averaged 0.287 and 0.127 cm^3/cm^3 in the respective depth zones. Similarly, saturated hydraulic conductivity (Ksat) averaged 4.45 and 1.38 cm/h, respectively. The soils were well supplied with the exchangeable bases, especially Ca and Mg. Organic carbon levels were high, while available phosphorus was moderately high. The main constraints to agricultural production are the small size of the valley bottoms, low subsoil water transmission and poor drainage, and weed growth. Poor drainage can be alleviated by adapting the farming of the land to the wet condition, example, by growing rice or by introducing mound-tillage, and growing rice at the base and a toposequence of "dry foot" crops on the mounds. Mound-tillage with shallow drainage ditches can also be used to improve soil–water relations for dryland farming in the bottomlands. These soil and water management practices will enhance intensive uses of the potentially productive inland valley bottoms and increases in the productivity of the farmers.