Magnesium Adsorption in Selected Cocoa Growing Soils Within Southwestern Nigeria

Magnesium is one of the vital nutrients required by Theobroma cacao L. for optimum growth and yield. Several authors have reported the deficiency of magnesium in Nigerian cocoa plantations and ended up recommending the application of magnesium fertilizer based on agronomic soil test. Application of fertilizer without considering the potential of each soil to retain certain proportion of the applied fertilizer will lead to reduced available Mg in the soil solution. The study was carried out to evaluate the sorption capacity of selected cocoa growing soils in southwestern Nigeria. Soil samples were equilibrated with 20, 40, 60, 80 and 100 mg Mg L-1. Result showed that, Freundlich equation best described the adsorption of magnesium onto the soil surfaces. Adsorption of magnesium was highest in Owena soil. Hence, more magnesium fertilizer will be required by Owena soil compared with Ekiti, Ibadan, Ile-Ife and Bodo soils to produce equal amount of available magnesium ions in soil the solution.