Potassium supplying power of selected soils of Akwa-Ibom state

Potassium (K) supplying power of soils is the capacity of a soil to fix and release potassium into the soil system in the exchangeable as well as in the non-exchangeable forms. Potassium supplying power of ten Akwa-Ibom State surface soils- a coastal oil producing state of Nigeria- were evaluated through a study of the forms and quantity-intensity relation of K in the soils. The total K contents ranged from 250-3,200 mg/kg with the lowest value obtained from soils at Ikot-Osute coastal plain sands and the highest at obotme. The exchangeable K ranged from 0.13-0.46 me/100g soil. The quantity-intensity isotherms derived from potassium potential studies were similar in all the soils. The activity ratio (AR.) ranged from 1.00-1.90/1000 (m/1)1/2 and correlated significantly with exchangeable K (r = 0.809**). The labile K varied from 0.20-0.90 meg/100g soil and correlated significantly with exchangeable K. Higher values of most of the parameters were observed in soils developed on mixed sandstones giving high K supplying power due to their high clay content which favours K adsorption and fixation in soils.