Forms and Status of Potassium in Some Soils Supporting Oil Palm (Elaeis guineensis,Jacq) Plantations in Cross River State,Nigeria

The status of the various forms of potassium (K) in soils derived from sedimentary sandstone and basement complex rocks that support oil palm plantations was investigated. The investigation revealed that in the surface and subsurface soils of sedimentary sandstone, water-soluble K ranged from 0.02 to 0.07 cmol per kilogram (cmol kg^?1), exchangeable K from 0.07 to 0.40 cmol kg^?1, difficultly exchangeable K from 0.15 to 0.88 cmol kg^?1, acid-soluble K from 0.48 to 2.00 cmol kg^?1, nonexchangeable K from 12.31 to 36.39 cmol kg^?1, and total K from 12.80 to 38.39 cmol kg^?1, where S. in soils derived from basement complex rocks, values ranged from 0.02 to 0.08 cmol kg^?1, 0.10 to 0.23 cmol kg^?1, 0.16 to 0.57 cmol kg^?1, 0.67 to 1.50 cmol kg^?1, 13.87 to 31.90 cmol kg^?1, and 15.36 to 33.28 cmol kg^?1 for water-soluble, exchangeable, difficultly exchangeable, acid-soluble, nonexchangeable, and total K, respectively, in both the surface and subsurface soils. More K was found in soils derived from sedimentary sandstone than in soils derived from basement complex rocks. In all soils, the contents of all forms of K generally decreased with depth. The low values of total K indicate that these soils are deficient in K; hence these soils require adequate K fertilization for efficient production of the oil palm.