Potassium Status of Soils in Relation to Land use Types in Ngor-Okpala, Southeastern Nigeria

Study of the potassium status of soils provides useful information needed for rational K fertilizer management and for environmental control against K pollution. Potassium status of soils of cassava, fallow, oil palm and pineapple land use types in Ngor-Okpala, Southeastern Nigeria was evaluated. This involved determination of the total K, structural or mineral K, non-exchangeable or fixed K, available K, exchangeable K and solution K. Also intercorrelationship between K forms, correlation between K forms and soil properties as well as regression models of available K and selected K forms were determined. Equally K fixation and exchange capacities were evaluated. Total, structural or mineral, non-exchangeable or fixed, available, exchangeable and solution K ranged from 11.65-20.35, 11.52-19.65, 0-2.25, 0.07-0.92, 0.05-0.90 and 0.002-0.022 cmol (+) kg-1 respectively, with distributions varying with soil depths for each land use type. Intercorrelationship amongst the K forms was significant (P ? 0.05) between available K and exchangeable K and structural K with total K but none distinct (P ? 0.05) between the other K forms. The regression model showed that non-exchangeable, exchangeable, structural and total K accounted for 39, 51, 96 and 97% of soil available K. Soil K forms correlated with selected soil properties especially OM, pH, ECEC, %BS, Na, Ca, Mg, H, clay, silt/clay ratio, sand and silt. Potassium exchange and fixation capacities ranged from 1.33-7.83 and 0.03-2.23cmol (+) kg-1 respectively with pattern of distribution irregular for the former but increased with rates of added K for the later. In general, variations in soil K forms suggests the imperative for regular K evaluation to guide against environmental K pollution and for promotion of sustainable K fertilizer use in soils of varying land use types. Keywords: Potassium, Soils, Landuse, Ngor-Okpala and Southeastern Nigeri