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

Abstract

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, 0.07-0.92,0.05-0.90and 0.002-0.022cmol (+) 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 1.33-7.83and 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.