DISTRIBUTION OF EXCHANGEABLE CATIONS IN SOILS UNDER DIFFERENT AGRICULTURAL LAND USES OF SIMILAR LITHOLOGY IN EDO STATE, NIGERIA

Abstract

This study was carried out to examine the distribution of exchangeable cations in soils under cassava-cultivated land use, mixed-tree plantation and secondary forest of similar lithology in Edo State, Nigeria. The study sought to determine the concentrations of exchangeable cations under each land use; evaluate the distribution of exchangeable cations across the different land uses; examine the impact of the different land uses on exchangeable cations; and ascertain if significant relationships exist among the exchangeable cations under each land use. Using transect sampling design, a total of 54 soil samples were collected for the study. The soil samples were prepared and analyzed for exchangeable cations: pH, calcium (Ca) magnesium (Mg) potassium (K), sodium (Na), exchangeable acidity (EA), effective cation exchange capacity (ECEC) and base saturation (BS) in the laboratory using standard methods. The results revealed heterogeneous effects of land use and soil depths on the exchangeable cations (Ca, Mg, Na and K), especially as Na and K showed significant (p < 0.05) variations. The values of Ca, Na, K and BS were rated as moderate and adequate in all the test soils, but Mg concentrations were deficient. Soil pH was rated slightly acidic to neutral in all the soils. Effective cation exchange capacity values revealed that the soils of the studied sites had a low capacity to hold cations. Pearson correlation analysis indicated significant correlations (p < 0.05) between some soil properties at the 0-15 and 15-30 cm soil depths in the different land uses. The study concluded that exchangeable Mg was the most adversely impacted soil property in the studied land uses and recommended liming and incorporation of organic manure to soils to boost their ECEC.