PHYSICO-CHEMICAL AND GEOCHEMICAL PROPERTIES OF SOILS UNDER SAWAH SYSTEM OF INLAND VALLEYS IN NIGERIA

This study investigated the physico-chemical and geochemical properties of soils under sawah in Nigeria. It was found that soils under sawah were majorly sandy loam to sandy clay loam having acidic reactions, low exchangeable Ca, Mg, K and Na. These soils were deficient in available P, SiO2, S, Total Nitrogen and Total Carbon while SiO2, Al2O3 and Fe2O3 dominated total elemental composition, accounting for a cumulative average of 96.16%. Except total elemental TiO2 and K2O which showed average values >1%, MnO, MgO, CaO, Na2O and P2O5 showed average values <1%. Soils under sawah exhibited intermediated to extreme weathering degree with majority of the soil sampled falling into the category of extreme weathering. With extreme degree of weathering, rapid loss of mobile species such as basic cations from soil is imminent which may account for the results observed in this study. Thus, combination of conservative agricultural practices is recommended.