MINERALOGY AND COMPRESSION CHARACTERISTICS OF AGRICULTURAL SOILS IN SELECTED PARTS OF EI{ITI STATE

Abstract

Landlocked States in Nigeria are daily faced with the reality of the need for rapid agricultural development for socio-economic transformation. The magnitude of the need for most of the States requires massive mechanisation of the agricultural production process and this comes with its attendant environmental problem. Thus it is desirable that a pre-investment investigation be carried out on soils for sustainable development. In this study, the mineralogy of agricultural soils in selected parts of Ekiti State, Southwest Nigeria were investigated from washed salt-free, freeze-dried, fine clay fraction of samples from the sites using x-ray diffractogram. The selected parts included: Oye-Ekiti, Ire-Ekiti and Ikere-Ekiti. The chemical compositions were determined using standard procedures. The load bearing (support) capacity at different moisture content were established from the plot of pre-compression (preconsolidation) pressure at varying moisture regimes. The relationship between load support capacity and soil mineralogy for soil was thereafter examined. The result showed that the mineralogy of the studied sites were Ikere - Oxisols, Ire - Inceptisols, and Oye - Ultisols. Moisture retention capacity ranges in the studied sites were generally low viz Ikere; 0.05 - 0.20 kg/kg, Ire A horizon; 0.05 - 0.23 kg/kg; Ire B horizon; 0.03 - 0.35 kg/kg, Oye A horizon; 0.05 - 0.20 kg/kg, and Oye B horizon; 0.10 - 0.25 kg/kg. Load Support capacity (500kPa) were highest in Ultisols samples from Oye B-Horizon and the Oxisols from Ikere. It can be concluded that most samples from agricultural sites in Ekiti State would support mechanisation of the farming process. However, due to the low moisture retention ranges, shallow depth and the thinness of the A- Horizon, mechanisation process should be carefully handled in order not to destroy the soil structurally. Experience from literature suggest that such soil need more preparatory steps, with medium size implement to avoid losing soil layer above the preconsolidation pressure, when natural recovery will be impossible and degradation will be rapid. This study has laid a good foundation for large-scale estimation of soil workability data for similar soil types in Southwest Nigeria. It appears that soil trafficability in cultivation could be inferred from the compression and mineralogy characteristics.