ASSESSMENT OF VARIABILITY OF SOIL PROPERTIES UNDER DIFFERENT VEGETATIONS IN AN ULTISOL IN IFE AREA, OSUN STATE, NIGERIA
Soil variability leads to undesirable effects on crop yield. Knowledge of soil variability is necessary to estimate reliable average values for soil properties. A field trial was conducted at the Teaching and Research Farm of the Obafemi Awolowo University, Ile-Ife, to assess the variability of some soil properties under citrus, cacao and oil palm plantations in an Ultisol with a view to documenting the effects of vegetation on the variability of the selected soil properties. Soil samples were collected from the surface (0-20 cm) and subsurface (20-50 cm) horizons with the aid of a Dutch auger. These were processed and analysed for selected physical and chemical properties. The results showed that there were no significant differences (p>0.05) among the physical properties across the plantations at the surface and subsurface horizons. At the surface horizon, sand and clay contents were least variable, irrespective of the plantation; silt content was highly variable in the citrus and oil palm plantations with CV of 40.86% and 37.88%, respectively but was least variable in the oil palm plantation. The pH was least variable in all the plantations. Organic matter (OM) content was least variable in the oil palm plantation but moderately variable in the citrus and cacao plantations. The Na content was moderately and least variable in the surface and subsurface horizons, respectively in the plantations while K, Ca and Mg contents were highly and moderately variable at the surface and subsurface horizons, respectively across the plantations. Compared with the previous works on the variability of soil properties, vegetation was found to have a mitigating effect on soil variability.