Spatial Relationships Between Soil Properties and Oil Palm Growth Dynamics in Southwest Nigeria

Understanding the spatial variability of soil properties is essential for optimizing oil palm growth and productivity, particularly in ecologically diverse regions such as Southwest Nigeria. In order to establish baseline dataset for spatial soil management in a long-established oil palm plantation, this study was conducted to determine the spatial semivariance structures and interdependence between soil properties and oil palm growth at the Oil Palm Research Station at Ekiti State University, Ado-Ekiti, Nigeria. Soil samples were collected from the 0 - 10 cm surface layer of eighty-one (81) georeferenced from points comprising six distinct transects, with a separation distance of 10 m. The spatial semivariance characteristics and spatial dependence of the oil palm diameter at breast height and soil physical (bulk density (BD) , water content (SWC), total porosity (Pt), particle density (Pd), texture, air capacity (AC), field capacity (FC) and saturated hydraulic conductivity (Ksat)) and chemical properties (pH) and soil organic matter (SOM)) were determined using the semivariogram algorithm while the spatial interdependence was determined using the isotropic cross-semivariogram option in the geostatistical software. Except for FC/Pt (spherical), all the soil variables and oil palm diameter at breast height (DBH) were fitted to exponential model. Four variables, DBH, sand, silt and total porosity had nugget effect values far from zero. Soil bulk density and organic matter showed strong spatial dependence (< 25%) while other soil variables and oil palm diameter at breast height showed moderate spatial dependence (25-75%). The maps showed the spatial heterogeneity of the soil variables and DBH. The cross- semivariograms between DBH versus soil variables were fitted to spherical model except soil organic matter (linear) and particle size (exponential). The cross-semivariogram nugget effect was zero (0) for AC, SWC and AC/Pt while the highest (~ 12) was obtained from silt. The degree of spatial interdependence between DBH versus soil variables was strong (< 25%) for air capacity, soil water content, particle density, pH, and field capacity; weak (> 75%) for soil organic matter; and moderate (25-75%) for other variables evaluated. Employing both semivariogram and cross-semivariogram analyses enhances our understanding of spatial variability significantly and makes a crucial contribution to developing site-specific agricultural practices and promoting sustainable oil palm plantation management in tropical agroecosystems.