INFLUENCE OF SLOPE AND DEPTH ON SOIL PROPERTIES UNDER OIL PALM PLANTATION IN NIFOR, BENIN NIGERIA

Abstract

A study was conducted to assess the influence of slope and depth on soil properties in a 28-year old oil palm (Elaeis guineesis) plantation established on a gently sloping terrain in NIFOR, Benin Nigeria. A line transect was delineated along the slope of the selected plantation. The line transect was 45 m long and 45 m wide. It was divided into three equal slope segments namely; Summit, Mid and Bottom slopes respectively. Each slope was further sub-divided into three (3) quadrants measuring 15 m x 15 m making a total of nine (9) plots. A total of 180 samples covering four depths (0-15 cm, 15- 30 cm, 30-45cm and 45-60 cm) for soil physico-chemical properties determination were collected by a random sampling strategy. Each sampled point was geo-referenced using a Garmin 12 GPS. Soil physico- chemical properties (pH, O.C, N, P, Ca, Mg, K, Na, H, M.C, BD, Porosity, and Ksat) were determined in the laboratory using standard methods. The result of the statistical analysis revealed a significant difference (P<0.05) among the soil properties in different slope positions and depths. Slope position had a significant effect (p<0.05) on soil pH, N, Ca, Mg, K, H, ECEC, bulk density and porosity. Soil depth significantly affected (p<0.05) all soil properties studied. Inverse Distance Weighting (IDW) was used in generating the surface distribution maps in ArC GIS 10.1. Environment. The highest clay content occurred at the bottom slope position and depth (11.90, 19.81). The more clayey sites are characterized with higher effective cation exchange capacity and thus plantations cultivated on such sites would be more productive and sustainable. The findings from this work revealed that slope position and depth had a significant effect on the soil properties studied. The correlation studies showed that depth had a more significant correlation (positive and negative) than slope position with all soil properties under the study as depicted by the correlation coefficients. Plantations of the same age in different topographic positions would need to be managed in a different way so as to optimise yield.