Variability in Soil Properties as Influenced by Different Land Use Types in an Ultisols of the Tropical Region, Delta State, Nigeria

The study was conducted in the 2010 - 2012 cropping seasons in a typical ultisols of the tropics. The aim was to assess variability in soil properties as influenced by three land use types namely: oil palm plantation, maize and yam cultivated lands. The study consisted of both field and laboratory studies. The field study was made up of a land use that was carefully surveyed, mapped into 20 × 30 m2 and plotted into 5 homogenous units of 0.25 ha. Soil samples were randomly augered by grid survey at 5 m equidistant points and surface 0-15 cm samples collected using screw auger for laboratory analysis of the particle size distribution and some chemical characteristics of the soils in the different land use types. Variation in properties within land use types was measured by estimating the coefficient of variance. The results of the study showed that particle size distribution varied from sand in the oil palm land use type to sandy loam in the maize and yam land use types. The variant ratio tests were 84.4%, for sand, 0.51% for silt and 27.4% for clay, and were less variable. The soil pH ranged from strongly acid (5.25) to moderate acid (5.65) and less variable (CV% = <15%). The variant ratio test was statistically not significant (10.7%). The organic carbon (35.7%), total nitrogen (34.5%) and available phosphorus (27.2%) variant ratio tests were non-significant and less variable. The exchangeable bases, exchange acidity and ECEC were also non significant and less variable. The results indicated clearly that variability could occur within soil units and therefore called for caution in assessing uniformity of soil properties within soil areas under cultivation