Particle size fractions and pedogenesis of coastal plain sands

This study established the influence of particle size fractions (psf) on the characteristics of coastal plain soils of southeastern Nigeria. A total of 180 samples were collected according to genetic horizons on 30 profile pits prepared on the upper, middle, and lower slope positions of 10 toposequences. The samples were analyzed for hydraulic conductivity, pH, bulk density, moisture content, electrical conductivity, exchangeable bases and acidity, organic carbon, available and total phosphorus (P) contents, dithionite citrate bicarbonate (DCB) extractable and amorphous iron and aluminum (Al) contents. Particle size distribution was also analyzed, including total sand, very coarse, coarse, medium, fine and very fine sand, clay, and silt. Statistical analysis carried out included analysis of variance, correlation, and principal component. Very coarse sand influenced the distribution of P and DCB-Al within the toposequences. Active pedogenesis was located in the fourth horizons of the profiles that manifest inverse relationship of very coarse sand with P and amorphous Al. The association between sand particles and sesquioxides, especially of Al, was responsible for the low pH associated with coastal plain soils. Principal component analysis confirmed that total sand fractions are the determinants of rate and extent of pedogenesis and influences the properties of coastal plain soils.