Total and Available Micronutrients in Soils of Contrasting Parent Materials in Southeastern Nigeria

Abstract

The status of micronutrients in the surface (0-20cm) soils developed on Coastal Plain Sands, Sandstone, Shale and Basement Complex parent materials in south-eastern Nigeria was investigated. This involved determining total and extractable forms of Fe, Mn, Zn and Cu in the soils, and evaluating the relationships between the extractable micronutrients and soil properties. The total contents were determined by tri-acid digestion while the extractants for determining extractable forms were Coca-cola, EDTA, NH4OAC + EDTA, 1N NH4OAC and 0.1N HCl. Parent materials did influence the concentrations of total Fe, Mn, Zn and Cu in the soils while extractable Fe, Mn, and Cu content varied significantly (P<0.05) with the extractants used. EDTA extracted the least amount of the micronutrients. Extractable Fe correlated positively with organic matter (r = 0.439) and ECEC (r = 0.461) but negatively with pH (r = -0.54), silt (r = -0.45) and clay content (r = -0.601). Extractable Mn correlated negatively with silt (r = -0.483), clay (r = -0.483) and pH (r = -0.663) but positively with organic matter (r = 0.473). There was significant positive correlation of Zn with ECEC (r = 0.684) and silt (r = 0.550) but negative correlation with clay (r = -0.646), soil pH (r = -0.655) and organic matter (r = -0.485). Extractable Cu correlated positively with silt (r = 0.422) and ECEC (r = 0.698) but negatively with clay (r = -0.597), soil pH (r = -0.52) and organic matter (r = -0.661). The high correlations of the available micronutrients with some soil properties show the potentials of these extractants. The nature of parent materials is responsible for the variable micronutrients in the soils.