ABSTRACT
This experiment was conducted in the University of Benin teaching and Research farm, Benin City, to determine the various iron forms and the physical and chemical properties of soils found along a toposequence. Soil samples were collected from four different toposequence sites designated as; Crest, Middle, Lower and Bottom at a depth of 0-15 cm, 15-30 cm and 30-45 cm in each toposequence using an auger, making a total of 36 samples. Soil samples were taken to the laboratory for analysis using standard procedures. Some of the parameters analyzed were: particle size distribution, pH, total organic carbon (TOC), total nitrogen (N), available phosphorus (P), Carbon (C), Hydrogen (H), Magnesium (Mg), Potassium (K), Sodium (Na), ECEC and Aluminium (Al) and also the various forms of iron. Results showed that pH was least in crest, having pH 4.10 at depth (30-45 cm) and highest in bottom area, having pH 5.80 at depth (0-15 cm to 30-45 cm). pH, Total organic C, Total N, Available P, Ca, K, Mg, H, Na and ECEC, sand content and the forms of Fe, all had their highest values varied across all the depths of the toposequence studied. The result from the correlation table also showed that organic matter correlated positively (P < 0.01) and significantly with organic bound Fe (r = 1.000) and residual Fe correlate negatively and significantly (P <0.001) with sand (r = 0.997) and silt (r = 0.997) at the crest. But all the bottom sand correlated significantly (P < 0.001) and negatively with Fe- Mn bound fraction (r = - 0.959) and positively with residual fraction (r = 0.997).
