FORMS AND DISTRIBUTION OF EXTRACTABLE IRON AND ALUMINIUM IN THE SOILS OF THE LOWER SLOPE OF BOLORUNDURO CATENA, ILORIN, NIGERIA

Abstract

Form and distribution of iron and aluminium oxides in four soil profiles representing the lower slope of a carena at Bolorunduro, llorin were studied. The ranges in the values obtained for iron oxide were 179-3821, 71-693, 4-143 and 1-7 mgs/100g. of soil; while for aluminium oxide the ranges in values were 94-434, 72-272, 5-198 and 14-72 mgs/10g. of soil in the DCB, oxalate, pyrophosphate and acetate extractants respectively. The distribution of these sesquioxides is a variable function of the profile depth.

Positive and significant correlations were found to exist between DCB-iron and clay. DCB-aluminium and clay, pyrophosphate-iron and clay, acetate-aluminium and clay and oxalate-iron and organic matter. Oxalate-iron was negatively correlated with clay, though the correlation was insignificant. The mean weathering indices calculated for the soils (silt/clay, DCB-Fe/clay. DCB-Al/clay. Oxalate- Fe/clay, Oxalate-Al/clay) gave values that increased with drainage impedance