Extractable and total Fe and Mn contents of three sand dune soils in NW Nigeria

The profile distribution of total, diethylene triamine penta-acetic acid (DTPA)- and 0•1 HCl-extractable Fe and Mn were determined in 12 pedons formed on three contiguous sand dunes in the semi-arid savanna of Nigeria. The total Fe and Mn contents varied from 100 to 3750 and 40 to 11,375 μg g−1, respectively. Values of 0•1 HCl-extractable Fe and Mn varied from 8•0 to 123 and 1•5 to 43•5 μg g−1, respectively. The corresponding values of DTPA-extractable Fe and Mn were 4•5 to 16•0 and 1•0 to 38•8 μg g−1. Total Fe and Mn correlated significantly with clay in nearly all the dunes (p≤ 0•01) but were not significantly correlated with organic matter. The 0•1 HCl-extractable Mn had a positive significant correlation with soil pH (r= 0•58*) in Illela dunes but a negative significant correlation with pH in the Sangiwa dunes (r= −0•75***). The values of extractable Fe and Mn in the sand dune soils are above the critical limits reported in other literature, thus deficiencies of these micronutrients do not pose a problem to crop production in the study area.