EXTRACTABLE AND TOTAL FE AND MN CONTENTS OF 3 SAND DUNE SOILS IN NW NIGERIA

The profile distribution of total, diethylene triamine penta-acetic ac id (DTPA)- and 0.1 M HCl-extractable Fe and Mn were determined in 12 p edons formed on three contiguous sand dunes in the semi-arid savanna o f Nigeria. The total Fe and Mn contents varied from 100 to 3750 and 40 to 11,375 mu gg(-1), respectively. Values of 0.1 M HCl-extractable Fe and Mn varied from 80 to 123 and 1.5 to 435 mu gg(-1), respectively. The corresponding values of DTPA-extractable Fe and Mn were 4.5 to 16. 0 and 1.0 to 38.8 mu gg(-1). Total Fe and Mn correlated significantly with clay in nearly all the dunes (p less than or equal to 0.01) but w ere nor significantly correlated with organic matter. The 0.1 M HCl-ex tractable 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 ot her literature, thus deficiencies of these micronutrients do not pose a problem to crop production in the study area. (C) 1998 Academic Pres s Limited.