Extractable and total Fe and Mn contents of three sand dune soils in NW Nigeria B. A. Raji*, V. O. Chude* & I. E. Esu† *Department of Soil Science, Institute for Agricultural Research, Ahmadu Bello University, Zaria †Department of Soil Science, University of Calabar, Calabar ( R eceiv ed 4 October 1997, accepted 11 December 1997) The profile distribution of total, diethylene triamine penta-acetic acid (DTPA)- and 0·1 M 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 μgg –1 , respectively. Values of 0·1 M HCl-extractable Fe and Mn varied from 8·0 to 123 and 1·5 to 43·5 μgg –1 , respectively. The corresponding values of DTPA-extractable Fe and Mn were 4·5 to 16·0 and 1·0 to 38·8 μgg –1 . Total Fe and Mn correlated significantly with clay in nearly all the dunes ( p ² 0·01) but were not significantly correlated with organic matter. The 0·1 M 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. ©1998 Academic Press Limited Keywords: total; extractable; sand dune soils; iron; manganese; semi-arid savanna Introduction The problem of micronutrient deficiencies in African soils has increased with the use of more nutrient-demanding crop varieties in place of the tradition fallow system. Current farming practices increasingly depend on fertilizer compounds leading to reports of micronutrient depletion (e.g. Bharadwaji & Omanwar, 1994). In view of the many reports of micronutrient deficiency reported worldwide (Maclean & Langille, 1976; Liu et al ., 1983; Katyal & Sharma, 1991), but especially for sandy soils and soils with ustic to aridic moisture regimes (Katyal & Sharma, 1991), a study of Nigerian Sudano-Sahelian soils is needed. Previous studies on different locations in Nigeria (Agboola & Corey, 1976; Lombin, 1983; Fagbami et al ., 1985) have reported deficiencies of micronutrients. Micro- nutrients in the sand dune soils, which are currently extensively cultivated for millet ( Pennisetum typhoideum Rich), guinea corn ( S orghum bicolor (L) Moenoh) and cowpea ( Vigna unguiculata (L) Walp), need to be quantitatively studied and documented for Journal of Arid Environments (1998) 38: 585–596 0140–1963/98/040585+ 12 $25.00/0/ae970355 © 1998 Academic Press Limited