EXTRACTABLE SESQUIOXIDES IN SIX MEDITERRANEAN SOILS DEVELOPED ON BASALT AND SCORIA

Iron, Al, and Mn were extracted by oxalate and dithionite from two Brown Mediterranean Soils, two Red Mediterranean Soils, one Vertisol and one Gley soil, all derived from basalt or scoria in the sub-humid and humid Mediterranean regions of the Golan Heights. Ratios of oxalate: dithionite extracted iron (Fe_o:Fe_d) were low in all soils, indicating that the predominant form of free iron is crystalline. Fe_o accumulates in the argillic B horizons of the Mediterranean soils, while Fe_d accumulates in the surface horizons. A large part of the free iron oxide in the surface horizons of Mediterranean soils is associated with non-clay fractions. While manganese behaves in a manner somewhat similar to that of iron, no definite trends could be discerned in the vertical distribution of free aluminium. In the Vertisol, Fe_o and Mn_o accumulate in the subsoil. Fe_d and Mn_d increase slightly with soil depth. In the Gley soil, amorphous iron accumulates in the surface horizon, total free iron in the bottom horizon. Both amorphous and total free Mn had been depleted from the upper horizons of the Gley soil.