Magnetic susceptibility of soil separates of Gleysolic and Chernozemic soils

The major horizons of Gleysolic and Chernozemic soils and the underlying deep till of five cores were separated into sand-, silt- and clay-sized fractions. Pedogenesis increased the ranges of magnetic susceptibility (χ) and oxalate (Feo) and dithionite-citrate extractable (Fed) iron in bulk samples and size separates of the A, B and IC horizons compared to the deep till. In the A, B and IC horizons the relationships between χ of the bulk (< 2 mm diameter) soil and χ of the sand and silt fractions was much stronger than in the deep till. Generally, χ of the clay was much lower than that of the coarser fractions, whose χ was similar or slightly larger than that of the bulk samples, except for two buried, burned horizons. Treatment of the sand fraction of 15 soils with dithionite -citrate to remove pedogenic ferrimagnetics showed that the latter decreased in the order: burned, buried horizons > gleysolic and chernozemic A horizons > gleysolic B horizons > IC horizons. The low χ of the gleysolic horizons cannot be attributed to a decrease in pedogenetically formed ferrimagnetics; they must have lost part of their inherited ferrimagnetics, possibly sand-sized magnetite. Key words: Magnetic susceptibility, soil separates, extractable iron, gleysols, chernozems