| Abstract: | Abstract The effects of heating on the solubility and plant uptake of Cr from three soils variously influenced by ultramafic parent materials were evaluated. Chromium extracted by 2 M HNO3 and by M KCl increased with degree of serpentine influence and with temperature of ignition in air. In contrast, solubility of the element was only slightly influenced by ignition in a N2 atmosphere. Heating enhanced the solubility of soil Cr by at least two oxidative reactions: (1) the destruction of a relatively heat‐stable, probably organic, complex with the release of Cr(III), and (2) the oxidation of free Cr(III) to Cr(VI). Corn (Zea mays L.) grew poorly in the ignited soils, but normally in ignited and leached soils. Growth depression from ignition was related to shoot Cr levels (r2 = 0.494) and is attributed to the readily absorbed and translocated chromate formed at elevated temperatures. Under more usual soil conditions, as in the untreated and ignited then leached soils, the less readily soluble forms of the element are the principal contributors to available Cr. |
