Application of chromium to soils at different rates and oxidation states. I. Effect on dry matter yield and chromium uptake by radish

Abstract

An experiment was carried out to study plant responses to the addition of chromium (Cr) both in hexavalent and trivalent oxidation states to soil. A pot experiment with two soils, Ferric Lixisol (LXf) and Stagnic Luvisol (LVj), was conducted in the greenhouse. Chromium was added at four rates (0, 10, 50, and 100 mg kg−1), and radish (Raphanus sativus) was used as plant test. Radish was sown after 25 days of incubating the soil with Cr. In LVj dry matter yield showed greater values for both Cr oxidation states, except when 100 mg kg−1 of Cr(VI) was applied. The increase of Cr concentration in the plant, in both soils, did not always correspond to yield decreasing. With few exceptions [especially in the case of LVj soil and Cr(VI)] the content of Cr in shoots was higher than in roots. Content for both oxidation states of Cr was always higher in the LVj soil. This is probability due to the presence of Mn oxides [which induce Cr(III) oxidation], smectites and to the low contents of iron oxides in the soil. These soil characteristics caused a decrease on Cr(VI) adsorption, thereby increasing its mobility and availability. On the other hand, in the LXf soil iron oxides and kaolinites acted as a sink for Cr(VI).