Impact of crop rotation and crop residue cycling on the cadmium concentration of the subsequent crop in a rotation.

摘要

Crop rotations can affect both the biological and chemical characteristics of the soil, thus affecting cadmium (Cd) availability. The release of Cd from decomposing crop residue may also influence Cd availability to the following crop. Two growth chamber studies were conducted to study the effect of crop rotation and Cd cycling from crop residue on the Cd concentration of the succeeding crop in a rotation.;In both growth chamber experiments, the tissue Cd concentration was higher in flax than in durum wheat. In experiment one, Cd concentration in flax tissue increased with the application of canola and barley straw compared to when no straw was applied, but the type of straw applied did not affect the Cd concentration in the flax. However, the Cd concentration in durum wheat was not influenced by the application of crop residue. In contrast, the soil from the previous crop influenced the Cd concentration in durum wheat, as the durum wheat Cd concentration increased when grown on the soil where canola was the previous crop. However, the soil from the previous crop of the rotation did not influence Cd concentration in flax. In experiment two, the Cd concentration of flax tissue increased with increasing Cd concentration of the applied durum wheat straw, but durum wheat tissue was not affected. In both experiments the Cd concentration in the test crop tissue was not related to the Zn concentration in crop tissue. The Cd concentration in flax, but not durum wheat may be influenced by Cd released from the decomposition of the crop residue, whereas the Cd concentration in durum wheat and not flax may be influenced by soil effects caused by the crop rotation.;The first experiment included treatments of soil where the previous crop was canola (Brassica napus L.) or barley (Hordeum vulgare L.) and the application of no straw, canola straw or barley straw, equivalent to 5000 kg residue ha-1 The second experiment involved soil application of durum wheat straw equivalent to 5000 kg residue ha-1, containing concentrations of Cd ranging from 50 to 217 mug kg-1 In both experiments the indicator crops of flax ( Linum usitatissimum L.) and durum wheat (Triticum turgidum L.) were grown as indicator crops in clay loam soil in pots, with the chopped straw added to the soil and allowed to decompose for seven weeks prior to seeding.