Transference of heavy metals from a calcareous soil amended with sewage-sludge compost to barley plants

Barley plants were cultivated in a calcareous soil (pH 8.77) amended, at different rates, with sewage-sludge composts containing different heavy-metal contents and the transference of these heavy metals to the plant was studied. The addition to the soil of contaminated compost (mainly in Cd) at a high rate led to a decrease in grain yield but did not affect straw yield. Cadmium and Zn were easily absorbed by barley plants, increasing their concentration with respect to the control in plants grown in the soil amended with compost containing high amounts of these metals. However, Ni and particularly Cu were retained by organic matter and were not transferred to plants. Regardless of the compost heavy-metal contents, plants grown in amended soils showed higher N and P contents than control plants. The concentrations of Cd and Zn in soils were positively correlated with Cd and Zn contents in the plants, while no correlation was found between the concentrations of Cu or Ni in soil and plant. After cultivation, amended soils showed a better nutritional state than control soil (higher N-NO3− and total- and available-P than the control).