Plant uptake and DTPA-extractability of Cd, Cu, Ni and Zn in a Norwegian alum shale soil as affected by previous addition of dairy and pig manures and peat

Abstract

Residual effects of cow manure, pig manure and peat soil on the DTPA-extractability and plant uptake of cadmium, copper, nickel and zinc were investigated in the second and third years after application to an alum shale soil. Wheat and barley were grown in alternate years. The effects of the organic matter applied differed among metals, sources of organic matter and time after application. The Cd concentrations in grain was reduced by the rates of peat soil, whereas the manures had no significant effect. Copper concentrations in grain and Zn concentrations in both grain and straw generally increased with rates of organic matter. Nickel concentration in grain tended to decrease with increasing rates of cow and pig manure applied, whereas it tended to increase with the addition of peat soil.The concentrations of DTPA-extractable metals in the soil were generally higher in the second and third years than in the first year after application of organic matter. Some of the metals bound by organic matter in the first year were probably released as the organic matter was decomposed. Decreases in DTPA-extractable Cd and Ni were found by the addition of pig and cow manure, whereas these manures resulted in increased DTPA-extractable Zn. The application of peat soil, on the other hand, resulted in increased amounts of DTPA-extractable Cu, Zn and Ni, probably due to decreased soil pH. Key words: Heavy metals, solubility, plant uptake, organic matter