Effect of heavy metals in sludge on agricultural crops [Tests on maize, uptake, phytotoxicity]

Four years of field tests and a one-year greenhouse test were conducted to determine the effect of heavy metals in wastewater sludge on agricultural crops in the San Francisco Bay region. In the field tests, marginal soil was used, with field corn as the test crop. The total plant content of heavy metals increased but the corn grain was not affected. The data suggest that the amount of plant-available forms of metals may reach a "steady-state" condition or revert to less available forms after initial sludge applications. In the greenhouse and laboratory studies, results showed that sludge application to calcareous soils at up to 160 metric tons/hectare had minimal impact and resulted in plant tissue concentrations similar to those found in plants grown on acid soils unamended by sludge.