Growth and Metal Uptake of Snap Beans Grown on Sewage Sludge‐Amended Soil: A Four‐Year Field Study

Abstract

AbstractTo establish the consequence of land application of sewage sludge on the extent of sludge‐borne metal accumulation in the food chain, long‐term trace metal accumulations in edible snap bean (Phaseolus vulgaris L. var. Tendergreen) tissue were measured, over a 4‐year period, for beans grown on a sludge‐amended sandy Udorthentic Haploboroll soil. The objectives of this study were to i) establish the effect of annual sludge applications on trace metal uptake, and ii) study the residual effect of adding a single, large sludge application on metal uptake on subsequent crops. For the first phase of this study, we applied a total of 0, 350, 700, and 1,400 metric tons/ha of anaerobically digested sludge in three equal applications. The second phase of the study consisted of a single sludge application of 0, 112, 225, and 450 metric tons/ha. Crop yields increased as rates of sludge application increased under both cultural systems and often exceeded those of a well‐managed, fertilized control. The Zn and Cu contents of edible tissue increased as rates of sludge application increased, and reached an apparent maximum value from which they did not decrease once sludge applications ceased. Cadmium levels in edible tissue did not respond directly to sludge applications and never exceeded 0.1 µg Cd/g tissue.