Effect of Sewage Sludge on the Mineral Composition of Corn

For the past 12 years, digested sewage sludge from the Milwaukee Metropolitan Sewerage District has been applied to a Plano silt loam (prairie) soil near Elkhorn, Wisconsin, and corn raised as the indicator crop. The corn has been harvested as silage and fed to dairy cnttle. The amounts of macro-, micro-, and heavy metals contained in this forage were compared with the amounts contained in the untreated areas, and in the forage produced by a sustainable agriculture study on the same experimental station. None of the heavy metals have moved out of the plough layer (lop 25 cm). The uptake of heavy metals (Cd, Pb, etc.) in the forage has been well under the standards set by the Wisconsin Department of Natural Resources and the US Environmental Protection Agency for forages fed to livestock.