YIELD, HEAVY-METAL CONTENT, AND MILLING AND BAKING PROPERTIES OF SOFT RED WINTER-WHEAT GROWN ON SOILS AMENDED WITH SEWAGE-SLUDGE
Kirleis, AW; Sommers, LE; Nelson, DW
This study determined yield, metal content, and milling and baking properties of soft red winter wheat grown on soil treated with three municipal sewage sludges. Sewage sludge application ranged from 56 to 448 tonnes/ha, levels in excess of those allowed by current federal regulations; the data, therefore, represent a worst-case situation. Sludge applications increased the protein content of wheat gain and flour and decreased alkaline water retention capacity of flour, but they did not affect test weight, thousand-kernel weight, and particle size index. Baking studies indicate that sludge applications decreased the baking quality of flour by increasing protein content, resulting in smaller-diameter cookies. Sludge applications also increased concentrations of zinc, cadmium, manganese, and nickel in wheat grain. Because the sludges applied contained CaCO3, which increased soil pH, metal levels in wheat were not directly related to sludge-borne metals added to the soil. Concentrations of zinc, copper, nickel, cadmium, iron, and manganese were typically 5-to 10-fold greater in the bran than in the flour. Metal concentrations in the flour were nearly always less than those found in whole wheat grain with, on the average, <24% of the zinc, copper, nickel, cadmium, iron, and manganese in grain being recovered in the flour. The distribution of metals in the bran and flour was similar for wheat grown on sludge-treated and untreated soils.