High Rates of Sewage Sludge in Wheat Production

A greenhouse experiment was conducted at the University of Arizona, Tucson, Arizona, to study the effects of sewage sludge loading rates on the vegetative growth, yield, and heavy metal contents of wheat grain and straw. Vegetative growth, grain and straw yields were similar whether wheat was fertilized with the recommended rate of inorganic N (112 kg/ha) or equivalent amounts of plant-available N from sewage sludge. Sewage sludge loading rates higher than three times the recommended plant- available N level delayed maturity and decreased wheat stands in the seedling stage; however, grain and straw yields were similar for all sewage sludge loading rates. Concentrations of cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) in wheat grain and straw and in the soil following each harvest were low and similar for all fertilizer treatments