Accumulation of Cadmium and Zinc in Barley Grown on Sludge‐Treated Soils: A Long‐Term Field Study

Abstract

Abstract A sludge land application experiment was initiated near Riverside, Calif. in 1975. Upon the incorporation of the annual sludge treatment, winter barley ( Hordeum vulgare L.) was planted. The Cd and Zn contents of barley grown at the sludge application site were analyzed. Statistical testing indicated that the concentration of Cd and Zn in the barley increased significantly with the rates of sludge application. Although the Cd and Zn concentrations in the soil have risen rapidly with repeated sludge applications, there was little indication that the Cd and Zn contents of the barley increased with the increased deposition of Cd and Zn in the soil. By assuming the observed Cd and Zn contents of barley under a given sludge treatment follow a normal distribution, the probability of Cd and Zn in the harvested barley to exceed a given upper limit may be calculated. It shows that the probability for Cd and Zn contents to exceed the threshold increases with the rates of sludge application. For example, the probability for Cd in the barley grain to exceed 0.1 mg kg −1 increased from < 1% to almost 60% when the composted sludge application on Greenfield sandy loam (coarse‐loamy, mixed, thermic Typic Haloxeralf) increased from 0 to 90 Mg ha −1 y −1 . Under the identical sludge treatment, the probability to exceed the limit is considerably lower in the heavier textured soil (Domino loam—fine‐loamy, mixed, thermic Xerollic Calciothid).