Cadmium‐Enriched Sewage Sludge Application to Acid and Calcareous Soils: Effect on Yield and Cadmium Uptake by Lettuce and Chard

Abstract

AbstractEight soils with pH values ranging from 4.8 to 7.8 were treated with 1% sewage sludge amended with variable amounts of CdSO4. The concentration of Cd in the soils ranged from 0.1 to 320 µg Cd/g. Lettuce (Lactuca sativa var. longifolia) and Swiss chard (Beta vulgaris vat. cicla) were grown to maturity in pot cultures on the treated soils to determine the effect of soil pH on yield and Cd uptake. Fifty percent yield decrements for acid and calcareous soils, respectively, were associated with the following concentrations of Cd in soil: lettuce—214 and 139 µg/g; chard—175 and 250 µg/g. Tissue concentrations of Cd associated with the 50% yield decrement for acid and calcareous soils, respectively, were as follows: lettuce—470 and 160 µg/g; chard—714 and 203 µg/g.Multiple regression analysis of yields as a function of pH, CEC, % CaCO3, % organic carbon (OC), % sand‐silt‐clay, and Cd addition rate revealed a highly significant yield relationship with Cd addition rate, % OC, % clay, and pH (lettuce: R2 = 0.82***; chard: R2 = 0.93***). Leaf Cd was significantly related to soil parameters as follows: lettuce—saturation extract Cd and CEC, R2 = 0.82***; chard—saturation extract Cd and pH, R2 = 0.89***.