Heavy Metal Reductions in Soils Amended With Compost and Water Treatment Residuals

Abstract

The present work was carried out to evaluate the effect of rice straw compost, water treatment residuals (WTR), and their mixture (2:1 and 1:1 wet weight), on heavy metal immobilization in contaminated soils and on growth of canola (Brassica napus). The results showed that the Pb, Cd and Zn concentrations were significantly reduced in the root and shoot of canola plant grown with the application of rice straw compost and WTR amendment. Extractability of the metals was also significantly reduced in this treatment compared with the control. The dry weight and root depth of canola plants were significantly increased with the application WTR and compost treatments at two levels 10 or 20 mg kg−1 soil compared with the control. The addition of compost and WTR (2:1 or 1:1 wet weight ratio) at 10 g dry weight kg−1 dry soil gave the best reduction in the soil metal extractability and in plant growth compared with other treatments. Thus, the combination of rice straw compost and WTR was successful in lowering the bioavailability of metals and increasing yield of canola grown on the contaminated soil.