Influence of amendments on Cd and Zn uptake and accumulation in rice (Oryza sativa L.) in contaminated soil

Cadmium is a toxic metallic element that poses serious human health risks via consumption of contaminated agricultural products. The effect of mixtures of dicalcium phosphate and organic amendments, namely cow manure (MD) and leonardite (LD), on Cd and Zn uptake of three rice cultivars (KDML105, KD53, and PSL2) was examined in mesocosm experiments. Plant growth, Cd and Zn accumulation, and physicochemical properties of the test soils were investigated before and after plant harvest. Amendment application was found to improve soil physicochemical properties; in particular, soil organic matter content and nutrient (N, P, K, Ca, and Mg) concentrations increased significantly. The MD treatment was optimal in terms of increasing plant growth; the MD and LD treatments decreased soil Cd concentration by 3.3-fold and 1.6-fold, respectively. For all treatments, all rice cultivars accumulated greater quantities of Cd and Zn in roots compared with panicles and shoots. Among the three cultivars, RD53 accumulated the lowest quantity of Cd. Translocation factors (< 0.28) and bioconcentration coefficients of roots (> 1) indicate that the three rice cultivars are Cd excluders. Our results suggest that a mixture of organic and inorganic amendments can be used to enhance rice growth while reducing accumulation of heavy metals when grown in contaminated soil.