Effect of Nitrogen Fertilizers on Pb and Cd Uptake of Rice Plants and Associated Food Safety Lssues

Effect of nitrogen fertilizers on the uptakes of Pb and Cd by rice plants was studied. A pot experiment was conducted using amide, ammonium or nitrate nitrogen fertilizer to determine the responding soil properties, heavy metals bioavailability in rhizosphere soils, and metal uptakes by the plants. The heavy metal contaminations in different parts of a rice plant were evaluated by the pollution indices, and the food safety risk by an assessment model. The results showed that the pH in soil was lowered by the application of ammonium fertilizer, while raised by that of nitrate, as compared to amide. Among the three different nitrogen fertilizers, ammonium introduced significantly less Pb and Cd in the soil, as well as in the rice plants. The risk assessment on the rice did not raise a concern on Pb with ammonium but suggested its use to minimize Cd contamination.