Cadmium in Rice Is Affected by Fertilizer-Borne Chloride and Sulfate Anions: Long-Term Field Versus Pot Experiments

In order to investigate the effects of Cl- and SO42- based fertilizers on the accumulation of cadmium (Cd) in rice plants, a long-term experiment, which has been conducted since 1975, and a short-term pot experiment were designed. The results of the long-term experiment showed that the highest total grain Cd was found in the treatment of fertilizers with rich Cl-, which was 72.7% higher compared to conventional fertilization (CF). However, there was no significant difference between the CF and fertilization with rich SO42- treatments. This phenomenon can be explained by the concentrations of the EDTA extractable Cd being significantly increased by 60% under Cl- treatment, while SO42- treatment showed no significant effect. In the short-term trial, compared to CF, Cd concentrations in the roots increased by 1.07 and 0.93 times in the Cl- and SO42- treated soils, respectively, under Cd1.2 exposure. Meanwhile, Cd concentrations in the shoots enhanced by 96% in Cl- treated soil but decreased by 34.6% in SO42- treated soil. It was therefore concluded that fertilizer-borne Cl- significantly increased the Cd concentration in rice grains in the long-term experiment, but fertilizer-borne SO42- had no significant effect on the Cd concentration in rice grains. However, in the pot experiment, SO42- based fertilizers decreased Cd transport to the shoots of a rice plant grown in a Cd contaminated soil. These findings will improve the rational fertilization of Cd contaminated soils and the production of safer rice.

Automated summary

The long-term experiment showed that Cl- based fertilizers significantly increased the accumulation of Cd in rice plants, while SO42- had no significant effect. However, the short-term experiment revealed that SO42- based fertilizers reduced the uptake of Cd by rice plants from Cd contaminated soils. These findings are important for rational fertilization and safer rice production.