Effects of Polymer-coated Zinc Fertilizer Combined with Liming on Cadmium Accumulation in Different Rice Tissues

Objective The aim was to explore the effect of polymer-coated zinc (Zn) fertilizer and its combination with lime on reducing rice cadmium Cd).

Methods Water-based polyacrylate-coated Zn fertilizer was prepared in this study, six treatments including the control (no application of Zn and lime), application of normal Zn, coated Zn, lime, and normal or coated zinc combined with lime were designed, to study their effects on soil available Cd and Zn and Cd accumulation in rice tissues through a pot experiment.

Results ①The concentration of soil dissolved Zn was 0.56 - 2.96 times higher than that of normal zinc fertilizer treatment from day 4 to 50, compared with the control with no addition of Zn and lime. Zn concentrations of tillering roots and shoots were increased by 35.4 - 36.6% in coated zinc treatment, but decreased by 29.4 - 43.4% in lime treatment. ②Compared with the control, coated Zn treatment reduced tilling shoot and brown rice Cd by 36.4% and 34.0%. This reduction was 9.6% higher than that of normal Zn treatment. Lime treatment greatly decreased soil CaCl₂-extractable Cd by 74.7- 92.7%, but the translocation factor of Cd from the root to brown rice was increased by 42.1%, thus brown rice Cd was decreased by only 43.1%. ③ Compared with the application of coated Zn or lime alone, the reduction rate of brown rice Cd was elevated by 25.1% or 16.0% in their combination treatment, revealing an obvious synergistic effect.

Conclusion Coated Zn fertilizer can extend the lifespan of exogenous Zn in the soil, and enhance the antagonism of Zn and Cd to a certain extent during the whole growth period of rice, resulting in a higher reduction of brown rice Cd. This reduction could be further elevated by the combined application of lime and coated zinc.