A tillering application of zinc fertilizer based on basal stabilization reduces Cd accumulation in rice (Oryza sativa L.)

Cadmium (Cd) contamination in paddy fields has received extensive attention throughout the world, especially in China. In this study, treatments of a lime application with or without zinc sulfate as basal fertilizer, a basal or tillering application of zinc sulfate, and basal stabilization using lime combined with a tillering application of zinc sulfate were designed in a field trial to investigate their contributions to the uptake and translocation of Cd in rice plants. The results showed that basal stabilization using lime significantly decreased brown rice Cd by 42%; the CaCl2-extractable Cd in the soil was decreased by 46-51%, but the phytoavailability of Zn in the soil was also inhibited. The basal or tillering application of zinc sulfate significantly inhibited the upward transport of Cd (from the root to the shoot) while having no significant impact on CaCl2-extractable Cd; consequently, the concentration of Cd in the brown rice was reduced by only 17-25%. Compared with the lime application alone, the basal application of lime together with zinc sulfate did not further reduce the Cd in brown rice. However, basal stabilization using lime combined with the tillering application of zinc decreased the Cd in brown rice by 73%, which was attributed to the reduced CaCl2-extractable Cd and the competitive effect of Zn on Cd, in which the inhibition of the upward transport of Cd inside the root played an important role. Two field verification tests conducted during the next year also demonstrated that this combined method significantly decreased the level of Cd in brown rice.