Effects of Different Amendments on Cadmium Accumulation in Rice Safety in Cadmium-Contaminated Farmland Under Two Flooding Treatments

Abstract

Cadmium (Cd) accumulation in rice has become a serious public concern; thus, it is important to find an effective approach to reducing Cd accumulation in rice grains to ensure food safety. To investigate the effects of different amendments on Cd accumulation in rice in Cd-contaminated farmland under different flooding treatments, a field experiment with three amendments (jade powder, biochar, and fly ash) and two flooding treatments (intermittent flooding and flooding throughout the whole growth period) was conducted. The results showed that:① without amendment application, the soil pH significantly increased, whereas the soil available Cd concentration decreased by 3.81%-17.27% and 2.25%-6.74% with the treatments of flooding throughout the whole growth period and intermittent flooding, respectively. Additionally, the immobilizing efficiency of the treatment of flooding throughout the whole growth period was better than that of intermittent flooding; ② under different flooding treatments, amendment application improved soil pH, resulting in a decrease in the soil available Cd concentration along with an increase in the residual Cd concentration. Under the treatment of intermittent flooding, the soil pH increased by 0.19-2.20 units, and the soil available Cd concentration and Cd concentration in rice grains decreased by 4.72%-22.68% and 2.60%-75.75%, respectively, with the application of different amendments. Under the treatment of flooding throughout the whole growth period, the application of different amendments decreased the soil available Cd concentration and Cd concentration in rice grains by 5.06%-36.63% and 13.28%-77.01%, respectively. The immobilizing efficiency in both flooding treatments was jade powder > biochar > fly ash. ③ Under different flooding treatments, the application of amendments significantly reduced the soil available Cd concentration and Cd concentration in rice grains. Among the three amendments, jade powder showed the best capacity of immobilizing efficiency with the treatment of flooding throughout the whole growth period; the soil Cd reduction rates were 36.63% and 25.16%, and the Cd concentrations in rice grains were 0.058 and 0.170 mg·kg-1 in 2019 and 2020, respectively. The Cd concentrations in rice grains were within the limitation of the National Food Hygienic Standard of China. Therefore, combining flooding throughout the whole growth period with jade powder can be considered as an ideal strategy for ensuring rice safety in Cd-contaminated farmland.