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The safe production of rice is linked to a range of critical needs such as regional food supplies, people's livelihoods, and human health. Arsenic (As) and cadmium (Cd) are two highly toxic elements, and As-Cd co-contamination in paddy soils is prevalent, posing significant food safety challenges. The biogeochemical contrasts of As and Cd complicate the management of their co-contamination in paddy soils. This review synthesized advances in understanding the distinct behaviors of As and Cd in rice paddies, along with synergistic strategies for reducing As and Cd bioavailability in the soil-rice system. The strategies included the use of synthetic soil amendments, optimizing water, fertilizer and cropping management practices, developing low As/Cd-accumulating rice cultivars through genome editing and mutation breeding, and combined measures. Finally, future research perspectives were provided to maintain sustainable rice production in As-Cd co-contaminated paddy soils. This review offers a comprehensive overview of both foundational insights into the behavior of As and Cd in paddy systems and practical applications for mitigating their co-contamination, ensuring safe rice production. [ABSTRACT FROM AUTHOR]

The active effect of soil Cd and Zn and their interaction was studied in typical paddy field in south China by monitoring the contents of Cd and Zn in soil and rice in rice fields applied with pig manure, chicken manure or rice straw for 4 years continuously. The results showed that applying pig manure, chicken manure or rice straw had no significant impact on the soil total Cd content , soil available Cd content and soil Cd activity, but tended to increase the soil total Cd content and increased the soil total Zn content, soil available Zn content and Zn activity significantly. Applications of pig manure, chicken manure and rice straw all reduced the Cd content of brown rice, in order of pig manure > chicken manure > rice straw. The Cd contents of brown rice, stem and leaf in the treatment applied with pig manure were lower than in the control by 37.5% , 44.0% and 36.4%, respectively; the Cd contents of brown rice, stem and leaf in the treatment applied with chicken manure were lower than in the control by 22.5% , 33.8% , and 22.7% , respectively; the Cd content of brown rice in the treatment applied with rice straw was lower than in the control by 7.5% but its contents in stem and leaf increased by 8.2% and 22.7% , respectively. The reduction in the brown rice Cd content was mainly due to the reduction of Cd enrichment from soil to brown rice alter application of pig or chicken manure, but mainly due to the reduction of Cd transportation from stem to brown rice alter straw application. Applications of pig manure, chicken manure and rice straw increased Zn contents in rice stem by 53.4%, 53.4% and 13.9%, respectively, but all had no significant effect on brown rice and leaf's Zn contents. Zn and Cd had the significant antagonistic effects in the soil and rice stem. The increase of Zn content in soil and rice stem inhibited the adsorption and accumulation of Cd in the brown rice, stem and leaf significantly, and with the increase of the proportion of Zn/Cd, the competitive absorption between Cd and Zn by rice was the main control factor affecting the Cd absorption by rice than their competitive adsorption by soil. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination of paddy fields is a global concern, as it can cause the accumulation of Cd in food. To explore the effects of equal application of silicon fertilizers on the bioavailability of cadmium and soil Cd uptake at different growth stages of rice, a field experiment was conducted with five silicon fertilizers under the same silicon dose (225 kg·hm -2 ). The results revealed that the Cd contents in roots, stems, and leaves increased with the extension of the rice growth stage. The application of silicon fertilizers reduced the Cd contents in roots, stems, and leaves in brown rice by 14.9%, 28.2%, and 12.2%, respectively. Compared with that in the control, the Cd content of brown rice in the SiCaMgFe and SiW treatments was decreased by 21.1% ( P <0.05) and 21.2% ( P <0.05), respectively. Similarly, Cd content in iron plaque (DCB-Cd) increased with the extension of the rice growth period, which accounted for 15.8%-42.8% of the total Cd content in roots, and the DCB-Cd content was different in each stage of rice. The content of exchangeable Cd (Exc-Cd) in soil at the mature stage of rice decreased by 36.4%, and the other fractions increased by 12.5%-48.2%. The results showed significant negative correlations between the Cd contents and Si in roots, DCB-Cd and soil available Cd and available Si, Exc-Cd and Car-Cd, and soil available Cd and pH value. Cd content in roots was positively correlated with DCB-Cd. With the equal dose of silicon fertilizer, the treatments of SiCaMgFe and SiW could effectively reduce the Cd content in rice. The application of silicon fertilizer promoted the transfer of Exc-Cd to Carb-Cd by increasing the soil pH value and the soil available Si content, meanwhile reducing the soil available Cd, Exc-Cd contents, the adsorption of Cd by the iron film on the root surface, and the adsorption capacity of iron plaque and root, thereby reducing the absorption of Cd by rice.

To clarify the primary factors affecting soil bioavailable cadmium (Cd) and arsenic (As) by silicon fertilizer, we chose different properties of silicon fertilizer, including three types of alkaline silicon fertilizer[Na 2 SiO 3 , CaSiO 3 , and ASSF (pH 9-11)] and one weak acid neutral soluble silicon fertilizer (NSSF, pH 5-6), to carry out a pot experiment by adding different amounts of Si fertilizer (25-800 mg·kg -1 , calculated as Si). After 21 days of flooding, soil basic physical and chemical properties, along with diffusive gradients in thin film Cd and As (DGT-Cd and DGT-As) were investigated. The results showed that the application of Si fertilizer with different properties had different significant effects on the basic physical and chemical properties of soil. Specifically, the three types of alkaline silicon fertilizer significantly increased the soil pH ( P <0.05), among which Na 2 SiO 3 exhibited the strongest ability; however, the application of NSSF remarkably reduced soil pH ( P <0.05), and per unit (mg) Si application of NSSF could reduce soil pH by 0.0017 units. Furthermore, with each fertilizer application rate that reached 400 mg·kg -1 (calculated as Si), the changes in soil pH and Eh tended to be gentle. The ability of the four types of silicon fertilizer to improve soil available silicon ranked as NSSF>Na 2 SiO 3 >ASSF>CaSiO 3 . Additionally, the application of the three types of alkaline silicon fertilizer apparently decreased soil DGT-Cd while increasing soil DGT-As ( P <0.05). When the addition rate of CaSiO 3 was up to 100 mg·kg -1 (calculated as Si), soil DGT-Cd concentration could be significantly decreased by approximately 50.89% without causing a significant increase in soil DGT-As concentration. Conversely, when the NSSF application rate was up to 400 mg·kg -1 (calculated as Si), the soil DGT-As basically reached its steady-state, and the DGT-As reduction rate reached 85.87%. Strikingly, the correlation analysis of the influencing factors of soil DGT-Cd and DGT-As showed that soil pH was the main factor affecting soil bioavailable Cd and As (DGT-Cd and DGT-As), and the effect of soil available Si and P on soil Cd and As bioavailability was negligible. Consequently, soil DGT-Cd and soil DGT-As could reach a minimum when soil pH was adjusted to 6.5-7.0 or 5-5.5 by alkaline silicon fertilizer or NSSF, respectively. It is undoubtedly of great significance, to clarify the primary factors that influence soil bioavailable Cd and As to ensure food security production.

The active effect of soil Cd and Zn and their interaction was studied in typical paddy field in south China by monitoring the contents of Cd and Zn in soil and rice in rice fields applied with pig manure, chicken manure or rice straw for 4 years continuously. The results showed that applying pig manure, chicken manure or rice straw had no significant impact on the soil total Cd content, soil available Cd content and soil Cd activity, but tended to increase the soil total Cd content and increased the soil total Zn content, soil available Zn content and Zn activity significantly. Applications of pig manure, chicken manure and rice straw all reduced the Cd content of brown rice, in order of pig manure > chicken manure > rice straw. The Cd contents of brown rice, stem and leaf in the treatment applied with pig manure were lower than in the control by 37.5%, 44.0% and 36.4%, respectively; the Cd contents of brown rice, stem and leaf in the treatment applied with chicken manure were lower than in the control by 22.5%, 33.8%, and 22.7%, respectively; the Cd content of brown rice in the treatment applied with rice straw was lower than in the control by 7.5% but its contents in stem and leaf increased by 8.2% and 22.7% , respectively. The reduction in the brown rice Cd content was mainly due to the reduction of Cd enrichment from soil to brown rice after application of pig or chicken manure, but mainly due to the reduction of Cd transportation from stem to brown rice after straw application. Applications of pig manure, chicken manure and rice straw increased Zn contents in rice stem by 53.4%, 53.4% and 13.9%, respectively, but all had no significant effect on brown rice and leaf' s Zn contents. Zn and Cd had the significant antagonistic effects in the soil and rice stem. The increase of Zn content in soil and rice stem inhibited the adsorption and accumulation of Cd in the brown rice, stem and leaf significantly, and with the increase of the proportion of Zn/Cd, the competitive absorption between Cd and Zn by rice was the main control factor affecting the Cd absorption by rice than their competitive adsorption by soil.