Safe production on large areas of cadmium (Cd)-contaminated paddy soil in China is an important issue for people’s health and sustainability of agriculture. Cost saving and high efficient remediation strategies for controlling rice Cd content are urgently needed. The effects of three water management modes i.e. drought (D), intermittent flooding (IF), continuous flooding (CF) and the combined application of water management and amendments iron silicon rich materials (IS) and biochar (B) on Cd uptake of different rice varieties were studied by field experiment, and the possible mechanisms of their effects were discussed. The results showed that the content of brown rice Cd under CF condition from tillering to maturity stage was reduced by 0.2%-45.43% and by 37.67-62.11%, respectively, compared with IF and D treatments. Under three water management modes, the content of brown rice Cd of low accumulative rice cultivar G82168 was 35.03%-54.61% lower than that of conventional variety. Under the condition of three modes of water (D.IF, CF) management, the content of Cd in brown rice treated with IS amendment decreased by 64.26%, 55.74% and 38.14% compared with that treated with water management only, and the effect of combined amendment IS+B was much weaker. Brown rice Cd was the lowest with the combined application of low cumulative variety, continuous flooding and IS. Continuous flooding could promote the fixation of Cd by root iron plaque which acted as a barrier for Cd entering rice plant. On the other hand, continuous flooding also significantly decreased soil available Cd (extracted by 0.01M CaCl2) by 29.71%-63.13%. Both the mechanisms helped to reduce the Cd uptake by rice. IS had no significant effect on the root iron plaque fixed Cd. It decreased rice Cd uptake mainly by decreasing the content of soil available Cd dramatically. The combined application of low accumulative rice variety, continuous flooding and IS can guarantee the safety of rice production on Cd contaminated paddy soil. Planting low accumulative rice cultivars coupled with continuous flooding during the critical growth stage are of great significance to inhibit Cd uptake by rice. Application of amendments and low accumulative rice varieties should be emphasized in water shortage seasons or areas.
This study was supported by the National Key R&D Program of China (SQ2018YFD0800700); National Key Technologies R&D Program of China (2015BAD05B05); the National Natural Science Foundation of China (No. 41877121).