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Silicon-rich biochar provides novel strategy for simultaneously solving the problems of soil silicon deficiency and heavy metal pollution, while the practice and research was still rarely reported. To investigate the performance and mechanisms of the silicon-rich biochar improving the soil available silicon and immobilizing heavy metals, the rice straw derived biochar was applied as the silicon-rich biochar, while Miscanthus sinensis derived biochar, desiliconized rice straw biochar as well as soluble silicate were selected as references. During the 25 weeks of incubation after soil application, the soil available silicon, speciation of heavy metals and the leachable content of heavy metals were determined, to demonstrate the multi-functional restoration effects by the silicon-rich biochar. Results showed that the application of rice straw biochar significantly improved the soil available silicon, and promoted the transferring the heavy metals like lead, copper and zine from exchangeable fractions to more stable fractions so that lowed the leaching risks of heavy metals. The immobilized heavy metal content was found to be positively correlated with the relatively decreased available silicon. It was thus implied that silicon-rich biochar could effectively promote the multi-functional restoration of the polluted soil through both the ways of increasing the available silicon and immobilization heavy metals. [ABSTRACT FROM AUTHOR]