Arsenic (As) and cadmium (Cd) affect rice under different redox regimes with As more bioavailable under flooded conditions and Cd more bioavailable under nonflooded conditions. Recent work has shown that Si addition to paddy soils can alleviate As and Cd bioaccumulation in rice. Biochar derived from Si-rich rice husk could provide sufficient Si to compete with arsenite for plant-uptake while also increasing Cd sorption in soil but requires optimization to create the best conditions for minimizing both As and Cd under a variety of water/redox regimes. Here, we prepared biochars under different physicochemical conditions and tested their ability to decrease As and Cd accumulation in rice. We expected that soil incorporation of biochar with sufficient plant-available Si and other nutrients combined with alternate wetting and drying (AWD) will maintain or increase rice yields while minimizing plant As and Cd. Biogeochemical processes of Si, As, and Cd and their bioaccumulation will be discussed in detail regarding implementable chemical and agronomic strategies to ensure food security.