Several strategies exist to mitigate As impacts on rice and each has its set of trade-offs with respect to yield, inorganic As content in grain, and CH emissions. The addition of Si to paddy soil can decrease As uptake by rice but how rice will respond to elevated As when soil is amended with Si-rich materials is unresolved. Here, we evaluated yield impacts and grain As content and speciation in rice exposed to elevated As in response to different Si-rich soil amendments including rice husk, rice husk ash, and CaSiO in a pot study. We found that As-induced yield losses were alleviated by Husk amendment, partially alleviated by Ash amendment, and not affected by CaSiO amendment. Furthermore, Husk was the only tested Si-amendment to significantly decrease grain As concentrations. Husk amendment was likely effective at decreasing grain As and improving yield because it provided more plant-available Si, particularly during the reproductive and ripening phases. Both Husk and Ash provided K, which also played a role in yield improvement. This study demonstrates that while Si-rich amendments can affect rice uptake of As, the kinetics of Si dissolution and nutrient availability can also affect As uptake and toxicity in rice.

Arsenic (As) and cadmium (Cd) are two toxic elements found in rice (Oryza sativa L.) grain that pose threats to human health. While attention has focused on major rice-growing regions, rice has been grown on small-scale farms in the northeastern United States since approximately 2005, but the grain As and Cd levels were not previously reported. Unpolished grain from these farms have mean As of 0.12 mg kg −1 and mean Cd of 0.007 mg kg −1 , more than 40% lower than previously reported in U.S. rice. Therefore, rice from these farms poses low risk for consumers. INTRODUCTIONArsenic (As) and cadmium (Cd) are trace elements of concern in rice (Oryza sativa L.). Both are toxic to humans (