The contamination of rice grains by arsenic is a global problem. Since arsenic is a poison, rice consumption may pose a threat to human health. This project aims to decrease the arsenic concentration in rice grains and thus protect human health from rice consumption by amending soil with soluble silicon (Si). Increased dissolved silicon can decrease root-uptake and grain-levels of arsenic due to competition for plant-uptake of arsenite (the dominant form in rice paddy soil solution) by dissolved silicon because arsenite and silicon share an uptake pathway in rice. While the total amount of silicon in soils is high, the soluble (and thus plant-available) silicon is much lower, particularly in older (more weathered) soils where most rice is grown and where silicon accumulating plants (such as rice) mine silicon out of soil and are removed. Return of silicon to soil from rice residues with a high Si content may decrease arsenic uptake/grain storage, increase yields, and thus protect human health. Since fresh plant material may promote greenhouse gas production, this project will test the effect of rice husk ash (which is high in silicon) on decreasing arsenic uptake and concentration in rice grains.
If proven effective, this management practice could be adopted worldwide, including small-holder farms in the developing world, with minimal cost or change to current management strategies. This project will allow for the purchase of a closed-vessel microwave digestion unit which will aid the Principal Investigator, Dr. Seyfferth, in establishing her research group and allowing her and her group to conduct basic science for years to come. Finally, Dr. Seyfferth has a proven record of involving members of underrepresented groups in science, which will continue throughout this project and in future projects.
Since rice is a staple food for nearly half of the global population, global food security is threatened by both the quantity (yield) and quality (health) of rice. Arsenic is a poison and its presence in flooded rice paddy soils can decrease rice quality and quantity. Increasing plant-available silicon has the potential to positively affect both the quantity and quality of rice because it can improve yields and compete with arsenic for uptake at the plant root. The purpose of this project was to understand how soil incorporation of fresh rice husk or the ash of the husk, which are both high in silicon, affect arsenic cycling in rice paddies, and how this practice affects cycling of iron and carbon. We grew several globally-important rice varieties in flooded soil that had either fresh husk, ash of husk, or no amendment from seed to seed. We monitored the water chemistry and methane production from each pot throughout the growth period, and we evaluated yield parameters and elemental distributions of arsenic and plant nutrients upon rice harvesting. We found that although each variety responded differently, the general trend was that increasing plant-available silicon helped to alleviate arsenic accumulation in the plants and to increase rice yield. These outcomes have important implications for global food security aimed at increasing rice quality and quantity for future generations. This work also promoted the scientific pursuits of women and minority groups at the high-school (2 students), undergraduate (3 students), graduate (1 student), post-graduate (1 student) and faculty level.
