Increased levels of atmospheric carbon dioxide (CO2) reduce the nutritional content of rice grains, particularly iron (Fe) and zinc (Zn). Rice serves as a staple food crop for more than two billion people across the world; substantial portions of these rice-dependent populations also suffer from iron and zinc deficiencies. In rice, the effect of increased CO2 on Fe and Zn differs between cultivars. With better mechanistic understanding as to why, informed plant breeding and cultivar selection is a likely path towards ameliorating this problem. Little is known about the mechanisms behind CO2-induced reduction of grain nutrition. Increased CO2 changes the pH of rice paddy soil, facilitating the release of cations (including Fe and Zn), which leads to increased uptake to above ground plant tissues. However, this does not result in increased concentrations of these compounds in the rice grain. Several explanations have been advanced for this paradox, but most work on the topic has relied on free-air carbon enrichment (FACE) installations, which cannot control many potentially important variables. In particular, reduced transpiration under elevated CO2 may obscure differences between CO2-induced carbohydrates. Additionally, the fine-scale impacts of elevated CO2 on the rice rhizosphere have been poorly studied. Our study is attempting to close these knowledge gaps: we have grown rice plants under elevated and current CO2 conditions, while maintaining even transpiration between treatments via controlled relative humidity. We have paired these experimental manipulations with oxygen optode-based visualizations of the undisturbed rice rhizosphere, which has directed accurate soil sampling of rhizosphere and bulk soil porewater samples for analysis of pH, redox, total organic carbon (TOC), and quantification of Fe, As, Ca, Mg, and Zn. Our study seeks to better understand the mechanistic role of increased CO2 on the rice rhizosphere, and its downstream effect on rice grain nutrient quality.