Arsenic (As) poses a double threat to global food security by lowering rice yields and directly impacting human health via consumption of As-contaminated grain. The flooded soil conditions under which most rice is grown facilitate As mobilization through reductive dissolution of As-bearing Fe (oxyhydr)oxide minerals. This released As can be re-adsorbed by soil minerals including Fe plaque, methylated by soil microbes, or taken up by rice roots and eventually transported to grain. The fate of arsenic in the rice rhizosphere and plant depends upon the interplay of these controlling factors, which may change with agronomic conditions. Here, we couple conventional and advanced spectroscopic techniques to elucidate As(III) uptake at root tips and lateral root junctions, and show how changes in Si availability affect root Fe plaque mineralogy, and As speciation and localization in planta. These processes occurring at the soil-plant interface will be discussed in the larger context of global food security.