<p>Annual grass invasion is a global ecological problem. Invasive annual grasses are thought to alter biogeochemical cycles, particularly nitrogen (N), through positive belowground feedbacks. Nitrogen acquisition is hypothesized to be a key factor driving invasion, but the mechanisms by which invasive annual grasses access nitrogen remain unclear. We investigated the influence of root exudation on the soil environment beneath cheatgrass (<i>Bromus tectorum</i>), an invasive annual grass that is widespread across North America. In a greenhouse experiment, we contrasted the effects of drought on root exudation by cheatgrass and a grass that is native to the western USA (squirreltail; <i>Elymus elymoides</i>), and subsequent effects on soil processes. This was followed by an incubation experiment that directly tested how root exudates influence soil biogeochemical cycling. We found that throughout the greenhouse experiment, droughted cheatgrass plants acquired more nitrogen than squirreltail or their watered counterparts. Cheatgrass soils had lower nitrifier abundance and net nitrification rates, as well as accelerated carbon cycling and greater microbial biomass compared to soils from beneath squirreltail. These effects were greatest in soils from cheatgrass plants that had experienced drought. Cheatgrass plants produced more root exudates, which had greater organic acid content. When experimentally added to soil, root exudates from cheatgrass accelerated microbial respiration and decreased net nitrification—mirroring observations in greenhouse soils. Effects were strongest with exudates from droughted cheatgrass. Our findings suggest that by stimulating heterotrophic soil microbes, cheatgrass root exudates increased carbon cycling and altered the rate at which nitrogen becomes available in the rhizosphere. When considering cheatgrass’ phenology, root exudation may provide cheatgrass with greater access to soil nitrogen in dry conditions compared to native species.</p>