Crops have the potential to exploit the predicted increase in atmospheric carbon dioxide concentration ([CO2]). Growth is typically stimulated at elevated [CO2], but a sustained and maximal exploitation of rising [CO2] is dependent on an adequate supply of nutrients, principally nitrogen, and sufficient sink capacity to utilize the additional carbon fixed at elevated [CO2]. We have examined the effect of elevated [CO2] on carbon and nitrogen metabolism in soybean grown in the field using Free Air CO2 Enrichment (FACE) technology where soybean is able to complete it's entire life cycle at an elevated concentration of CO2 under fully open air conditions. In both fully expanded and developing leaves we have shown that increased carbon availability at elevated [CO2] improved nitrogen assimilation. The additional carbon available at elevated [CO2] allowed soybeans to overcome an early season nitrogen limitation and suggests that soybeans were able to acclimate to the increased nitrogen demand at elevated [CO2].