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].