Plants employ a variety of mechanisms to acquire nitrogen from their environment ranging from carnivory to symbiotic relationships with bacteria. Most plants, however, obtain the majority of their nitrogen as nitrate and ammonium that their roots absorb from soils. To compete successfully against soil micro‐organisms for soil nitrate or ammonium, plants adjust their growth, development and physiology to exploit the distinct properties of each ion.Nitrate is more mobile than ammonium through most soils. Plants can store high concentrations of nitrate, but not ammonium, within their tissues. Yet, assimilation of nitrate into amino acids is far more energy‐intensive than that of ammonium. Plants offset some of the energy costs of nitrate assimilation by coupling it with photorespiration. Rising carbon dioxide levels in the atmosphere inhibits photorespiration and, thereby, nitrate assimilation. Therefore, ammonium and nitrate management will become even more critical in the future.