Elevated CO₂, drought and soil nitrogen effects on wheat grain quality

• The likely consequences of future high levels of atmospheric CO₂ concentration on wheat (Triticum aestivum L.) grain nutritional and baking quality were determined. • Two free-air CO₂ enrichment (FACE; 550 mmol mol^-1) experiments were conducted at ample (Wet) and limiting (Dry) levels of irrigation, and a further two experiments at ample (High-N) and limiting (Low-N) nitrogen concentrations. Harvested grain samples were subjected to a battery of nutritional and bread-making quality tests. • The Dry treatment improved grain quality slightly (protein +2%; bread loaf volume +3%). By contrast, Low-N decreased quality drastically (protein -36%; loaf volume-26%). At ample water and N, FACE decreased quality slightly (protein-5%; loaf volume -2%) in the irrigation experiments and there was no change in the nitrogen experiments. At Low-N, FACE tended to make the deleterious effects of Low-N worse (protein -33% and -39%, at ambient CO₂ and FACE, respectively; loaf volume -22% and -29% at ambient CO₂ and FACE, respectively). • The data suggest that future elevated CO₂ concentrations will exacerbate the deleterious effects of low soil nitrogen on grain quality, but with ample nitrogen fertilizer, the effects will be minor.