Effects of free-air CO2 enrichment and nitrogen supply on grain quality parameters and elemental composition of wheat and barley grown in a crop rotation

With respect to European growth conditions very little information is available on how future atmospheric CO2 concentrations [CO2] might affect quality characteristics of important crops. Winter wheat cv. ‘Batis’ and winter barley cv. ‘Theresa’ were grown for two growing seasons each under ambient [CO2] (ca. 375 μmol mol−1) and elevated [CO2] (550 μmol mol−1) with two different nitrogen (N) fertilization levels (adequate N supply / ca. 50% of adequate N) in the course of a six year crop rotation. Effects on grain quality and grain elemental composition were investigated. Grain crude protein concentrations were lowered under elevated [CO2] by −4% to −13% in wheat and by −11% to −13% in barley. Reduced N supply decreased crude protein concentrations in wheat and barley by −14% to −22% and by −12% to −19%, respectively. In both species, starch concentration was increased by +4% on average due to reduced N fertilization. In wheat, both CO2 enrichment and low N supply reduced the activity of total and soluble β-amylase (−11% and −7%), Hagberg falling number (−7%), and single kernel hardness (−18%). In barley, both of the treatments induced reductions in the viscosity of the water extract (−25% on average). Concerning minerals, sulphur concentrations were depleted under both elevated [CO2] and low N supply by averages of −5% in wheat and −14% in barley. Reduced N supply caused −8% lower means of wheat grain calcium concentrations and reduced zinc concentrations on average by −23%. According to these results, flour from cereal grains grown under elevated [CO2] and/or low N fertilization will have a diminished nutritional and processing quality and an altered elemental composition.