Some influences of CO2 enrichment, nitrogen nutrition and competition on grain yield and quality in spring wheat and barley

Spring wheat and spring barley were grown in elevated atmospheric CO 2 in controlled environments. Wheat was grown in monoculture and in competition with three weed species. In monoculture, wheat had 30% more grain yield and 28% less grain nitrogen in elevated compared to ambient atmospheric CO 2 . In competition, wheat had no significant increase in yield with elevated atmospheric CO 2 . In competition, grain nitrogen concentration was reduced in response to CO 2 with the largest reduction occurring with the smallest competitor and the smallest reduction occurring with the largest competitor. Spring barley was grown in monoculture at three nitrogen fertilizer supplies