Growth, Yield and Water Use of Wheat under Elevated Carbon Dioxide

The Australian Grains Free Air Carbon Dioxide Enrichment (AGFACE) project in Horsham, Victoria, was designed to simulate atmospheric carbon dioxide (CO₂) levels in the year 2050 and then to use those data to model and predict spring wheat (Triticum aestivum) responses. The experiment measures the interacting effects of carbon dioxide (ambient aCO₂ ~380 µmol/mol, elevated eCO₂ ~550 µmol/mol) with variations in water supply, temperature during grain fill, N, and cultivar on wheat growth and productivity. Carbon dioxide was injected over the crop in open-air 12 m rings from emergence until maturity in 2007, 2008, and 2009. The effect of eCO₂ was to increase crop biomass at maturity by 20% in 2007 and 30% in 2008. Harvest index was not affected in 2007, but declined from 0.31 to 0.26 in the later sowing in 2008. Mean grain yields across all treatments increased under eCO₂ from 2.68 t/ha to 3.23 t/ha (2007) and from 2.47 t/ha to 3.08 t/ha in 2008. Both sowing time and additional water affected growth and yield in both years. Further, in 2008 there was a significant interaction between CO₂ and sowing time, with the later sowing showing no response to eCO₂. There was no clear increase in a particular yield component in response to eCO₂. ANZ-02