Growth, Yield and Water Use of Wheat under Elevated Carbon Dioxide
Research on how elevated carbon dioxide will affect the growth and yield of wheat crops under future climates.
IPNI-2010-AUS-02
28 Jan 2010
2009 Annual Interpretive Summary
While higher CO2 is likely to stimulate plant growth, it seems that the interaction with changing water supply and rising temperatures will largely offset that “fertilizer” effect. To gain an understanding of these interactions, field experiments were conducted from June to December in 2008 at Horsham, Victoria, Australia on a Vertisol used for a range of winter grain crops.
Atmospheric CO2 was raised from ambient (380 ppm) to a target of 550 ppm using a FACE system, consisting of sixteen 12 m diameter experimental areas, with each area split for two irrigation treatments. Eight rings were sown on June 3 and the other eight on August 6. Within each half ring, the cultivars Yitpi or Janz were sown with no added N, and Yitpi was sown with added N.
Significant main plot effects were observed for sowing time and watering regime on biomass at Zadoks growth stage (GS) 30 (stem elongation), GS65 (mid flowering), and GS90 (ripening), as well as grain yield.
However, the results for growth, N concentration, and N uptake showed very few interactions between atmospheric CO2 and sowing time, watering regime, or cultivar treatment. Across the three sampling times, the higher level of CO2increased aboveground biomass by 25%, 31%, and 32%. However, the plant N contents were significantly lower with higher CO2 in all except the first sampling. This decline was also seen in leaf N concentration at GS65 where the leaf N declined from 3.78 to 3.54%, and at GS90 the grain protein content declined from 18.0 to 17.3%. We reported a similar decline in grain protein in 2007 and lower grain protein content under high CO2has been noted in other studies. It is likely that this effect is a consequence of lower N contents in the plant during growth, which leads to a lower labile N pool for N translocation during grain filling. In this experiment, the mean straw C:N ratio was 49.5±1.4 and it was not significantly affected by the carbon dioxide level. Even though this ratio was not affected, there was more stubble with elevated atmospheric CO2and this may lead to a larger demand for soil N to breakdown the stubbles. This research is on-going. ANZ-02