CO2's impact on wheat

With CO2 levels predicted to increase by about 40 per cent over the next 40 years, the AGFACE program – a joint initiative of the Victorian Department of Environment and Primary Industries (DEPI), the University of Melbourne and the Grains Research and Development Corporation (with support from Birchip Cropping Group) – was set up in 2007.

The objective was to provide tools and information that will enable the grains industry, through policy makers and pre-breeders, to remain productive and competitive despite changes in climate.

AGFACE program researchers at Horsham’s DEPI have discovered while most wheat varieties will benefit in terms of yield potential under elevated CO2, grain quality is likely to decline.

According to DEPI research scientist Cassandra Walker, elevated CO2 has been found to adversely affect important grain traits such as protein content, mixing properties and baking properties, as well as the micronutrients in wheat.

But she said as different cultivars respond differently when grown under elevated CO2 conditions, breeders will be able to select for traits that are better adapted to elevated CO2.

“So far the research has found that the quality premium grade wheat varieties such as Yitpi and Janz suffer greater effects of elevated CO2 than H45 or Silverstar,” Dr Walker said.

Depending on the variety, the research suggests that wheat grown under elevated CO2 is generally one to 1.5 per cent lower in grain protein content than its equivalent grown under ambient conditions.

Dough rheology properties are also adversely affected by elevated CO2 which is significant from a baking perspective.

“Potentially, grain now classified as AH could become ASW,” Dr Walker said.

“But some varieties aren’t as affected as others.”

AGFACE research involves fully replicated wheat trial plots grown at a purpose-built facility at Horsham which achieves CO2 levels expected in 2050 (550 parts per million) by means of a cleverly engineered system that sees CO2 injected into the atmosphere from pipes circling the research plots.

The grain produced under elevated CO2 levels is compared with plots grown under the current CO2 concentration (400ppm).

In 2010, 2011 and 2012 wheat cultivars grown at the Horsham facility included Janz, Silverstar, Yitpi and H45.

Back at the lab the grain’s protein, weight and screenings are recorded. Each sample is then milled and its baking and milling qualities are assessed.

The impact of elevated CO2 is perhaps most noticeable after baking with grain grown under elevated CO2 producing smaller and denser loaves (up to a 10 per cent reduction in volume).

Dr Walker said a likely consequence of this reduction in baking quality is increased baking costs and a demand for higher quality wheat.

“This would flow onto the farmer with increased input costs, particularly in terms of fertilisers and nutrients,” she said.

A reduction in wheat micronutrients is also showing to be a consequence of elevated CO2 which researchers say will need to be considered in terms of future human and animal nutrition and food security.

Dr Walker said maintaining productivity and reducing on-farm costs in the future will require new crop cultivars that can maintain yield and grain quality under elevated CO2, in conjunction with changes in rainfall patterns and increasing temperatures.

“The AGFACE facility is helping researchers to provide vital information on benchmarking existing cultivars and monitoring potential new cultivars,” she said.

“Data from this research will help to ensure key quality parameters such as protein content, dough rheology and loaf volume is not compromised as CO2 increases in the future.”