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Adapting crops to the bittersweet impact of rising CO2

The predicted increase in carbon dioxide levels in the atmosphere is bittersweet news for the nation’s grain growers.

Research partly funded by the Grains Research and Development Corporation (GRDC) has shown that elevated carbon dioxide (CO2) increases growth and yield in wheat, peas and other crops by on average 25 percent, but at the same time decreases protein content in wheat grain by up to 15 pc.

Other positive and negative crop production responses have been recorded during the studies into the effects of elevated CO2 levels predicted for the year 2050.

The research, being undertaken by the Victorian Government and the University of Melbourne at the low rainfall environment Australian Grains Free Air CO2 Enrichment Facility (AGFACE) at Horsham, will assist in the development of crop adaptation strategies to enable future increases in crop production.

Dr Glenn Fitzgerald from the Victorian Department of Economic Development, Jobs, Transport and Resources (DEDJTR) says AGFACE studies into the effects of elevated CO2 levels on crop production have been carried out over the past nine years.

Speaking at GRDC Grains Research Updates in the southern cropping region, Dr Fitzgerald said with atmospheric CO2 levels predicted to rise, it was important to understand both the positive and negative impacts that were likely to occur, to prepare farmers and the agricultural industry for the future.

“By conducting studies into the response of crops under the levels of CO2 we anticipate for 2050, we have time to develop adaptation strategies,” Dr Fitzgerald said.

“These strategies will need to consider elevated CO2 impacts on crops to accentuate the positive effects (such as traits to enhance yields) and to overcome the negative aspects (such as reversing reductions in grain protein and bread quality).

“This will allow continued improvement in yields despite changes in climate.”

AGFACE research has so far shown that elevated CO2:

  • Increases growth and yields in wheat, peas and other crops by on average 25 pc, but with a large range from 0 to over 70 pc, depending on variety and location;
  • Decreases protein content in wheat grain by up to 15 pc;
  • Increases water use efficiency by on average 25 pc, but water use may only be reduced slightly;
  • Decreases bread loaf volume and other quality factors;
  • Increases the incidence of barley yellow dwarf virus;
  • May reduce the impacts of heat waves near anthesis (flowering).

Atmospheric CO2 levels have risen from 280 parts per million (ppm) in 1870 to 405 ppm in 2015. This concentration is predicted to increase to 550 ppm by 2050.

Work being undertaken at the AGFACE facility has been simulating such atmospheric levels of CO2 in experimental field trials in which crops are grown in octagonal rings, comprising metal pipes that emit CO2 into the wind.

Crops in half of the rings are subjected to elevated CO2 and the other half are grown under current ambient concentrations, so future and current conditions can be compared.

Various treatments have been tested, including times of sowing, different irrigation levels, and different varieties of wheat, field peas, lentils and canola.

Nitrogen use efficiency responsiveness and nitrogen management treatments are currently being tested.

Dr Fitzgerald said there were several AGFACE sub facilities as well as glasshouses and chambers used for more controlled studies for physiology and pest and disease assessment so the mechanisms can be understood to inform pre-breeding adaptation strategies.

Computer simulation is an important tool to synthesise results from AGFACE, particularly where information is not easily obtained from field studies.

Results need to be taken in the context of other possible implications of climate change, including changes in temperature, average annual rainfall and seasonal rainfall distribution.

Integration with economic data will also be valuable in understanding farm-level impacts.

Ongoing research includes synthesising years of AGFACE data to provide a glimpse into future impacts of elevated CO2 under a range of possible environments.

“This will provide information for development of adaptation strategies for trait selection and management practices (such as sowing time and nitrogen management) to take the most advantage of elevated CO2,” Dr Fitzgerald said.

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