Increased levels of carbon dioxide have been shown to increase wheat yield under certain circumstances.
Trials in Victoria have demonstrated a yield increase of 26 per cent in wheat under elevated carbon dioxide levels.
The result, from DEDJTR’s Australian Grains Free-Air CO2 Enrichment trial site in Horsham, shows there may be a silver lining to increased atmospheric CO2 concentrations.
The trials compared present CO2 levels of 390 parts per million with elevated levels of 550ppm by pumping CO2 into the air above trial plots.
DEDJTR research scientist James Nuttall said elevated CO2 reduced water loss from the plants’ leaves.
‘‘At higher concentrations of CO2, the stomata in plants do not have to open as much to absorb the required carbon, so less moisture is lost through leaf transpiration, which means more water may be available for plant growth,’’ Dr Nuttall said.
Farm consultants from south-east Australia recently visited the AGFACE site as part of regular six-monthly attendances at carbon farming workshops through the Carbon Farming Knowledge Project.
It is a Federal Government-funded initiative to help advisers prepare clients for the impacts of climate change and understand the potential benefits of future carbon management policy, including the government’s Emissions Reduction Fund.
Advisers work with about 600 broadacre farmers and at least 25 grower groups to increase their knowledge base and carbon farming skills.
Dr Nuttall said the results were not all good news for grain growers and their advisers.
‘‘The trials have shown that when looking at the impacts of increased CO2 levels, yields are significantly higher,’’ he said.
‘‘However, in practice, this will not happen in isolation and the effect of higher temperatures on yields may offset this benefit.’’
The optimal temperature for wheat development is 22°C to 25°C, with temperatures above 32°C leading to reduced grain size and quality.
Climate change modelling indicates higher temperatures and more frequent occurrences of extreme heat increased yield caused by higher CO2 will likely be countered by a heat-based reduction in yield.
Because climate change is likely to result in greater climate variation, it is difficult to predict the extent of this effect.
Researchers are investigating ways growers may be able to take advantage of the improved yield response.
‘‘This is great news for growers who will need to find a way to profitably grow crops in a more variable climate,’’ Dr Nuttall said.
‘‘The trials so far have shown a reduction in protein content of about one per cent but we are currently investigating varietal differences and agronomic practices to determine if we can minimise this loss.
‘‘The objective is to give growers the best tools to use in the changing environment.’’