The world's need for food is expected to increase strongly over the next decades but, as new research from the CSIRO highlights, the impacts of climate change will pose a major challenge.
The OECD estimates that agricultural production will have to ramp up by 60 per cent by 2050 to meet growing global demand, but says that this has to be achieved through increased productivity rather than an expansion in arable land.
A related study by the CSIRO, recently published on the website of the Grains Research & Development Corporation (GRDC), indicates that the level of crop yield potential is itself a driver of yield gaps. Monitoring 250 paddocks for four years, the researchers revealed that significant gaps arise when the yield potential exceeds 4.8 tonnes per hectare.
According to study author Dr Roger Lawes, it indicates that the higher the average rainfall is in a crop region, the higher is the yield potential and yield gap.
The researchers were also able to determine nitrogen deficiency is often the major limiting factor for crop yield, while other variables such as insufficient crop rotation, free-living nematodes and diseases such as Fusarium crown rot also play a role.
As a major producer of food, and one of the world’s largest wheat exporters, Australia could play an important role in delivering global food security, and benefit from it. Currently a Parliamentary Inquiry explores the possibility of growing the value of Australian food production from around $60 billion in 2019 to $100 billion by 2030.
However, there are major challenges, most notably the predicted impacts of climate change.
A study from 2017, published by CSIRO scientists in Global Change Biology, showed that instead of ramping up production, Australia’s wheat yield actually stalled in the 90s, after trebling in the first 90 years of the 20th century.
A follow-up study by the CSIRO recently published in Climatic Change has now looked at the impact changing rainfall patterns have on the wheat yield potential in major rain-fed crop-growing regions of Australia.
Large parts of Australian grain production in the country’s southwest rely on rain as the only source of water, which is therefore the limiting factor of how much wheat can be produced in a certain climatic region and soil type if best farming practices are applied.
The CSIRO researchers focussed on the Western Australian wheatbelt, an area which covers around 60,000 square kilometres and produces close to one quarter of the nation’s crop, valued at $1.4 billion.
Drawing on climate data from the period between 1900 to 2016 they determined for each of the 117 years the wheat yield potential at numerous points across the Western Australian wheat belt.
They found that over the period a significant decrease in rainfall, most a result of climate change, shifted the regional wheat yield potential to the southwest of the wheatbelt, by an average of 70 kilometres.
This was despite the impact of changing weather patterns being partially offset by rising CO2 level in the atmosphere, which promotes plant growth.
“Overall, the benefits of increased CO2 are far outweighed by a reduction in rainfall, the major limiting factor to crop growth,” senior experimental scientist Dr Chao Chen, one of the authors of the study, said.
That the overall yields achieved by farmers haven’t decreased is due to better crop varieties and better farm management, which has closed the gap between the yields farmers can potentially expect, and what they actually achieve.
As the researchers point out, it highlights the need to constantly evolve cropping systems, with every aspect of agronomy and genetics to be considered.
“Without continuing improvements, there will likely be a decrease in wheat yield across this cropping region,” they say, and it is likely that similar shifts in yield potential have occurred in other parts of the country.