33 - The Challenge of Yield Advancement ― we are not alone
Crop production in Australia since the late 1980s has increased by about 2.4 per cent per annum. However, the bulk of this increase in grain production has been attributable to an increase in the area sown to crops, with crop yields only increasing by 0.6 per cent per annum.
Over the next decade it is unlikely that the crop area increases observed in the 1990s and early 2000s can be repeated. Already since the mid-2000s the area sown to crops in Australia has changed very little. So, in coming years, crop production increases will increasingly rely on yield increases.
Will grain yields increase at a similar rate to that observed since the late 1980s; especially given the projections for further adverse climate change affecting crop production, most notably in southern Australia? Hochman et al. (2017), for example, examined simulated wheat yields at sites across Australia. These sites had high quality weather data and these researchers found that the water‐limited yield potential at these sites declined by an average 27% over a 26 year period from 1990 to 2015. Importantly, these researchers found that despite the adverse trend in climate, an unprecedented rate of technology‐driven gains was closing the gap between actual and water‐limited potential yields by 25 kg/ha/yr and so expected yield decline was not observed in practice.
A key question for Australia’s grains industry is: Will plant breeding and agronomic improvements more than offset the projected adverse trend in climate in Australia’s grain-growing regions? Australian plant breeders have been highly skilled at producing reliable, high yielding crop varieties, and valuable, research based agronomic improvements are adopted rapidly by farmers. But their challenge is that Australia’s climate for crop production seems to be changing. Stephens (2017), for example, reviewed weather station historical data across Australia and concluded that a shift is occurring in Australia’s climatic zones. He identified the following climate shifts across Australia (see Figure 1):
1) The summer dominant rainfall region has shifted south from near Longreach to Charleville,
2) The summer rainfall zone has shifted south from Gunnedah towards Dubbo,
3) The uniform rainfall zone has shifted southwest from southern New South Wales into central Victoria, while in Western Australia the uniform rainfall zone has shifted west from Kalgoorlie to Southern Cross.
4)The winter rainfall zone in Western Australia has shifted southwest leaving a smaller winter dominant zone along the west coast.
Australia is not alone among major grain exporters in facing adverse climate change. In the USA, for example, Crane-Droesch et al. (2019) reviewed studies of the impact of climate projections on crop yields in the USA and concluded that crop yields and crop areas in the USA were likely to decline unless improvements in agricultural technology kept pace with the growing weather stress. Although the areas and yields of corn, soybeans and wheat in the USA are projected to decline under future climate scenarios, there is substantial variability in crop areas and yields across the USA.
Production losses are generally largest in southern USA where corn and soybean yields become affected by an increased occurrence of extreme heat. By contrast, production increases up to 10 per cent are forecast for some northerly parts of the USA. Winter wheat is the least affected crop, as it is not exposed to increased summer heat. Nonetheless, for all crops including wheat, their riskiness of wheat production increases.
The key message is that Australia is not alone as a grain exporter who faces the challenge of an unfolding trend of adverse climate. The USA produces and exports far more grain than Australia, so it has a far greater commercial incentive to develop technologies that allow farmers to adapt to the adverse trend in climate. Some of those technologies developed in the USA will be applicable in Australia and so we can benefit from their R&D investments.
Crane-Droesch, A., Marshall, E., Rosch, S., Riddle, A., Cooper, J. and Wallander, S. (2019). Climate change and agricultural risk management into the 21st Century, ERR-266, U.S. Department of Agriculture, Economic Research Service, July 2019.
Hochman, Z., Gobbett, D. and Horan, H. (2017) Climate trends account for stalled wheat yields in Australia since 1990. Global Change Biology 3, 2071-2081.
Stephens, D. (2017) Australia’s changing climate: implications for wheat production. Agrometeorology Australia. Guest Blog for AEGIC. Available at: https://www.grainsinnovation.org/blog/2017/10/2/australias-changing-climate-implications-for-wheat-production