Managing rainfall variability has become one of the defining challenges of the WA growing season. In this article, Dr Cam Beeck looks at five decades of CSIRO and Bureau of Meteorology data, what the later autumn break and falling cool-season rainfall mean for crop establishment, and where products like Aquifer fit into the response.
Managing rainfall variability in south-west WA
Over the past 50 years, rainfall patterns across south-west Western Australia have undergone a significant and well-documented shift. This shift is increasingly shaping how growers approach the start of the season. April and May, traditionally relied upon to deliver the “break of season,” are no longer as dependable as they once were. Instead, growers are facing a combination of declining rainfall, later seasonal onset, and greater variability at precisely the time when soil moisture is most critical.
According to the CSIRO and the BoM, cool-season rainfall (April to October) across south-west WA has declined by around 15-16% since 1970. More critically, the core early winter period (May through July) has seen declines closer to 19-20%, representing the most substantial reduction of any seasonal window (references are below if you would like to dig a bit deeper). This is particularly important because May has historically marked the beginning of reliable planting conditions for much of the WA wheatbelt.
April rainfall trends are more variable, but the data shows a clear increase in inconsistency. Long-term records from the Bureau of Meteorology indicate a higher frequency of below-average April rainfall years since the 1990s, interspersed with occasional extreme rainfall events. For example, April 2023 ranked among the wettest Aprils on record in parts of WA, highlighting a growing tendency toward episodic rainfall rather than steady seasonal opening conditions. This variability increases the risk of false breaks, where early rainfall triggers germination, only to be followed by extended dry periods that compromise establishment.
The shift toward a later break of season is closely linked to changes in large-scale atmospheric patterns. Research from the CSIRO attributes much of the decline in early-season rainfall to a strengthening subtropical high-pressure ridge, which has reduced the frequency and intensity of cold fronts penetrating into south-west WA during autumn.
For growers, the implications are both practical and immediate. Establishing crops into marginal moisture conditions is becoming more common, while reliance on a timely and uniform autumn break is increasingly risky. Dry sowing strategies are more widely used, not only due to increased variability of rainfall but also due to increased farm sizes shifting growers into an April sowing pattern in an effort to “get the program done” in time. But dry sowing comes with its own challenges, particularly when follow-up rainfall is delayed or uneven. In this environment, the value of stored soil moisture has increased significantly, as it often determines the success or failure of early crop establishment.
Farming systems have already adapted in response to these conditions. The widespread adoption of no-till practices has improved the ability of soils to capture and retain moisture by reducing evaporation, maintaining ground cover, and enhancing and focusing infiltration. These systems are critical in ensuring that rainfall, when it does occur, is preserved within the soil profile rather than lost to the atmosphere.
However, as variability increases, there is a growing need to further optimise how moisture is managed at the seed level. Technologies designed to enhance the availability and retention of soil moisture are becoming increasingly relevant in modern farming systems. Products such as Aquifer from 4Farmers, are formulated to attract moisture and retain moisture in the immediate seed zone, offering an additional layer of support under challenging seasonal conditions. By helping to maximise the effectiveness of limited and inconsistent rainfall, these technologies can improve germination uniformity and reduce the risks associated with delayed or unreliable season breaks.
When April and May rainfall can no longer be relied upon with confidence, the focus must shift from waiting for a break to actively managing variability. The data from the CSIRO and the BoM is clear: less rainfall, later breaks, and greater inconsistency. Maximising stored soil moisture through no-till systems and technologies like Aquifer will be essential to maintaining productivity in Western Australia’s evolving growing environment.
References:
Bureau of Meteorology. (2023). Climate statistics for Australian locations and monthly climate summaries. Australian Government. https://www.bom.gov.au/climate/
Commonwealth Scientific and Industrial Research Organisation. (2024). State of the Climate 2022. CSIRO & Bureau of Meteorology. https://www.csiro.au/en/research/environmental-impacts/climate-change/state-of-the-climate
Commonwealth Scientific and Industrial Research Organisation. (2020). Climate change in Australia: Technical report. CSIRO. https://www.climatechangeinaustralia.gov.au
Bureau of Meteorology. (2023). Monthly climate summary – Western Australia (April 2023). Australian Government. https://www.bom.gov.au/climate/current/month/wa/archive/202304.summary.shtml
For all enquires, call the team at 4Farmers on 9356 5445 or send an email to sales@4farmers.com.au.
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