The optimum window for grain crops to flower is narrow in most Australian settings. Caught between the yield-punishing impacts of frost and terminal drought, growers’ ability to hit the window is an area GRDC has targeted for innovation. A series of investments is now maturing into a tool that is ready for testing by growers and agronomists.

It takes the form of an online calculator that provides the optimum sowing date for wheat, barley and canola cultivars. This includes new varieties or varieties sown into new regions.

Called the Crop Flowering Calculator, the tool helps ensure that sowing dates and cultivars are selected so that flowering occurs in the optimum window. It achieves this by drawing on the advanced crop growth modelling capability of APSIM-NG (the Agricultural Production Systems sIMulator – Next Generation).

The tool integrates new understanding of flowering time genetics and how they interact with environmental conditions and management practices. This includes insights gained through GRDC’s investment in four different projects focused on flowering physiology. Its development involved simulations with more than 60 years of weather data at 100-plus locations across the cropping zone.

Try it yourself

Having led the calculator’s development, CSIRO is hosting a website that allows the public to try the pre-release prototype and participate in its final validation. The Crop Flowering Calculator can be accessed. CSIRO is also welcoming feedback, suggestions and comments about the calculator via the email address feedback@canolaflowering.com.au.

Once accessed, the calculator can be operated in two main modes (see Figure 1).

It can answer the question: Which variety should I select given a preference for certain sowing dates? Alternatively, it can answer the question: When should I sow given a preference for certain varieties?

The calculator will consider the complex interplay of crop genetics, soil characteristics and regional climate to predict flowering periods. The answer is generated with a view to maximising yield and reducing risk.

Accuracy

To make sowing date predictions, the APSIM-NG model requires a specific type of input. This relates to how a cultivar responds to temperature, vernalisation and photoperiod. Traditionally, generating this input required costly, ongoing and time-consuming field experiments.

This need was bypassed by CSIRO, which instead generates the input by using genomic analysis and machine learning techniques. This approach was validated against National Variety Trials (NVT) data.

The version of the calculator, therefore, links genetics and NVT data to minimise the cost of keeping cultivars current. It is an approach that relies on the willingness of breeding companies to share genotypic data and NVT to collect detailed flowering information.

To ensure accuracy, the team has also derived the optimum flowering periods for wheat, barley and canola at more than 3000 sites. It is focusing the tool at 150 key regional sites with complete Bureau of Meteorology (BOM) weather records. This involved running the APSIM-NG model against BOM weather data spanning the 68-year period from 1957 to 2024.

Importantly, new modules within the APSIM suite of algorithms permitted CSIRO to apply frost and heat damage to crop growth simulations relating to a range of cultivars. This allows for more considered risk mitigation calculations.

Figure 1: Example of the results page produced by the Crop Flowering Calculator.

Source: Commonwealth Scientific and Industrial Research Organisation (CSIRO)

More information: Crop Flowering Calculator; Julianne Lilley, julianne.lilley@csiro.au; Jeremy Whish, jeremy.whish@csiro.au

Resources: GRDC Update Papers (2025): Crop Flowering Calculator – an online tool to assist sowing date decisions for wheat, barley and canola.