Research showed that sowing delays can cut potential yields on duplex soils by up to 14 kg per hectare per day in a short season environment, or 9 kg/ha/day in a long season environment.

Last season’s challenging conditions saw Western Australia’s canola crop shrink from a five year average of half a million hectares to 300,000ha, meaning many growers missed out on record prices. Dry conditions vindicated the decision not to sow, but in more moderate seasons, such as that expected this year, the choice may not be so clear.

With support from growers and the Federal Government through the Grains Research and Development Corporation (GRDC), CSIRO Plant Industry researcher, Imma Farre has run a century of weather statistics through state-of-the-art modelling software to help zero in on the ‘point of no financial return’ for canola crops.

"Canola is sensitive to water deficiencies during grain filling. So, when filling occurs later in the season, as rainfall subsides and soil moisture diminishes, yield suffers and returns can plummet or be lost altogether.

"Delaying sowing pushes grain filling further into spring and shortens the time from sowing to flowering, which can also reduce yield. In short season environments, with dry finishes, these effects are more profound," Dr Farre said.

According to Dr Farre’s simulation, the 100 year average yield fell from 1.6 t/ha when sown at April 1 to 0.6 t/ha at June 30 in Mullewa (short season) and from 2.6 t/ha to 1.9 t/ha at the same dates in Kojonup (long season).

The GRDC project involved collaboration from the Agricultural Production Systems Research Unit (Qld), which supplied the modelling system. Inputs for the system were derived from weather records at the two sites and were calibrated against trial results from Department of Agriculture projects.

"These systems will help predict likely yield under prevailing conditions, so growers can calculate whether to persist with a canola crop if the break is delayed," she said.