Managing frost risk

Page last updated: Wednesday, 1 September 2021 - 3:25pm

Please note: This content may be out of date and is currently under review.

Time of sowing - manipulating flowering times

When wheat is sown in frost risk areas, a good tactic is to ensure the flowering window of the cropping program is widely spread.

This can be done by:

  • using more than one variety and manipulating sowing date
  • selecting varieties with difference phenology drivers so the crop flowers over a wide window throughout the optimal flowering window.

It should be noted that flowering later than the frost risk will result in lower yields in seasons with hot, dry finishes due to heat and moisture stress and is generally not a sound long term management strategy as the loss of yield potential with late sowing is often greater than loss due to frost.

Sowing time is a major determinant of crop yield because in partnership with the variety chosen, it determines the timing of key growth and development stages such as canopy closure, flowering and the subsequently the environmental stresses at these key stages. Crop yields are particularly sensitive to stresses in the period from about 3-4 weeks prior to flowering through to the start of grain fill as this is when grain number is determined and stem reserves are accumulated.

Staging sowing dates over a 3-6 week period is recommended. If sowing just one variety, this would provide a wide flowering window. If sowing more than one variety: sow winter wheat first; then a long season spring wheat or a day length sensitive wheat; then an early maturing wheat last. This equates to the whole wheat program flowering over a wider period, potentially exposing it to more frost risk but maximising the yield potential in the absence of frost. Even with this strategy in place it is possible to have more than one frost event that causes damage. Flowering over a wide window will probably mean that some crop will be frosted but the aim is to reduce extensive loss.

Sowing time remains a major driver of yield in all crops with the primary objective to achieve a balance between crops flowering after the risk of frost has passed but before the onset of heat stress. Crops sown early within the sowing window will establish faster and have the potential to maximise water use efficiency. However early sowing increases the chance of frost damage and can limit weed control options and increase disease pressure. The loss of yield from sowing late to avoid frost risk is often outweighed by the gains from sowing on time to reduce heat and moisture stress in spring.

To minimise frost risk there needs to be a mix of:

  • sowing dates
  • crop types
  • maturity types.

In years of severe frost, regardless of which strategy is adopted it may be difficult to prevent damage. Flower Power, an online tool, will help inform time of sowing decisions further as it predicts wheat flowering times of up to three different varieties at the same time gives the subsequent risk of frost or heat stress for these scenarios. Ben Biddulph (DPIRD) and Garren Knell (ConsultAg) explain the risks and how to minimise the downside of a frost event without delaying planting in this Weedsmart webinar.

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