As many growers have experienced, higher frost frequency and severity in spring across the Western Australian grainbelt is increasing the risk of damage to maturing grain crops.
To lessen the financial impact, research and experience are showing that a fast assessment of crops after frost can help to optimise returns from affected areas as well as guide future planning of crop rotations, sowing time and variety choices.GRDC-funded research, led by CSIRO researcher Dr Steven Crimp, says the data confirms a steady shift since the 1960s to higher frost incidence and severity in August and September in WA.
This is linked to a long-term southerly change in the position and intensification of high-pressure systems.
As a result, ‘frost window’ start and end dates have been pushed back by between one and four weeks in many WA cropping areas.
Dr Crimp says consecutive frost events – when minimum temperatures are at or below 2ºC – are also now more likely to occur in August and September in southern areas of the state. Further, average duration of such consecutive events has stretched out to three days in a row.
GRDC Western Panel chair Peter Roberts (left) and
DAFWA research officer Ben Biddulph inspect crops
for frost damage in 2012.
“At the same time, the climate has been warming and this has tended to shorten the growing season and bring crop flowering back into periods of higher risk,” Dr Crimp says.
“This means crop type, time of sowing and variety selection are vital decisions to help growers manage exposure to frost risk each season.”
Assessing frost damage
Losses in grain yield and quality from frost damage primarily occur between stem elongation and late grain filling.
After a suspected frost, the Department of Agriculture and Food, WA (DAFWA), recommends growers check cereal crops for signs of damage to stems, florets and flowers (anthers) and collect a sample of heads to estimate the percentage of yield loss.
Symptoms of frost damage in wheat include:
- florets – bleached, shrivelled or dwarfed;
- stems – pale green to white rings on peduncle (where stem attaches to the head), crimped, cracked and/or blistered peduncle or blisters or cracks on leaf sheaths surrounding the stem and nodes;
- flowers – when husk is peeled back, anthers are white or brownish and can be banana shaped;
- developing grain – white and turning brown, dimpled/crimped, dry and spongy when squeezed; and
- mature grain – regular creases along the axis, sometimes a blue/grey appearance and usually dented or scalloped out on the dorsal or back.
Options for frost-affected crops
ConsultAg consultant Garren Knell says harvesting is usually the most profitable option – unless it is a very weedy paddock – as any grain captured will provide a return.
He estimates 150 to 200 kilograms per hectare of grain should cover harvesting costs.
Fast assessment of frost damage is most critical if crops are going to be cut for hay to maximise recovery and quality.
Mr Knell says in WA is it vital to investigate hay demand, marketing opportunities and likely costs (including machinery and labour) versus returns.
“Generally, cutting for hay is only economic if growers have their own machinery and some marketing experience,” he says.
Other options for frost-affected crops include silage, cutting and swathing, desiccation using herbicides and green manuring.
Dr Steven Crimp,
02 6242 1649, email@example.com;
08 9881 5551, firstname.lastname@example.org
A fact sheet on Managing the Risk of Frost is available at: www.grdc.com.au/GRDC-FS-FrostRisk
GRDC Cereals – Frost Identification: The Back Pocket Guide: www.grdc.com.au/GRDC-BPG-FrostCereals
GRDC Pulse and Canola – Frost Identification: The Back Pocket Guide: www.grdc.com.au/GRDC-BPG-FrostPulses
GRDC Managing Frost Risk – A Guide for Southern Australian Grains: www.grdc.com.au/GRDC-Booklet-ManagingFrostRisk
Bureau of Meteorology – frost forecasts and temperature outlooks: www.bom.gov.au
DAFWA Flower Power: http://grains.agric.wa.gov.au/flower-power
DAFWA statistical seasonal forecast service: www.agric.wa.gov.au/forecast
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