- In recent years there has been a tendency to move some earlier maturing varieties into earlier sowing times, increasing frost risk at flowering.
- It is critical to match variety and sowing date to ensure that the flowering period is late enough to avoid damage by frosts in early spring.
- Understanding how each variety responds to the environment will help target varieties to their best sowing time.
- Northern wheat growers are being warned against an early plant on particular varieties or risk devastating crop damage from frost.
Frost damage can strip tens of millions of dollars in yield from northern region crops, but the risk can be managed by matching variety selection and sowing times.
Research Agronomist with Howqua Consulting, Dr Peter Martin, told growers and agronomists attending the recent Grains Research and Development Corporation (GRDC) Northern Grains Research Updates that there had been a tendency to move some earlier maturing varieties into earlier sowing times in recent years, increasing frost risk at flowering.
“It is critical to match variety and sowing date so that flowering occurs early enough to allow a long grain filling period before the high evaporative demands and soil water deficit of early summer but additionally, the flowering period must also be late enough to avoid damage by frosts in early spring,” Dr Martin said.
“Because the timing of the autumn break can range from April until June, farmers in NSW have the choice of a range of varieties with differing maturities.
“Understanding how each variety responds to the environment will help target varieties to their best sowing time.”
According to Dr Martin, the relative maturity of varieties is controlled by responses to photoperiod, vernalisation and what researchers refer to as “earliness per se”.
Photoperiod response is a plant’s response to day length (the number of hours of daylight); vernalisation is a plant’s response to cold temperature (in wheat, vernalisation accumulates most rapidly between about 3°C and 10°C); while earliness per se, also called propensity to flower, is the period from floral initiation until flowering independent of photoperiod and vernalisation.
Based on the response of varieties to vernalisation and photoperiod, wheats are categorised as either a winter, facultative spring or spring wheat, and within each category there is a range in flowering dates between varieties.
“When sown in a period of the year with long days and warm temperatures, when vernalisation is not being satisfied, spring varieties and some facultative varieties flower very early. Winter wheats, however, will not iniate flowering until their vernalisation requirement is met,” Dr Martin said.
“As sowing is progressively delayed into the cooler period of the year, varieties requiring vernalisation, that is winter varieties as well as the facultative and spring varieties, flower much more closely together.
“For example when sown on 10/3/2006 Janz flowered 115 days before EGA Wedgetail, but when sown on 10/5/2006 Janz flowered 6 days before EGA Wedgetail.
“Understanding how and why varieties fall into certain classifications and then matching sowing date accordingly can have a significant impact on frost risk management and therefore crop production and profitability.”
The GRDC is making a considerable investment to reduce the frost susceptibility of Australian wheat and barley crops through a combination of genetics and crop management research. A Ground Cover Supplement on frost has recently been released detailing the scope of the GRDC frost investment across each of its cropping zones. To download a copy of the Ground Cover Supplement, visit www.grdc.com.au/GCS109
Photo Caption: Dr Peter Martin, Research Agronomist, Howqua Consulting, Yeronga, QLD
Download the audio file from the downloads box below to listen to Dr Peter Martin discussing the management of frost risk through matching variety and sowing date.
Peter Martin, Howqua Consulting, Wagga Wagga
Sarah Jeffrey, Senior Consultant Cox Inall Communications
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