Optimum Flowering Dates of Wheat in SW Victoria
With late Spring frosts continuing to cause big headaches for growers in South West Victoria, it is a harsh reminder of the importance of wheat varietal selection and key sowing dates to achieve optimum flowering windows.
By getting back to some basic agronomy we can often have a large impact on profit margins. Considering that there are no added costs for choosing the right sowing dates, there is potentially excellent financial returns from just spending a little more time getting this right specifically for your growing environment.
There are other factors to consider when you look at how to achieve optimum yields for your variety. Frost, heat and water are three major factors which should be considered when determining sowing dates and varietal choice. For example, if flowering occurs too early, there is an increased risk of frost and if flowering is too late then there is increased risk of moisture stress leading to poor grain fill. Therefore, it is important to find a balance.
Traditionally in the western districts of Victoria a lot of wheat has been sown from early May through to the middle of June. Longer season winter type wheats will however allow for earlier planting dates, which can significantly improve yield and frost risk.
As can be seen in figure 1, at Lake Bolac the highest wheat yield occurred when the flowering date was around the 20th of October. In order to achieve this flowering date around Lake Bolac with a slow maturing winter type we would need to sow around the 15th of April or earlier. This will vary slightly year to year due to season variability but the crop phenology and days to flowering for each variety will remain constant.
Winter wheat: Winter types have a strong vernalisation requirement meaning they must experience a certain period of low temperature before they can begin their reproductive phase. This allows popular winter varieties like Accroc, Revenue & Adagio to be planted much earlier than spring types. There is still some degree of risk to the grower however as there will need to be enough moisture to germinate and sustain the crop until winter kicks in. Winter wheats have a longer season length to accumulate dry matter, grow root mass and ultimately set a higher number of grains/m2 and therefore better yields. Studies conducted by James Hunt (Research scientist CSIRO) have shown that including a slow maturing variety (early April sowing) in your program you will increase your average whole farm wheat yield whilst reducing frost risk. These varieties are a good option to put into frost prone areas such as paddocks with low elevation zones.
Spring wheat: Spring types have a weak vernalisation sensitivity and while exposure to cold temperatures will speed up their development rate, they will eventually flower regardless of whether they are exposed to cold temperatures or not. They have a stronger response to photoperiod (day length). Planting these cultivars too early will cause them to go into the reproductive phase earlier then is optimum. This shortens the vegetative phase which ultimately reduces potential yield as well as causing flowering to occur during a higher frost risk period.
Sowing windows to achieve optimum yield potential in south west Vic
Winter wheat (Revenue, Accroc, DS Bennett, Adagio) - Early March to mid-April.
Slow maturing spring wheat (Beaufort, Bolac, Phantom, Trojan) – Late April to early May
Mid-fast spring wheat (Derrimut, Beckom) – Early to mid-May
Obviously, there will be exceptions to some of these optimum planting windows as there is such a large variation of influencing factors across the south west. These sowing windows give a general guide as to when we should be looking to get our seed in the ground.
With drier finishes and historically a longer frost period around flowering, sowing dates have become a hot topic. This is something that you should discuss in depth with your agronomist to work out what sowing dates and cultivars best suit your area and business.
Article produced by - Lachlan Bullen, Western AG Ballarat