Australia - New winter wheats add agility in low-rainfall regions

Date:02-23-2023

Research into long-season wheats for the lower-rainfall areas of central and southern New South Wales is expected to significantly increase the management agility needed to accommodate changing seasonal conditions.

The research and trials from 2018–20 confirmed the risk-management value, and potential production gains, from varieties able to be sown early and with vernalisation traits that delay flowering until after the frost risk period.

The objective for the project, ‘Improving grower profits through longer-season wheat crops’, was to demonstrate the performance of different varieties to counter the declining frequency of the traditional autumn break. It was also in recognition of the opportunities arising from related agronomic advances and practice changes.

Central West Farming Systems (CWFS) chief executive officer Diana Fear explains that the GRDC-supported research exploring the role and performance of long-season wheats was needed because growers in central and southern NSW are interested in sowing wheat earlier than the traditional May sowing window, but the data to guide this had not been captured in standard National Variety Trials work.

As well as the need to counter diminishing autumn breaks, Ms Fear says grower interest has also been driven by advances in summer fallow management leading to improved soil water storage, better understanding of pre-emergent herbicides for early sowing, improved no-till seeding technology (for example, more-accurate seed placement for reaching moisture) and increased farm sizes requiring more time for sowing.

″So this project was developed to increase farmer and adviser confidence in taking greater advantage of these advances by maximising varietal choice and early sowing window options,″ she says.

Phenology changes required

To ensure crops flower in the preferred window to minimise frost risk, earlier sowing requires a change in phenology and hence in variety. Most Australian breeding programs have increased their emphasis on developing varieties with a vernalisation (cold) and/or photoperiod (light) response.

It is these responses that can hold a variety in the vegetative state until it has either met its vernalisation and/or photoperiod requirements before moving into reproductive stages. The outcome of this trait development is a variety that can be sown earlier, with delayed flowering to minimise the exposure to frost.

While past trials have shown that traditional high-rainfall winter wheats with these properties, such as EGA Wedgetail, can perform well in lower-rainfall areas when grown on long fallow, it has been found that new, quicker-developing winter varieties are better-suited to drier conditions. The first of these new varieties was Longsword, released by Australian Grain Technologies in 2017.

To put all of these to the test and accumulate the data that growers and agronomists need, the CWFS project tested multiple times of sowing. These were late March/early April, late April and mid-late May.

The varieties trialled were selected to include a mix of true winter wheat such as EGA Wedgetail, new fast winter wheat such as Longsword and short-season wheat such as Condo and Vixen. The trials were undertaken at Condobolin and Rankins Springs in 2018, Rankins Springs in 2019 and Lake Cargelligo in 2020.

The trials over three starkly contrasting seasons allowed the collation of data showing longer-season wheat varieties can fit the needs of growers in this region and can be sown early if suitable environmental conditions, such as sufficient soil moisture, are present.

These varieties also create more options for growers, who have the opportunity to sow wheat to coincide with earlier rain events or who need to start earlier due to a large cropping program.

Some specific findings included:

• The premise held by some to ‘sow early sow light’ might not always be the best option. Sowing rates of 15 kilograms per hectare might result in lower yields when sowing longer-season wheat varieties within their recommended windows, compared to sowing rates of 30 to 45kg/ha.

• The importance of sowing varieties in the right window was clearly demonstrated. The lowest yields were recorded when either short or long-season varieties were sown well outside the recommended window, for example Accroc sown in May.

For example, at Rankins Springs in 2019 it was clearly shown that sowing too early when there is inadequate moisture and soil temperatures are too warm can compromise germination.

Detailed data for all of the varieties trialled at all of the locations is available from CWFS.

Broadly speaking, key measures such as water use efficiency and yield mirrored in-season rainfall, which varied over the three years and sites from 98.5 millimetres to 282mm.

Income and profitability was, as always, dictated by the prices a grower secured. In other words, the key benefit of the longer-season varieties is crop management flexibility that enables growers to make the most of each season’s circumstances.

Overall, the trials showed longer-season wheat varieties appear to be a good fit in Central West NSW when the autumn break occurs before the traditional Anzac Day sowing.

These varieties could allow a grower to spread the sowing window over a longer period and reduce the pressure of trying to keep within the late April to mid-May sowing window for main-season wheats.

Having the option to graze these longer-season wheat varieties also integrates well into the mixed-farming businesses typical of Central West NSW.

While these wheat varieties might not fit into a cropping program every year, increased summer storms and earlier autumn breaks could see them become more prevalent.