Getting a farm cropping program sown on time, enabling all flowering in the window that will maximise yield and reduce frost risk, is difficult in WA’s Mediterranean climate and with increasingly variable rainfall.
No-till and – increasingly – dry sowing tactics have gone a long way towards achieving this goal, but the Grains Research and Development Corporation (GRDC) is now funding researchers to find ways to push the boundaries even further.
The specific aim is to help WA growers more efficiently use March and April rain events when they occur to maximise wheat production.
This will be made possible through performance analysis of existing and new wheat varieties when planted to take advantage early sowing opportunities and developing more locally-adapted mid and longer season varieties for early sowing.
These innovations exploit the use of modern no-till systems, improved weed seed control, summer fallow management and cost effective insecticides and fungicides.
In the past few decades, wheat breeding has focused on short and mid maturing varieties suited to sowing in May-June (or April if dry sown).
Responding to earlier planting opportunities requires varieties that are not yet widely grown in WA and are much slower to mature to ensure they still flower in the optimum window.
This can be achieved because they have a strong requirement for vernalisation/cold (called winter wheats) – and remain vegetative until flowering is induced by winter cold – and/or a requirement for photoperiod/day length (long maturing spring wheats).
But GRDC-funded research in south-eastern Australia has demonstrated that longer maturing varieties sown early can yield more than mid-short varieties sown later when they flower at the same time.
This is because early sowing increases rooting depth and water use, reduces evaporation and improves transpiration efficiency.
CSIRO Agriculture’s Dr James Hunt says APSIM modeling indicates that – even with WA’s Mediterranean climate – sowing opportunities in this State occur often enough so that adoption of longer maturing varieties for earlier planting has potential to increase whole farm wheat yields, particularly in medium and high rainfall zones.
He says this is due to the yield advantage of long maturing varieties and the ability to plant a greater area of short maturing varieties on time when some of the wheat progam is sown early.
As part of a GRDC-funded national CSIRO project investigating early sowing of wheat, Dr Hunt and several WA grower groups set up a series of trials in 2014 at Doodlakine, Cunderdin, Wickepin and Kojonup.
These trials will be repeated this year and the aim is to assess whether long maturing varieties sown early in the year can yield as well as – or better than – short maturing varieties (such as Mace) when these are sown in their optimal window in WA environments.
Results from the first year of the project indicated that across the four WA sites, the best currently available longer and mid maturing varieties – when sown early in mid-April – produced similar yields as the common mid-short maturing varieties used in WA – when sown later in or after May/June – when they flowered at the same time.
Dr Hunt says this potentially provides WA growers with some alternative variety options if there are sowing opportunities from March through to late April. This is when the commonly used mid-maturing varieties in WA (eg. Yitpi and Magenta) are suitable.
Across all of the 2014 WA trial sites, results also indicated that the short maturing winter wheat, Whistler, appeared to adapt well to local conditions when sown early.
When planted in mid-April, it yielded as well as – or better than – Mace planted in late May at three out of four trial sites.
Dr Hunt says using a variety such as Whistler to bring sowing dates forward would allow growers to take advantage of early planting opportunities across a broad window from late March to early May and its stable flowering date would reduce frost risk.
But he says use of this variety – and some other longer maturing lines – would be limited by inferior quality classification and low seed availability.
Dr Hunt says this reinforces the value of continued research to find modern, high quality winter wheat varieties adapted to WA conditions that can help increase production and reduce frost risk.
To this end, four near isogenic lines (NILs), developed with GRDC funding by Ben Trevaskis at CSIRO, were included in the CSIRO WA trials and yield data from these lines is shown in Figure 1.
These NILs are 97 per cent genetically identical but differ in their genes controlling maturity. Their use will help to identify genotypes that are best suited to early sowing in WA.
Dr Hunt says the NILs confirmed the results of the commercial varieties at the trial sites - that the short maturing winter line (similar to Whistler) achieved the highest yields from the mid-April sowing date.
He says this was 17 per cent higher than the short spring line (similar to Mace) sown in late May and represents the level of potential yield gain if adapted winter wheats able to be sown early were available to WA growers.
Dr Hunt will present his WA trial site findings at the WA Agribusiness Crop Updates, to be held on February 24-25 at Crown Perth. Registrations and the full program for the Updates are available at: http://www.giwa.org.au/2015-crop-updates
Figure 1. Mean yield from Doodlakine, Cunderdin, Wickepin and Kojonup for the four different near isogenic lines (NILs) expressed relative to the fast maturing spring wheat sown in late May.
Dr Mike Ewing, GRDC western panel
Dr James Hunt, CSIRO
02 6246 5066
Melissa Williams, Cox Inall Communications
0428 884 414
GRDC Project Code