Western Australia
March 30, 2015
Dry sowing wheat in April can help to optimise farm yields, increase farm area sown and reduce the risks of later season heat shocks across much of Western Australia without significantly affecting frost risk.
Less is known about the effects of dry sowing on wheat yields when there are early season soil water deficits.
But there is growing anecdotal evidence that wheat plants can recover well from moisture stress in May and June in some areas/seasons.
That is the advice from CSIRO research scientist Dr Andrew Fletcher, who is undertaking GRDC-funded research using the Agricultural Production Systems Simulator (APSIM) model (which also underpins Yield Prophet®) to simulate whole farm responses to dry sowing.
Using data from 54 seasons at seven sites across the WA grainbelt, APSIM modelling found farm-level yield benefits of up to 35 per cent (or 0.5-1.2t/ha) from dry seeding wheat before autumn rains, compared to wet sowing wheat after the season break.
The modelling found the biggest yield benefits of dry sowing wheat came from:
- Heavy soils
- Drier locations
- Northern areas
- Bigger cropping programs relative to sowing capacity
- Years with low-medium yield potential.
The average yield difference between a completely dry-sown farm and a farm with no dry seeding ranged from a 0.5t/ha increase to a 0.2t/ha loss.
The bulk of the yield increase occurred when 33 per cent of the farm was dry sown and this was driven by both increased crop yield and increased cropped area (from increased area sown in the sowing window).
Dr Fletcher presented the dry sowing project data to a GRDC Geraldton Port Zone Regional Cropping Solutions Network (RCSN) group meeting and the Liebe Group Regional Crop Update this month, as this is a big priority identified by both groups.
When to start sowing
Dr Fletcher’s APSIM simulations are based on a wheat sowing program starting on April 20.
He says individual growers will start sowing wheat by determining the number of sowing days available to them based on their target end date of sowing – driven by crop flowering windows.
Planfarm Benchmark data from 2011-13 suggests that of those growers who are dry sowing, the preference is to sow canola and lupins dry – rather than wheat.
But the CSIRO research indicates wheat plantings can be bought forward by about a week in many parts of the state by dry sowing.
Yield data
A CSIRO strip trial carried out with the WA No Tillage Farmers Association (WANTFA) at Cunderdin in 2014 showed Mace
wheat yield was maintained when the crop was sown between April 29 and early June.
The trial involved sowing Mace and canola (IH30RR) every three days from April 29.
For sowing dates after the first week of June, Mace yield fell by 56kg/ha/day.
The trials were unreplicated, but will be repeated in 2015 and potentially be expanded to other sites in WA.
Dr Fletcher says the trial found that with canola, the longer the sowing date was delayed, the more yield was lost.
He says the trial found canola yield fell by 16kg/ha/day for every sowing date after April 29.
Less risk of end-of-season heat stress/shock
The APSIM modelling conducted by CSIRO showed a marked decline in the number of heat stress events that occurred during grain fill for dry sown wheat programs compared to later, wet sown crops. This led to higher yields and better grain quality.
Dr Fletcher found the risk of heat shock fell from 25 to 14 per cent when wheat was sown dry, mainly due to a tighter and earlier flowering window compared to wet sowing of wheat.
He recommends using a range of wheat varieties for dry sowing to spread the flowering window, rather than sowing only one variety.
Increased risk of frost at flowering
The APSIM modelling found dry seeding led to only a slight increase (up to 4 per cent) in the area of wheat frosted during flowering, compared to late wet sowing – even in high frost risk areas.
This was offset by higher yields across the whole crop program from early sowing.
The risk of frost during flowering was determined by location and - at the farm level - the decision to dry sow or not had a negligible impact.
Dr Fletcher says, based on this APSIM data, it appears the risks of frost are outweighed by the potentially higher returns of beating the risks of heat shocks in a dry sown crop program.
Early moisture stress
When dry sowing wheat, there is an increased risk of exposure to moisture stress in May and June.
Dr Fletcher says CSIRO and DAFWA researchers are working on quantifying how this might compromise yields.
He says GRDC-funded trials will be set up at Merredin this year using rain shelters and controlled moisture conditions.
Time-based risks
WANTFA advises there are potential problems arising from all time-based risks - including weeds, pests and diseases - when dry sowing wheat crops.
Planning is needed to determine the impact of these risks, while playing the season and optimising the attributes of individual properties and cropping practices.
To dry sow wheat successfully, recommendations include:
- Selecting paddocks with low weed, pest and disease burdens
- Seeding into a wheat stubble load of at least 1.5t/ha
- Seeding into completely dry soil.
Growers surveyed by WANTFA in 2011 and 2012 indicated a low weed seed bank was the most important management strategy when dry sowing wheat, followed by stubble retention and use of no-tillage farming systems.
There is an increased reliance on pre-emergent herbicides when dry sowing wheat because there is no opportunity for a knock-down and this has potential for the evolution of resistance.
WANTFA says crop residue retention after harvest is also integral to success when dry sowing with no-tillage fallow systems because of the beneficial effects on soil water availability for crops.
Useful resources
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CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USE
Any research with unregistered pesticides or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the authors’ organisations. All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region.
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