Retaining stubble – can it work in the western districts?
Traditionally a great percentage of grain growers in the western districts burn, bale or incorporate cereal
stubble residues from previous crops. There are many valid reasons to do this. For example;
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Reduces seeder blocking up with straw at sowing
Removes a source of disease carry over in cereal on cereal rotations
Improves herbicide contact on soil & weeds
Removes habitat for pests such as mice, slugs, earwigs, millipedes
Reduces frost risk
There are also many benefits to retaining stubble;
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Reduces water & wind erosion risk
Improves infiltration of rainfall into soil profile for moisture conservation
Increases moisture retention from early breaks to allow timely crop establishment
Decreases labour requirements for burning under stricter restrictions
Reduces fire risk and air pollution
GRDC, project number BWD00024, are funding research across the Southern Agro-ecological zone and as
part of this funding SFS in conjunction with Birchip Cropping Group, Irrigated Cropping Council and Vic NoTill are investigating how growers can retain stubble and maintain the current level of profitability.
SFS undertook a series of trials in 2014 as scoping studies into stubble retention systems that might work in
this region. The western districts have high cereal yield potentials, up to 10T/ha, and this leads to very high
stubble loads, greater than 10T/ha. We aimed firstly to determine if and how crops could be established in
this level of stubble. Then to investigate if and why yield penalties might be incurred as a result of stubble
retention.
Key learnings from 2014
1. Canola can be established successfully in retained stubble with accurate auto steer guidance
systems using knife point & press wheels.
Figure 1. Gason bar sowing incorporated and 30cm tall retained stubble. Thanks to Noel, Tim & Simon Barr for their cooperation. Also many thanks to Craig Drum, Gorst Rural, for his contributions.
2. Burning marginally increased yields in canola compared to stubble retention
3. Harvesting at low heights reduces harvest efficiency. 10% less efficient for every 10cm harvest
height is reduced.
4. A drop of 15cm in harvest height increases costs by $13/ha due to extra time & fuel.
5. 15cm harvest heights capture 65%, in Bolac wheat, and 94%, Gairdner barley, of weed seeds of ARG
2015 trials
After reviewing 2014 trials we set up a range of trials to see if we could increase profitability in a retained
stubble system to levels similar to a stubble burn system. To achieve this we needed to use farmer seeding
equipment that is specifically suited to stubble retention systems.
1. JD single disc opener sown into tall retained stubble, short retained stubble & tall stubble cut and
baled for straw. The trial replicated, randomised single block design and each treatment is split to
assess rolling post sowing as a slug control measure.
2. JD single disc opener v Morris tyne & press wheel trial. JD disc sowing into tall, 30cm retained
stubble, Morris Contour 1 tyne seeder into short, 15cm retained stubble. Replicated randomised
single block design with each treatment split for plus & minus rolling. Early slug bait strips 90
degrees to sowing direction. Temperature sensors in each treatment to determine if there is
variation.
3. Cover crop impacts on subsequent winter crop. Unreplicated on farm demo to investigate how a
summer cover crop effects soil moisture, nitrogen, crop dry matter, yield & grain quality.
4. Grass weed control efficacy of harvest weed seed capture techniques. 2 replicated trials comparing
30cm high stubble + burn, 15cm stubble + windrow burn and 15cm retained stubble + prototype
integrated weed seed mill.
5. Select herbicide efficacy at different timings of application in retained & burnt stubble. Select
applied at 0.5l/ha at 1.5 leaf, 3 leaf, early tillering & late tillering. Replicated small plot trial.
Figure 2: Windrow burn
Figure 3: Prototype weed mill
Figure 4: Blanket burn
Field days.
1. Seeder demonstration field site days Inverleigh, June and Bradvale, July.
2. DvT trial site field day – August
3. Weed seed capture trials field days - August
The project has thrown up some interesting challenges for retaining stubble in the western districts. Many
growers are already meeting these challenges head on and are leading the way in developing this sytem.
We look forward to assisting growers in any way we can. For information contact Paul Breust 0417 154945