- Break crops can be grown profitably in the southern HRZ retained stubble systems but more system specific research is needed to develop best management practice.
- Southern HRZ mixed farms have additional break crop opportunities and can use legume based pastures and crops to minimise disease pressure, reduce weed seed banks, build soil N levels, provide livestock fodder and reduce financial risk.
- Inter-row sowing using RTK guidance and seeding equipment designed for high stubble loads is critical to establishment in cereal stubble retained systems.
Break crops provide mixed farming systems in the southern Victorian high rainfall zone (HRZ) with additional opportunities via the use of legume and brassica based pastures and crops (summer or winter) to minimise disease pressure, reduce weed seed banks, build soil N levels, provide livestock fodder and reduce financial risk. All of these benefits underpin profitable and sustainable cropping and mixed farm systems.
The SFS high rainfall zone (HRZ) regions of south west Victoria and Tasmania have specific problems in relation to stubble retention and break crops, which in this region predominantly comprise canola, faba beans and legume-based pastures.
High cereal yield potentials significantly increase stubble loads which subsequently have a negative impact on crop establishment, disease levels, pest incidence, frost damage and herbicide efficacy. Traditionally, cereal stubbles have been burnt to reduce these risks.
SFS research: 2014
Effect of sowing methods on establishment of faba beans
The faba bean trial compared establishment using three established sowing methods. Establishment was not significantly different for any of the methods used (Table 1).
Table 1. Faba bean establishment (plants/m²) according to sowing method.
|Fabe bean sowing method||
Plant establishment (plants/m2)
|Spread onto surface and buried by incorporating stubble with a disc||
|Direct drilled into residue stubble 100mm deep to delay emergence||
|Direct drilled into residue stubble 25mm deep in late April||
Sowing and stubble management effect on canola performance
Two canola trials and one on-farm demonstration examined the impact of a range of sowing and stubble management methods on crop performance.
- Disc and tyne seeders in burnt, incorporated and retained stubble
- Early and late maturing varieties sown with disc and tyne seeders
- Canola establishment in burnt, incorporated, baled and retained stubble (sown with commercial equipment)
Effect of seeders type and stubble management on canola establishment
The results showed some yield differences according to sowing and stubble management practice (Figure 1). Access the full article here.
Effect of seeder type and variety maturity on canola establishment
Unfortunately the Clearfield technology selected for this trial was ineffective due to 95 per cent herbicide resistance to Intervix® and 20 per cent resistance to Select® in the ryegrass population. This was discovered after trial establishment. No comparisons could be made with the RT 525 direct drilled in May. The results from this trial can be accessed here.
Canola establishment and slug control in burnt, incorporated, baled and retained stubble
While this was a demonstration, the following comments were made:
- Using auto steer for inter-row sowing allowed successful establishment of canola in retained stubble.
- Slug control was the same for a range of control products.
- Slug control was improved in the burnt and incorporated treatments
For full discussion about this demonstration can be accessed here.
Key challenges for growing break crops in retained cereal stubble as identified by research and grower consultations are as follows:
- Canola – pest incidence particularly slugs, trash handling capacity of machinery, herbicide efficacy/weed control & nutritional requirements.
- Faba beans – disease management in a range of seasons, variety specific management packages, grower/agronomist confidence in management, stubble handling weed control options, price stability.
Break crop research, however, has also clearly identified several benefits to stubble retention systems. Opportunities exist that are specific to the southern HRZ in Victoria and Tasmania.
Cover cropping over summer, or spring sown cropping, has the potential to provide fodder for livestock, fix N, de-water soil profiles to alleviate winter water logging, act as subsoil ‘breakers’ to increase soil water holding capacity or maintain soil biology in a traditional fallow period. Developing systems to do this successfully has potential to increase overall profitability. This system also gives rise to several potential challenges such as green bridges for pest survival, profitability losses due to dry conditions and lower nitrogen and moisture availability for subsequent crops.
Annual ryegrass control in canola
Group A resistant annual ryegrass (ARG) is an increasing issue in stubble retained and cultivated farming systems. Clethodim (Select®) is popular choice of Group A herbicide to tackle ARG in canola crops and it is important that it be applied correctly to avoid resistance.
In 2015, a trial compared timing of clethodim application along with the use of both medium and medium angled nozzles to see which combination provided the best control of ARG.
At early growth stages of annual ryegrass, no significant difference was observed when using flat vs angled nozzles. Using angled nozzles provided greater control of ryegrass populations at later growth stages by increasing coverage, which shortened time taken to kill ryegrass.
The full report from this trial can be accessed here.
Break crops can be grown profitably in the southern HRZ in retained stubble systems but more system specific research is required to develop best management practice.
Mixed farming systems in the southern Victorian HRZ provide additional break crop opportunities via the use of legume based pastures and crops (summer or winter) to minimise disease pressure, reduce weed seed banks, build soil N levels, provide livestock fodder and reduce financial risk.
Inter-row sowing using RTK guidance systems and high load stubble handling seeding equipment will be critical to successful establishment in cereal stubble retention systems (e.g. coulters in front of tynes, disc seeders).
Research into profitability of existing and proposed break crop ‘systems’ is seen as critical to maintaining a sustainable cropping industry in the southern HRZ.
This research is being conducted by BCG as part of the GRDC Maintaining profitable farming systems with retained stubble initiative (project BWD00024 ‘Maintaining profitable farming systems with retained stubble in Victoria and Tasmania’).