- 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 growers with an opportunity to minimise disease risks, implement a range of integrated weed management (IWM) options, fix nitrogen (N) and provide fodder for livestock. All of these benefits under pin 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
Three trials and one on-farm demonstration were conducted in 2014 looking at the impact of specific stubble management practices on canola and faba beans.
The faba bean trial compared establishment using three established sowing methods, and yielded the following results:
- Spread onto surface and buried by incorporating stubble with a disc: 22.33 plants/m2
- Direct drilled into residue stubble 100mm deep to delay emergence: 20.00 plants/m2
- Direct drilled into residue stubble 25mm deep in late April: 19.67 plants/m2
Establishment was not significantly different for any of the methods used.
Two canola trials and one on-farm demonstration examined the impact of a range of sowing and stubble management methods on crop performance, including:
- 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)
The results showed some yield differences according to sowing and stubble management practice.
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.
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 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 SFS 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’).