What are the benefits of break crops in a stubble-retained system
In a stubble-retained farming system cereal stubble can allow the build-up of weeds and diseases. Break crops provide a unique opportunity to target pests, weeds and diseases and address nutrient deficiencies. But to get the most out of a break crop it is important to know what you are trying to achieve.
What are the key factors limiting cereal crop production?
Look at your particular situation to identify the key factors limiting cereal productivity (Table 1):
- If grass weeds are the main issue choose a competitive break crop with suitable grass‐selective herbicide options
- If nitrogen fixation is needed consider a legume
- For disease issues grow a grass-free break crop.
Table 1. The key factors limiting cereal productivity will influence the choice of break crop.
Key limiting factor
Break crop options
Canola, hay oats, legume-dominant pasture, fallow and pulse crops
Canola, hay oats, grass-free pasture, fallow, vetch and pulse crops depending on the specific disease pressure
Low soil nitrogen
Legume-dominant pasture, vetch and pulse crops
Poor soil moisture
Fallow or a spray-topped legume
Marketing and prices, soil type, machinery and crop use (grain, grazing or hay) will also be important in determining the break crop options in the rotation.
While break crops can be perceived as higher risk in medium to low rainfall areas the Eyre Peninsula Agricultural Research Foundation Inc (EPARF) has demonstrated that a one or two year break can be more profitable than maintaining a continuous wheat cropping sequence.
What are the benefits of break crops?
Trials have shown that break crop profitability is largely determined by the benefit in the productivity of cereals grown after the break. The benefits of improved weed control can make break crops very profitable compared with continuing with high grass weed populations in cereals.
Managing grass weeds
Break crops provide more options for diversity in herbicide and non-herbicide weed control. For instance, by growing a broadleaf crop provides the flexibility to use chemicals grass-selective herbicides that are not suitable for use in cereal crops.
When weed control is the major issue, trials have shown the wheat-yield benefits of a break crop are greater from a two-year break compared to a one-year break.
Grass and cereal free break crops of medic, canola or pulses will not only reduce cereal disease inoculum for soil-borne cereal diseases such as take‐all, CCN and rhizoctonia, but also fungal diseases carried over by spores on cereal stubble such as yellow leaf spot and white grain.
A single, non-cereal crop free from grassy weeds can dramatically reduce rhizoctonia inoculum levels to a lower disease-risk category compared to a cereal crop, however these only last for one cropping season.
A legume break crop will improve the nitrogen supply to the following cereal crop. On average, 20 kilograms of nitrogen per hectare is fixed for every tonne of legume shoot dry matter produced.
Sowing break crops into retained cereal stubble provides early protection of both small plants and soils from wind damage. Cereal stubble provides a trellis to enable pulse crops to grow taller and more erect plants, which can help with harvestability.
Including break crops within crop rotations may increase pest levels. Chemical control options may be necessary to control the pests in break crops depending on seasonal timing, pest density and other beneficial insects in the system.
Farming systems groups
- BCG Break crops in retained stubble systems in the Wimmera and Mallee
- CWFS The benefit of break crops in retained stubble systems in Central West NSW (PDF 517kb)
- EPARF Break crops in low rainfall farming systems (PDF 281kb)
- EPARF Economic and risk analysis of break crops compared to continuous wheat farming systems (PDF 1.8Mb)
- Farmlink Break crops in stubble (PDF 1.0Mb) and resources (PDF 844kb)
- MFMG Role of Break Crops in Retained Stubble Systems (PDF 833kb)
- MSF Ten things to consider when planning a break crop
- SFS Break crops in retained stubble systems in south west Victoria
- UNFS Break crop options (PDF 1.2Mb)
- GroundCoverTM Supplement (2018) Reduce risk with a two-year break from cereals
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