Guidelines for growers
- Harvest height is predetermined by crop type and height. The stubble height remaining after harvest can be managed in the future if required.
- On irrigated paddocks, many cereal stubbles are too thick for even the best seeders. Consequently stubbles must be managed over summer with livestock or machinery.
Stubble cover is valued for its ability to protect the soil surface from raindrop damage (resulting in hard setting) and water and wind erosion.
To a lesser extent, stubble is used for moisture conservation and reducing evaporative losses after irrigation. This benefit is particularly valuable in spring where stubble cover extends the period between pre-irrigation and the first post-emergent irrigation, allowing the crop to become well established and more tolerant of the waterlogging that can occur with later irrigations.
Unlike dryland situations where crop growth can be highly variable, stubble loads under irrigation are more consistent and therefore management decisions are relatively straight forward – what worked last season is probably going to work again next time. This also makes the decision to invest in seeding or stubble management machinery less risky, as it is likely to be needed each season.
Desired stubble characteristics for an irrigated retained-stubble system
The general principles of stubble characteristics adopted by dryland farmers hold true for irrigation, given that irrigators simply have to deal with more stubble.
The following crop is going to play a large part in how the stubble should be managed at, or after, harvest. Therefore, planning for next season well in advance is useful.
Many irrigators are situated close to animal industries that may purchase baled stubble. Having long stubble or windrows post-harvest enables the stubble to be directly baled, or mown and baled, removing most of the problem.
Sowing crop varieties with early maturity and short height can make stubble management easier, particularly if the winter crop is to be followed with a summer crop almost immediately.
Faba bean stubbles are a valuable product, both as a source of N for future crops and as livestock feed. Faba bean crops are generally cut low (to harvest any low pods produced) and then grazed with livestock. Depending on the intensity of grazing, mulching may be necessary to enable sowing.
Most canola stubbles on irrigation are generally thin and do not present an issue for the next winter crop. Some canola stubble management may have to take place in a double cropping situation such as baling the chaff rows to allow sowing.
Initial trials on Plant Growth Regulators (PGRs) have been unreliable in ensuring decreased crop height, with examples of initial height suppression evaporate by harvest.
Current cereal practice is to harvest the crop at a height for maximum speed and harvest efficiency and then worry about the stubble post-harvest.
This guideline was produced by ICC 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’).