- Desired stubble characteristics differ depending on the crop species that is being sown. Each crop needs to be examined to see where it best fits in the rotation based on the stubble residue it is following.
- Just like any other area, the high rainfall zones needs to follow the same rules of thumb when sowing into standing stubble. The rules vary when comparing disc verse tine seeders and also the row spacing that they deal with.
- Livestock grazing stubble over the summer fallow pushes over standing residue. The same guidelines apply for livestock and seeder setup, as the trampling with produce similar results to decomposition of the stubble.
- For the increase efficacy of IBS and PSPE herbicides it is common to return after harvest and bail some of the excess residue.
As the saying goes “sowing starts at harvest”, however this comment is far more complex then it first appears. The desirable stubble characteristics for retaining stubble in south western Victoria vary greatly depending on the seeder type used, livestock, and the crop rotation of the farming system. It might sound simple to mimic a reputable farmers practice or to follow a guideline, but the fact of the matter is that every scenario needs minor tweaks to arrange a system to work for you.
Rotations and crop establishment in stubble:
Canola often proves problematic when establishing a crop in the autumn. Heavy slug burden the south west due to the heavy residue that it produces previous year. The most important factor when growing canola in a stubble retained system is rotations. Canola grown in high cereal stubble may experience establishment difficulties through shading and hair pinning on fallen stubble from decomposition or grazing. The same scenario is seen with lower cut and spread stubble as Bruce et al. (2006) found with young plants experiencing difficulties establishing under the conditions. The knitted residue creates a longer hypocotyls, reduced leaf number, and reduced biomass as it struggle to find sunlight. The best option is to grow canola following a pulse such as faba beans. The faba bean residue will provide a profitable grazing opportunity over the summer fallow, hence creating an unrestrictive seed bed for canola to emerge in the autumn. There is also anecdotal evidence that canola following beans in the rotation is the best option for the slug pressure associated with stubble retention. On the contrary, some farmers have the opinion that slug numbers increase following beans due less baiting in the bean phase.
Wheat & Barley
Wheat and barley although begin different species are relatively similar when establishing into stubble. They will establish well enough following most crops however it is often seen as unacceptable to sow a cereal into another cereal. This is due to difficulties two year forward when there can be two years of high stubble loads to deal with.
Bean and peas are a great option following a cereal. Bean will rapidly grow above the stubble height to find light and will make harvesting easier due to high podding. Peas will use the stubble as a “ladder” to climb to sunlight, however there might be harvesting complications from with the cereal stubble entangled.
Desired characteristics for sowing into:
Tine seeders can operate smoothly in a retained stubble system as long as they follow the key rules of thumb. The stubble should be cut at harvest to be equal to the row width of the seeder. The wider the row spacing the easier it will be for the seeder to track thought the stubble, with 300 mm (12 inch) being the consensus for optimal conditions.
Disc seeders can generally cope with taller stubble than tines. Depending on the make, disc seeder are designed to deal with standing stubble, hence difficulties may arise from grazed stubble or high levels of decomposition, resulting in hair pinning.
Grazing stubble is considered an essential component of most farming systems in south west Victoria. The residue of most crop species have the ability to fill the summer feed gap while also provides the farmer an alternative to spraying out summer weeds and volunteers. Even if not directly grazing the stubble, there is always the opportunity to bail the residue to be exported to dairy production further south. Although exporting some of the stubble is not directly classified as full retention, the end results may allow sowing into the paddock without difficultly.
Stubble has an influential role in the control of early season weeds using pre and post emergent herbicides. Chemical tie up and restricting the ability to get the product on the soil directly relates to the stubble characteristics created at harvest. When harvesting keep in mind that IBS and PSPE herbicides work most effectively when the majority of the stubble is standing and with the use of high water rates.
It also comes back to rotations. Active ingredients such as trifluralin have tendancy to bind to heavy cereals, so the use of trifluralin in canola would not be recommended Perhaps change this to something like: “More work needs to be conducted for a reliable canola establishment system for the High rainfall zone”a high yielding barley in the HRZ. Chemicals such as prosulfocarb and pyroxasulfone are much better choices for high stubble loads as they will wash off the stubble.
The stubble characteristics that we create play a significant role in success of the next year’s operations. It is not only the harvest process that dictates the stubble elements that the following crop has to deal with. The importance of grazing is an essential tool that HRZ that drastically alters the physical properties of the stubble. Growers will not give up summer grazing at the expense of stubble retention, however the two practices can work cohesively if the process is planned for. Crop rotations have to be thoroughly planned when deciding how species adapt to the pervious years residue. Herbicides follow similar guidelines, with some active constituents favouring particular conditions. How you choose to manage the characteristics of stubble is dependent upon a mixture of cropping situations, therefore it is essential to plan for the circumstance the individual circumstances of the enterprise.
S. E. Bruce, J. A. Kirkegaard, J. E. Pratley, G. N. Howe, Impacts of retained wheat stubble on canola in southern New South Wales
Birchip Cropping Group, Trifluralin Use in No-Till Farming Systems
New South Wales Department of Primary Industries, Using pre-emergent herbicides in conservation farming systems
Jack Desbiolles, AMRDC, University of South Australia, Disc seeders under the microscope
Dr. Nicole Dimos, Integrated Grazing And No-Till Cropping Systems
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’).