While stubble retention has provided a multitude of benefits to Wimmera growers, heavy cereal stubble loads in recent seasons have created new challenges, particularly for canola establishment.

These kinds of trends are captured by Agriculture Victoria and the Wimmera Catchment Management Authority, which conduct land management surveys across the Wimmera twice a year. The data revealed that 35 per cent of canola is grown on cereal stubble. For half of these paddocks, the cereal stubble is actively managed through burning, cultivation, windrow burning or some other form of disturbance prior to sowing canola.

Previous research and grower experience indicate that high stubble loads can affect canola establishment due to factors including:

• the impediment to sowing operations;
• inaccurate seed depth placement;
• shadowing of emerging seedlings and loss of early growth and vigour;
• chemical tie-up; and
• stubble-based harbouring of pests (such as slugs).

In response, GRDC has invested in a new project to help growers mitigate risks to canola establishment following high-production years.

The project is designed to deliver a two-year field trial that will demonstrate the effects of a variety of stubble management and sowing systems on canola establishment. It is led by Agriculture Victoria, in collaboration with the Wimmera Catchment Management Authority, Arapiles South Ag Group and the Wimmera Farming Network.

Trial design

The researchers sought input from Arapiles South Ag Group members when deciding on the trial design. They provided local expertise to guide the selection of stubble and sowing systems, as well as general agronomic management.

The team has subsequently established a trial at Douglas in the southern Wimmera. Canola represents about one-quarter of the cropped area in the district, where there is a high potential for heavy cereal stubble loads.

The trial will allow canola performance to be compared against different stubble treatments, including:

• varied height of cutting;
• stubble mulching;
• baling of stubble for straw;
• burning; and
• added straw to simulate an even higher-yielding environment.

Sowing treatments will include a comparison of tyned versus disc machines and the inclusion of row cleaners.

The project also involves a survey of canola establishment in paddocks across the Wimmera relative to stubble management and sowing system in order to benchmark current practices.

A key focus of the project is communication and extension, with findings to be promoted through GRDC and Agriculture Victoria networks. This includes local workshops, with the first event, focusing on slug management and its interaction with stubble, held in February. Future events will include a post-emergence field day to demonstrate the performance of the various systems.

A decision-making guide will also be developed focusing on rapid assessment of stubble load, stubble condition and potential management options.

More information: Ashley Wallace, ashley.wallace@agriculture.vic.gov.au