How can I reduce high stubble loads after harvest

While optimal outcomes can often be obtained with standing stubble, it is sometimes necessary to reduce stubble loading.

The benefits of stubble retention are achieved at stubble loads between two to three tonnes per hectare (Figure 1). Cereal stubble loads greater than 2-3t/ha post-sowing are unlikely to provide any additional yield benefits and in favourable seasons can reduce yield.

Photos of wheat and barley stubble loads at different row spacings

Figure 1. The optimal stubble loads are between two to three tonnes per hectare. Photo standards for estimating stubble loads in wheat and barley. Source: Brett Masters (PIRSA) via Upper North Farming Systems Monitoring stubble (PDF 1.2Mb)

Some breakdown of crop residue occurs between harvest and sowing but in drier areas this is minimal. Approximately 70 percent of stubble present at harvest remains at sowing. Canola and pulse stubbles break down more easily (and quicker) than wheat and barley stubble. Standing stubble can act as a trellis for lentils, improving growth, harvestability and yield, regardless of seasonal conditions.

The challenge of retained stubbles is to manage high level stubble loads (> 3 t / ha) without affecting other system approaches including erosion prevention, disease and insect pressures, soil moisture retention, seeding or pre-emergence herbicide applications.

If stubble is at a threshold where management is necessary, there are a number of options available to make the residues more manageable or to reduce the overall amount of residue. When considering a stubble management option, farmers should take their seeder set-up into account to decide on the best practice for their machinery capabilities.

There are three opportunities to manage stubbles:

  • At harvest – includes comb and cutter bar height, even residue spreading and HWSC techniques such as chaff carts and the iHSD. Read more about How do I set up my harvester to manage stubble?
  • Post-harvest – incorporation, restructure and removal of stubble including HWSC techniques such as narrow windrow burning. Factor in disease, nutrition and seeding machinery capabilities.
  • At seeding – use of sowing techniques and equipment that can handle heavy stubbles. Read more about How do I setup my seeder to handle stubble?

Choose the most appropriate tool or technology to achieve the desired levels of stubble components and characteristics for maintaining ground cover and the ease of sowing the next crop. This will vary between different cropping operations and may include a combination of several strategies that vary between seasons.

It is important plan stubble management ahead of harvest to optimise the both the benefits of stubble retention and the success of the following season.

All practices to change stubble characteristics will impact on future operations and this needs to be considered as part of the entire operation.

What are my post-harvest stubble management options?

Stubble retention is the preferred option, but it may not be ideal in every situation. Post-harvest stubble management allows growers to retain the benefits of stubble retention without risking losses in higher yielding seasons.

How stubble is managed during the post-harvest period will ultimately affect ground cover levels. For instance, stubble in contact with soil will break down more quickly than standing stubble (Figure 2). As stubble breaks down it can tie-up nitrogen making it unavailable to the crop. Read more about How do I manage nitrogen in a stubble-retained system?

Photo of stubble that is standing, rolled, chained or cultivated

Figure 2. Ground cover (70 percent) in situations where stubble was left standing, rolled, chained or cultivated. Source: Mallee Sustainable Farming Stubble management: A guide for Mallee Farmers

Retention

'Retention' is maintaining as much as possible of the stubble intact and is well suited to disc seeders or inter-row seeding operations.

Heavy stubble loads decompose slower than lighter stubble loads, which can make management more difficult especially with high levels of stubble that are damp at time of seeding

Standing stubble reduces wind speed minimising erosion and soil-water evaporation. Pre-emergent herbicide efficacy is improved when stubble is standing, rather than on the ground.

Incorporation

Cultivating stubbles to incorporate them into the soil will speed up stubble break down. The longer the time that the stubble is incorporated into the soil, the more it will break down before sowing. The rate of breakdown is also increased by moist soil conditions during the post-harvest period.

Removal – all or part

Stubble removal is done to eliminate the potential for seeder blockages when sowing the next crop. It can take many forms and removes all or part of the stubble in the post-harvest period. Techniques include burning and baling.

Restructuring stubble

Restructuring can help to increase decomposition of stubble. Mulching techniques include slashing, chaining or rolling. Grazing is another option that has the benefit of providing feed to livestock. Rotational grazing is recommended to avoid uneven reduction of stubble and patchy erosion.

Restructuring often results in stubble laying across ground that may cause issues with disc seeders especially when seeding small seeded crops including canola.

More Information

Farming Systems Groups

Calculators

  • Stubble Management Optimiser to calculate the overall financial and nutritional cost of managing stubble both at harvest and during post-harvest treatments

Other resources