Santa's summer stubble management

AG ADVICE - December 2021

Phil Cranney - Senior Land Services Officer, Pastures

Managing your cereal stubble starts at harvest. You and/or your harvesting contractor can control the height and how the stubble trash is distributed. Due to the large amount of stubble expected this year there are some issues to be considered this season.

Here are the top 5 issues with stubble management in 2021/22:

  1. High stubble loads help reduce evaporation over the hot summer
  2. High stubble loads can severely reduce available soil nitrogen
  3. Stripper fronts allow greater height of stubble which increases shading, thus cools the soil and reduces evaporation
  4. High disease risk paddocks should be identified and stubble management applied to reduce disease risk for the following crop
  5. Low stubble height or incorporation of stubble will make summer fallow weed control a much easier task

Some lessons from the Riverina GRDC Stubble Project (2013-18) could be applied to our Central West Slopes area this fallow. The key learnings from this research were as follows:

  1. Lowering harvest height can reduce stubble load while maintaining benefits of retained stubble
  2. Mulching or lightly cultivating stubble soon after harvest increases soil-stubble contact and aids stubble breakdown before sowing
  3. While burning can help to reduce stubble loads at sowing and can improve pre-emergent herbicide efficacy, it increases the risk of erosion and impacts on soil moisture retention during the summer fallow.

If you know your soil pH, then now may be the perfect opportunity to incorporate lime into the stubble in order to keep your soil pH above 5.5 (CaCl).

Often wet harvest can leave you with big wheel ruts and tracks through the paddock that can damage machinery when spraying and planting.

Therefore, a strategic tillage operation soon after harvest to incorporate heavy cereal stubble and lime, may be just the ticket this year.

Also, depending on your rotation and soil pH, some of these paddocks may be suited to a pulse crop next year. If the inoculum is applied correctly and soil conditions suit the rhizobia, the legume will help fix nitrogen to help offset the lost soil nitrogen needed to break down the high carbon load of stubble entering the soil.

This year is the perfect time to consider stubble incorporation with lime. Dr Mark Conyer’s research suggested that minimum till practices would help repair soil structure 1-4 years after the strategic tillage event.

The 10 key lessons from the overall GRDC funded stubble initiative were as follows:

  1. Be flexible – no strategy is perfect for every farm or paddock
  2. Diverse systems and practices are the platform for success
  3. Pro-actively manage stubble to suit your crop, seeding system and farm structure
  4. Water management – maintain a critical threshold – and control fallow weeds
  5. Weed management in stubble retained systems - At harvest and during the fallow
  6. Weed management in stubble retained systems - In-crop weed management
  7. Stubble retained system may need more early N - Avoid yield penalties from N immobilisation
  8. Stubble retained system may need more early N - Stubble is not a good source of N for crops
  9. A lack of nutrients (NPS) can limit soil C sequestration from stubble under continuous cropping
  10. Pest management

Managing the enormous stubble load this year instead of burning it, could mean increased PAW in the dry years to follow this La Nina event.

So, this is your take home message: please, think ahead before you plan to burn stubble next autumn, keep your stubble, it provides a soil moisture buffer for the dry years!

So be good, for goodness sake!

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