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Corangamite Region   'Brown Book'   - How to optimise your soils to enhance productivity
How do I manage the impact of tillage?
Most relevant to grazing and cropping industries
Key Points
Understanding the problem
Managing the problem
Other related questions in the Brown Book
Resources
References

Source: DEPI Victoria
Key Points
  • Tillage contributes to the decline in soil structure
  • Avoid or reduce tillage & trafficking, particularly when wet
  • For broadacre grazing, increase the establishment of perennial pastures, with a preference for direct drilling
  • For cropping promote the adoption of minimal tillage and no-till practices

  • Occasional tillage may be required for stubble incorporation or deep ripping
  • Cultivate the soil only when the soil moisture content is right – do the ‘worm’ test


Understanding the problem
Why is it important to me as a farmer?
  • There is an imperative to minimise tillage through cultivation practices to address soil structure decline. Soil structure decline leads to:
    • reduction in the efficiency of water entry & use in soils
    • increased erosion
    • increased soil crusting
    • reduced plant growth


  • If cultivation is necessary, undertake the ‘worm’ test to determine if the soil is at a suitable moist content that makes it least susceptible to structural decline.


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How and why tillage practices impact on farming
  • Annual croppers have traditionally used cultivation for:
    • seedbed preparation;
    • weed control; and
    • moisture conservation (via mechanical fallowing)
  • Conventional cultivation describes the common practice involving primary and secondary tillage operations which generally results in <30 % crop residue on the surface. It involves more than three (including seeding) tillage passes.
  • Cultivation physically disrupts the soil, exposing the soil surface to erosive forces, and facilitating the oxidation of organic materials. Cultivation can include reduced infiltration, erosion, crusting, and reduced plant growth.
  • It is especially prevalent in dry conditions, particularly on loam topsoils in the region. These soils are particularly vulnerable to over-tillage, which under dry conditions breaks down the soil aggregates to a ‘flour’ easily blown by wind or washed by excessive rainfall.


  • This problem is more likely to occur prior to crop or pasture establishment and can threaten water quality by adding suspended sediments to waterways (turbidity).
    Figure 1 - Areas of high to very high soil structure decline susceptibility in the Corangamite region – Source: CCMA Soil Health Strategy
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Managing the problem
What is the best practice?

  • Currently, about 60% of cropping land is minimal tilled and 30% conducted under ‘no till’ in the Corangamite region (Ward DPI, pers. comm. 2003)
  • For grazing the establishment of perennial pastures should be promoted, with a preference for direct drilling
  • Cropping land in the region needs to experience a wider adoption of minimal tillage and no-till practices
  • The following four practices can be included as minimum tillage. The systems differ mainly in the degree to which the soil is disturbed prior to sowing:
    • Reduced tillage
    • Direct-drill
    • No-till
    • Zero-till


  • The no-till and zero-till systems generally have the least amount of soil disturbance and greatest soil cover remaining from previous crop residues
  • The adoption of minimum tillage practices can lessen and even reverse soil structure decline by maintaining organic carbon and limiting soil disturbance
  • Using disc seeders instead of tyned implements for crop sowing can also cut soil disturbance


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How can you achieve this?
  • Reduced tillage
    • Involves one or two cultivations before seeding and can still contribute significant damage compared to direct-drill, no-till and zero-till
    • It is convenient to call this reduced tillage to separate it from the fully minimized forms of tillage
  • Direct-drill
    • Crop or pasture is sown directly into an untilled soil. The level of disturbance is variable
  • No-till
    • Crop is sown into an untilled soil but using narrow or knife points to minimise disturbance (<30%) to soil
  • Zero-till
    • Crop is sown with one pass with a disc seeder for minimal soil disturbance
  • In general:
    • Appropriate tillage may still be required for the breaking of hard pans (deep ripping), stubble incorporation and rhizoctonia (root killing fungi) control
    • Appropriate cultivation patterns are important on sloping paddocks
    Figure 2 - Wide row spacing to allow easier management of stubble loads - Source: Soil Types and Structures Module, DEPI Victoria
    Figure 3 - Zero-till - one pass seeding using discs for minimal soil disturbance - Source: Soil Types and Structures Module, DEPI Victoria


  • Limitations of minimum tillage systems are weed management, herbicide resistance, machinery suitability, and occasional outbreaks of pests.
  • Long-term practitioners of minimum tillage cropping (particularly no-till systems) have developed strategic and effective herbicide management and application. This includes timely control of any summer weeds and a grass control product in a mix with a knockdown product in front of the seeder, then early application of any in-crop weed control if required.

Cultivate the soil only when the moisture content is right!
  • A simple test called the ‘rod’ or ‘worm’ test will help you avoid compacting and degrading the soil structure.
  • Rapidly squeeze a small lump of soil into a ball and try to roll it into a 50mm long rod about 3-4mm in diameter.
  • If you can make a rod easily, the soil is too wet and will compact if it is worked or has animals or machinery on it.
  • If you can just make a crumbly rod the water content should allow traffic and cultivation without compaction.
  • If you can’t make a rod at all, the soil could be too dry for tillage in a sandy or loamy soil.
  • You need to do this test at several points over the full depth of any proposed cultivation.
    Figure 4. The ‘worm’ test for suitability to cultivate. - Source: DEPI Victoria
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Other related questions in the Brown Book


Brown Book content has been based on published information listed in the Resources and References sections below

Resources
References
  • Dahlhaus, P.(2005) Evaluating the public benefit from the soil health actions. Discussion paper for Corangamite Soil Health Strategy 2006-2012. Dahlhaus Environmental Geology
  • Clarkson T, Department of Primary Industries on behalf of the Corangamite Catchment Management Authority (2007). Corangamite Soil Health Strategy 2007. Corangamite Catchment Management Authority, Colac, Victoria
  • Johnston T (2011), Soil Types and Structures Module. Victorian Department of Primary Industries
  • Cultivation/Tillage for Broadacre Cropping. Victorian Resources Online. Victoria Department of Primary Industries
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This project is supported by the Corangamite Catchment Management Authority, through funding from the Australian Government’s Caring for our Country

Page Updated: September 2013
Produced by AS Miner Geotechnical