- 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.
|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
- 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
|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
- 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
- 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
|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
- Crop or pasture is sown directly into an untilled soil. The level of disturbance is
- Crop is sown into an untilled soil but using narrow or knife points to minimise
disturbance (<30%) to soil
- 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
|Other related questions in the Brown Book
Brown Book content has been based on published information listed in the Resources and References sections below
- 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
- Cultivation/Tillage for Broadacre Cropping. Victorian Resources Online. Victoria
Department of Primary Industries