FROM THE REGIONAL SOIL COORDINATOR
BRIDGET WATKINS

Amelioration Considerations

Wickepin, Western Australia

July 18, 2025

The Facey Group facilitated an amelioration demonstration day in conjunction with the Western Australian No-Tillage Farmers Association (WANTFA) near Wickepin in early July 2025. A range of different cultivator bars were on display and test strips were run with each bar in succession to allow attendees to see the equipment in action and assess the results on-ground.

It was an opportunity to discuss the benefits of ameliorating soils and the considerations to keep in mind. Support was provided by soil scientists from the Department of Primary Industries and Regional Development (DPIRD) with Jenni Clausen, Gaus Azam and Bindi Isbister highlighting specific aspects of the soil at the demonstration site, considerations for equipment selection and the broader impacts of compaction.

It is anticipated that the heavier, more structured soil type at this location will not settle as quickly as can occur in the northern wheatbelt on more sandy soils. Sands can resettle as water enters the system, whereas the clay and organic matter content of this site is expected to facilitate the maintenance of the soil structure for several years. This is likely to be dependent on traffic management in minimising the reoccurrence of compaction.

The Facey Group will monitor the results from the trial strips established during the demonstration, with the aim of assessing future yield results to consider the differences delivered by the range of implements.

Some of the implements used in the demonstration are shown in the images below. Note, there are many variations in makes and models available.

Compaction

One of the primary constraints noted at the demonstration site was a strong compaction layer present at approximately 150 mm. Compaction layers limit plant root growth and cause plants to expend more energy trying to extend roots into the compaction layer. In a crop, this redirected energy is essentially wasted and decreased tillering and yield often result. In heavier soils, the compaction layer can also exacerbate waterlogging with decreased infiltration of water moving through the profile.

Other factors that can increase the severity of induced compaction include:

- moist soil,
- poor soil structure with a uniform distribution of soil particle sizes (i.e. soils with a diversity of particle sizes have better structure),
- lack of clay distributed throughout the soil profile,
- lack of organic matter, and
- heavy machinery traffic across the surface.

Livestock compaction impacts tend to be limited to the upper surface, shallower than 150 mm, and can often be rectified by standard seeding procedures.

Ameliorating deeper compaction allows access to a deeper bucket of resources, including water and nutrients. It was estimated the soil at the demonstration site, with some clay content, could hold approximately 10 mm of rainfall in 100 mm of soil. Assuming similar water holding content to depth, a 500 mm profile would hold approximately 50 mm of rainfall. However, if plant roots can only reach to a depth of 150 mm, then you are operating on 15 mm of rainfall. This scenario limits resilience and requires more regular rainfall to support plant growth. Without regular rain events, the yield potential of the crop will be limited – possibly by missing tiller development, dropping tillers early or early senescence (haying off).

Removing the compaction limitation may also allow for lime to disperse further into the profile to address subsoil acidity.

Things to consider in the paddock

Determine the constraints that you are aiming to manage within the paddock and keep in mind they may be numerous i.e. soil water repellence, subsoil acidity and compaction. Different implements are designed to address different scenarios with a range of depth capabilities and surface mixing techniques.
Undertake good baseline soil testing, in 100 mm increments, extending to 100 mm below the working depth of the deep tillage tool you are going to use. Get soil analysed for pH, salinity and nutrients including potential toxicities – you don’t want to make your problems worse. Take enough samples to understand the soil variability across the paddock.
Consider digging a pit or trench to have a closer look at the soil profile if possible.
Assess compaction through the profile using a handheld penetrometer or push probe to determine the depth of amelioration required.
When looking at amelioration results from different implements, consider how well the soil is mixed, how much of the subsoil has come to the surface, how is it incorporated and how much has the loosening had an effect in between the tines and across the entire profile.
Consider incorporating lime, gypsum or other soil amendments to maintain soil structure and address other constraints in conjunction with amelioration activities.
Reduce the risk of erosion by carrying out amelioration activities when the subsoil is wet. Although, be sure to consider the soil types present as heavy soils may not backfill effectively when deep ripping if there is excess moisture. Seed a cover crop soon after amelioration to prevent erosion.
The application of nutrients, including nitrogen, after ameliorating needs to account for improved access to soil resources, increased nutrient use efficiency and greater crop potential.