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Advice Article •Garden, Outdoor

Improving your soil

In this article

  • The importance of good soil and mulching
  • The best way to mulch your garden
  • How soil types vary across regions

Good soil is the foundation of a healthy waterwise garden. The healthier your soil, the more drought resistant your plants will be.

Improve the soil every time you dig

Sandy soil, commonly found in WA, has low water and nutrient holding capacity, which isn’t great for gardens. The ideal soil type for most exotic plant species is a loam, made up of clay, silt and sand. It slows water movement through the soil, allowing more absorption for plants. You can mimic a loamy style soil and enrich your garden by:

  • Adding clays to improve water and nutrient holding capacity.
  • Adding compost for healthy plant growth. Animal manure, worm farm residue, bagged soil improver and soil conditioners are good sources.

The best time to improve soil is before you plant a new garden, either in autumn or spring. If planting a new garden, make sure the organic matter is thoroughly mixed through the top 30cm of soil for optimal results. If improving soil to an established garden bed, apply improver to the surface area and lightly mix it into the soil with a hoe or rake and hand water well.

Follow the tips below to create a healthier garden from the root up.

Read a transcript of this video

Mulch is like sunscreen for your soil

Applying mulch to your garden can greatly reduce evaporation loss, improve the soil, reduce weed growth and improve the appearance of your garden. Applying a generous amount of waterwise mulch can help you save up to 20% of water in the garden.

Tips for mulching your garden

To help your garden thrive:

  • Apply between 5–10cm of good waterwise mulch across the surface of the soil.
  • Choose a chunky coarse mulch, which is better for water saving over soft, fine mulches like straw and lucerne.
  • Choose waterwise approved products displaying the Waterwise and Smart Approved WaterMark symbols.

For more tips on mulching watch this video:

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Wetting agents do wonders for your soil

Sandy soils are known to be water repellent (hydrophobic), making it a challenge to maintain a healthy garden in WA. The simplest way to improve the absorption of water in your soil and help it spread more evenly throughout, is to add a wetting agent.

When should I apply wetting agents?

The best time to apply a soil improver with a wetting agent is at the start of winter, in early summer and as recommended by the manufacturer. Always water in wetting agents until they foam. This means they are activated and doing their job.

Watch this video to learn more about how wetting agents can improve your soil profile:

Read a transcript of this video

Soil improvement in the regions

Soil types across WA vary greatly. To keep your soil healthy it's important to understand the soil characteristics that might apply to your region. While some local native species of plants will grow in natural soil without any soil improvement, all still benefit from it, especially during the establishment phase. Planting most exotic species in the regions will require soil improvement before planting.

Soil types in the South West vary greatly. Common soils include the deep sands on the coast to sandy peats, bare rock, gravel, loams and clays, and complex duplex soils where one type sits on top of another.

Some characteristics of South West soils

Soil type Becomes non-wettable Water holding capacity  Nutrient holding capacity Benefits from organic matter   Benefits from soil amendments
Sand Very commonly Poor Poor Greatly Greatly
Sandy loam Occasionally Medium Medium Greatly Some 
Clay Very rarely Good Medium Greatly A little
Rocky or stony soils Occasionally Medium Medium Greatly A little
Potting mix Very commonly Good Good N/A A little

Soils in the Great Southern Region vary from deep sands to sandy peats, loams and clays and complex duplex soils where one type sits on top of another.

Some characteristics of Great Southern soils

Soil type Becomes non-wettable Water holding capacity  Nutrient holding capacity Benefits from organic matter   Benefits from soil amendments
Sand Very commonly Poor Poor Greatly Greatly
Sandy loam Occasionally Medium Medium Greatly Some 
Clay Very rarely Good Medium Greatly A little
Rocky or stony soils Occasionally Medium Medium Greatly A little
Potting mix Very commonly Good Good N/A A little

Soils in the Mid West region range from deep sands on the coast to sandy peats, loams and clays, and complex duplex soils where one type sits on top of another. There are also areas of rocky stony soils.

 Some characteristics of Mid West soils

Soil type Becomes non-wettable Water holding capacity  Nutrient holding capacity Benefits from organic matter   Benefits from soil amendments
Sand Very commonly Poor Poor Greatly Greatly
Sandy loam Occasionally Medium Medium Greatly Some 
Clay Very rarely Good Medium Greatly A little
Rocky or stony soils Occasionally Medium Medium Greatly A little
Potting mix Very commonly Good Good N/A A little

Soil types in the Goldfields region include sand, gravel and clay, with the most common combinations being sandy loam and loamy clay.

The area around Kalgoorlie is undulating plains on granite, which have areas of calcareous loamy earths with red loamy earths, red deep loamy duplexes and red shallow loamy duplexes. In some town gardens, the soil cover over rock is shallow and can have a limiting effect on root development.

Some characteristics of Goldfields soil

Soil type Becomes non-wettable Water holding capacity  Nutrient holding capacity Benefits from organic matter   Benefits from soil amendments
Sand Very commonly Poor Poor Greatly Greatly
Sandy loam Occasionally Medium Medium Greatly Some 
Clay Very rarely Good Medium Greatly A little
Rocky or stony soils Occasionally Medium Medium Greatly A little
Potting mix Very commonly Good Good N/A A little

The most common natural soil types in the Pilbara are sand, sandy loam and rocky stony soils. In some areas the soil is strongly alkaline with a pH level of 9 or above.

Some characteristics of Pilbara soils

Soil type Becomes non-wettable Water holding capacity  Nutrient holding capacity Benefits from organic matter   Benefits from soil amendments
Sand Very commonly Poor Poor Greatly Greatly
Sandy loam Occasionally Medium Medium Greatly Some 
Clay Very rarely Good Medium Greatly A little
Rocky or stony soils Occasionally Medium Medium Greatly A little
Potting mix Very commonly Good Good N/A A little

The most common soil types within the Kimberley town boundaries vary from sand, sandy loam and rocky stony soils. Black cracking clay is also common.

 Some characteristics of soil in the Kimberley

Soil type Becomes non-wettable Water holding capacity  Nutrient holding capacity Benefits from organic matter   Benefits from soil amendments
Sand Very commonly Poor Poor Greatly Greatly
Sandy loam Occasionally Medium Medium Greatly Some 
Clay Very rarely Good Medium Greatly A little
Rocky or stony soils Occasionally Medium Medium Greatly A little
Potting mix Very commonly Good Good N/A A little

Waterwise product advice

Using waterwise approved products to improve your soil like wetting agents, organic matter, and soil improver will help you use water efficiently in the garden. Together with Australia’s water conservation label, Smart Approved WaterMark, our waterwise product endorsement program makes it easy for you to identify these products.

Look out for the waterwise logo when shopping for waterwise approved products at your local garden centre, or browse recommended products on the Smart Approved WaterMark website.

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