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Think of soil as the foundations of your garden. If you build a house without strong foundations your house will fail as will your plants.

Soil is vital to healthy plant growth as it:

  •  Supports the plant’s roots.
  •  Supplies the majority of nutrients needed by the plant.
  • Provides the water needed to carry nutrients throughout the plant.
  •  Provides oxygen to the plant.
  •  Is home to countless symbiotic organisms that the plant depends on for survival such as worms, fungi and bacteria.

Ideal Soils should be:

  •  Be high in organic matter.
  • Have good drainage.
  •  Have good aeration.
  • Hold nutrients.
  • Have healthy soil flora and fauna – fungi, bacteria, and worms.
  • And be friable.

Main Soil types:


  • Poor water holding ability.
  • Excellent drainage.
  • May be hydrophobic.
  • Leaches nutrients.
  • Easy to cultivate.


  • Poor water holding ability.
  • Excellent drainage.
  • May be hydrophobic.
  • Leaches nutrients.
  • Easy to cultivate.


  • Good water holding ability.
  • Good nutrient retention.
  • May have poor drainage.
  • May have low aeration.
  • May be difficult cultivate.

All of these soil types can be improved by adding organic matter Poor drainage and hydrophobic soils are the most common issues faced on clay soils. For heavy sodic clay soils apply a heavy dressing of gypsum and dig it in. If your clay is not sodic you are wasting your money on Gypsum. To test for sodic clay simply put a small handful of the clay into a glass jar with a screw top lid, 3⁄4 fill with water, close lid firmly and give the whole thing a good shake and place on a bench for 12 hours. After 12 hours if the water is cloudy then you have sodic clay soils.


Gypsum is a naturally derived mineral product. Its breaks up clay & improves drainage without altering the pH. It does this by aggregating the clay particles Follow the application with a good layer of mulch and keep it topped up as it decomposes.


You might consider building mounds if:

Your soil is dreadful; adding garden loam on top seems the easiest way. Your soil drains badly and you need to build it up. You need to create a sound or visual barrier around your block or add aesthetic appeal. But consider that mounds dry out faster than un-mounded beds and they can be difficult to water as water runs off the sides. Careful cultivation and preparation eliminates the need to mound.

Hydrophobic Soils and Soil Wetting Agents:

When you stand watering your garden with a hose for hours and all it does is run off then this is a hydrophobic soil

  • All types of soils can become hydrophobic.
  • Soils have to be “reminded” how to take up water again by the adding organic matter.
  • Use aged composts and manures, or a native soil blend.
  • Application of a “granular soil wetter” to improve water penetration? but: be aware that some soil wetters can harm frogs and small reptiles.

Improving your Soil:

  • Compost can be made at home or is readily available commercially.
  • Aged animal manures and worm compost are rich in nutrients.
  • Mulch layers will also break down over time to add nutrients to the soil.
  • Compost teas make excellent garden fertilisers.


  • Mulch keeps the soil temperature cool in hot conditions assisting root development and growth.
  • Prevents weeds from germinating by blocking light from dormant seed.
  • Bark chips, leaf litter, shredded paper, lucerne and straw are all examples of organic mulches.
  • Organic mulches are broken down by soil microbes adding valuable nutrients to the soil.

Soil Flora and Fauna:

  • Millions of microorganisms (e.g. fungi and bacteria) make up the living
  • Microorganisms thrive in clay soils and soils rich in organic matter.
  • Three quarters of all soil microorganisms live in the top 50mm of the soil.
  • Microorganisms break down organic matter and release nutrients back

To maintain healthy populations of soil fauna:

  • Reduce unnecessary soil cultivation.
  • Continually top up organic matter on the soil surface.
  • Improve drainage in heavy clay soils or where the soil is compacted.
  • Protect the soil from harsh temperatures and moisture loss.
  • Reduce or stop the use of garden chemicals e.g. herbicides, fungicides,
  • Stop the use of artificial garden fertilisers.

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