Looking after your soil
Canberra soils can be very clayey, subject to compaction and drying out. Water will be wasted on compacted soil and soil low in organic matter because it runs off the soil surface or drains below the plant root zone.
Soil acts as a reservoir, holding water in pore spaces where it is extracted by plant roots, so having a good quality soil to a depth of at least 250 mm is one of the keys to having healthy plants and a water efficient garden.
You can improve poorly structured soill by:
- digging, aerating or ripping the soil to a depth of 250 mm; and
- by incorporating decomposed organic matter (e.g. compost, worm castings, leaf litter, aged animal manure, grass clippings), but avoid uncomposted woody materials which can rob the soil of nitrogen.
If your soil becomes water repellent (hydrophobic), the water will not enter the soil or be available for your plants. The water could puddle on the surface, drop straight through leaving the soil dry, or stay in beads and then run off without sinking in. Apply a wetting agent or surfactant to the soil to reduce the surface tension of the water and help it penetrate the soil. Soil wetters come in granular form that you sprinkle on the surface of the soil and lightly dig through. You can also buy liquid wetting agents.
Water crystals are different to wetting agents. Water crystals are synthetic plastic materials that swell into a jelly-like substance when they absorb water. In theory they hold water in the soil for the plant to access. Do not sprinkle dry crystals on the surface of soil or potting mix. If you do, they will swell up and absorb water that they remove from the soil. It is best to hydrate (add water to) crystals before adding them as a slurry to the planting hole around the roots of new plantings.