Mulching

Mulch covers the surface of the soil and an essential component of waterwise landscaping.

Reasons for mulching

• Reduces evaporation allows water to percolate through to soil rather than run off
• Reduces radiant heat
• Deters weeds which compete with plants for water and nutrients

Inorganic mulches

Inorganic mulches consist of gravels, pebbles, shell grit etc.The benefits of inorganic mulch are:

• That it does not break down so that although initial cost is higher there is noreplacement cost.
• It does not absorb any water so all water percolates through to the soil.
• It has good insulation properties providing a cool root run when laid to sufficient depth.

Organic mulches

For most general landscaping applications a long lasting, covering mulch is required.Pinebark, chipped green waste and other high carbon mulches are useful as they:

• Have large particles
• Are non-absorbent
• Allow rapid water penetration
• Are long lasting
• Are not hospitable to weeds

It is not necessary to apply manures or fertilisers to accelerate the breakdown of these mulches as they are used to prevent evaporation rather than ‘feed’ the plants.

Products such as Lucerne, pea hay and animal manures which are added to productive gardens should be classified as fertilisers/soil improvers rather than water saving mulches.

Laying mulch

A minimum of 50mm of coarse organic mulch should be laid over existing soil surface and 40mm of inorganic mulch (preferably over weed mat). Care should be taken to keep mulch away from the base of the plant to allow airflow and prevent disease.

Mulching slopes

When mulching steep slopes, biodegradable jute matting may be required to prevent erosion and run off.

There is a tendency to overwater lawn. Although maximum growth rate is achieved by supplying water at about 90% of pan evaporation, healthy minimal growth can be achieved with as little as 30% of pan evaporation. Most amenity turf can be maintained at this lower end of the scale if necessary.

Key factors in producing healthy turf with minimal water are:

• Grow warm season grasses such as Kikuyu, Buffalo season couch, Queensland Blue and
  Paspalums.
• Control irrigation via soil moisture sensors.
• Design irrigation systems to have uniform application and minimal evaporation losses.
• Improve and maintain good soil structure to maximise water holding capacity and to enable deep-root penetration. This maximises the size of the reservoir of water for the turf

Design Tips

• Avoid turfing slopes unless absolutely essential.
• Avoid lawn in small areas of median strips, median strips, parking bays etc. These dry
  out quickly and are prone to overspray and water wastage.
• Where possible, avoid lawn that slopes towards roads and ensure that lawn is not
  installed too high – ideally should be installed 50mm below curb level to allow for
  thickening over time.
• Avoid turf use for areas which are not functional, use alternative surfaces for open spaces
  where recreational zones are not required.
• Minimise use of turf for access, use paths, open gravel areas with trees or shade structures
  or trafficable.
• Where possible, lay lawn in cooler months so it can get established.