Mulching and composting
Mulch is any protective covering for your soil that allows water to penetrate. It can consist of organic material such as wood chips, ‘living mulch’ in the form of groundcover plants, or inorganic material such as gravel or pebbles. Mulch helps to conserve water, keeps weeds at bay, keeps the soil cool in summer, slows run-off, reduces erosion and can improve soil quality.
Organic mulches are the most popular because they can improve the soil structure and add nutrients as they decompose. The best organic mulches are made up of coarse material that allows rain and irrigation water to penetrate through to the soil. The following materials can be used as organic mulch:
- composted and aged manure
- fresh grass clippings
- fallen leaves
- sugar cane mulch
- tea tree mulch
- lucerne hay
- straw
- wood chips and tree bark
- composted horticultural bark
- shredded newspaper
- groundcover plants as ‘living much’.
Inorganic mulches such as gravel, scoria, pebbles and crushed rock are non-flammable and useful in areas where it is important to minimise fire risk, for example against your house.
Quick tips for the applying organic mulch
- Remove all weeds first.
- Break up the soil surface and water well.
- Spread the mulch evenly across the soil surface to a depth of 75mm (any more can reduce the ability of water to reach the soil, and could remove water and nutrients from the soil).
- Clear the mulch from around the plant stems to avoid collar rot.
Important tips for maintaining mulch
- If the mulch becomes too dry and repels water, rake it to break the surface crust, then water it. This is most likely to occur with small particle mulches.
- If weeds appear, remove or spray them before they can flower and seed.
- When removing weeds, be careful not to bring soil to the surface as this can encourage weed growth.
- Top up the mulch periodically as it will generally decompose over time.
Groundcover plants or ‘living mulches’ can be very useful in keeping weeds under control and reducing water evaporating from the soil. They also shelter the root system of other plants, allowing a ‘cool root run’ which is very important for the health of many plant species.
Compost is decomposed organic matter. Adding it to the soil opens the structure, allowing water to infiltrate and to drain, as well as adding nutrients. Adding compost to your garden soil will improve soil quality, plant growth and resilience to drought.