Material placed on soil to cover and protect it is called mulch.
Types of mulch
There are two types:
- Organic mulches which include bark, wood chips, leaves, lawn clippings, straw, paper and other organic by products.
- Inorganic mulches include crushed stone, asphalt and concrete.
Covering the soil with plastic materials
Often the soil is covered with polythene or a geotextile fabric [ weed mat ] and then its covered with an organic or inorganic product.
Benefits of mulch
- Soil moisture is conserved
- Soil erosion and water loss are reduced
- Soil fertility is usually increased
- Weed competition is reduced
- Soil structure is improved
- Soil compaction is reduced
- Soil microbial activity increases
- Soil temperature is moderated
Problems caused by mulch
- Insufficient water and air is a problem under plastic
- Nitrogen deficiency may occur especially in wood chips and bark. To counter act this it may be necessary to add extra nitrogen to the soil
- Some diseases and pest may be more serious especially if there is excessive moisture. Keep an eye open for slugs!
- Some mulches are toxic these include: fresh lawn clippings, eucalyptus wood chips and leaves, redwood and cedar wood chips, douglas fir, larch and spruce bark.
- Toxic substances can be removed by correct composting.
- In trials carried out in North America comparing various mulching compounds including: fibre glass, hay, bark, plastic and wood chips, the latter were found the most effective material particularly for retaining soil moisture.
- Do not pile mulch against the stem of trees this provides an ideal environment for, causing collar rot.
- Apply about 100mm [ 4 inches ], any deeper could have adverse effects on soil properties.
- If using black plastic or geotextiles make sure the soil slopes away from the plants for drainage, and prick the plastic to provide holes for air and water.
- Up grade wood chip or bark mulch every few years as it will slowly break down.
- If growth is vigorous and the leaf colour dark no fertiliser is required.
- If leaves are yellow and growth slow a light application of a slow release nitrogen fertiliser should be broad cast.
- Mulching is very important to woody plants not only does it look good , and reduces maintenance, but produces a healthy plant.
- It will stop damage to bark and roots from lawn mowers and string trimmers.
- Mulching will mean that you will not have to use herbicides to control weeds.