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Site preparation - Moisture conservation


In most revegetation projects it is usually the lack of availability of water that leads to poor survival or growth. You can increase the success of your planting by maximising the amount of water available to your plants or seeds, particularly in the first few years. Reducing competition by controlling weeds is the most effective way to do this. As mentioned in section 5a, controlling weeds for 2 years before planting can allow moisture to be banked in the soil, ready for your new plants to use it. 'Moisture banking' is a technique commonly used for growing agricultural crops. During this fallow period before planting, you can use a surface mulch to reduce the evaporation of moisture from the soil surface. Mulching can also improve the permeability of the soil surface, so more rain soaks into the soil rather than running off.


After planting mulches can also act to conserve existing soil moisture and even prevent weed growth. You can apply a mulch around the base of the plant to a radius of at least 50cm. Material for mulch can include straw or hay, bulk organic material such as wood chips, sawdust or cotton waste, pebbles or rocks, commercial jute mulch mats, newspaper or woven polypropylene or jute matting.


It is important that mulching materials are kept clear of the stem of the young plant or the stem or crown can rot. In very cold areas, mulches should not be used in winter as they can prevent the soil from warming and lead to frozen soil around the roots.



Tree guards help to conserve moisture and prevent browsing.


Tree guards can also be useful in conserving moisture. They act by reducing wind speed around the young plant, which lowers the amount of water lost through the leaves. Guards are usually only used for small to medium scale tubestock plantings. Tree guards add considerable cost to large scale plantings, and their use should be carefully weighed up against the cost of replacing plants lost in the first few years of the planting. Milk cartons or translucent plastic guards are the most commonly available tree guards available. When using tree guards to combat moisture loss, it is important to seal the point where they come in contact with the soil, usually by hilling soil up against the base of the guard.  Failure to do this can actually increase moisture loss by speeding up the airflow through the tree guard, which may expose the seedlings roots (see diagram).


Tree guards are also used for protection from browsing and frost.


Next  Site preparation - frost protection


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