Eliminating or reducing competition from other plants helps a crop to make the most of available soil moisture. Weed eradication is one method; allowing extra spacing between plants is another. Also, well-chosen ground cover plants help to reduce evaporation due to wind or sun.
Mulching is another method of conserving soil moisture. This involves covering the soil with a 5-8 cm (2-3 in) layer of leaf mould, peat, spent mushroom compost, pulverized bark or well-rotted manure. As well as reducing evaporation, mulching suppresses weeds. Manure also leaches small amounts of nutrients into the soil. Care is needed, however, to keep it away from the stems of plants, which it might damage.
Mulching is particularly valuable in the vegetable garden, for it provides the cool, moist root conditions that such crops as peas and beans enjoy. Straw placed under strawberries is another form of mulching, for it shades the soil as well as helping to keep the fruits clean.
Paper and plastic mulches of various kinds have become popular in recent years. In particular, covering the soil around newly-planted trees with black polythene has proved very effective.
Pine needles are one of the few organic materials not recommended as a mulch. They contain large amounts of resin and can be harmful to most plants, so they are best burned. However, if mixed with well-rotted leaves they appear not to harm such plants as rhododendrons and azaleas.
Conversely, acid-loving plants react badly to a mulch of spent mushroom compost, which contains lime.
Mulch for fruits, trees and shrubs
Mulches are used to keep the soil round growing plants cool and moist, and to suppress weeds. Organic mulches are popular, but purpose-made strips or sheets of black polythene are less messy and ideal over the root area of newly planted trees and shrubs. Water the ground thoroughly before covering it with a polythene mulch suitably weighted down.
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