Soils are produced, in the first instance, by the weathering and disintegration of rocks. Rock disintegration is an extremely slow process and is brought about by the continued action of water, sunshine, frost and wind on the rock surface. Disintegration is also assisted by chemical means and by the action of vegetable and animal life. It has been estimated that the disintegration of limestone rock to a depth of 1 metre (39 inches) would take over 70,000 years, so soil making could be truly stated to be an extremely slow process.

In their natural state, soils contain mineral and organic matter, water, gases and bacteria. The mineral matter is derived from rocks and forms the largest constituent in ordinary soils. The organic matter represents the remains of decaying vegetable matter, and is known as humus. Water is received from rain or by drainage. Gases enter from the air or are partly manufactured in the soil (for example, carbon dioxide). All healthy soil contain bacteria.

A good soil should have the following qualities:
  • It should be neither hard nor compacted.
  • It should be reasonably deepabout 22 cm.
  • It should be neither very acid nor alkaline and it should be easy to work.
  • It should contain essential minerals to sustain plant life.
It has been said that the topsoil is not that much different from the subsoil below. The main difference is that the topsoil normally contains humus - decayed vegetable matter in varying amounts.

So, to improve a soil, it is necessary to dig in a good supply of animal manure
or decayed vegetable matter to a depth of about 20 cm. Also, lightly turn in a complete fertilizer at the rate of 120 grams to just under a square metre. Some crops need lime and when this is indicated, apply garden lime or dolomite - about a handful to the square metre. On the other hand, lime must be rigidly excluded from the soil when preparing it for such plants as azaleas, daphne, gardenias and rhododendrons,

At all times, check before using lime. If in doubt, use dolomite as plants are usually more tolerant of this material. In addition, it contains magnesium and calcium, essential elements needed for plant health.
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