Air and water and its role in soil

Oxygen, which circulates through fissures and cavities in the soil, is essential for the existence of soil bacteria and for the respiration of plant roots.

All living things need water to survive and even the most lukewarm gardener knows water is essential for plant survival. Water whether supplied as rain water or from a cheap water butt penetrates the soil and some of the moisture is retained between the soil granules.

Water is essential as a solvent of plant nutrients and as a carrier of hydrogen and oxygen. In well drained soil the surplus water leaches through the subsoil.

The top water layer just below the soil is known as the water table. The depth at which the water table is located may vary from a few inches to several hundred feet, according to the area. For example, in low lying areas the water table may be quite near the surface during winter. While in other areas it may be necessary to bore deep into the ground to reach the water table.

Water logged soil occurs where the drainage is bad and the water table is high. There is no air in waterlogged soil and with a high water table and poor drainage consequently root restriction occurs.

During the growing season, plants need to extract water held in the soil on a more or less constant basis, therefore an adequate supply must be available at all times.

It is important to water the soil to a depth of at least 12". Watering above this depth means that the moisture will evaporate from the surface. In order to reduce evaporation from occurring watering should be carried out in the evening. On dry soils, loss of moisture can be reduced by mulching and a thick layer of worm compost is ideal for this task.

Organic matter is the decomposed remains of plants and animals, often referred to as compost which provides plant nutrients. These nutrients include carbon, nitrogen and trace elements. Organic matter also provides food for the living soil organisms. The presence of bulky organic matter improves the physical condition of the soil by adding bulk to a porous sandy soil and by opening up a heavy clay soil.

Well rotted cows manure is an excellent form of organic matter and once included in the soil the quality improves permanently. Worm cast is another excellent form of organic matter and is a pretty mulch.