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What is soil?

Soil is one of the world's most important natural resources. Together with air and water it is the basis for life on planet earth. It has many important functions which are essential for life. Not only does it play the major part in allowing us to feed the world's population, but it also plays a major role in the recycling of air, water, nutrients, and maintaining a number of natural cycles, thereby ensuring that there will be a basis for life in generations to come. Without soil, the world's population neither would nor could survive.

Soil forms the surface skin over the landscape of the earth at the junction between the atmosphere and the lithosphere. Think of soil as a thin carpet covering the land portions of the earth. The distance from the surface of the earth, at which the soil is situated, to the very centre of the earth deep below, is over 6,000 kilometres. Of this, the soil layer is a mere one to two metres thickness of this 6,000 kilometres. It is thus a very, very thin skin indeed - both fragile and extremely precious.

Soil consists of a mixture of mineral grains that come from the rock deposits and sediments beneath them. This mixture gives the overall texture of the soil, namely whether the soil is mainly sandy, loamy or clayey. Importantly, soil also contains organic matter, mainly in the top 20 cm. Organic matter comes from rotted and decomposed vegetation, broken down by soil organisms. Soil also contains varying amounts of water depending on the climate and the water holding capacity of the soil. The remaining important ingredient is air. The amounts of each of these components varies in time and across the landscape. This is a magical mixture of ingredients that allows the soil to perform many vital needs of living beings.