Some refer to it as earth, local farmers occasionally call it dust, and others even dare calling it dirt; however, to most of us, it is just soil.

Soil is that loose material on the surface of the Earth produced through centuries or even millennia of rock weathering and decomposition of organic matter. These destructive and neo-formation processes, brought about by the combined effect of climate, topography and the activity of living organisms, over time transform the parent rock into a mixture of fine particles, that together with other minerals and organic matter, produce soil, a resource that supports life.

Second only to air and water, soil is the next important factor in the Earth’s life supporting systems. Historians tell us that where water was abundant and soil was and remained fertile, civilisations took root and flourished; however where soil fertility was not sustained and soil deteriorated, civilisations collapsed. When soil failed, settlements were abandoned and people moved on and migrated in search of new fertile ground.

Soil not only produces food; it also generates a vast number of products and ecosystem services. Fibre, timber and certain medicinal substances are obtained from plants grown in soil.

Where soil is deep, it serves as the foundation for buildings and roads, and in some Third World countries, soil still constitutes a large proportion of the construction material.

Soil plays an important role in the storage and purification of water. Water is absorbed in deep soil during the rainy season and stored for plant use in the dry months. Absorption of water by soil reduces run-off and flash floods. Soil is an important buffer, and with the help of the microorganisms that it harbours, detoxifies percolating water from many toxic contaminants.

Soil also plays a crucial role in recycling waste. Dead animals, their excreta, dead plants and added organic matter like compost and manure are degraded by microorganisms, forming humus and recycling important mineral nutrients in the process that are essential to plant life.

Second only to air and water, soil is the next important factor in the Earth’s life support systems

Soil can be described as the most complex biomaterial on Earth. It provides a habitat for a large number of organisms, ranging from small mammals to the smallest bacterium.

Bacteria and other microorganisms like fungi play an important role in soil function. They drive the mechanisms of decomposition, nutrient cycling, and in many instances, detoxification. The number and diversity of microorganisms in soil are immense, and vary depending on the soil type and environmental conditions.

One gram of healthy soil may harbour up to a billion bacteria, 900,000 fungi and a few thousand other microorganisms. Most of these benefit the environment and only a few might pose a serious threat to health or behave as pests.

Soil plays a significant role in the control of climate. A relatively small proportion of mineral soil is organic matter and a major constituent of organic matter is carbon. Soil, with its reserve of organic matter, is one of the major carbon pools on Earth.

As plants fix the greenhouse gas carbon dioxide from the atmosphere, a portion of this fixed carbon is locked in the soil as organic matter such as peat, humus and microorganisms. Degradation of soil organic matter increases the carbon dioxide level in the atmosphere, which in turn may contribute to global warming.

Unfortunately, as global temperatures increase, more soil organic matter is degraded and more carbon dioxide is released into the atmosphere.

Sadly, despite its importance, soil is not given the right attention it deserves. Proper management ensures the well-being and protection of soil.

Excessive tillage and intensive agricultural activity damages the fine and delicate structure of soil. Tillage opens the soil and pulverises it, thus encouraging rapid decomposition, oxidation and loss of organic matter. Organic matter sustains a healthy microbial population that in turn maintains good soil function.

Loss of organic matter, apart from contributing to an increase in atmospheric carbon dioxide, results in a reduction of microbial biomass, microbial activity and subsequently the degradation of soil. This in turn increases the risk of soil loss by wind and water erosion.

(To be concluded)

Anthony Sacco is a senior lecturer in soil sciences and environmental microbiology at the Department of Rural Sciences and Food Systems of the University’s Institute of Earth Systems.