Piret Vacht: What Does Soil Consist of?

What does soil consist of and why is it so important for life diversity? Piret Vacht, a doctoral student at Tallinn University Institute of Ecology will explain.

When we think about endangered natural resources, we first remember the rain forests, fresh water and panda bears. Yet, one of the Earth’s most critical natural resources is something we see and feel under our feet evert day. The soil that provides for our everyday needs is left neglected. This natural resource, that is mostly non-renewable, offers us 90 per cent of our everyday food. We also get the fibres for making cloth and wood for building and heating thanks to soil.

Soil has a mineral and an organic part, which form about half of the top layer of fertile soil. The mineral part is much larger than the organic and is formed by rocks and minerals of different chemical compounds with different shapes and sizes. For example, the soil’s ability to hold water is determined by the relation between the shapes of different sizes.

Living organisms and organic waste in different states of decomposition compose the organic part. The best-known living organisms are earthworms and moles, but in reality, the ecosystem of soil is much more varied and copious.

In addition to the aforementioned, the soil hosts numerable protozoa, nematodes, algae and many other invertebrates as well as vertebrates. Since many of these domains are very biodiverse, we can deduct that the life in soil is not only copious, but also very diverse.

About a quarter of the world’s biodiversity is in the soil. The main task of the living organisms within the soil is to decompose organic material and keep the structure of the soil stable. A less-known fact is that these organisms are the source of our antibiotics and other medicine.

Another vital part of the soil’s structure is the existence of various holes, tunnels and grooves, also known as pores. These help important contents of the soil, such as water, air and various gases, enter the soil and move around in there. The water- or air-filled pores are also vital to the living organisms, for these offer microhabitats to them. The proportion of air and water in the soil is in constant change and depends on precipitation and the proportions on the mineral and organic parts of the soil. This means all components of the soil are linked to each other.

To keep the soil in a good state, so it could give us healthy food and other benefits, the soil should be porous, hold enough water, air and organic material with a diversity of living organisms. Only then can the soil offer nutrients to plants, keep it structure intact and filter our drinking water.

Did you know that…

• one handful of soil has more living organisms in it than the number of people that have ever lived on Earth
• a quarter of the word’s biodiversity lives in the soil
• the UN has declared 2015 to be the International Year of Soils
• it can take more than 500 years to create 1cm of fertile soil