Humans tend to see the world as a solid ball of rock coated with a thin layer of soil and life. But lately, scientists have been finding out planet looks more like a wheel of cheese, one whose thick, leathery rind is perpetually gnawed and fermented by the microbes that live in the planets innards.

You would need a microscope to see the life in this subterranean biosphere, however scientists have estimated the total amount of life on Earth that exists below ground, is vast. It’s made up mostly of Soil organisms (biota), such as bacteria and their evolutionary cousins, the archaea think microscopic flora and fauna. With “Something like 70% of the total number of microbes on Earth in the soil below our feet”. The role all these organisms play in shifting carbon about the Earth is profound, you cannot begin to understand soil carbon on Earth without understanding the diversity and influence of underground life. Microbes in the soil turn over carbon, take in carbon, and breathe it out. They do amazing things to transform the soil environments, and are vital to produce health crops and livestock

There is a two-way relationship between soil biota and agricultural production. Soil organisms (biota) carry out a vital range of processes that are important for soil health and fertility in both natural and managed agricultural soils. This subterranean microscopic biosphere provides the energy and nutrients for the biota, which consume the organic matter (OM), and improve nutrient availability and soil structure. Agricultural practices can be both beneficial and detrimental to the soil biota.

Soil organisms (biota), can range in size from microscopic e.g. bacteria to centimetres (or metres Giant Gippsland Earthworm)

• Most Soil biota activity is concentrated in the top 1m of soil, but extends deeper than 50~100 m.
• Millions of organisms exist but only a fraction have been identified e.g. 5% of fungi and 3% of nematodes.
• 80 – 90% of soil biological activity is carried out by bacteria and fungi.
• Resistance to extreme changes in the soil environment increases as organisms decrease in size.
• The reproductive interval reduces with a decrease in organism size e.g. bacteria reproduce themselves in hours whilst earthworms may take weeks.
• In natural and managed farming environments a complex food web exists. These ‘predator-prey’ relationships help control the balance of species present in the soil, and the balance can be destroyed with poor farming practices.
• Studies have shown that not only does heathy Soil biota activity improve yields, it reduced the incidence of plant disease.

Further reading

Life in the Soil CSIRO Authors: VVSR Gupta, SM Neate, E Leonard  – This information is based on research carried out by the Cooperative Research Centre
for Soil & Land Management and other national and international institutions.  More information on Soil Biota can be found on the University of Adelaide web page:

Deep life – Researchers at the Deep Carbon Observatory announce the results of the 10-year study suggesting 70% of bacteria and archaea exist in the subsurface of the Earth.