Some key soil biology facts

Original re-posted from the April 2010 Soil Foodweb Australia Newsletter:

Leonardo Da Vinci: “We know more about the movement of celestial bodies than about the soil underfoot” – not a lot has changed in the last 500 years.

It never hurts to be reminded of the key facts about the living soil beneath our feet. The US Natural Resources Conservation Service (NRCS) has a succinct page available on the Internet with some good information.

For instance, did you know that:

  • in most ecosystems, there is more life and more diversity below ground than above
  • arid systems have few earthworms, but have ants, termites and other invertebrates that perform similar functions
  • grasslands have near equal bacterial and fungal biomass, or may be dominated by bacteria. Coniferous forests may have 100 to 1,000 times more fungal biomass than bacterial biomass
  • soil microorganisms drive carbon and nitrogen cycling
  • mature trees can have as many as 5 million active root tips
  • a single spade of rich garden soil contains more species than can be found above ground in the whole Amazon rainforest
  • the plants growing in a one hectare wheat field can have more than 30,000 kms of roots – more than enough to go around the Equator
  • soil can act as either a source or a sink of greenhouse gasses – 30% of the carbon dioxide, 70% of the methane and 90% of the nitrous oxide released to the atmosphere each year pass through the soil
  • in agricultural soils, more than 1,000 arthropod legs support your every step
  • one cup of soil may hold as many bacteria as there are people on the earth
  • five thousand soil species have been described
  • twenty thousand nematode species have been identified, but it is thought that 500,000 species may exist
  • earthworms move soil from the lower strata to the surface and move organic matter from the surface to lower layers. Where earthworms are active, they can turn over the top 150mm of soil every 10 to 20 years

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