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True or false?

Lizzie27Lizzie27 Posts: 12,494
in Problem solving
November's issue of GW contains the following statement :-

"it can take 500 years to form just 20cm of topsoil"

Rather a sweeping statement I thought - how they do know and who measured it?

What do you think?
North East Somerset - Clay soil over limestone
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Posts

  • Arthur1Arthur1 Posts: 542
    Have watched wildlife programmes about new volcanic islands where they have measured the depth if soil that has developed since the island formed. I guess if you do that then you can extrapolate to 500 years?
  • JennyJJennyJ Posts: 10,576
    The leaves and stuff that accumulate underneath the paving slabs on breeze blocks that my water butts stand on seem to be well on the way to making half an inch or so of soil every time I get under there and clean it out. I will admit that just maybe I don't do it as often as I should :o
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • JennyJJennyJ Posts: 10,576
    Maybe the 500 years is about stone weathering down into the inorganic components of soil (the particles of sand, clay etc) rather than the organic component forming from leaf litter and other organic debris? Thinking about it from that angle, it doesn't seem very long at all.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • FireFire Posts: 19,096
    JennyJ said:
    Maybe the 500 years is about stone weathering down into the inorganic components of soil (the particles of sand, clay etc)

    I would think so

  • MikeOxgreenMikeOxgreen Posts: 812
    It takes about 12 months in my compost heap  :D
  • DovefromaboveDovefromabove Posts: 88,147
    edited October 2022
    MikeOxgreen said:
    It takes about 12 months in my compost heap  :D
    Surely a compost heap makes compost … not topsoil? 🤔 

    Edited to add: 

    https://horticulture.co.uk/compost-vs-soil/

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • DovefromaboveDovefromabove Posts: 88,147
    This may be of interest …

    https://www.jic.ac.uk/advances/soil-the-foundation-of-life-on-earth/

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • BigladBiglad Posts: 3,265
    I would imagine that has to be a ball park figure and will vary depending on local conditions.
    East Lancs
  • bédébédé Posts: 3,095
    edited October 2022
    Most journalism is just entertainment.  Usually they get the basic science wrong.  OK to start  a discussion.

    Darwin did some experiments to see how quickly worms buried stones.  Maybe relevant.
     location: Surrey Hills, England, ex-woodland acidic sand.
    "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
  • bédébédé Posts: 3,095
    edited October 2022
    It will depend on the definition of soil and topsoil.

    My daughter gardens in the Chilterns.  Above the chalk stratum is a stratum called "clay-with flints".  It can be very thick.  Is that soil or not?  Where does the topsoil turn into just soil?  

    Most gardeners would regard one spit as topsoil.  That\s about the 20cm stated.
     location: Surrey Hills, England, ex-woodland acidic sand.
    "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
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