Bring Me The Soil Horizon

Up at my Mother-In-Law's place, there's some construction work going on, shoring up the house next door or some some such. We went to have a look at and there, where the soil had been dug away, was another of those wonderful times that the text book description that you've been looking at in various books for years is perfectly rendered in real life. In this case, a perfect example of soil horizons.

Here's the text book version:

And here's the real deal:

So yeah, looks like a load of dirt, huh? Well, on the top layer is, ya know, grass and stuff and you don't have to be a biologist to know that grass 'and stuff' is organic. Organic - i.e. living - matter dies and then decays, being broken down by microbes and fungi and stuff. This creates what gardeners call a 'rich humus', which is kind of food for plants. Not hummus, that's food for vegetarians.

Anyway, from the bottom of the picture up, is the underlying rock, which is chalk and is fairly typical of the south of England. Chalk is basically dead sea shells, built up over a very long time and is alkaline, if you remember the post I made a couple of weeks ago attempting to explain acid and alkaline soils: http://punkrockecology.blogspot.co.uk/2016/06/orchidorama.html 

Also, it doesn't hold water very well, as we can see as the darker brown soil at the top washes out very quickly to light brown and then the pure white of the chalk. This creates the alkaline and not very fertile chalk downland that I also attempted to explain here: http://punkrockecology.blogspot.co.uk/2016/06/over-hills-and-far-away.html

If you're a gardener, or a farmer, or indeed if you're a plant, then there is a 'perfect' soil, which is called loam and is a rich dark brown, very mildly acidic and a mixture of clay, sand and silt. Rusty coloured soil, incidentally, is coloured that way precisely because it is full of tiny particles of ferris oxide, or rust, and this rust is an indication of air and water being able to penetrate deep into the soil. White soil, grey soil and black soil (the latter being peat soils, such as that described in 'Orchidorama') show the opposite of this, usually that the iron and everything else is being washed away or that air is not able to penetrate.

If ya wanna get even more geeky, then look up 'munsell soil colour chart', or have a look at the following links:

Soil types explained for gardeners: https://www.rhs.org.uk/advice/profile?PID=179

A very tech description of soil horizons: http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447025&topicorder=4

Or you can just slack off and watch this. I like it. It's got a citroën van in it.