As we continue on our study of the soil – we pause for a visual of the players. The Micropores!
“Micropores are fine soil pores, typically a fraction of a millimeter in
diameter. They are responsible for the water holding capacity of soil.
Micropores hold water by capillary forces, like the fine pores in a
sponge or towel. Much of the water held in micropores is available
to plants, while some is held so tightly that plant roots cannot tap it.”
Since Micropores are harder to see – the spaces between the soil granuals – They are harder to study than Macropores,
“Large pores, or macropores, control the permeability and aeration of a
soil. Macropores include earthworm channels and many root channels.
They are large enough that water moves through them rapidly by gravity,
allowing rainfall and irrigation water to infiltrate into the soil and
excess water to drain through the soil.”
Filling out trusty beaker with Tennis Balls, Marbles and Paper Punches, the boys could visualize how Sand, Silt and Clay form together to create these Micropores in the soil.
The Sand, or Tennis Balls went into the beaker first, then we poured in the marbles or Silt. These two items formed together quite nicely, – then – when we poured in the tiny flat layers of clay – the paper punches – the clay sort of layered – invaded – all of the open spaces. Those flat layers form together layer by layer. A simple shake of the beaker, and the Silt and Clay would settle to the lowest available macropore space.
This weekend, as the tourrents of rain swept away the gravel, we saw the layers stripped away to the clay – it is interesting that as we removed the tennis balls, one simple shake – and the clay moved underneath the silt. We tried it several times, and each time, one shake, and the clay went beneath the silt. Interesting.
Our next question? What layers do we have in our yard? What does it mean?