Garden with Insight v1.0 Help: Soil patch next day functions: settle the soil if it rained
Whenever it rains, the soil may settle as water moves through it during percolation. What "settle" means in this context is that the soil
particles are disrupted by the movement of water down through them, and they pack closer together.
Shifting of soil particles causes the pore spaces in the soil to become smaller.
How much settling occurs in each soil layer depends on: the amount of
sand in the soil (more sand = more settling, because larger soil particles are freer to move around), the
amount of water percolating through each soil layer (more water = more settling), and the depth of each
soil layer (more settling tends to happen near the top of the soil). These factors are all used to create a
scaling factor for soil settling. The scaling factor is used with
an S curve to calculate the degree to which the bulk density approaches the settled bulk density for the soil. The
settled bulk density is a parameter for the bulk density when the soil
has settled as much as possible.
Notice what two things are not done here: the porosity has not been
changed, and the depth of the soil layers has not been changed. Probably to be more complete one would
want to adjust the porosity by the same factor as the bulk density, since soil settling should affect both.
The depth of soil layers probably changes to such a tiny extent during soil settling that it is not important
to simulate that change, but we should still be aware of the assumption that the change is negligible.
calculation of percolation