Garden with Insight v1.0 Help: porosity

Soil porosity is a measure of how much of the soil volume is made up of pore space (air) as opposed to solid materials. Some of this pore space may be filled with water, so the amount of water a soil can hold is partly determined by its porosity. Typically the constituents of soil volume look like this:

(Redrawn from Troeh & Thompson 1993)

Porosity is often described in units of percent pore space. In this simulation we describe porosity in units of depth of water over depth of soil (as in m/m or a fraction) over a constant soil area. This is the same as percent pore space divided by 100.

In this simulation porosity is maintained in a close relationship with bulk density, which is also related to soil pore space. It changes when the bulk density changes (when the soil settles with rain, when the soil is mixed with a tool, and when the soil is aerated with a tool). When the soil is mixed, the porosity of some layers may change due to mixing of the soil particles. Wilting point, field capacity, and porosity are used extensively in the model as standards against which to compare the soil's current water content.

How it works:
mixing soil
aerating soil
soil settling with rain