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2.1 Physical Characteristics
Saturation
We start with a saturated soil, for example after a
heavy rain or an irrigation event.
At saturation, root function is limited because there
is no oxygen available in the soil to help power their
cellular activities (for more on this see “Biological
characteristics,” page 51).
Note: The soil structure is weakest at the point of
saturation, and so this is not a good time to run
machinery over it.
Field Capacity
As time goes on, water drains due to gravity and soil
reaches field capacity.
At field capacity, the soil’s largest pore spaces will be
filled with air.
Sandy soils reach field capacity about two days after
a major rainfall or irrigation event, but soils with more
clay take much longer to reach field capacity.
Permanent Wilting Point
As the soil continues to dry due to evaporation and
drainage, it will reach the permanent wilting point.
In conditions of true permanent wilting point, a plant
will not recover.