Water Required (min)

This equation estimates water requirements for plant growth as the minimum amount of water you want to apply to initially moisten soil so that plants will not wilt, wither and die.

The percentage of water typically required for most plants to survive is based on a rough estimate derived from a factor known as the permanent wilting point. the permanent wilting point, `sigma_"wp"`, is given as a range because different plants endure different levels of dry soil.  We have used the upper bound of this range so that this equations computes the safe minimum of water for your specified volume of soil.

DERIVATION

The value for the permanent wilting point (`sigma_"pwp"`) is estimated between 0.01 `"vol water"/"vol soil"` and 0.25 `"vol water"/"vol soil"`.  This equation uses the upper bound of this permanent wilting point range.  To be more conservative  you will want to use more water than this equation estimates but this equation will give you a starting point for your estimates.