Re: Definition of Water Holding Capacity

[Steve]

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Rick,

I recommend that you get rid of "water holding capacity" as a separate concept.
This is because it can be confusing, and there are more widely understood and
accepted ways of saying the same thing. For instance, if the definition is "the
water that a soil can hold above oven dry", then saturated water content is
widely understood to mean the same thing unless you mean "hold after free
drainage". The term "water holding capacity" can be confusing because it is
close to another term, "available water holding capacity", that is often used
and defined as the water content between wilting point (WP) and field capacity
(FC). This is the same definition as you have for available moisture. Another
confusing usage of "water holding capacity" is given in the fourth edtion of
Sprinkler Irrigation where it is described as the amount of water that can be
placed on a field repeatedly for disposal of liquid waste.

Rick, I don't envy your task of trying to sort out these definitions. I took a
quick look through four of the water resource engineering reference works on my
shelves (dated 1962 through 1983) and the new Handbook of Soil Science (1999)
and found that the terminology was different in every one (as different as
available moisture is from available water holding capacity). Many of the
concepts remain the same, but the words used to express them change from author
to author.

Good luck,

Steve