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NOTE: To get off this list, send email to majordomo@aqua.ccwr.ac.za with the body of the message containing the line: unsubscribe sowacs Rick I am doing some calibration of moisture sensors, and I need a book or books detailing definitions of moisture terms (eg field capacity and moisture content) as well as the experimental procedure of carrying out such tests. I would appreciate if you would recommend to me any literature in this area. You may reply directly to my email address. If there is anyone else who can help in directing me to literature articles or books that cover this subject please email me the information. Thanking you in advance, Phillip Email address : pat12945@pegasus.cc.ucf.edu At 06:22 PM 02/21/2000 GMT, you wrote: >NOTE: To get off this list, send email to majordomo@aqua.ccwr.ac.za >with the body of the message containing the line: >unsubscribe sowacs > >I know that this is "old ground", but I need help in clarifying >definitions. The Irrigation Association is currently refining a glossary >of irrigation terminology. The glossary includes soil water terms. > >My question concerns the best definition to use with the term "water >holding capacity." In my mind, water holding capacity is defined as >the amount of water that the soil can "hold" above oven-dry. It is >expressed in terms of mm/m (in the US as in/ft). > >WHC contrasts with the term "available soil water" in that available >soil water is defined as the difference between field capacity and >wilting point. > >I realize and appreciate that water holding capacity is an old and >perhaps outdated term, as well as are field capacity and wilting point. > These latter two have been redefined as dynamic rather than static >values and have sometimes been given the names drained upper limit >and crop extractable limit, etc. > >My main question is whether the above definition for WHC is valid >and widely held, or if it should be modified. > >WHC is contrasted with AM as indicated by their calculation: > >In the classical approach: >AM = FC - WP >WHC = FC > >I believe that it is useful to have a term as WHC that describes the >total amount of measurable water that we can expect to see retained >in a soil profile. This is useful for comparing against methods that >measure total water such as neutron meter, TDR, etc. In addition, >many old soil surveys contain soil water holding information that is >often equivalent to the above definition of WHC. Therefore, it is useful >to keep a term around that is compatible with the old data. > >Thanks. > >Rick Allen >Univ. Idaho > > > > > Phillip A. Thomas Graduate Research Assistant University of Central Florida