Dereck,

I've seen three answers to your question so far, but don't forget to try
the "soil" creation program in the DSSAT shell itself.  It is under DATA,
SOIL, CREATE, and allows you to enter sand, silt, clay, OM, coarse
fraction, etc. to create your own soil with water holding capacity
limits.  It is much the same as the RITCHIE 1999 paper in the reference
given.  In fact, that approach is patterned after earlier Ritchie work.

There are still problems out there to get this right, and what I'm about to
say is not the last word on it, but here is my impression.  The DSSAT or
the Ritchie approach (old or new) is  sort of for the average soil classes,
and has underestimated available water holding capacity for soils with any
significant clay content, say above 20% clay.  In our experience the Saxon
method has been best for soils with significant clay, say above 20% clay,
whereas the Ritchie/DSSAT methods are OK for the rest.

I'm sure this will generate more discussion.

Ken Boote


At 01:42 PM 10/3/01 -0600, you wrote:
>Dear Members,
>Can anyone tell me how to access the look-up tables, provided in DSSAT 3.5,
>to determine plant available water limits?  Also, does anyone know of any
>algorithms to estimate plant available water limits from textural
>data?  Thank you for your help.
>
>Derek McNamara
>
>Derek McNamara
>Graduate Research Assistant
>Mountain Research Center, Montana State University
>P.O. Box 173490, 106 AJM Johnson Hall
>Bozeman, MT 59717-3490, USA
>406-994-5073
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