Tesfalidet
The volumetric saturated soil water content is by definition the moisture
content when all pore space is occupied by water. However in real world you
probably will not find 100% of the soil porosity occupied by water, because
there's always air trapped in micro pores. Now, how much of the total
porosity is occupied by entrapped air is open to discussion. If I'm not
wrong, Ritchie proposes 92% as a reasonable value. 85% seems too high, but
I don't know the reference you mention.


At 07:44 PM 9/5/2002 +0200, you wrote:
>Dear all,
>Rithcie (1985) soil water balance model requires saturated soil water
>content as an input. I am not so sure but the saturated soil water content
>is  equal to 100* (1- bulk density/particle density) or the total
>porosity. I am wondering why Piara Singh in his online technical manual
>has calculated it as (1- bulk density/particle density) * 85 or 85% of the
>total porosity. Can someone explain this to me?
>
>Thank you for your time.
>
>Tesfalidet A. Ghebreab
>University of Natal
>Department of Soil Sciences and Agrometeorology
>Post Bag X01 Scottsville, Pietermaritsburg
>South Africa.


Jon I. Lizaso
Dep. Agricultural & Biosystems Engineering
124 Davidson Hall
Iowa State University    515 294 7350 (Voice)
Ames IA 50011            515 294 2552 (Fax)