c$Author: fredfox $
c$Date: 2002-06-21 23:49:15 $
c$Revision: 1.2 $
c$Source: /weru/cvs/weps/weps.src/hydro/proptext.for,v $

      subroutine proptext( nlay, clayf, sandf, organf,
     &                 settled_bulkden, partden )

c     + + + PURPOSE + + +
c     
c     This subroutine updates the properties that depend on soil texture 
c     (texture can change in the model due to mixing and removal by wind)

c     + + + KEYWORDS + + +
c     texture properties 

c     + + + ARGUMENT DECLARATIONS + + +
      integer nlay
      real sandf(*),clayf(*),organf(*),
     &      settled_bulkden(*), partden(*)

c     + + + ARGUMENT DEFINITIONS + + +
c     nlay     - number of soil layers to be updated
c     clayf    - fraction of soil mineral portion which is clay
c     sandf    - fraction of soil mineral portion which is sand
c     organf   - fraction of total soil mass which is organic matter
c     settled_bulkden - settled bulk density (Mg/m^3)
c     partden  - particle density (Mg/m^3)

c     + + + FUNCTION DECLARATIONS + + +
      real   setbds

c     + + + LOCAL VARIABLES + + +
      integer lay

c     + + + LOCAL VARIABLE DEFINITIONS + + +

c     + + + END SPECIFICATIONS + + + 

      do lay=1,nlay
c         settled bulk density
          settled_bulkden(lay) = setbds( clayf(lay), sandf(lay),
     &                                   organf(lay))

c         calculate an average soil particle density
c         Particle density of organic matter
c         1.37 in Baver, Soil Physics, 1972 p.44 (humus)
c         1.1  in Marshall and Holmes, Soil Physics, 1979, p.277 (soil organic matter)
c         Old incorrect formula
c          partden(lay) = organf(lay)*1.23
c     &                 + (1.0-organf(lay))*2.65
c         New correct formula
          partden(lay) = 1.0/(organf(lay)/1.23
     &                 + (1.0-organf(lay))/2.65)

c         make sure particle density is significantly greater than settled bulk density
          if( partden(lay).lt.(1.2*settled_bulkden(lay)) ) then
              partden(lay) = 1.2*settled_bulkden(lay)
          endif
      end do

      end