! !$Author$ !$Date$ !$Revision$ !$HeadURL$ ! subroutine crust (crustf_rm,tillf,crustf,lmosf, lmosm) ! + + + PURPOSE + + + ! ! This subroutine destroys the surface crust after a tillage event. ! ! + + + KEYWORDS + + + ! crust, tillage (primary/secondary) include 'p1werm.inc' ! ! + + + ARGUMENT DECLARATIONS + + + ! real tillf, crustf, crustf_rm, lmosf, lmosm ! ! + + + ARGUMENT DEFINITIONS + + + ! ! lmosf - fraction of crusted surface containing loose erodible material ! lmosm - mass of loose erodible material on crusted portion of surface ! crustf - Current fraction of surface crusted (before & after operation) ! crustf_rm - Fraction of crust removed (0 <= crustf_rm <= 1) ! tillf - Fraction of the surface tilled (0 <= tillf <= 1) ! ! + + + ACCESSED COMMON BLOCK VARIABLE DEFINITIONS + + + ! ! ! + + + PARAMETERS + + + ! ! + + + LOCAL VARIABLES + + + ! ! + + + LOCAL VARIABLE DEFINITIONS + + + ! ! + + + END SPECIFICATIONS + + + ! ! ! crf = cri * ( (1.0 - tillf) + (tillf * (1.0-crustf_rm))) ! determine fraction of surface that remains crusted crustf = crustf * (1.0 - tillf * crustf_rm) ! Currently the crust function doesn't modify the loose erodible ! material variables on the crusted surface. That could be changed ! in the future if it was deemed necessary. ! The following should be removed. Need to check SOIL and EROSION ! first to make sure they aren't adversely affected. - LEW ! 8/25/1999 ! check to see if the loose material on the surface is still there ! if enough of the crust is removed set lmosf to zero (loose material) ! This was done according to L. Hagen ! just clear them out if it close to zero ! (LH shouldn't have erosion or soil submodels this sensitive) if (crustf .lt. 0.01) then lmosf = 0.0 lmosm = 0.0 endif return end