c
c
      subroutine rough 
     i              (rrimpl,till_i,tillf, 
     o               rr) 

c     + + + PURPOSE + + +
c     
c     This subroutine performs a random roughness calculation 
c     after a tillage operation.
c
c     + + + KEYWORDS + + +
c     random roughness (RR), tillage (primary/secondary)
c
c     + + + ARGUMENT DECLARATIONS + + +
c
	  real tillf,rrimpl,rr,till_i       
c
c     + + + ARGUMENT DEFINITIONS + + +
c
c     tillf	    - Fraction of the surface tilled (0-1)
c	  till_i	- Tillage intensity factor (0-1)
c     rrimpl	- Assigned nominal RR value for the tillage operation (mm) 
c     rr		- current surface random roughness (mm) 
c
c     + + + ACCESSED COMMON BLOCK VARIABLE DEFINITIONS + + +
c     
c
c     + + + PARAMETERS + + +
c
c     + + + LOCAL VARIABLES + + +
c
c     + + + LOCAL VARIABLE DEFINITIONS + + +
c
c     + + + END SPECIFICATIONS + + + 
c
c	  Perform the calculation of the surface RR after a tillage
c     operation.  Check to see if the tillage intensity factor is
c     needed before performing the calculation. 
c
      ! Is RR going to be increased?  If so, then just do it.
	  if (rrimpl .ge. rr) then
	    rr = tillf*rrimpl + (1.0-tillf)*rr
	  else
		rr = tillf*(till_i*rrimpl + (1.0-till_i)*rr)
     &       + (1.0-tillf)*rr
	  endif

	  return
	  end