I checked the line lengths, they are fine. The calculations are also trivial - and they used to work fine before the program got expanded.

Do you in general recommend strongly to use IMPLICIT NONE?
Right now, we don't use any IMPLICIT statement.

Anyway here they are:

1:
EPSIL = (23.452294- (1.30125E-2+ (1.64E-6-5.03E-7*T)*T)*T)*PID180

2:
                 SOILTEMP_NPLUS1(I) = (D / (1 + 2*BETA*D))
     &                           * (BETA*(SOILTEMP_NPLUS1(I+1)
     &                           + SOILTEMP_NPLUS1(I-1))
     &                           + (1-BETA) * (SOILTEMP(I+1)
     &                           - 2*SOILTEMP(I) + SOILTEMP(I-1)))
     &                           +  SOILTEMP(I)/(1+2*BETA*D)

3:
V1 = PI*RX1*RY1*(HUP-(HUP**2/RZ1)+(HUP**3)/(3*RZ1**2))