Grace,
Your equations for PLAG either when XN<4 and otherwise are not correct. You
forgot the AMIN1 for the model to choose the most limiting stress factor,
instead of both:

              ! PLAG - Leaf area growth, cm2/plant/day
              PLAG   = 3.0*XN*XN*TI*AMIN1(TURFAC*(1.0-SATFAC))

              IF (XN .LT. 4.0) THEN
                  ! XN - number of oldest expanding leaf
                  PLAG = 4.0*XN*TI*AMIN1(TURFAC*(1.0-SATFAC))
                  ! Allow first 4 leaves to expand 30% faster
              ENDIF

In fact the most current CSM-CERES-Maize includes now P and K stress
factors.

About your question, I'm not sure how accurate the comment (Allow first 4
leaves to expand 30% faster) is. I think is wrong. Interestingly, in the
original model, coefficients 4.0 (XN<4) and 3.0 (XN>4) were 3.0 and 3.5.
Meaning the leaf expansion rate was always less for the first 4 leaves. This
assumption seems more reasonable. Anyway, the proportion of the first 4
leaves on the total leaf area is small, so this should not be a major worry.


Hope this help.
Regards,
Jon

-----Mensaje original-----
De: DSSAT - Crop Models and Applications [mailto:[log in to unmask]] En
nombre de Grace Kepler
Enviado el: Tuesday, May 10, 2011 5:33 PM
Para: [log in to unmask]
Asunto: Maize question

Hello,

I have a question about the following portion of the maize growth model in
the
ISTAGE = 1 (Emergence to End of Juvenile Stage) section.

              ! PLAG - Leaf area growth, cm2/plant/day
              PLAG   = 3.0*XN*XN*TI*TURFAC*(1.0-SATFAC)

              IF (XN .LT. 4.0) THEN
                  ! XN - number of oldest expanding leaf
                  PLAG = 4.0*XN*TI*TURFAC*(1.0-SATFAC)
                  ! Allow first 4 leaves to expand 30% faster
              ENDIF

In its current form, the rate of growth when XN < 4.0 is only faster for
XN<1.4.

Is the code correct, or should there be another XN factor in the equation
for
PLAG when XN<4.0?

Thank you,
Grace Kepler