Behnam:

What is PEST?  I don't know what that is?

You should not change any Ecotype parameters.  It would be dangerous to calibrate RUE (which is in the Ecotype file), as that is viewed as a constant across all maize hybrids.  The only exception is for a low RUE for pure inbred lines used in plant breeder plots (and that is not something you are looking at).  If you see a value for RUE of 4.5 in ecotype file, that is not a good number and will disappear by the time of release of V4.5 DSSAT.

The principle is that you should calibrate genetic coefficients only for the optimum irrigation (and N fertilization) treatments.  That way, any failure to predict accurately the growth and yield at low irrigation or low N fertilization indicates a problem with the prediction (and inputs) related to water and N balance.  So, yes, the genetic coefficients will change if you optimize them with all the treatments being considered (as you already say you observed).

Good luck.
Ken Boote

________________________________________
From: DSSAT - Crop Models and Applications [[log in to unmask]] On Behalf Of Behnam [[log in to unmask]]
Sent: Sunday, April 24, 2011 3:44 AM
To: [log in to unmask]
Subject: Does the irrigation regime affect the crop parameters while              calibration?

Dear users,
I am using PEST to calibrate cultivar parameters of MAIZE.

1) Do I have to change any Ecotype parameters in this process? By
default, there are only 2 Ecotypes in DSSAT database.

2) Is it true if I find cultivar parameters different for different
irrigation treatments? When I used all irrigation treatments, the
calibration results got worst in comparison to the time I used only 1
or 2 irrigation treatments.

Best
Behnam