Dear Larrauri,

I feel that the model should be calibrated with the detailed and most
reliable, if possible with multi-season and multi-location (varying in
latitude) data. As far as I understand the multitrial may be treated as
replications, if these do not vary in latitude of site or date of
sowing. Also the crop should not have experienced the water r

For validation one should use (of course reliable) but much less
detailed data. One can take anthesis and maturity dates with yield of
main product or both the main and byproduct data from several locations
varying in productivity situations, including those experiencing
usually occuring stresses. Data from cultivators field should be
sufficient. In principle the data used in calibration should not be
used for validation or should not be held back for use in
validation.Hope it will help.

Best regards,

Dr Dharam Singh Dabas
CCS Haryana Agricultural University,
Hisar 125004 India
Ph: +91-1662-24163 (at Residence)

----- Original Message -----
From: Luis Alvarez <[log in to unmask]>
Date: Tuesday, June 3, 2003 10:11 am

> Dear Modellers:
> During three rice crop seasons (1997 and 2000 rainy seasons and
> 2001 dry season) I have collected soil, weather, cultivar and
> management data in order to calibrate, evaluate or validate? CERES-
> rice.I have used the information of 4 tryals in 2 fields (rice
> farms) to calibrate, and used these information for model validation.
> I know that in the iterative process I only calibrate the model.
> With information of other places and years I could validate it.
> I would like to have your and Dr. K.J. Boote (I don´t have his e-
> mail) opinion about this problem. Should I use the same
> information to calibrate and validate or not?. Perhaps this
> process could take many years, so where are the advantages of
> modelling?. I know that I can use the validated model in many
> important features, but it is still expensive in time and money,
> and in our tropical environment events goes very fast.
> Thanks for your advise.
> Sincerely yours:
> Luis E. Alvarez Larrauri
> Universidad Ezequiel Zamora. UNELLEZ.
> Guanare. Estado Portuguesa. Venezuela.
>