Dear Luis,

From our experience and other modelling works, I suggest that model calibration and model validation should use independent data sets.
For your cases, you may use 1997 trials for model calibration and use remaining years for model validation.

Once you validate the model in the given soil-climate zone, it can be used to simulate other year's trials, including previous or future scenarios/treatments. This is one advantage of the simulation model.

Regards,

Jingyi (Bill) Yang, Ph.D.
Soil Science and Modelling

Environmental Health National Program
Water Quality and Quantity
Central Experimental Farm, K.W. Neatby Building
960 Carling Avenue, Ottawa, Ontario K1A 0C6
Tel: (613) 759-1412     Fax:(613) 759-1924
E-mail: [log in to unmask]





>>> [log in to unmask] 06/03/03 12:41am >>>
 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.