Thanks Andarzian, I got a chance to look at the paper. You were correct
about the nitrogen and water simulations. The assumptions for
calibration are totally wrong! It is a pity those things went unnoticed
and the paper found its way through to the press!
sasi

Saseendran S Anapalli,  Ph. D.
Agricultural Systems Research Unit
USDA-ARS
2150 D Center Ave.
Fort Collins, CO-80526


-----Original Message-----
From: DSSAT - Crop Models and Applications
[mailto:[log in to unmask]] On Behalf Of Bahram Andarzian
Sent: Wednesday, March 05, 2008 9:57 PM
To: [log in to unmask]
Subject: weakness of CERES-wheat

Dear my friends DSSAT servers
  Hi
  Please if possible, see the article entitle" validating CERES-wheat
under North-German environmental condition" by M. Langensiepen and
co-authors in Agricultural Systems Journal (article in press). This
article challenges the using and performance of CERES-wheat model to
simulate grain yield and biomass production under different water and
nitrogen conditions.
  In my idea genetic coefficients are cultivar-dependent and should not
be changed over years, but in their calibration procedure, they assume
genetic coefficients are environment-dependent which according to
environmental condition of each year have changed! If so, what is the
mean of the yield variability? In my idea, yield variability is the
yield of a crop over different years or in the other word, running the
model with fixed genetic coefficients over different years.
  Apparently, it seems that they did not calibrate water and nitrogen
modules in their work!
  This case may be a good discussion topic for DSSAT servers and sharing
information about strength and weakness points of the DSSAT models with
each others.

  Best
  Bahram Andarzian
  Ph.D in Crop Eco-physiology
  Agricultural and Natural Resources Research Center of Khuzestan
  Ahvaz-Iran


---------------------------------
Never miss a thing.   Make Yahoo your homepage.