Aston,

I also have problems to calibrate the wheat model to measured data,
especially lai and top biomass during the growing season.  My experience is
that the model is very sensitive to N and water and temperature stresses.
Make sure you have a good handle on N fertilization, initial soil moisture,
correct field and wilting point soil water of the soil.

How about the total biomass and the growth curve?  If they are acceptable,
you can change the G1 and G2 in the .CUL file to change the harvest index
and therefore the grain yield.

John zhang


-----Original Message-----
From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]]
On Behalf Of Chipanshi, Aston
Sent: Wednesday, February 14, 2007 10:33 AM
To: [log in to unmask]
Subject: problems in calibrating barley and wheat models





Hi,

Could someone assist with how to go about tinkering with genetic
coefficients when calibrating the CERES models (in particular barley and
wheat)? We tried to follow the changes suggested in DSSAT v4.2 but we
are getting extremely low yield values. We have  a very good dataset on
phenology and grain yield from experimental plots over a period of about
3 years. The yield values that we are getting don't make sense at all!!

Thank you,



ASTON