Dear Dr Alagarswamy

Thanks very much for your email.

I had thought at first that the problem was starting in December under UK
conditions (i.e. about 80 DAS), as there were differences emerging between
the wet and dry years at that stage that were perpetuated until the end of
the season. However, I found that this was due to differences in temperature
between years slowing leaf area development which explained a small part
(~10%) of the large discrepancy between the model predictions and reality in
the dry year, but not all. I am now sure that most of this discrepancy (i.e.
the remaining 90%) is due to some problem with the water balance towards the
end of the season, although I haven't had time to find out exactly why. As
you suggest, I suspect it is the water stress factor.

Robin.

=========
Dr Robin Matthews
Institute of Water and Environment
Cranfield University, Silsoe, Bedfordshire MK45 4DT, UK.
Tel: +44 (0)1525 863008; Fax: +44 (0)1525 863384
mailto:[log in to unmask]
http://www.silsoe.cranfield.ac.uk/iwe/people/RobinMatthews.htm
http://ourworld.compuserve.com/homepages/rbmatthews/
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-----Original Message-----
From: Gopalsamy Alagarswamy [mailto:[log in to unmask]]
Sent: 16 February 2001 16:47
To: [log in to unmask]
Subject: Re: Problems with CERES-Wheat ...?


Hello Dr Mathews:

In trying to find out the problem in simulating wheat yields in dry
condition, You have mentioned "The difference is not just in the yield but
also in the total biomass produced, and seems to appear about mid-winter in
December(crop planted in September), ruling out summer drought affecting
grain-filling as an explanation." Please provide some more explanation for
what seems to appear about in mid-winter in Decemeber. By December how much
winter wheat would have grown?

Have you looked at the water stress factor given at the simulation overview
output file? Do you think the model simulates excessive water deficit than
actual stress experienced by the crop? Interested to know your response to
these questions? We are currently attempting to modify CERES Wheat model.
Your comments would be helpful.

Alagarswamy