Ken,

if cultivar coefficients are not site
or environment dependant we could perform
following comparative study:

A new wheat variety has been developed
in Sweden under temperate maritime climate
and terminal moraine soil conditions. To
be able to run the CERES-Wheat model
I would get in touch with some official
institution which performs standarized
breeding testing programs and ask for
their data. Such experiments are typically
carried out under optimum management
conditions, provide a wealth of data and
are thus suitable for performing the
calibration procedure (GENCALC). I would
re-run the calibration procedure to cover
experimental repetitions and different seasons.
If genetic parameters are not season specific
I would then possibly be able to obtain
relatively stable genetic parameters.
They would likely differ from those stated
in the "WINTER-EUROPE" standard set.

Now, only a few hundred kilometers apart
a Polish farmers association, located let's
say at Lodz, got interested in the high yield
potential feature of this new breed and asks
me to determine how this new breed will
possibly perform under their environmental
conditions. Since these conditions
are entirely different from those in Sweden
I would make the necessary modifications in
the soil.sol file and carefully check
the data that must be entered in the *.whx
file. Now, if genetic coefficients for
the new breed are universally applicable,
as you say, I would be able to run the
model under Polish conditions and base
my advise on these simulation outputs.

Can we have faith in such predictions ?

In case we don't, were should we start
adjusting ?

Is it really the model that needs to be
adapted first, or is it actually the
genotype that shows some degree of flexibility
in adjusting to the new environmental
conditions ?


Matthias Langensiepen
Modelling Plant Systems
Institute of Crop Science
Faculty of Agriculture and Horticulture
Humboldt-University of Berlin
Germany