The general reply that is being posted is that genetic coefficients
are fixed. This should be the first assumption, particularly for the
species parameters.
The original question, however, revolved around genetic
coefficients already established by the user. A direct answer would
be that if the data used to develop the new coefficients was from
experiments where water was non-limiting, then the water-related
coefficients may now need revision as well. The bigger question is
why were the modifications made in the first place? Is there really
a genetic basis for the changes? The first step in determining the
appropriate response is defining the problem. This is usually the
most difficult part.
There are, no doubt, situations where the environment and growing
conditions are divergent enough from those that the original
species parameters were developed that the plant behaves
differently. Some parameters may need to be refined as more
information is added to our knowledgebase. However, we must do
our best to make sure that we are changing the right thing for the
right reason.
If the model does not perform as expected, look at what is
happening throughout the model system. Key items to consider
are:
Initial conditions (soil moisture and nutrient levels)
Soil profile information. Pay particular attention to DUL and LL.
Runoff curve number can also be an issue, especially if you are
dealing with no-till or minimum tillage, see:
http://www.lmnoeng.com/Hydrology/hydrology.htm
and click on "Runoff Curve Numbers" or
ftp://ftp.wcc.nrcs.usda.gov/downloads/hydrology_hydraulics/tr55/tr5
5.pdf
for the entire paper. SBuild does not require any surface
cover/residue information, thus the curve number generated may
need manual adjustment when dealing with anything different than
a field plowed with a moldboard plow.
As much as we would like to think that these entries are straight
forward, available information is often incomplete and
interpretation of some of the parameters may differ between
people.
Another potential problem is if there is a process or behavior
observed in the field that is not included in the model. An example
would be winter or summer dormancy. The appropriate response is
to change the model code to include this behavior. Short of that,
you might be able to manipulate management or pest behavior to
improve the prediction (ex. reduce photosynthesis or partially
defoliate through the T file). This would not address the true
problem but may have fewer repercussions than changing the
species file.
Look for these sort of problems first. Change cultivar and ecotype
parameters if your variety has different growth traits. Species file
parameters have been tested fairly thoroughly and should be the
last place to look in adjusting the model.
Stu
Date sent: Tue, 3 Feb 2004 11:40:15 -0000
Send reply to: natp gsdas <[log in to unmask]>
From: natp gsdas <[log in to unmask]>
Subject: Thank u _Clarification about Genetic Co.eff
To: [log in to unmask]
>
> Dear All
> Thank you very much for your suggestion regarding genetic coefficient
>
> Harikrishna
> UAS-Dharwad
> Karnataka
>
>
>
>
>
> On Mon, 26 Jan 2004 Ajeet Nain wrote :
> >Dear Harikrishna
> >Genetid coefficients are cultivar specific (not environment specific) and if you have developed genetic coefficient for a culitvar in any condition, these shoould work in all environmental conditions for all levels of Inputs.
> >Regards
> >Ajeet
> >
> >
> >
> >------------------------------------------------
> >Dr Ajeet Singh Nain
> >Department of Agrometeorology,
> >Indira Gandhi Agricultural University,
> >Labhandi, Raipur- 492 006
> >Chhattisgarh, India
> >Ph: +91 771 2442557(O)
> >Fax: +91 771 2442557(O)
> >
> >Present Address
> >Zentrum für Agrarlandshaft und Landnutzungsforshung (ZALF) e.V.
> >Insititut für Landshaftssystemanalyse
> >Eberswalder Str. 84
> >D-15374 Müncheberg, Germany
> >Tel: 0049-3432-82379, Fax: 0049-3432-82334
> >------------------------------------------------
> >
> >
> >
> >
> >
> >> From: natp gsdas <[log in to unmask]>
> >>Reply-To: natp gsdas <[log in to unmask]>
> >>To: [log in to unmask]
> >>Subject: Clarification about Genetic Co.eff
> >>Date: Sun, 25 Jan 2004 08:49:46 -0000
> >>
> >>
> >>Dear All
> >>One of my research had used DSSAT's CERES-Maize model, Nitrogen was used as a input and came out with a well validated genetic co.efficients. But now I wanted to use the same maize model in another location using Irrigation levels as a inputs. Can I use the same Genetic co.efficients developed during earlier experiment for the new irrigation experiment. Please suggest.
> >>
> >>Harikrishna
> >>UAS-Dharwad
> >>Karnataka
> >>
> >
> >_________________________________________________________________
> >NRI’s, Free Money transfer to India. http://server1.msn.co.in/msnleads/citibankrca/citibankrca2.asp?type=hottag Click here.
> >
Stuart Rymph, M.S., CCA - Florida and Northeast Regions
11313 SW 138 St.
Archer, FL 32618
Phone/Fax (352) 495-3300
E-Mail: [log in to unmask]
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