Dear DSSAT-list readers,

A few days ago Hiroshi Hasegawa sent an email to the AGMODELS list server,
which obviously was meant for the DSSAT list server, as he realized himself
when sending a follow-up to the DSSAT list. But the DSSAT listers have not
seen his original message and my reply to it, both of which are interesting
for a wider audience. So I forward them both now to the DSSAT list.

Cheers,
Arjan Gijsman


-----Original Message-----
From: Gijsman, Arjan J. (CIAT)
Sent: Wednesday, December 22, 2004 8:37 AM
To: 'Agmodels-L Discussion List'
Subject: RE: Q about different versions

Dear Hiroshi,

Good to see that you upgraded to DSSAT v4.0, which is a lot more interesting
and esp. user-friendly than v3.5. Concerning your questions:
1.  It does not really matter whether SBUILD is about the same as the
utility that was in v3.5. It is only about a user-friendly utility (v4.0) or
an, in my opinion, lousy predecessor. The key point is whether the SOIL.SOL
file is the same and that is surely the case.

If you compare some of the generic profiles in the top section of SOIL.SOL
(IB00000001 .... IB00000012), then you will notice that some parameters
(like LL, DUL, SAT and BD) have changed. This is because when I did a
comparison of estimation methods for soil-water parameters, the method of
Joe Ritchie that was used in v3.5 did not come out as a winner (see: Gijsman
et al. 2002  Wading through a swamp of complete confusion: how to choose a
method for estimating soil water retention parameters for crop models.
European Journal of Agronomy, 18: 75-105). So, another method was used, as
explained just above the generic profiles.

This does not affect the non-generic profiles, because these have been
parameterized by the various researchers who developed them and of course an
outsider is in no position to question how this was done.

2.  One of the major differences between v3.5 and v4.0 is that the latter
has a new SOM/residue module that was based on the CENTURY model (see:
Gijsman et al. 2002 Modifying DSSAT for low-input agricultural systems,
using a SOM/residue module from CENTURY. Agron. Journal. 94:462-474). The
original SOM/residue module of DSSAT is also still included, so that who did
many simulations with v3.5 does not suddenly get different results with v4.0
(the two SOM modules do give quite different results, as shown in Fig. 5 of
the article).
The file SOILN980.SOL only serves for the original module. In v4.0 this file
has been updated and is called SOILN030.SOL. If you want to change some
parameters of the CENTURY-based module, then you have to go to the file
SOMFIX_C.SOL This has many parameters (about 130) but no parameter
explanation (we should add that).

Hope this helps,
Arjan Gijsman
PS: If you would like to receive any of the above-mentioned articles, please
let me know, but note that it can't be send to a Hotmail account, as this
has a limit of 1 MB.



-----Original Message-----
From: [log in to unmask] [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: Tuesday, December 21, 2004 11:33 PM
To: [log in to unmask]
Subject: Q about different versions


Dear users of version 4.0:

Q1. Is SBiuld in version 4.0 virtually the same as Soil Data
Retrieval Utility in version 3.0? If so, I will just transfer
existing soil parameters in SOIL.SOL created in version 3.0 to
SOIL.SOL in version 4.0.

Q2. In version 3.5, a SOILN980.SOL file enables us to change chemical
composition and decay rate constants of fresh organic matter. Where
can I do this in version 4.0?

Best,

Hiroshi Hasegawa