Or, the next generation of DSSAT needs to be able to "single-step"; i.e. allow some external entity to "peek" at its state variables, perform cross-factor interaction calculations, and then "poke" the changed variables back into DSSAT for the next step. Other interesting aspects are how to put the interacting programs into "suspended animation" while performing such peeking and poking, but there are known checkpointing and gdb tricks to do this.

Obviously this is non-trivial, and would probably involve at least several weeks of work by someone familiar with DSSAT internals. But it would be interesting to be able to link 2 or more DSSAT models, and then have something external look at the individual LAIs, nitrogen and moisture uptakes, etc, and then go back into each and "poke" the next step.

One would want to write that in a general-purpose manner, such that one might be able to externally blend in other factors, such as pests, as well.

Indeed, if anyone out there has a companion computer science department writing GRID-based research proposals (UFL?), hooking up DSSAT using such a mechanism to the stuff of: http://www.uvm.edu/giee/SME3 would allow for modeling crop interactions with surface hydrology, herbavores, hill shading, etc in scalable, location-specific manner.

Chris


-----Original Message-----
From:   Evert, Frits van [mailto:[log in to unmask]]
Sent:   Tue 6/8/2004 6:07 AM
To:     [log in to unmask]
Cc:
Subject:        Re: Modelling intercrops
Kropff, M.J. and H.H. van Laar, 1993. Modelling crop - weed
interactions. Wallingford, CAB International. ISBN:     0-85198-745-1
or 971-22-0038-8

-----Original Message-----
From: DSSAT - Crop Models and Applications
[mailto:[log in to unmask]] On Behalf Of ken boote
Sent: Tuesday, June 08, 2004 14:57
To: [log in to unmask]
Subject: Re: Modelling intercrops


Juan,

The present DSSAT models do not simulate intercrops or differential
height competition for light interception (dry matter accumulation)
purposes.  So, you can not do it in the DSSAT models.

To do this correctly, you would need to predict the height of each crop
and the corresponding (and competing) vertical LAI distribution of each
component.  I recommend that you see the approach followed in the
INTERCOM model of Martin Kropff, Wageningen Agricultural University, The
Netherlands.  His model predicts those aspects of species competition
nicely, but probably does not go to final yield like you would like.
Martin Kropff did write one of those Wageningen special publications on
the topic.  Either Pudoc Publications (Wageningen in-house) or Halstead
Press.

Can anyone give us the full citation of Kropff's book and where to
order?

Ken Boote


At 11:37 PM 6/7/04 -0700, you wrote:
>  My name is Juan and I am trying to simulate the performances of a
>wheat/soybean intercrop.  The design of the intercrop (or relay
> intercrop) is 3:1 and has a distance of 75cm, I have 3 rows of wheat
>to  17,5cm of distance and 1 row of soy to 17,5cm of distance from the
>rows  of wheat and again the same design.  The soy is sown 30 days
>before the  harvest of the wheat.  Because of the design, the wheat
>fails to capture  the totality of the radiation and the soy grows
>inside the wheat during  25-30 days until the wheat harvest and during
>this period the soy receives less radiation than the one that would
>receive it if sown alone. Any idea for this simulation is welcome.
>Greetings Juan Pablo Monzon