Chris,
    Congratulations on the accomplishment. Please send me reprints once the
papers are published.
    One of the big surprises here in Nebraska is the recent (last two years)
emergence of significant acreage in wheat/soybean relay intercropping. The
winter wheat is used to "clean up" residual soil nitrogen following seed
corn production in the irrigated cropping system.
    Those pursuing the intercrop models should watch carefully to see
whether interplant competition, in the particular system of interest, causes
significant changes in plant development. If so, the standard
thermal-time/daylength models for development will not work as expected.
Properly simulating plant height under the influence of interplant
competition is also a problem that needs to be looked at carefully.

Sincerely,
Bob Caldwell,
  Res. Assoc. Prof., Natural Resource Systems Analyst
  School of Natural Resources, University of Nebraska - Lincoln
  306 Keim Hall, P.O. Box 830910, Lincoln, NE 68583-0910
[log in to unmask]    Phone: (402) 472-4792. FAX: (402) 472-7904.


> -----Original Message-----
> From: DSSAT - Crop Models and Applications
> [mailto:[log in to unmask]] On Behalf Of Robin Matthews
> Sent: Tuesday, June 08, 2004 3:37 PM
> To: [log in to unmask]
> Subject: Re: Modelling intercrops
>
> Chris
>
> We have also done exactly what you have suggested with the
> PALM (People and Landscapes Model). Several of the DSSAT crop
> models have been rewritten as objects in Delphi, with the
> rates calculation and integration of state variables
> separated and callable from outside the object. Any number of
> these objects can be run in parallel along with others for
> livestock, tree growth, weed growth, and human decision
> making, and in fact different instances of the same object
> can even be run simultaneously (e.g. to simulate two crops of
> wheat growing in separate fields, each with its own
> management regime). A number of Field objects (containing
> various combinations of the above objects) can be assembled
> to represent a 3D landscape (i.e. areal x depth) if necesary.
> The overall controlling routine (i.e. main model) calls the
> rates calculation routine of each object in turn, followed by
> the corresponding state integration routine of each object in
> turn, and also provides the route for commu!
>  nication between objects. In fact, the objects are more
> reactive agents, with this communication via KQML messaging.
> The structure allows the overall model to run a timestep at a
> time, after which variables within each object can be peeked
> at (actually a request for information by the peeking object)
> and and this information used as a basis for decision-making
> by the decision module. Thus, decisions can be made in 'real
> time' on the basis of the instantaneous states of these
> variables, rather than after each model had run as the old
> structure enforced.
>
> Convesting the DSSAT models to this structure was not a big
> job once the architecture was worked out, although the system
> for routing and interpreting messages did take more time.
>
> Papers on (a) the model and its architecture, and (b) on its
> application to study sustainability of different cropping
> systems, have just been submitted and are under review at the moment.
>
> Robin Matthews
> Reader in Biosystems Modelling
> Cranfield University.
>