Juan,

It will be rather arbitrary to just change incoming radiation to mimic 
light capture by the wheat crop over the soybean.

You can do that, only if you measure the light penentration through the 
wheat crop, or if you know the leaf area index, in which case you can use 
an extinction coefficient for wheat and assume that the soybean gets only 
that light that passes through wheat.

Ken Boote

At 11:25 PM 6/9/04 +0000, you wrote:

>Ken<?xml:namespace prefix = o ns = 
>"urn:schemas-microsoft-com:office:office" />
>
>My idea is to resolve the problem in a very easy way and I want to change 
>the incoming radiation (by a multiplicative factor or just changing the 
>weather data) based on 1st year of experimental data and to use the 2nd 
>year for validation. Because the crop yield is a function of the absorbed 
>radiation and the intercrop yield of wheat and soybean is lower than in 
>sole crops because they had capture less radiation.
>
>What do you think?
>
>  Juan P. Monzon
> >From: ken boote <[log in to unmask]>
> >Reply-To: DSSAT - Crop Models and Applications <[log in to unmask]>
> >To: [log in to unmask]
> >Subject: Re: Modelling intercrops
> >Date: Wed, 9 Jun 2004 13:52:45 -0400
> >
> >Juan,
> >
> >The wheat model is not sensitive to row spacing, as it lacks row
> >spacing impact on light interception or on the extinction
> >coefficient for light interception.  It also does not predict height
> >or width.
> >
> >Ken Boote
> >
> >At 11:13 PM 6/8/04 +0000, you wrote:
> >
> >>Ken
> >>
> >>Thanks for your answer. I am reading a paper of M. Kropff. (Agri.
> >>Syst. 73: 173-203). I also have problems when I was trying to
> >>simulate wheat, when I change the row distance from 18cm to 36cm
> >>the yield does not change, even if I change it to 100cm.
> >>
> >>Juan Pablo Monzon
> >>
> >> >From: ken boote <[log in to unmask]>
> >> >Reply-To: DSSAT - Crop Models and Applications
> >><[log in to unmask]>
> >> >To: [log in to unmask]
> >> >Subject: Re: Modelling intercrops
> >> >Date: Tue, 8 Jun 2004 08:57:13 -0400
> >> >
> >> >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
> >>
> >>
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