Juan,

When you simulate a different row spacing in CERES-Wheat (e.g. 16 cm vs. 36
cm), you must adapt the plant population (both PPOP and PPOE) accordingly to
have an effect on the yield. The model seems to capture the effect of row
spacing through plant population and the concept sounds sturdy anyway as
these two components are related and influence light interception by the
crop. Because the model does not update automatically PPOP when row spacing
is modified, you will have to enter the figure yourself. Please try this:
recalculate the number of plants per m2 for row spacing 36 cm and run the
simulation- Thanks

Kofikuma

IFDC Africa division
Lome, Togo (West Africa)
[log in to unmask]
www.ifdc.org

-----Original Message-----
From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]]On
Behalf Of JUAN PABLO MONZON
Sent: Thursday, June 10, 2004 1:20 AM
To: [log in to unmask]
Subject: Re: Modelling intercrops

Hello Emmauel
I was referring to yield. The CERES-Maize respond to row spacing but the
CERES-Wheat is no sensite to row spacing.
Juan
>From: Emmanuel Xevi <[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: Thu, 10 Jun 2004 10:12:20 +1000
>
>Hello Ken
>
>What Juan was referring to is the Yield of Wheat (t/ha).  Even if the rate
of assimilate production is not sensitive to light interception or
extinction coefficient for light interception as far as row spacing is
concerned, the yield as expressed  in t/ha should ( I thought) depend on row
spacing and plant spacing.  The wider the rows the less plants we have per
hectare.  Have I confused the calculation of yield in maize with that for
wheat?
>
>Emmanuel Xevi
>Crop Modeller
>CSIRO Land and Water
>Griffith, NSW Australia 2680
>
>-----Original Message-----
>From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]]
On Behalf Of ken boote
>Sent: Thursday, June 10, 2004 3:53 AM
>To: [log in to unmask]
>Subject: Re: Modelling intercrops
>
>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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