Dear Arnold,
(it is thanks not tahks... :-))
Regarding the start of simulation, I only partly agree with what Louis du
Pisani wrote. Always running two years in advance only to get the water
balance right, might simply not be feasible because of lacking input data.
And even then it is questionable whether the simulated water balance for the
very day of planting is "better" than starting the simulation only a couple
of weeks before planting. I'd say it depends more on the availability of
observed data on soil water contents or tensions in this case. If you can
match observation made, say, two or three days before planting with a
simulation that started only two weeks before simulation, why would you want
to run two additional earlier years?
But this is regarding only soil water. What about your soil N and C contents
(more important Nmin)? Could your simulation reproduce observations? I could
imagine that in case your model setup triggers a fast depletion of Nmin by
leaching, then, of course, the earlier you start your simulation, the more
depleted the soil is! However, this implies that you didn't change the
initial conditions (Ntot, Corg, Nmin), once you changed the starting date of
simulation. Was this the case?
Regards,
Rolf
> -----Original Message-----
> From: DSSAT - Crop Models and Applications
> [mailto:[log in to unmask]] On Behalf Of Arnold Salvacion
> Sent: Wednesday, November 09, 2005 04:57
> To: [log in to unmask]
> Subject: Re: Date of Simulation
>
> Louis,
>
> Its Arnold not Arnolg, anyway, tahks for the information and idea. If
> you would not mind what if I was just running 1 season simulation or
> forecast, what do you recommend the start of simlulation date with
> reference to planting date?
>
> Thanks and regards,
>
> Arnold
>
> Louis du Pisani <[log in to unmask]> wrote:
> Arnolg,
> Of course your starting date will have a lot to do with your yield
> because
> this has everything to do with the amount of water in the soil when
> planting. I have found that only if I start two years before planting
> date
> can I have confidence in the modeled staring water content. So, whenever
> I
> make a 30-year run, I run 32 years of simulation and throw away the
> first
> two years. If you have a good handle on moisture content when starting
> simulation, this would help.
> Louis du Pisani
> ----- Original Message -----
> From: "Arnold Salvacion"
> To:
> Sent: Tuesday, November 08, 2005 1:54 AM
> Subject: Date of Simulation
>
>
> Dear Colleagues,
>
> Greetings!
>
> Recently I run a simulation in CERES-Maize and I found out that whenever
> I
> change the starting date for simulation,there were variation in the
> yield
> output data. Can anybody explain why is this so? and I just want to ask
> if
> there's any standard date to start simulation in relation to the
> planting
> date?
>
> Thank you and best regards,
>
>
>
>
>
> Arnold R. Salvacion
> ___________________
> University Research Associate
> Institute of Statistics (INSTAT)
> 3rd Floor, Physical Science Building
> University of The Philippines, Los Baņos
> College, Laguna
> Telefax: 049.536.2381
> E-mail: [log in to unmask]
>
>
>
>
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