Hi all,

I am not familiar with the rice model in DSSAT, but very familiar with the
soil-organic-matter / soil-N section of CROPGRO and CERES, as we just
developed a new modular version with two different SOM/soil-N modules (the
old one and a new one, which is based on the CENTURY model).

Though DSSAT v3.5 has a leaching and an N balance option, neither of the two
are great and have several code errors. It is hard to judge in how far this
affected your results, but I have experienced myself with a new CROPGRO
version, in which many of these errors were corrected, that the leaching
jumped up quite a bit. This is of no immediate use for you now, but may help
to understand why it goes as it does in the model.

This new DSSAT version is still in development and will probably not be
released before the Fall. In all likelihood, all the models (CROPGRO, CERES,
SUBSTOR, rice...) will have been turned upside down --- with hopefully many
errors fixed.

As Brian already indicated, the SOM dynamics under flooded, anaerobic
conditions may be quite different from a nonflooded soil. As far as I know,
the present rice model uses the same SOM code as the other (dryland) models,
but it could very well be that this does not make any sense at all. I am
therefore in doubt whether we can link the new CENTURY-based SOM module also
to the rice model; for CROPGRO and CERES it is a big improvement, but I
don't want to introduce new  errors in the rice model. In the Agronomy
Journal of May-June, you can read about this new SOM/soil-N module: Gijsman
et al. 2002 Modifying DSSAT Crop Models for Low-Input Agricultural Systems
Using a Soil Organic Matter-Residue Module from CENTURY


Greetings,

Arjan Gijsman
Univ. Florida / Centro Internacional de Agricultura Tropical (CIAT), Cali,
Colombia


-----Original Message-----
From: neda [mailto:[log in to unmask]]
Sent: Wednesday, January 30, 2002 2:19 PM
To: [log in to unmask]
Subject: Re: About nitrate leaching


Hi
I am very interested to know about your N leaching results. If you resolve
the problem, and got reliable answers , please inform me.
Yours
Neda Farahbakhshazad
******************************************************
Dr Neda Farahbakhshazad
(Wallenberg Fellow in Environment and Sustainability)
Massachusetts Institute of Technology
Ralph Parsons Laboratory for Water Resources and Hydrodynamics
15 Vassar Street, 48-114
Cambridge, MA 02139, USA
Phone: ++1 617 253 5450, Fax:++1 617 253 7475
Email: [log in to unmask]
  1/30/2002 +0700, you wrote:
>Dear sir /all
>
>I am using DSSAT-RICE model.My main purpose is to find out the
>nitrate  nitrogen and total nitrogen leaching from the paddy field.But I
>could not see nitrate leaching in DSSAT model.Only nitrogen leaching
>(code:NLCC=1.1 kg/ha) which is also vary low valve when comparing with
>measured value (measured value=3.63 kg/ha for nitrate and 18.2 kg/ha for
>Total nitrogen). I measured the daily value from the filed by the use of
>soil-water sampler and analyze in laboratory by phenate method  for
>nitrate, nessler method for ammonia  and Kjeldhal method for TKN. I also
>checked this data with mass balance approach, but  value is almost same
>.So I have problem about the model application.Could you
>help me  what's the problem? and how can solve it? I   tried but can not
>enclosed the RIX file , simulated file on RIN, RIO. herewith. I look
>forward your kind cooperation
>
>Yours Sincerely
>Bipin Kumar Pathak
>Mail Box No: 193
>Asian Institute of Technology
>P.O.Box: 4
>Khlong Luang, Pathumthani 12120
>Thailand
>Email:[log in to unmask]