Behnam,

I think you are not comparing this correctly.  Typically the crop model outputs yield on dry matter basis, and that is what you are getting from your version of DSSAT.  Your experimental value of 70 ton/ha is fresh weight.  In the latest version of DSSAT, we have the ability to output fresh weight of tomato (but that is Version 4.5, which was probably released after the version that you are using).  So, until you get the latest version, you cannot make comparison on fresh weight basis.

So, please make your comparison on the base of dry matter yields.  Tomato fruits are not much more than 6% dry matter concentration, so you would be off by more than a factor of ten, if you compare model output as dry matter, to your data as fresh mass.

Multiple harvesting is not the source of your problem.  DSSAT has a "pest" routine that could mimic partial multiple harvests if you want.  You would need to create a fraction "pod = tomato" removal on given harvest dates and enter that in the File T, and also turn on disease (to "Y") via the simulation controls via XBUILD.  But multiple harvest is not the cause of your lack of comparability.

Ken Boote

-----Original Message-----
From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]] On Behalf Of Behnam Ababaei
Sent: Sunday, October 23, 2011 3:55 AM
To: [log in to unmask]
Subject: Multiple Harvesting of Tomato Harvesting

Dear Users,

In the region of my study, tomato is harvested more than 5 times (even 7).
So, the total yield part exceeds even 70 ton/ha. But, in DSSAT, total yields
hardly becomes more than 16 ton/ha. I think this is because DSSAT doesn't
consider the number of harvesting. Am I right? Is there any way to simulate
such a situation (Multiple harvesting)?





Sincerely Yours.

Behnam Ababaei, Ph.D. Candidate,

Department of Irrigation & Reclamation Engineering,

Faculty of Agricultural Engineering & Technology,
College of Agriculture & Natural Resources,

University of Tehran, Karaj, Iran, 31587-77871.

P.O. Box: 4111.