Jeff,

Thank you for your quick response.  The model predicted little N stress and
moderate water stress after heading.  I will check on the excessive water
stress, and we did have more than normal precipitation during the vegetative
growth.

Thanks,

John zhang


************************************

From: "Jeffrey White" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 30, 2005 11:01 AM
Subject: Re: how to jack up LAI for winter wheat


> Hi John,
>
> Have you checked the various stress factors? You may be losing LAI and
> crop biomass because of excessive water or N stress. Besides checking the
> stress factors, you can run the model with no water or N balance.
>
> If that doesn't help, then I would contact Tony Hunt to get guidance on
> modifying the ECO coefficients.
>
> Best regards,
> Jeff
>
> Jeffrey W. White
> USWCL, USDA-ARS
> 4331 E Broadway Rd
> Phoenix, AZ 85040
> Tel. 1-602-437-1702 x 268
> Fax 1-602-437-5291
> [log in to unmask]
>
>
>
> John Zhang <[log in to unmask]>
> Sent by: DSSAT - Crop Models and Applications <[log in to unmask]>
> 09/29/2005 08:24 PM
> Please respond to
> DSSAT - Crop Models and Applications <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> how to jack up LAI for winter wheat
>
>
>
>
>
>
> Hi all,
>
> I am calibrating the wheat model of DSSAT v4 using measured data.  The
> measured maximum leaf area index was about 7.0, but the simulated was only
> 4.5.  The model seems to overestimate stem weight but underestimate the
> leaf weight for the most part of the growing season.  However, the
> simulated specific leaf weight was similar to measured values.  My
> question is: Which parameters should be tapped in order to increase LAID
> while decreasing stem weight?  I have tried a few leaf area related
> paramters in the ECO file, but had no luck.  Anyone out there has a magic
> bullet for this?  BTW, the biomass at harvest was underpredicted by some
> 20% by the model.
>
> Any advice or suggestion will be greatly appreciated.
>
> Thanks and Regards,
>
> John Zhang
> Hydrologist
> USDA-ARS Grazinglands Research Lab
> El Reno, OK
>