Ali,

The N-uptake module in DSSAT4 (at least the CROPGRO and CERES-based
models) does include a soil water factor when calculating potential N
uptake by the roots.  This function only works when the water and N
balance options are set to "Y" in the experiment file, if the N-balance
option is set to "N", N-uptake is assumed to be non-limiting and this
routine is bypassed.  The soil water adjustment factor sets maximum
N-uptake potential when the soil water content for a soil layer = the
drained upper limit and reduces potential uptake for both drier and
wetter conditions.  A unique adjustment factor is calculated for each
soil layer in the profile.  So while soil texture per se is not a part
of the equation, the adjustment is a function of soil-texture-related
factors (saturated water content, drained upper limit, and lower limit)
that are entered for the soil for each site.  I have seen the code that
does this but do not know of a reference that can be cited.  Maybe
someone else can help there.

Additionally, water-stress also affects (increases) partitioning of new
growth to the roots.  This would be another, albeit indirect, adjustment
to potential N-uptake related to water availability.

Hope this helps,

Stu

Ali Sadeghi wrote:
> I wonder if there is N uptake as a function of soil water content and/or soil texture.  Most of the existing watershed models don't have that.  I'm not familiar with the crop models?
>
> Any info is appreciated,
>
> Thanks
>
> Ali M. Sadeghi, Soil Physicist
> USDA-ARS, Hydrology & Remote Sensing Lab.
> Rm.102 Blg. 007, BARC-West
> 10300 Baltimore Ave.
> Beltsville, MD 20705
> Phone:(301) 504-6693
> Fax:    (301) 504-5048
> Email: [log in to unmask]
>
>
>

--
The Ag Guy, LLC
Stuart Rymph, Ph.D., CCA - Wisconsin and Northeast Regions
6063 Beckman Rd.
Mazomanie, WI 53560
Phone (608) 469-8538
Phone/Fax (608) 795-0021
E-Mail: [log in to unmask]