>
>Dear Uday Khodke,
>
>SGRF is primarily soils-related, but is partly crop dependent at
>present.  Maybe in our future work, the two aspects will be separated
>correctly.  However, rate of root depth progression is already a thermal
>time dependent parameter in the CROPGRO
>models, as you say you would like it to be.  The problem is that rate of
>depth progression should be soil-dependent (you probably have a problem soil
>with high clay content and compacted subsoil or acid).  Modeled rate of depth
>progression is NOT presently sensitive to that, and probably should be.  If
>you must, you can change rate of depth progression by changing the value
>from 2.85 (cm/photothermal day), to a smaller value in the PNGRO980.SPE
>file, a section of which is shown below.
>
>!*ROOT PARAMETERS
>    25.0 7500.
>.0100   0.1  0.01  1.50  0.04  RTDEPI,RFAC1,RTSEN,RLDSM,RTSDF,RWUEP1,RWUMX
>     0.0  2.85   3.0  2.85   6.0  2.85  30.0  2.85   XRTFAC,YRTFAC
>
>Everywhere 2.85 occurs, decrease that to something like 2.25
>
>P.S.  2.85 works fine for our sandy soil, against real data on root
>progression.
>
>Ken Boote
>
>At 11:46 AM 11/7/02 +0530, you wrote:
> >Dear All,
> >
> >I also found this difficulty in CROPGROW during simulating water balance for
> >peanut crop.
> >
> >During calibration I tried with a factor SLGF (root growth factor) of
> >SOIL.SOL file. I hope this factor is soil as well as crop dependent.
> >Observed root growth  data indicated that very few roots of peanut(local
> >variety) crop grow in a bottom soil layer of the rootzone(45-60 cm) at the
> >later stage of vegetative growth(75 DAS), so I set SLGF as 0.10 for this
> >layer.
> >
> >However model shows root growth in this layer at the earlier stage (30 DAS
> >onwards) which resulted in extraction of soil water form this layer quite
> >earlier.
> >
> >Can we set this root growth factor as time dependent so that the root
> >dynamics and consequently soil water balance can be simulated more
> >precisely.
> >
> >I am eager to hear whether there is some way to overcome this problem or
> >DSSAT v4.0 has made improvements in this regard.
> >
> >Thanking you in advance,
> >
> >Uday Khodke
> >............................................................................