Dear Mr. Yang,

The SLPF is the same as the soil fertility factor, and includes all soil
factors other than nitrogen-supplying and water-holding traits.  It has
nothing to do with the  genetic coefficient, LFMAX, potential
light-saturated leaf photosynthesis.  However, the SLPF will decrease that
potential genetic photosynthesis rate.

SLPF was calibrated to give values of 0.92 for Florida sandy soils and 1.00
for good Midwestern soils.  Your soil really should be in-between those
two.  We have used values like 0.95 to 0.97 for North Carolina soils, and
you should be similar.  Do not use a value of 1.00 which will overpredict
for you.  Note the value under SLPF in the three attached soil files, such
as 0.97 for an Orangeburg sandy loam.  I recommend you start with SLFP =
0.95 and see what happens.

The reason for the SLPF is that we do not have soil phosphorus or soil
potassium simulated.  We do not have, but could use good contributions from
soil fertility scientists in a manner like Barber and Silberbush did about
15-20 years ago.  Such modeling soil fertility types no longer are in our
profession.

Good luck,
Ken Boote


>*IBSB910015  Gainesville         180 Millhopper Fine Sand
>@SITE        COUNTRY          LAT     LONG SCS FAMILY
>  -99         -99              -99      -99 Loamy,silic,hyperth Gross.
> Paleudults ( 15)
>@ SCOM  SALB  SLU1  SLDR  SLRO  SLNF  SLPF  SMHB  SMPX  SMKE
>    -99  0.18   5.0  0.50  66.0  1.00  0.92 IB001 IB001 IB001
>@  SLB  SLMH  SLLL  SDUL  SSAT  SRGF  SSKS  SBDM  SLOC  SLCL  SLSI  SLCF
>SLNI  SLHW  SLHB  SCEC
>      5   -99 0.023 0.086 0.230
> 1.000   7.4  1.36  0.90   -99   -99   -99   -99   5.3   -99   -99
>     15   -99 0.023 0.086 0.230
> 1.000   7.4  1.40  0.69   -99   -99   -99   -99   5.4   -99   -99
>     30   -99 0.023 0.086 0.230
> 0.498  15.8  1.46  0.28   -99   -99   -99   -99   5.7   -99   -99
>     60   -99 0.023 0.086 0.230
> 0.294  28.0  1.47  0.20   -99   -99   -99   -99   5.8   -99   -99
>     90   -99 0.021 0.076 0.230
> 0.380  27.6  1.43  0.09   -99   -99   -99   -99   5.9   -99   -99
>    120   -99 0.020 0.076 0.230
> 0.133  17.5  1.48  0.03   -99   -99   -99   -99   5.9   -99   -99
>    150   -99 0.027 0.130 0.230
> 0.062   0.3  1.57  0.03   -99   -99   -99   -99   5.9   -99   -99
>    180   -99 0.070 0.258 0.360
> 0.031   0.1  1.79  0.03   -99   -99   -99   -99   5.9   -99   -99
>
>
>*IBSB910017  Quincy, FL          203 Orangeburg Sandy Loam
>@SITE        COUNTRY          LAT     LONG SCS FAMILY
>  -99         -99              -99      -99 Loamy,silic,hyperth Gross.
> Paleud(17)
>@ SCOM  SALB  SLU1  SLDR  SLRO  SLNF  SLPF  SMHB  SMPX  SMKE
>    -99  0.13   9.0  0.27  84.0  1.00  0.97 IB001 IB001 IB001
>@  SLB  SLMH  SLLL  SDUL  SSAT  SRGF  SSKS  SBDM  SLOC  SLCL  SLSI  SLCF
>SLNI  SLHW  SLHB  SCEC
>      5       0.125 0.198 0.294 1.000  -9.0  1.49  1.73  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>     15       0.125 0.198 0.294 0.874  -9.0  1.49  1.73  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>     25       0.125 0.198 0.294 0.874  -9.0  1.49  1.73  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>     34       0.117 0.226 0.323 0.351  -9.0  1.41  0.40  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>     43       0.117 0.226 0.323 0.351  -9.0  1.41  0.40  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>     53       0.138 0.250 0.332 0.310  -9.0  1.44  0.20  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>     64       0.138 0.250 0.332 0.310  -9.0  1.44  0.20  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>    102       0.167 0.281 0.331 0.302  -9.0  1.57  0.14  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>    145       0.182 0.291 0.334 0.077  -9.0  1.59  0.16  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>    175       0.162 0.272 0.320 0.036  -9.0  1.61  0.09  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>    203       0.154 0.263 0.319 0.006  -9.0  1.58  0.03  -9.0  -9.0  -9.0
> -9.00  -9.0  -9.0  -9.0
>
>*IBSB910026  Castana, IO         180 Ida Silt Loam
>@SITE        COUNTRY          LAT     LONG SCS FAMILY
>  -99         -99              -99      -99 Ida Silt
> Loam                                      ( 26)
>@ SCOM  SALB  SLU1  SLDR  SLRO  SLNF  SLPF  SMHB  SMPX  SMKE
>    -99  0.12   6.0  0.30  60.0  1.00  1.00 IB001 IB001 IB001
>@  SLB  SLMH  SLLL  SDUL  SSAT  SRGF  SSKS  SBDM  SLOC  SLCL  SLSI  SLCF
>SLNI  SLHW  SLHB  SCEC
>      5   -99 0.135 0.290 0.485
> 1.000   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>     15   -99 0.135 0.290 0.485
> 1.000   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>     30   -99 0.135 0.290 0.485
> 0.175   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>     45   -99 0.106 0.228 0.514
> 0.138   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>     60   -99 0.106 0.228 0.514
> 0.138   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>     90   -99 0.105 0.254 0.517
> 0.188   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>    120   -99 0.133 0.290 0.507
> 0.250   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>    150   -99 0.108 0.283 0.505
> 0.213   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99
>    180   -99 0.108 0.291 0.542
> 0.100   -99  0.00  0.00   -99   -99   -99   -99   -99   -99   -99



At 03:10 PM 3/8/02 -0500, you wrote:
>Dear members,
>
>I am using CROPGRO-Soybean model within DSSAT35 for simulating the rainfed
>growth of soybean in coastal plain soil in Virginia. The Soil Fertility
>Factor(SLPF) to be required in FILES was mentioned in some papers, such as
>G.G. Wilkerson etc.(2001) and T. Mavromatis etc. (2002).  However, I
>couldn't find such a factor in Table 10 Soil Data File (FILES) in Volume 2
>of DSSAT version 3. What matching "SLPF" I found in the Manual is
>Photosynthesis Factor.
>
>Is Photosynthesis Factor the synonym of the Soil Fertility Factor?
>
>Thank you in advance for any help.
>
>Jinzhong Yang