Dear Juan,

The CERES models (and I suppose the CROPGRO's) are very sensitive to soil
depth but I am not clear if they handle soil evaporation to the extent that
no tillage can be reflected as you intend it. You might want to check your
soil file and see if the parameters specified (esp. if generated by DSSAT)
reflect your growing conditions. For instance, once you limit soil depth to
40 cm e.g., the model will indirectly reflect the negative effect of soil
impediments on rooting conditions and nutrition- and therefore yield. It
sounds like in your case, the roots are rather thriving well even in shallow
soils- the positive effect on observed yields therefore. In the model, the
SRGF is also important (among others of course) in this process. You might
consider readjusting your SRGF values to reflect how no till influences root
distribution.

Best regards

Kofikuma

 -----Original Message-----
From:   DSSAT - Crop Models and Applications [mailto:[log in to unmask]]
On Behalf Of Juan Pablo Monzon
Sent:   Tuesday, July 06, 2004 9:41 AM
To:     [log in to unmask]
Subject:        Soil evaporation

Hello
I am trying to simulate no tillage soybean with the Cropgro, and I can not
lower the soil evaporation. Even if I change the SLU1 to 0.0 the model still
simulate a very high soil evaporation. And in very shallow soils (<40cm) the
yield are 100-200kg when the observed yields are 2000kg, and I think that if
I can transformed that soil evaporation into crop transpiration the yields
will improve. When I test the Cropgro with shallow soils in dry year the
model simulated very low yields, but I do not have any problem in more
normal year or more depth soils. I appreciate any collaboration.
Juan from Argentina