Dear Dr. Boote,
You sent Juan's letter to me.
Best wishes,
Sincerely,
Wang
Juan,
>
>The SLU1 is just stage 1 evaporation. Stage 2 evaporation which can
>be
>considerable, depends on the depth of water you have in your top
>layer,
>which should always start at 5 cm, then 10 cm. Maybe, define the
>second
>and third layers as 5 cm each to limit evaporation.
>
>Check your runoff (graph it). With very high clay content, you may
>be
>losing too much water to runoff, especially if your soil is a
>cracking clay
>which has good infiltration when cracked (which the curve number
>system
>does not know how to handle).
>
>On the other hand, the default DSSAT methods for calculating
>water-holding
>capacity typically under-estimate the true water-holding capacity of
>soils
>with any substantial clay content. Default is always near 13%
>volumetric,
>but our experience with many soils, shows that water holding
>capacity can
>be easily be 15-17% for such soils.
>
>Lastly, the model is configured (code problem) to have (too slow)
>soil
>water release with high clay content soils. This is my opinion, but
>the
>code has not been fixed yet.
>
>Good luck,
>Ken Boote
>At 01:40 AM 7/6/04 -0700, you wrote:
>>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
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