Angela,

Those MG are almost not affected by photoperiod and cool temperature is
your problem.  That is why GDD might work for Canada, but not for USA.
This would be true for R stages.  For V stages, we see no difference
among cultivars in rate of leaf appearance regardless of location.  All
have same base temperature, 8 C, which we apply for hourly temperature
cycle.  Our TRIFOL coefficient, of 0.32 per physiological day, means
that a leaf is formed every 1/0.32 days at optimum temperature of 28 to
35 C,  (a bit more than 3 days per leaf at optimum temperature).  Using
a Tb of 8, can you translate what that means for your GDD system for
leaf appearance?  Remember to go from hourly values to Tave which is the
typical for GDD systems.

Ken Boote

Angela Gessleman wrote:

>Ken: Thank you for the information. I have a correlation for GDD for
>soybean from Canada, but only for maturity groups 00, 0 and 1, so I was
>wondering if such a thing existed for the maturity groups grown in the
>US. We are in the process of trying to switch our crop models to the
>DSSAT ones, so I know there is going to be a "leap" in the complexity as
>we make the transition. I appreciate the help!
>Angela
>
>-----Original Message-----
>From: DSSAT - Crop Models and Applications
>[mailto:[log in to unmask]] On Behalf Of Ken Boote
>Sent: Thursday, April 06, 2006 3:58 PM
>To: [log in to unmask]
>Subject: Re: Growing Degree Day (GDD) Correlations for soybean
>
>Angela,
>
>I forgot to tell you  places to look for the phenological scales.  If
>you have the DSSAT CD-ROM, look in DSSAT4\Documentation for the Volumes
>1 to 4, and also in DSSAT4\Documentation\DSSATv3.5 for other volumes 1
>to 4.  I think phenological stages are in one of the v3.5 documents.
>The stages for soybean correspond to the Fehr and Caviness, Crop Science
>11:929 (1971), except that we predict first occurrences for R3, R4, R5,
>and R6 rather than occurrence at the top 4 expanded nodes.  The R stages
>for peanut are from Boote.  1982.  Peanut Science.  I don't know where
>to send you for the cereals.
>
>Ken Boote
>
>Ken Boote wrote:
>
>
>
>>Angela,
>>
>>The phenology in the DSSAT model for soybean does not translate into
>>GDD for two reasons:  1) our temperature function is more complex,
>>having a flat topped Topt, and a temperature (Topt2) above which the
>>rate of development slows down.  So you can not translate into GDD;
>>2) the reproductive stages are also mostly daylength sensitive, plus
>>having the complex temperature function, so even more reason you can
>>not translate to GDD.  So what you want, does not exist.  You will
>>need to use it the DSSAT soybean model the way we use it.  V stages
>>predict very well, and there is no need to adjust anything.  If you
>>have a soybean cultivar for which the R stages are not predicted
>>accurately, you need to adjust to the correct maturity group type (or
>>changing the CSDL) in the cultivar file.
>>
>>Good luck with it.
>>Ken Boote
>>
>>
>>
>>Angela Gessleman wrote:
>>
>>
>>
>>>Hello. I am a new user of the DSSAT program. Does anyone know of a
>>>reference which corresponds GDD with the Vegetative (V) and
>>>Reproductive
>>>(R) stages in soybean? Additionally, is there an area in the DSSAT
>>>software that lists the phenological scales that are used for barley,
>>>
>>>
>
>
>
>>>chickpea, potato, soybean and wheat. If anyone knows of someone doing
>>>
>>>
>
>
>
>>>work in DSSAT for canola, that would be appreciated as well.
>>>
>>>
>>>
>>>Regards...
>>>
>>>Angela Gessleman
>>>
>>>
>>>
>>>