Theo:
 
Time to harvest after physiological maturity of maize is highly variable.
At physiological maturity (black layer), the grain is quite wet (35%
moisture).  Producers wait for the maize to dry partially in the field.
That may take 10-15 days under good conditions, longer under poor drying
conditions.  In addition, many of these producers are slow on getting their
crop out (too many acres and too many other crops and enterprises taking
attention).  As a result they may take another 1 to 8 weeks before harvesting.
 
In other words, there is not a single good answer.  Why does it matter to
your simulations?  The yield is made by physiological maturity.  If you
need the time for scheduling planting of another crop (as in adaptation?),
then you need to talk to agr. engineers and economists relative to
harvesting rate and time to cycle to the next crop.  And that would be for
the good farmers.
 
Good luck.  Hope someone else gives advice that is more local.
 
Ken Boote
 
At 02:43 PM 4/8/98 -0600, you wrote:
>Gerrit Hoogenboom wrote:
>>
>> Theodorus :
>>
>> Bushels is a volume measure and varies from crop to crop.
>>
>> The models write out bushels for documentation purposes only.  We use
>> biomass for model evaluation, including crop biomass and yield.  Please
note
>> that the models also do NOT account for seed moisture and assume that seeds
>> are ovendry.  Yield trials and USDA reports normally include seed moisture
>> at 14 or 15 %.
>>
>> I was unable to locate the conversion from bushels to lbs or kg for our
>> variety trial reports.
>>
>> Gerrit
>>
>> At , DSSAT - Crop Models and Applications wrote:
>> >At 12:45 PM 2/11/98 -0700, Theodoros Mavromatis wrote:
>> >>Dear DSSAT users,
>> >>
>> >>working on the evaluation of CERES-Sorghum using experimental data from
>> >>southeastern USA I face the problem of conversion of bushels of sorghum
>> >>to lb. It seems that CERES-Sorghum assumes that 1bu = 60 lb while from
>> >>the experimental data 1 bu ranges from 45 to 55 lb with a mean round 52.
>> >>>From reports regarding agriculture at Kansas I found 56 to be the
>> >>conversion number.
>> >>
>> >>I would really appreciate If someone out there can tell me how this
>> >>number varies and how this affect the model validation taking into
>> >>account that my experiemntal yields are expressed in bu.
>> >>
>> >>Thank you in advance
>Dear DSSAT users,
>
>I am working on the validation of CERES-Maize at Louisiana and I am
>wondering if anyone could recommend me how many days on average after
>the physiological maturity harvest takes place for the medium and early
>corn varieties ?
>
>Thanks in advance,
>
>Theodoros
>--
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Theodoros Mavromatis                           tel: +303-497-8127
>National Center for Atmospheric Research       fax: +303-497-8125
>ESIG, P.O. Box 3000
>Boulder, Colorado, 80307
>USA
>