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# Calculating evapotranspiration of tomato crops in a greenhouse.

Thu 23 Jul, 2015 10:16 am
My group is developing a greenhouse for hot and humid environments as our final year project. Since we had to control the inside conditions like temperature and humidity, we included evapotranspiration in our greenhouse model. However we found that calculating the rate of evapotranspiration of tomato crops is not that easy after browsing through a lot of research papers. If anyone here could help me with estimating ET rate by just having greenhouse conditions and local weather data, I would be very obliged. Thanks in advance.
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Type: Discussion • Score: 2 • Views: 765 • Replies: 5

farmerman

3
Thu 23 Jul, 2015 02:10 pm
@talhajohar,
Heres a U Dept Commerce modification of the Thornthwaite Mather model.
http://www.glerl.noaa.gov/ftp/publications/tech_reports/glerl-101/tm-101.pdf
ossobuco

2
Thu 23 Jul, 2015 02:19 pm
@farmerman,
Reminds me of the days I first figured evapotranspiration rates for housing tract landscapes, not by computer.
Oy vey.

Even back then we did not only xeriscape, which I think of as a later word, but drought resistant planting when we could get away with it, re city ordinances, many cities still liking grass.

farmerman

1
Thu 23 Jul, 2015 03:30 pm
@ossobuco,
I remember writing some of the vry first Thornthwaite programs on computer cards and running the entire basin to satisfy some needed piece of **** about one of our mines.

thats when I started hiring people with computer skills in FORTRAN II and BASIC. Were talking late 70's

double oy veh
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talhajohar

1
Thu 23 Jul, 2015 11:21 pm
Thanks for the link. It seems that the Thornthwaite Method relies only on temperature to give evpotranspiration readings. My understanding is that relative humidity also plays a critical part in determining ET along with shortwave radiation from sun. Also I need to make calculations on a smaller time scale i.e. in the order of hour. Can you show me how to improve this method or provide some new method? Thanks again for the help.
farmerman

1
Fri 24 Jul, 2015 02:48 am
@talhajohar,
Thornthwaite is a method that uses calculated data not complex inputs. Ive compared it with other lab methods and its pretty good.
However, it is a "basin evel" calculation . Youre looking at ET values unique to a monoculture.
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