| Yield-potential graphs for hydroponic greenhouse tomato production
were developed for a decision model (HYTOMOD). In all cases,
yield represented marketable fruit and the highest yield was
assumed to be a function of both harvested weight per unit area
and high quality fruit.
The model and curves are unique in that they are based on
extensive scientific literature and were tested and validated
by four independent expert growers. During the validation
process, experts actually found the competition with HYTOMOD
to be stimulating to their own skills and knowledge!
While the yield-potential graphs are an essential component
of a computer decision model, they can also be used effectively
as teaching aids. Each graph can be useful to new growers
for basic plant production guidelines and each is a unique
tool for experienced growers to refine their growing skills.
These graphs are accessible at this site in the Graphical
Primer. The program HYTOMOD has been rewritten in Java so
that it is interactive and accessible over the internet. It
is also available here in the Interactive Decision Support
section.
Successful hydroponic tomato growing is assumed to be based
on five key tests during each of five growth stages. The five
growth stages are: 1) germination and early growth, 2) seedling,
3) vegetative, 4) early fruiting, and 5) mature fruiting.
The five key tests are 1) hydrogen ion concentration and 2)
electrical conductivity of the feeding solution, 3) root temperature,
4) greenhouse air temperature, and 5) relative humidity. Night
and daytime light levels are also independent considerations
for all growth stages except germination.
This decision support system, implemented in the Decision
Support Algorithm, is a model based in utility theory.
The optimal growing conditions for tomato plants are known
to the algorithm, and they are stored in a database. These
optimal growing conditions are known to be acceptable because
they are obtained from peer reviewed scientific literature.
The model, is a model of the behavior of a hydroponic tomato
grower. The model can recognize when growing conditions are
not optimal and recommend which conditions need to be modified.
It can also prioritize them according to the manager's preference,
this preference is called a utility. These utility levels
allow the conditions of the crop to be assessed. These values
are not the same as risk because they don't predict whether
a crop will be successful or not, they communicate the typical
expert grower's preference. This preference will in turn be
related to risk and other factors. Another factor which affects
the utility level is the managers aspiration level. This software
driven manager aspires to having a high yield, high quality
crop.
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Credits
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Special thanks for this effort goes
to a hard working engineering graduate student from
Egypt, Ahmed El-Attal for his work in creating the original
version of the model (HYTODMOD). Also, our thanks to
Jim Brown of CropKing, Inc, Seville, OH. Mr. Brown's
intensive course for beginning growers gave us the focus
for this work.
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