Diseases and Management of Crops under Protected Cultivation
Diseases and Management of Crops under Protected Cultivation
Diseases and Management of Crops under Protected Cultivation
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Loads For Greenhouse:<br />
(<strong>Diseases</strong> <strong>and</strong> <strong>Management</strong> <strong>of</strong> <strong>Crops</strong> <strong>under</strong> <strong>Protected</strong> <strong>Cultivation</strong>)<br />
• Green house should be low cost but effective structures.<br />
• Neverthless, they have to withst<strong>and</strong> outside weather stresses such as storm, rain, hail, <strong>and</strong><br />
snow (if snowfall occurs).<br />
• The main loads or action to considered are:<br />
• Dead loads or permanent load, self-weight <strong>of</strong> structural <strong>and</strong> non-structural elements,<br />
excluding the installation even if they are permanently present.<br />
• Wind loads are “action imposed on the structure by wind”<br />
• Snow loads have to considered in the region with snowfall.<br />
• Crop loads have to be considered where structures support crops.<br />
• Where crops are suspended on separate horizontal wires the horizontal tensile forces<br />
transmitted to the structure have to be taken into assessment.<br />
Minimum values <strong>of</strong> GH design loads<br />
Load<br />
1. Dead load :<br />
Pipe frame, double PE 10<br />
Buss frame lapped glass 25<br />
2. Live load : Fogging / misting system, crop load,<br />
mounted instrument etc<br />
3. Snow load 75<br />
Minimum, kg/sq-m<br />
4. Wind load Depending on prevailing wind<br />
speed<br />
Design requirement:<br />
• The general design requirement for plastic-film greenhouses are:<br />
• Sufficient stability against wind <strong>and</strong> crop loads. That means sufficient dimension <strong>of</strong> the<br />
construction component, <strong>and</strong> installation <strong>of</strong> wind braces.<br />
• The connection <strong>and</strong> connectors between the different construction component must not<br />
move or slide by load forces.<br />
• The foundation <strong>under</strong> the stanchions have to endure pressure <strong>and</strong> suction forces by wind.<br />
• The plastic film must not flutter by wind forces. It has to be stretched <strong>and</strong> fixed tightly on<br />
the structure.<br />
• Drops <strong>of</strong> condensed water should not fall down from the inner surface <strong>of</strong> the film onto the<br />
plants, but they have to run <strong>of</strong>f at the film.<br />
• Gutters are necessary to drain <strong>of</strong>f <strong>and</strong> collect the rainwater.<br />
• Windbreaks should be installed if the wind velocity is too high.<br />
Greenhouse Environmental Control<br />
• A greenhouse is essentially meant to permit at least partial control <strong>of</strong> microclimate within it.<br />
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