Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
appropriate size and power installed on the opposite side are needed to cool the green
house.
• Cooling pads should be kept clean of green algae. Dry the pads completely on regular
bases whenever possible. Use a T shaped dull object to scrape salts and dry algae from
the exposed surface of the pads. Be careful not to destroy the pads. Reverse the pads by
turning them around once every two years.
• Reduce sunlight exposure of the pads using a porous black shade cloth and use a black
sump tank with a black cover.
• Keep your greenhouse full of plants whenever possible. On a sunny day, a full grown
tomato plant will lose approximately one quart of water through transpiration. This loss of
water can lower the temperature of the house by at least 10 ºF.
• Use small fans (20 in. diameter) operating continuously above the plants. Half the number
of fans should push the air in one direction on one side of the house and the other half
should do the same thing in the opposite direction on the other side. Run the small fans
non-stop 24 hours a day.
• Leave some vents opened at night to let some fresh outside air enter the greenhouse to
reduce condensation. Closing all the vents at night to save energy may lead to the build up
of ethylene gas as a by-product of heating and may lead to flower abscission and/or reduce
the shelf-life of the fruit.
• Use anti-drip material sprayed on the interior surface of the plastic or use a plastic cover
containing anti-drip properties as part of its formulation to help reduce dripping of moisture
into the plant Eliminating condensation and reducing humidity should reduce the incidence
of botrytis and reduce the need for fungicides.
• Condensation on the fruit may cause minute cracks to develop on the skin. Fruit moisture
lost through the cracks will shorten fruit shelf life.
Using shade cloth to cool the greenhouse
• Shade cloth is not effective in providing significant reduction of air temperature inside the
greenhouse. A 50% shade cloth may lower air temperature by 3 to 4EF.
• However, shade cloth will provide a significant reduction in sunlight entering the
greenhouse.
• Most of the light absorbed by the fruit turns to heat leading to poor color and fruit cracking.
• Reducing light during summer will not retard plant growth because there is more than
enough light for the photosynthesis process, but it can reduce leaf and fruit temperature
leading to improved plant growth and fruit quality.
Growing medium
• Except for the nutrient film technique (NFT), a growing medium consists of solids and pore
space.
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