Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Greenhouses protect crops from too much heat or cold, shield plants from dust storms and
blizzards, and help to keep out pests. Light and temperature control allows greenhouses to turn
inarable land into arable land. Greenhouses can feed starving nations where crops can't survive in
the harsh deserts and Arctic wastes. Hydroponics can be used in greenhouses as well to make the
most use of the interior space. Biologist John Todd invented a greenhouse that turns sewage into
water, through the natural processes of bacteria, plants, and animals (Anon,2008).
2. Greenhouse Technology
Greenhouse technology implies production of plants for economic use in covered structure
that allows rapid harvesting of solar radiation and modification of agro-climatic conditions
conducive for plant growth and development. The technology embraces infrastructure modelling,
selection of plants for adaptation, production economics, agronomic management and commercial
potential etc.
“A greenhouse is a framed or an inflated structure covered with a transparent or
translucent material which permits at least partial control of plant environment and which are large
enough to permit a person to carry out cultural operations” (Chandra and Panwar, 1987). While full
advantages is taken of the available sunshine for crop production by way of selecting proper
covering materials, the enclosure provides an opportunity to control the other environmental
parameters. As a result greenhouse crop productivity is largely independent of outdoor
environmental conditions. However, environmentally controlled greenhouses are not popular in
Hilly region simply because of acute shortage of electric power in the region. Hence, greenhouse
technology is discussed with special emphasis on crop production in Hilly region. Types and
design of protected structures mainly depend on the availability of materials, purpose of protection,
climate of the region and market for quality produce. Environmental conditions in general include
light, temperature, air composition and nature of root medium. Depending upon the local climate
and crop requirements, adequate environmental control is attempted rather than full control of fall
components to maximize the profit.
2.2 Principle
A greenhouse is generally covered with transparent material such as polyethylene, glass or
polycarbonate. Depending upon the clading material and its transparency major fractions of
sunlight is absorbed by the crops and other objects. These objects in the greenhouse in turn emit
long wave thermal radiation for which cladding material has lower transparency with the result
solar energy is trapped and resist the temperature inside the greenhouse (Nimje and Shyam,
1991). This is known as greenhouse effect. This rise in temperature in greenhouse is responsible
for crop forcing in adverse climate. During winter month’s loss of trapped temperature should be
minimised whereas, during summer months air temperature in greenhouse is to be brought down
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