62 DIMENSIONS OF AGRICULTURAL SCIENCE
The majority of hilly (part of northern plain) areas have full of fertile land. Which is
perfect for vegetable production, but facing extreme temperature ranges from 0°–48°. Hence
it is not possible the year round production (Wani et al., 2011). At the plain area, during the
pre and post rainy season the crop become susceptible to biotic agent e.g. Tomato,
cauliflower, chilli, and okra. It has been found that the high altitude of hills affected with
extreme cold –5° to –30° consequently difficult to grow vegetable during November to
March. Protected agriculture, which includes polyhouse, shade net, poly-tunnel, polymulch,
etc., protects the agricultural cropsfrom sudden changes in weather and regulates the
environment inside these structures (Negi et al., 2013). Greenhouse/poly house/net house are
suitable technology under this diverse climate for year round and off season vegetable
production. The protected vegetables cultivation technology can be utilized production of
high value, low volume vegetables, crops production of virus free quality seedlings, quality
hybrid seed production and as a tool for disease resistance breeding programs. The need of
protected cultivation since last 10 years has been dramatically increased. The various cause
are reduced weed pressure, moistureconservation, reduction of certain insect pests, highercrop
yields, and more efficient use of soil nutrients (Negi et al., 2013).
Protective cultivation practices can be defined as cropping techniques wherein the micro
climate surrounding the plant body is controlled partially/fully, as per the requirementof the
plant species grown, during their period of growth (Mishra et al., 2010). The various types of
protective cultivation practices have been adopting based upon the prevailing climatic
condition. Among them, greenhouse/polyhouse is extremely useful for Round-the-year
vegetable cultivation in temperate condition (Mishra et al., 2010). Protected cultivation also
known as controlled environment agriculture (CEA) is highly productive, conservative of
water and land and also protective of the environment (Jensen, 2002).
Principles of Greenhouse Cultivation
The greenhouse cultivation based upon the principle called as greenhouse effects.
Actually, greenhouse is a structure made with the transparent covering material (polythene,
glass), that, transmit the solar energy inside the structure. This energy absorbed by the
vegetable crops and the objects inside the house releasing light of long wave length, finally
this light does not emit out as the cladding material is non-transparent for these light. Finally
the light gets trapped inside increasing the inside temperature. This rise in temperature in
greenhouse is responsible for growing of vegetable in cold climate. However during summer
increase in temperature can be managed by ventilation and cooling system, as in this period
temperature rose beyond the critical temperature.
Why Protected Cultivation ?
The open field production of vegetable encounter with many production constrains like
heavy rain, thunderstorms, excessive solar radiation, temperatures and humidity levels above
plant growth optima (Max et al., 2009), high insect pest infestation pressure (Nguyen et al.,
2009) and fungal diseases (Sringarm et al., 2013). Environment is the most determinate factor
in horticultural crop (Trivedi and Singh, 2015). Protected cultivation is being used to control