Protected Cultivation 193
17.3.2 Multipurpose Nets
Shade nets are used to reduce the adverse effect of scorching sun and heavy rain.
Shade houses are becoming popular for growing crops and nursery during summer
season. Net houses are used in high rainfall regions. Roof of the structure is cov-
ered with suitable cladding material mostly HDPE, which does not absorb moisture.
Sides are made of wire mesh of different gauges; 25%–90% shade depending upon
requirements. Such structures are popular in northeastern region of the country.
Insect proof nets are effective to reduce the incidence of pest and viral diseases in
crops. These nets are used like mosquito net around the crops, having 40–50 mesh
size without colours. If we are using the green and red coloured net houses; the prob-
lems of fungus infection (Figure 17.2), poor quality of fruits (smaller and deformed)
and lanky growth of trees results.
17.4 Irrigation
Plants depend on water within the protected structure with no rainfall to supply it
naturally and the added warmth to make the soil dry out more quickly. However,
near zero wind velocity under many protected environments such as polyhouses,
the water requirement of many crops decreases significantly (Rana and Sah 2010).
Traditional watering-cans are, of course, the simplest solution to the problem. They
are particularly useful in providing very specific, targeted watering for individual
plants, particularly if they are being grown in pots or containers.
17.5 Types of Irrigation Systems
A plant nursery requires an irrigation system to water plants effectively and
simultaneously. Nurserymen should think about which watering or irrigation system
best suits their nursery type and size.
FIGURE 17.2 Cercospora leaf spot under green net house.