Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
like tomato, chilli, capsicum, brinjal, cucumber, broccoli and exotic crops that can’t be normally
grown in Indian conditions. It also enables cultivation of off-season crops regular, thus fetching the
farmer a higher price. Parameters such as moisture, soil nutrients and temperature in the
polyhouse are controlled to ensure timely and abundant yields. Productivity is manifold in
greenhouses in comparison to growing the vegetables in open field. Engineering advances have
improved crop yields by controlling the environment in the polyhouses. The estimated area under
green house cultivation in India is 2000 ha that includes 500 ha area under net house, shed house
and 1500 ha under green house, which is mainly in Maharashtra, Uttarakhand, Karnataka, Jammu
& Kashmir. The total area under polyhouse in Uttarakhand is 200 hactares.
Protected structures on one hand provide ambient growing conditions to the plant, on the
other hand this condition is favourable to the plant pathogens also. Though protected farming has
advantage that pathogen do not enter easily from outside but once a pathogen has introduced, it is
very difficult to manage. Control of particularly soil borne plant pathogen under polyhouse is a
challenge, as traditional practices like crop rotation, fallow, mixed cropping etc. usually cannot be
applied. Solarization appears to be of major use in greenhouse culture. Many greenhouse and
nursery crops worldwide now utilize solarization. The ability of greenhouse operators to close up
greenhouses during the hot summer months allows higher solarization temperatures than
achievable in treatment of open fields. Another application for which solarization may come into
common use, particularly in developing countries, is for disinfestation of seedbeds, containerized
planting media, and cold-frames. As with use in greenhouses, these are ideal niches for
solarization, since individual areas to be treated are small, soil temperature can be greatly
increased, the cost of application is low, the value of the plants produced is high, and the
production of disease free planting stock is critical for producing healthy crops.
Weed Control
Solarization results in an effective weed control lasting in some cases for more than two or
three seasons (Abdel Rahim et al., 1988; Verma et al., 2005). In general most of the annual and
many perennial weeds have been found to be effectively controlled. Weed control may be effected
by direct killing of weed seeds by heat, indirect microbial killing of seeds weakened by sublethal
heating, killing of seeds stimulated to germinate in the moistened solarized soil, and killing of
germinating seeds whose dormancy is broken in the heated soil. Volatiles may also play a role in
weed control (Horowitz, 1980; Rubin and Benzamin, 1981).
Increased growth response
Plant growth in solarized infested soil is enhanced as compared to untreated, infested soil
as a result of pathogen control but solarization of soil which is apparently free of known pathogens
often results in improved plant growth. This could be attributed to increased micro and macro
nutrients in soil solution, elimination of minor or unknown pathogens, destruction of phytotoxic
substances in the soil, release of growth regulator like substances, and stimulation of mycorrhiza,
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