Vegetable Production under Protective Structure
Commercial cultivation of vegetables is profitable for the farmers. But most of the vegetables are very sensitive to different environmental adverse condition. If vegetables are grown under control environment condition with adequate requirement they grow well. Vegetable cultivation under different protective structure is not a new technique for developed countries but in many developing countries like Bangladesh this techniques is not so familiars to the village farmers.
- Vegetable production under protective structures reduces yield losses from insect pests, diseases.
- Quality of vegetables is higher than any other commercial production.
- It provides higher productivity and returns per unit area.
- Protective structures enable growers to produce vegetables successfully during the off-season, which enhances the availability of fresh produce at times when vegetables are usually in short supply.
- Vegetable prices are higher during the off-season. So, growers also enjoy higher returns per unit area.
- Initial cost is high
- Labour cost is high
There are different types of protective structures for vegetable cultivation. Some of them are-
Lath houses have many uses in propagation, hardening off and acclimation of liner plants prior to transplanting and with maintenance of shade loving and tender plants. It provides outdoor shade and protects plants grown in the container from high temperature. It also reduce moisture stress and decreases the water requirements of plant. Aluminum pipe or wood supports, covering materials such as saran, polypropylene fabric, UV-shaded cloth etc are used for making lath house.
It is most widely used structure. If it carefully constructed and properly maintained, can last for at least five years. Galvanized iron tube and nylon net are used for this structure. Coarse net and finer net is used for large sized insect (such as- lepidopteran moths ) and small sized insect ( such as thrips, whiteflies, and aphids) respectively. Leafy vegetables, tomato, eggplant, cabbage, cauliflower, broccoli, yard-long bean, and bitter gourd can be grown successfully in nethouses.
This structure lasting for about four to five years .The usual dimension of the plastic houses is 25m × 6.5m. Each house has a semicircular top covered with clear plastic treated with an ultraviolet (UV) light protectant. In the center of the semicircular top, a 30 cm portion along the entire length is left free of the plastic cover, but closed with nylon net. The ventilation facility is made rainproof by erecting a transparent plastic shade over the top. vegetables such as tomato, sweet pepper, and cucumber can be grown successfully in this structure.
Closed-Case Propagation System
Hot frames and heated sun tunnel:
The hot frame is a small, low structure used as propagating house. It is large wooden box or frame with a sloping, tight-fitting lid made of window sash. Heated sun tunnel is a another form of hot bed that is made from hooped metal tubing or bent PVC pipe, which is covered with polyethylene. The standard size is 0.9 by 1.8 m. For small propagating operation, this structures are suitable for producing many thousands of nursery plants with low cost.
Cold Frames and unheated sun tunnel
Wood frame with covering polyethylene structure is known as cold frames. In this structures, only the heat of the sun retained by the transparent or opaque white polyethylene coverings, is utilized. Proper ventilation, watering and cold protection is necessary for success of cold frames. It is used in conditioning or rooted cuttings or young seedlings.
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