Protected cultivation is the process of growing crops in a controlled environment. This means that the temperature, humidity, light and such other factors can be regulated as per the requirement of the crop. There are various types of protected cultivation practices like a forced ventilated greenhouse, naturally ventilated greenhouse and insect-proof net house, shed net house, plastic tunnel, mulcting, raising bed, trellising, drip irrigation etc. These practices can be used independently or in combination to provide a favorable environment to save the plant from a harsh climate and extend the duration of cultivation or off-season crop production.
Among all the protected cultivation practices, greenhouses are widely used. It provides maximum benefits.
What is the greenhouse effect?
When the short wave radiation from the sun enters the greenhouse structure, it refracts through the surface and get transformed into long wave radiations. These long-wave radiations do not escape the greenhouse entirely, thereby trapping the heat and thus continually increasing the temperature inside the structure. This is known as greenhouse effect.
Greenhouses are being commercially used for production of exotic( non-native) and off-season vegetables, export quality cut flowers and also for raising quality seedlings. Mostly the off-season vegetables are grown under greenhouse structure. Green houses are mostly used as rain shelters, particularly in high rainfall areas of India such as the North Eastern States and Coastal regions.
Objectives of Protected Cultivation:
· Protection of plants from abiotic stress (physical or non-living) such as temperature, excess / deficient water, hot and cold waves and biotic factors such as insect and pest.
· Efficient water use with minimum weed infestation with the help of drip irrigation.
· Enhancing productivity per unit area.
· Minimizing the use of pesticides in crop production.
· Production of high-value, quality horticultural produce.
· Propagation of planting material to improve germination percentage, healthy uniform disease-free planting material, and better hardening.
· Year-round and off-season production of flowers, vegetables and fruit crops,
· Production of disease-free and genetically better transplants.
Limitation of protected cultivation:
· The high initial cost of infrastructure.
· Non-availability of skilled human power and their replacement locally.
· Lack of technical knowledge of growing crops under a protected structure.
· All the operations are very intensive and require constant effort.
· Require close supervision and monitoring.
· Repair and maintenance are major hurdles.