Green House technology

Introduction

In the present scenario of perpetual demand flowers, vegetables, orchids and shrinking land holding drastically, protected cultivation is the best alternative for using land and other resources more efficiently. In protected environment, then natural environment is modified to suitable conditions for optimum plant growth which ultimately provide quality products.

Hence in tropical climate, Green House is an important place where green house or shade-loving foliage plants are kept. Green House is an artificial constructed shade and covered structures of plastic film, which allow the solar radiation to pass through but traps the thermal radiation emitted by plants inside and thereby provide favourable climatic conditions for plant growth.it is the ultra-mode device used for controlling temperature, humidity, light intensity, CO₂ level inside.If properly constructed, keeping in view the availability of light and circulation of air, green house may also be used for growing orchids both epiphytic and terrestrial.

Points to be considered while constructing green house

• East and south sun is excellent for the green house, which can remain open on both these sides, but it should be shaded on the north and the west to protect from winds.
• Construction: A plan should be prepared before constructing the green house together with plan of beds and paths on the ground.
• Selection of plastic film structure and roof slope
• Use of proper controlled climatic condition
• Area and Green house structure
• Plant protection measures

Types of green houses:

• Tunnel type (cold climate green house)
• Quonset (semicircular/subtropical green house)
• Gabble type (slopping roof)
• Tropical region green house
• Ridges and furrows green house
• Ground to ground green house

Low-cost greenhouse/polyhouse

The low-cost polyhouse is a zero-energy chamber made of polythene sheet of 700 gauge supported on bamboos with `sutli’ and `nails’. Its size depends on the purpose of its utilization and availability of space. Like the greenhouse, it has one opening kept azar for 1-2 hr during the day, especially in the morning to reduce the level of humidity inside. The temperature within polyhouse increases by 6-10⁰C more than outside. In UV-stabilized plastic film covered, pipe framed polyhouse, the day temperature is higher and night temperature lower than the outside. The solar radiations entering the polyhouse is 30-40% lower than that reaching the soil surface outside.

Medium-cost greenhouse/polyhouse:

With a slightly higher cost, a Quonset-shaped polyhouse (greenhouse) can be framed with GI pipe (class B) of 15 mm bore. This polyhouse has a single layer covering UV-stabilized polythene of 800 gauge. The exhaust fans are used for ventilation those are thermostatically controlled. Cooling pad is used for humidifying the air entering the polyhouse. The polyhouse frame and glazing material have a life span of about 20 years and 2 years respectively.

Hi-tech greenhouse/polyhouse

This type of greenhouse consists of a sensor, a comparator and an operator. The temperature, humidity and light are automatically controlled. These are indicated through sensor or signal-receiver. Sensor measures the variables, compare the measurement to a standard value and finally recommend to run the corresponding device. For example, temperature control system consists of temperature sensor, heating/cooling mechanism and thermostat-operated fan. Similarly, relative humidity is sensed through optical tagging devices. Boiler operation, irrigation and misting systems are operated under pressure sensing system. This modern structure is highly expensive, requiring qualified operators, maintenance, care and precautions.

Advantages of green house technology:

• Protection from adverse climatic conditions
• Increase yield 4-5 times than traditional planting
• Harvesting time can be adjusted
• Off-season crop produce may be obtained
• Disease free plants may be obtain
• More profit due to continuos supply of produce through out the year
• Water saving as use of drip/sprinkle system
• Barren and uncultivable land may be brought under use
• Get more foreign exchange due to export
• Useful technology for hybrid seed production
• Employment generating technology