greenhouse

Greenhouse Technology is the technique of providing favourable environment condition to the plants. It is rather used to protect the plants from the adverse climatic conditions such as wind, cold, precepitation, excessive radiation, extreme temperature, insects and diseases. It is also of vital importance to create an ideal micro climate around the plants. This is possible by erecting a greenhouse / glass house, where the environmental conditions are so modified that one can grow any plant in any place at any time by providing suitable environmental conditions with minimum labour.

Greenhouses are framed or inflated structures covered with transparent or translucent material large enough to grow crops under partial or fully controlled environmental conditions to get optimum growth and productivity.

 Advantages of greenhouse :

• The yield may be 10-12 times higher than that of out door cultivation depending upon the type of greenhouse, type of crop, environmental control facilities
• Reliability of crop increases under greenhouse cultivation
• Ideally suited for vegetables and flower crops
• Year round production of floricultural crops
• Off-season production of vegetable and fruit crops
• Disease-free and genetically superior transplants can be produced continuously
• Efficient utilisation of chemicals, pesticides to control pest and diseases
• Water requirement of crops very limited and easy to control
• Maintenance of stock plants, cultivating grafted plant-lets and micro propagated plant-lets
• Hardening of tissue cultured plants
• Production of quality produce free of blemishes
• Most useful in monitoring and controlling the instability of various ecological system
• Modern techniques of Hydroponic (Soil less culture), Aeroponics and Nutrient film techniques are possible only under greenhouse cultivation.

Classification of greenhouses: Greenhouse structures of various types are used for crop production. Although there are advantages in each type for a particular application, in general there is no single type greenhouse, which can be constituted as the best. Different types of greenhouses are designed to meet the specific needs. The different types of greenhouses based on shape, utility, material and construction are briefly given below:

1. Greenhouse type based on shape:

For the purpose of classification, the uniqueness of cross section of the greenhouses can be considered as a factor. The commonly followed types of greenhouses based on shape are:

Lean to type greenhouse.

Even span type greenhouse.

Uneven span type greenhouse

Ridge and furrow type

Saw tooth type.

Quonset greenhouse

Interlocking ridges and furrow type Quonset greenhouse.

Ground to ground greenhouse

2. 2. Greenhouse type based on Utility

Classification can be made depending on the functions or utilities. Of the different utilities, artificial cooling and heating are more expensive and elaborate. Hence based on this, they are classified in to two types.

Greenhouses for active heating

Greenhouses for active cooling

3. Greenhouse type based on construction

The type of construction predominantly is influenced by structural material, though the covering materials also influence the type. Higher the span, stronger should be the material and more structural members are used to make sturdy tissues. For smaller spans, simple designs like hoops can be followed. So based on construction, greenhouses can be classified as

Wooden framed structure.

Pipe framed structure.

Truss framed structure.

4. Greenhouse type based on covering material

Covering materials are the important component of the greenhouse structure. They have direct influence on greenhouse effect, inside the structure and they alter the air temperature inside. The types of frames and method of fixing also varies with covering material. Hence based on the type of covering material they may be classified as

Glass glazing

Fibre glass reinforced plastic (FRP) glazing

1. Plain sheet
2. Corrugated sheet.

Plastic film

1. UV stabilized LDPE film.
2. Silpaulin type sheet.

iii. Net house.

Based on the cost of construction involved (which includes various factors mentioned from a to c )

i High cost Green House ii Medium cost Green House iii Low cost Green House The structural requirements and the cost per unit area for different models of low cost green houses for cultivation of vegetables are detailed below with diagrams to enable an interested enterprenur to construct a low cost green house on his own accord. However, the local weather conditions and the individual’s necessity play a major role in the selection of the model.