The Himachal Pradesh government is promoting farming inside modern greenhouses called polyhouses to improve the earning potential of farmers in the state, especially during the harsh winters.

The economy of the hill state is highly dependent on agriculture, apart from hydroelectric power and tourism. But most of its farmers have small landholdings on hill slopes, and need to augment their incomes.
It is difficult to grow anything outdoors in the harsh Himalayan winters. So the government is now promoting polyhouse farming, especially for off-season cultivation.

Polyhouses are based on the greenhouse concept to let in heat and light, while preventing the heat from getting out. But instead of the glass on a greenhouse roof, polyhouses are made of cheaper polythene or plastic.By reducing evaporation, they also allow farmers to use sprinkler and drip irrigation systems, thus saving water.

The National Bank for Agriculture and Rural Development (NABARD) has sanctioned a loan of Rs.1.55 billion (Rs.155 crore) to the hill state under which 30,000 polyhouses would be set up in the next four years to promote off-season farming, particularly in the lower- and mid-hills.

“The government will provide 80 percent subsidy for land up to 1,000 square metres to establish sprinklers and drip irrigation systems, and the remaining 20 percent would be borne by the farmer himself”.
The farmer would be provided 50 percent financial assistance for the creation of water resources like shallow wells, pumps and water-drawing systems for the polyhouses.
“The main objective of the project is to promote high-yield production of cash crops and judicious use of natural resources like land and water”.

Farmers in the state are ready to cash in. They said the polyhouses would enable improvement in crop productivity, which reduces drastically during winter.

PROTECTIVE CULTIVATION TECHNOLOGY:

Protected cultivation practices can be defined as a cropping technique wherein the micro climate surrounding the plant body is controlled partially/ fully as per the requirement of the plant species grown during their period of growth. With the advancement in agriculture various types of protected cultivation practices suitable for a specific type of agro-climatic zone have emerged. Among these protective cultivation practices, Green house/poly house cum rain shelter is useful for the hill zones.

PRINCIPLES OF PROTECTIVE CULTIVATION:

The green house is generally covered by transparent or translucent material such as glass or plastic. The green house covered with simple plastic sheet is termed as poly house. The green house generally reflects back 43% of the net solar radiation incident upon it allowing the transmittance of the “photosynthetically active solar radiation” in the range of 400-700 Nm wave length.

The sunlight admitted to the green house is absorbed by the crops, floor, and other objects. These objects in turn emit long wave thermal radiation in the infra red region for which the glazing material has lower transparency. As a result the solar energy remains trapped in the green house, thus raising its temperature. This phenomenon is called the “Green house Effect”. This condition of natural rise in green house air temperature is utilized in the cold regions to grow crops successfully. However in the summer season due to the above stated phenomenon ventilation and cooling is required to maintain the temperature inside the structure well below 350C. The ventilation system can be natural or a forced one.

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In the forced system fans are used which draw out 7-9m 3 of air / sec / unit of power consumed and are able to provide 2 air changes / minute.
The various types of cooling systems employed are as follows :

A. Roof Shading

B. Water film covering

C. Evaporative cooling which includes the following

i) Fan and pad cooling
ii) High pressure mist system
iii) Low pressure mist system

However in the cold regions like Shimla,natural ventilation is sufficient to maintain the desired temperature in the poly house. This can be achieved using the agro-shade net or by providing doors (on opposite sides) in order to facilitate cross ventilation.

BENEFITS OF GREEN HOUSE TECHNOLOGY:

The benefits which can be derived from the green house cultivation are as follows :

1. Environment control allows raising plants anywhere in the world at any time of the year i.e. crops could be grown under the inclement climatic conditions when it would not be otherwise possible to grow crops under the open field conditions.

2. The crop yields are at the maximum level per unit area, per unit volume and per unit input basis.

3. The control of the microcosm allows the production of higher quality products which are free from insect attack, pathogens and chemical residue.

4. High value and high quality crops could be grown for export markets.

5. Income from the small and the marginal land holdings maintained by the farmer can be increased by producing crops meant for the export markets.

6. It can be used to generate self employment for the educated rural youth in the farm sector.

Protective cultivation technology:

Protected cultivation practices can be defined as a cropping technique wherein the micro climate surrounding the plant body is controlled partially/ fully as per the requirement of the plant species grown during their period of growth. With the advancement in agriculture various types of protected cultivation practices suitable for a specific type of agro-climatic zone have emerged. Among these protective cultivation practices, Green house/poly house cum rain shelter is useful for the hill zones.

Principles of protective cultivation:

The green house is generally covered by transparent or translucent material such as glass or plastic. The green house covered with simple plastic sheet is termed as poly house. The green house generally reflects back 43% of the net solar radiation incident upon it allowing the transmittance of the “photosynthetically active solar radiation” in the range of 400-700 Nm wave length.

The sunlight admitted to the green house is absorbed by the crops, floor, and other objects. These objects in turn emit long wave thermal radiation in the infra red region for which the glazing material has lower transparency. As a result the solar energy remains trapped in the green house, thus raising its temperature. This phenomenon is called the “Green house Effect”. This condition of natural rise in green house air temperature is utilized in the cold regions to grow crops successfully. However in the summer season due to the above stated phenomenon ventilation and cooling is required to maintain the temperature inside the structure well below 350C. The ventilation system can be natural or a forced one.
In the forced system fans are used which draw out 7-9m 3 of air / sec / unit of power consumed and are able to provide 2 air changes / minute. The various types of cooling systems employed are as follows :

A. Roof Shading

B. Water film covering

C. Evaporative cooling which includes the following

i) Fan and pad cooling
ii) High pressure mist system
iii) Low pressure mist system

However in the cold regions like Shimla,natural ventilation is sufficient to maintain the desired temperature in the poly house. This can be achieved using the agro-shade net or by providing doors (on opposite sides) in order to facilitate cross ventilation.

Benefits of green house technology:

The benefits which can be derived from the green house cultivation are as follows :

1. Environment control allows raising plants anywhere in the world at any time of the year i.e. crops could be grown under the inclement climatic conditions when it would not be otherwise possible to grow crops under the open field conditions.

2. The crop yields are at the maximum level per unit area, per unit volume and per unit input basis.

3. The control of the microcosm allows the production of higher quality products which are free from insect attack, pathogens and chemical residue.

4. High value and high quality crops could be grown for export markets.

5. Income from the small and the marginal land holdings maintained by the farmer can be increased by producing crops meant for the export markets.

6. It can be used to generate self employment for the educated rural youth in the farm sector.

Himachal Pradesh annually earns more than Rs.25 billion (Rs.2,500 crore) from the cultivation of fruits and vegetables. The cultivation of exotic vegetables and flowers in polyhouses will add to the prosperity of the growers.

PRESENT NATIONAL SCENARIO OF GREENHOUSE TECHNOLOGY:

Application for the green house technology for commercial purpose is however in its infancy in India. The green houses which existed in 1960s were used for commercial purposes but the impetus and the much required thrust came only in the mid 1980’s with the emergence of the industries manufacturing U.V. stabilized Low Density Poly Ethelene (L.D.P.E.) and the development of the indigenous technology for low cost green houses. Indian Petro Chemicals Limited (I.P.C.L) was one of the foremost industries operating in collaboration with the agricultural scientists in this field. In 1985, Indian Agricultural Research Institute (I.A.R.I) designed and set up green house at Leh (J&K). Today there are more than 1840 small and medium sized greenhouses at Leh.

Farmers are also utilizing low and medium cost greenhouses for raising potted plants and seedlings in the nursery. In the Northern Gangetic plains especially in Punjab, Haryana and Uttar Pradesh, the farmers are using this technology to raise healthy seedlings of high yielding crop varieties so that they can be transplanted early in the fields during the onset of the spring season so as to capture the early markets and thus reap higher returns. In the North Eastern states, especially in Assam, efforts are on to raise vegetable crops in the greenhouse-cum-Rain Shelter Structures during the long south west monsoon periods. In these regions stress is being given for the development of low cost greenhouses using bamboo frame structures as these construction materials are readily available in these regions. The results obtained in this regard from
the concerned agricultural universities are encouraging.

The State Seed Corporation of India is utilizing at present the medium and the high cost greenhouse technology in their seed production units so as to maintain higher degree of purity of parental lineage and genotype. A large number of private companies are utilizing at present the high cost multispan greenhouse technology which has provisions for microprocessor controlled environment control system like operation of motorized shading system, on line drip irrigation system, supplementary heating and lighting system
and the likes for vegatative propagation of chrysanthemums, roses, carnations, gladiolus etc.

Development of indigenous evaporative cooling system have taken place in recent times to control greenhouse air temperature during the long summer months. Exhaust fans of upto 60 cms diameter and some specialized equipment are being widely manufactured nowadays in the country. At the same time great strides have been made to develop advanced cellulose and polyfab nylon cooling pads for usage in these cooling systems. The thermostats, thermocouples, high pressure mist and fogging system etc. and other environmental control equipment are being manufactured now a days in the country itself. Similarly, various brands of glazing material which include the U.V. stabilized polythene sheets, the fibre glass reinforced plastics, the twin wall polycarbonate sheets, etc.are also available in the local market
now-a- days. Micro irrigation system and application procedures for applying the chemical and bio-fertilizers in the liquefied form are available for ready usage in the greenhouse.