As warming of the climate gathers alarming pace posing a danger to agriculture, greenhouse cultivation is the only answer to save crops of flowers and vegetables, experts have said.
Greenhouse farming, which is cultivation of plants inside a building with glass walls and roof under controlled condition, has become necessary as temperature ideally required for flower cultivation is no longer available, not even during winter. Floriculturists say that the ideal day and night temperatures for flower cultivation are 28 and 18 degrees celsius respectively.
However, they point out, the temperature in most parts of the country remained above this level even in the peak winter season.
In the wake of the climate change, greenhouse farming is the only way to protect crops and manage a better yield than in normal condition.
Farming under controlled condition, protects crops from wind, rain, radiation, and precipitation.
farmers in several states like Maharashtra, Gujarat, Himachal Pradesh, Karnataka and Andhra Pradesh adopted the greenhouse technology; the farmers in Orissa were yet to start on it.
While over 1,30,000 hectares of area were under flower cultivation in the country, only 1,100 hectares now come under protected cultivation.
Net houses: These are used to reduce adverse effect of scorching sun and rains in vegetables, ornamentals and herbs.
Plastic low tunnels: These are used to raise early nurseries of vegetables and flowering annuals.
Green houses: These are framed structure covered with a transparent material in which crops could be grown under controlled environment.
Glasshouse: Glass is used as a Glazing material in the green house. Glass houses are fitted with the help of wooden or metal frame. The glass houses are constructed in all shapes and sizes and is quite effective for winter cultivation but due to increase in day temperature in summer, it becomes unfit for cultivation during summer. High initial cost, difficulty in construction and frequent damage of glass panels by strong winds have limited its use in both the regions.
Gable Type: A number of wooden structures, constructed gable type, uneven span type and even span type structures are used in Kashmir valley and are covered with 200 micron ultra violent stabilized polythene. Generally wooden structure fabricated gable type greenhouses are predominant in the valley with an average size of 40 sq. m (4 x 10m).
Gothic Type: Big size polyhouse is generally made of gothic type in Kashmir valley because the use of heavy iron structure which can sustain heavy snow load.
Walk in Tunnel: It is most popular type greenhouse which is small semi spherical structure frame made of materials like wood or plastic, iron , G.I. pipes and covered with polyethylene or fiber reinforced plastics. Department of Horticulture is providing these types of green houses to the farmers on subsidized rates. The various sizes of tunnel type green houses that were being utilized by the farmers and installed by different development departments are 40 sq. m (4 m x 10 m), 80 sq. m (5 m x 16 m) and 54 sq. m ( 9 m x 6 m).
Ladakhi Polyhouse: The most common green house in the Ladakh region is the Ladakhi polyhouse and is constructed by three side mud brick wall in place of polyethylene sheets which not only cuts down the installation cost but also reduces the adverse effects of strong winds and increases temperature retention in the green house. The polyhouse has three sides made of sun dried mud bricks. The polythene is supported on wooden poles and side walls.
Trench: This is a very simple, cheap and common green house structure. The various sizes of the trenches are (9 x 3 x 0.9 m) and (10 x 4 x 1 m) respectively. In this pit type of structure, wooden poles are used to hold UV stabilized polyethylene film. The polyethylene is also covered by an additional polyethylene film or woolen or cotton sheet during night to reduce heat loss in extreme winter.
FRP Greenhouse: The glazing material used in the green house is fiber reinforced polyester. The normal dimensions of the green house are (30 x 9 m) with an centre height of 3.04 m and a side height of 1.82 m. The initial cost required for fabrication of the greenhouse is high but the comparative life of the green house is much more than other.
Double layered Polycarbonate Greenhouse: The glazing material used in the green house is double layer polycarbonate. The normal dimensions of the green house is 16.8 x 9.1 m with a center height of 3.3 m and a side height of 1.8 m. The variation in temperature between outside and inside conditions is 20º C.
Polyench Greenhouse: This type of green house combines the trench and green house technology for achieving more temperature inside green house during peak winter. The glazing material utilized in the green house is polyethylene, FRP, double layer and triple layer polycarbonate. The normal recommended dimensions of the green house are (18 m x 4.5 m x 0.8 m).
Solar Polyhouse Drier: Field Research Laboratory (DRDO), Leh has designed and developed a low cost non-conventional zero energy based solar polyhouse drier for scientific and hygienic dehydration of surplus fruits and vegetables like apricot, apple, cauliflower, cabbage, tomato, etc. when there is a glut in the market and to facilitate its availability during the snow bound winter. The drier works on the principle of greenhouse effect where it traps the solar radiation and maintains the temperature inside between 55-69o C. Provision has also been made for removal of hot and moist air from the chamber. It reduces drying period by 40 – 50 % as compared to sun drying.
Light transmission: The green house should have adequate transmission of visible portion of sunlight depending upon crop requirement.
Crops: Tomato, capsicum and cucumber could be grown during off season in Northern plains.
Size: Size may be upto 1000 sq. mt growing area or as small as 20 sq. mt for hardening of tissue culture.
Environmental control: It depends on location of green house. The initial and operating cost become high for some structures. Cooling is generally avoided in this region.
Frame: It could be constructed with wood, aluminium, steel bamboo, bricks, stone, concrete, etc.
Glazing material: UV stabilized LDPE, PVC, EVA acrylic, fibre glass and polycarbonate are being used nowadays.
Structural designs: It must provide adequate safety from wind and snow. Life span of green houses is 25 years, tolerance against atleast 130 km/hr wind speed, temperature extremes, etc.
Green house technology: Green house is the framed or inflated structures cover with transient material large enough to grow crops under partially or fully controlled environmental conditions to get optimum growth and productivity.
Advantages of green house:
1. Crops can be grown all through the year
2. Higher yield
3. Quality produce
4. Plant moisture requirement optimized
5. Good control on pests and diseases
6. Less requirement of intercultivation practices
Points to be considered for planning of green house construction:
1. Site selection - size and future expansion
2. Water supply - source - well, tank, pipeline, river, etc.
3. Fencing - type, gate, cattle trap, etc.
4. Greenhouse - design, plant layout and working drawing
5. Plant system - soil, pot, bags, platform or soil less media