Design And Maintenance Of Green House - AgriMoon

25d ago
39 Views
2 Downloads
7.68 MB
281 Pages
Last View : Today
Last Download : 6d ago
Upload by : Annika Witter
Share:
Transcription

Design and Maintenanceof Green HouseDr. R.F. Sutar

Design and Maintenance of Green HouseAuthorDr. R.F. SutarAAU, Anand,

INDEXLesson NameModule 1. History and types of greenhouseLesson 1 History and Types of GreenhouseModule 2.Function and features of greenhouseLesson-2 Function and Features of GreenhouseModule 3.Scope and development of greenhouse technologyLesson 3 Scope and Development of Greenhouse TechnologyModule 4.Location, planning and various components ofgreenhouseLesson 4 Location, Planning and VariousComponents of GreenhouseModule 5.Design criteria and calculationsLesson 5 Criteria for Design and Construction of GreenhouseLesson 6 Design Load Calculations : Part ILesson 7 Design Load Calculations: Part IIModule 6. Construction materials and methods ofconstructionLesson 8 Construction MaterialLesson 9 Methods of constructionModule 7. Covering material and characteristicsLesson-10 Greenhouse CoveringModule 8. Solar heat transferLecture 11 Solar RadiationLecture 12 Heat Transfer for Solar Energy UtilizationModule 9. Solar fraction for greenhouseLesson 13 Solar Radiation in GreenhousesLesson 14 Effect of Different Spectrum of solarRadiation on Plant GrowthModule 10. Steady state analysis of greenhouseLesson15 State Analysis of A Ridge Ventilated GreenhouseLesson 16.Greenhouse Steady State Energy Balance and MassBalance ModelsModule No. 11 Greenhouse Heating, Cooling, Shedding andVentilation SystemLesson 17 Heating 1-134

Lesson 18 Cooling, Shedding and Ventilation Systems ofGreenhouseModule 12. Carbon dioxide generation and monitoring andlighting systemsLesson 19 Carbon dioxide generation and monitoring and lightingsystemsModule 13. Instrumentation and & computerizedenvironmental control systemsLesson-20 Portable Instruments to Control the GreenhouseEnvironmentLesson 21 Computerised Environmental Control of theGreenhouseModule 14. Watering, fertilization, root substrate andpasteurizationLesson 22 Watering, Fertilization, Root substrate andPasteurizationModule 15. Containers and benchesLesson 23 Containers & BenchesModule 16. Plant nutrition, Alternative cropping systemsLesson 24. Plant Nutrition and Alternative Cropping SystemModule 17. Plant tissue cultureLesson 25 Plant Tissue Culture: History,Terminologies and Laboratory RequirementsLesson 26 Plant Tissue Culture: Basic Process and TechniquesUsedModule 18. Chemical growth regulationLesson 27 Chemical Growth regulationModule 19. Disease control, integrated pest management,Lesson 28 Disease Control, Integrated Pest ManagementModule 20: Post Production Quality and HandlingLesson 29 Post Production Handling of Greenhouse ProductionLesson 30 Post -Harvest Quality of Greenhouse ProduceModule 21: Cost analysis of greenhouse ProductionLesson 31 Cost Analysis of Greenhouse ProductionModule 22. Application of greenhouse & its repair &maintenanceLesson 32 Repair and Maintenance of 9270-274275-280

Design and Maintenance of Green HouseModule 1. History and types of greenhouseLesson 1 History and Types of Greenhouse1.1 INTRODUCTION:What is Greenhouse Technology?Today about 92% of plants, raised by man, are grown in the open field. Since the beginning ofagriculture, farmers have had to cope with the growing conditions given to them by MotherNature. In some of the temperate regions where the climatic conditions are extremelyadverse and no crops can be grown, man has developed technological methods of growingsome high value crops by providing protection from the excessive cold and excessive heat.This is called Greenhouse Technology. “Greenhouse Technology is the science of providingfavourable environment conditions to the plants”. It also protects the plants from theadverse climatic conditions such as wind, cold, precipitation, excessive radiation, extremetemperature, insects and diseases. An ideal micro climate can be created around the plants.Greenhouses are framed or inflated structures covered with transparent or translucentmaterial large enough to grow crops under partial or full controlled environmentalconditions to get optimum growth and productivity.1.2 HISTORICAL BACKGROUND OF GREENHOUSESBefore the 20th century - Agriculture production inside protected structures was initiated inFrance and Netherlands in the 19th century. This method was applied in simple, low, glassstructures, which provided climate protection, and were used mainly for the growth ofornamental plants.Modern Times - By the beginning of the 20th century, mostly after the end of 2nd world war,the technology of greenhouse construction accelerated its development, especially in WesternEurope cold countries, Netherlands leading the course. Agro-technical systems, aerationsolutions and accompanying accessories were gradually added to the structures, while thestructure foundations improved to the known, traditional heavy steel constructions coveredby rigid glass boards.New Materials - By the end of the fifties of the 20th century the greenhouses technologyflowed to the north and center of Europe, extending its influence and benefits to Israel, wherea wave of experiments and research in the field had begun. The sixties revealed a new kind ofstructure covering sheets. They were the flexible, low priced polyethylene sheets, whichcaused a conceptual revolution in the field of greenhouses. Simultaneously appeared othertypes of good light transition coverings, such as polycarbonate (a kind of covering made ofplastic polymers) leaving behind the traditional glass covering.New Technologies - The method of modular structures (Lego-like method) leads to thedevelopment of growth technologies suitable for most types of crops, thus creating5www.AgriMoon.Com

Design and Maintenance of Green Housecustomized structure projects, customer-tailored according to specific needs. This new trendcaused the breakdown of the traditional, conservative Dutch hegemony ruling until then inthe field of greenhouses. Nowadays, light-weighted structures with covering made of flexiblepolyethylene or stiff-flexible polycarbonate are more common and widespread than themythological rigid glass greenhouses.1.3 TYPES OF GREENHOUSESGreenhouse structures of various types are used for crop production. Although there areadvantages in each type for a particular application, in general there is no single type ofgreenhouse, which can be constituted as the best. Different types of greenhouses aredesigned to meet the specific needs. The different types of greenhouses based on shape,utility, material and construction are briefly given below:1.3.1. Greenhouse Type Based On Shape:For the purpose of classification, the uniqueness of cross section of the greenhouses can beconsidered 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.1.3.1.1 Lean-to type greenhouseA lean-to design is used when a greenhouse is placed against the side of an existing building.It is built against a building, using the existing structure for one or more of its sides(Fig.1.3.1). It is usually attached to a house, but may be attached to other buildings. The roofof the building is extended with appropriate greenhouse covering material and the area isproperly enclosed. It is typically facing south side. The lean-to type greenhouse is limited tosingle or double-row plant benches with a total width of 7 to 12 feet. It can be as long as thebuilding it is attached to. It should face the best direction for adequate sun exposure.The advantages of the lean-to type greenhouse are; It is usually close to available electricity, water, and heat. It is a least expensive structure.6www.AgriMoon.Com

Design and Maintenance of Green House This design makes the best use of sunlight and minimizes the requirement of roofsupports.Disadvantages of the lean-to type greenhouse are;1. Limited space, limited light, limited ventilation and temperature control.2. The height of the supporting wall limits the potential size of the design.3. Temperature control is more difficult because the wall that the greenhouse is built on,may collect the sun's heat while the translucent cover of the greenhouse may lose heatrapidly.Fig. 1.3.1. Lean-to-type type greenhouses(source: www.howtobuild-a-greenhouse.org, www.small-greenhouses.com,)1.3.1.2 Even span type greenhouseThe even-span is the standard type and full-size structure, the two roof slopes are of equalpitch and width (Fig.1.3.2). This design is used for the greenhouse of small size, and it isconstructed on level ground. It is attached to a house at one gable end. It can accommodate 2or 3 rows of plant benches. The cost of an even-span greenhouse is more than the cost of alean-to type, but it has greater flexibility in design and provides for more plants. Because ofits size and greater amount of exposed glass area, the even-span will cost more to heat. Thedesign has a better shape than a lean-to type for air circulation to maintain uniformtemperatures during the winter heating season. A separate heating system is necessaryunless the structure is very close to a heated building. It will house 2 side benches, 2 walks,and a wide center bench. Several single and multiple span types are available for use invarious regions of India. For single span type the span in general, varies from 5 to 9 m,whereas the length is around 24 m. The height varies from 2.5 to 4.3 m.7www.AgriMoon.Com

Design and Maintenance of Green HouseFig 1.3.2. Even Span Type Greenhouse(source: www.arcadiaglasshouse.com,)1.3.1.3 Uneven span type greenhouseThis type of greenhouse is constructed on hilly terrain. The roofs are of unequal width; makethe structure adaptable to the side slopes of hill (Fig.1.3.3). This type of greenhouses isseldom used now-a-days as it is not adaptable for automation.Fig 1.3.3. Uneven Span Type Greenhouse1.3.1.4 Ridge and furrow type greenhouseDesigns of this type use two or more A-frame greenhouses connected to one another alongthe length of the eave (Fig. 1.3.4). The eave serves as furrow or gutter to carry rain and meltedsnow away. The side wall is eliminated between the greenhouses, which results in a structurewith a single large interior, Consolidation of interior space reduces labour, lowers the cost ofautomation, improves personal management and reduces fuel consumption as there is lessexposed wall area through which heat escapes. The snow loads must be taken into the frame8www.AgriMoon.Com

Design and Maintenance of Green Housespecifications of these greenhouses since the snow cannot slide off the roofs as in case ofindividual free standing greenhouses, but melts away. In spite of snow loads, ridge andfurrow greenhouses are effectively used in northern countries of Europe and in Canada andare well suited to the Indian conditions.Fig. 1.3.4. Ridge and furrow type greenhouses(Source: www.nafis.go.ke )1.3.1.5 Saw tooth type GreenhouseThese are also similar to ridge and furrow type greenhouses except that, there is provision fornatural ventilation in this type. Specific natural ventilation flow path (Fig. 5) develops in asaw- tooth type greenhouse.Fig. 5. Saw tooth type greenhouses(Source: www.netafim.com )9www.AgriMoon.Com

Design and Maintenance of Green House1.3.1.6 Quonset greenhouseThis is a greenhouse, where the pipe arches or trusses are supported by pipe purling runningalong the length of the greenhouse (Fig. 1.3.6). In general, the covering material used for thistype of greenhouses is polyethylene. Such greenhouses are typically less expensive than thegutter connected greenhouses and are useful when a small isolated cultural area is required.These houses are connected either in free, standing style or arranged in an interlocking ridgeand furrow. In the interlocking type, truss members overlap sufficiently to allow a bed ofplants to grow between the overlapping portions of adjacent houses. A single large culturalspace thus exists for a set of houses in this type, an arrangement that is better adapted to theautomation and movement of labour.Fig. 1.3.6 Quonset Type Greenhouse(source: www.gothicarchgreenhouses.com )1.3.2. Greenhouse Type Based on UtilityClassification 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 areclassified in to two types. Greenhouses for active heating. Greenhouses for active cooling.1.3.2.1 Greenhouses for active heatingDuring the night time, air temperature inside greenhouse decreases. To avoid the cold bite toplants due to freezing, some amount of heat has to be supplied. The requirements for heatinggreenhouse depend on the rate at which the heat is lost to the outside environment. Variousmethods are adopted to reduce the heat losses, viz., using double layer polyethylene, thermopane glasses (Two layers of factory sealed glass with dead air space) or to use heatingsystems, such as unit heaters, central heat, radiant heat and solar heating system.1.3.2.2 Greenhouses for active coolingDuring summer season, it is desirable to reduce the temperatures of greenhouse than theambient temperatures, for effective crop growth. Hence suitable modifications are made in10www.AgriMoon.Com

Design and Maintenance of Green Housethe green house so that large volumes of cooled air is drawn into greenhouse, This type ofgreenhouse either consists of evaporative cooling pad with fan or fog cooling . Thisgreenhouse is designed in such a way that it permits a roof opening of 40% and in some casesnearly 100%.1.3.3. Greenhouse Type Based on ConstructionThe type of construction predominantly is influenced by structural material, though thecovering material also influences the type. Higher the span, stronger should be the materialand more structural members are used to make sturdy tissues. For smaller spans, simpledesigns like hoops can be followed. So based on construction, greenhouses can be classifiedas Wooden framed structure. Pipe framed structure. Truss framed structure.1.3.3.1 Wooden framed structuresIn general, for the greenhouses with span less than 6 m, only wooden framed structures areused. Side posts and columns are constructed of wood without the use of a truss (Fig1.3.7)Pine wood 8 is commonly used as it is inexpensive and possesses the required strength.Timber locally available, with good strength, durability and machinability also can be usedfor the construction.Fig 1.3.7. Wooden Framed Greenhouses(Source:www.mcgreenhouses.com, www.greenhouseandsunrooms.com )11www.AgriMoon.Com

Design and Maintenance of Green House1.3.3.2 Pipe framed structuresPipes are used for construction of greenhouses, when the clear span is around 12m (Fig.1.3.8). In general, the side posts, columns, cross ties and purlins are constructed using pipes.In this type, the trusses are not used.Fig1.3.8. Pipe Framed Greenhouse Structures(Source: www.angrau.ac.in, www.hiddenvalleyhibiscus.com, www.albertahomegagardening.com )1.3.3.3 Truss framed structuresIf the greenhouse span is greater than or equal to 15m, truss frames are used. Flat steel,tubular steel or angular iron is welded together to form a truss encompassing rafters, chordsand struts (Fig. 1.3.9). Struts are support members under compression and chords aresupport members under tension. Angle iron purlins running throughout the length ofgreenhouse are bolted to each truss. Columns are used only in very wide truss frame housesof 21.3 m or more. Most of the glass houses are of truss frame type, as these frames are bestsuited for pre-fabrication.Fig 1.3. 9. Truss Framed Greenhouse Structures(Source: www.angrau.ac.in, www.gothicarchgreenhouses.com , www.redpath.co.nz )12www.AgriMoon.Com

Design and Maintenance of Green House1.3.4. Greenhouse Type Based on Covering MaterialCovering materials are the major and important component of the greenhouse structure.Covering materials have direct influence on the greenhouse effect inside the structure andthey alter the air temperature inside the house. The types of frames and method of fixing alsovaries with the covering material. Based on the type of covering materials, the greenhousesare classified as glass, plastic film and rigid panel greenhouses.1.3. 4.1 Glass greenhousesOnly glass greenhouses with glass as the covering material existed prior to 1950. Glass ascovering material (Fig.1.3.10) has the advantage of greater interior light intensity. Thesegreenhouses have higher air infiltration rate which leads to lower interior humidity andbetter disease prevention. Lean-to type, even span, ridge and furrow type of designs areused for construction of glass greenhouse.Fig.1.3.10 Glass Greenhouse(source: www.gothicarchgreenhouses.com)1.3.4.2 Plastic film greenhousesFlexible plastic films including polyethylene (Fig. 1.3.11), polyester and polyvinyl chlorideare used as covering material in this type of greenhouses. Plastics as covering material forgreenhouses have become popular, as they are cheap and the cost of heating is less whencompared to glass greenhouses. The main disadvantage with plastic films is its short life. Forexample, the best quality ultraviolet (UV) stabilized film can last for four years only.Quonset design as well as gutter-connected design is suitable for using this coveringmaterial.13www.AgriMoon.Com

Design and Maintenance of Green HouseFig.1.3.11 Polyethylene film greenhouse(Source: www.poly-ag.com )1.3.4.3 Rigid panel greenhousesPolyvinyl chloride rigid panels, fibre glass-reinforced plastic, acrylic and polycarbonate rigidpanels (Fig.1.3.12) are employed as the covering material in the quonset type frames or ridgeand furrow type frame. This material is more resistant to breakage and the light intensity isuniform throughout the greenhouse when compared to glass or plastic. High grade panelshave long life even up to 20 years. The main disadvantage is that these panels tend to collectdust as well as to harbor algae, which results in darkening of the panels and subsequentreduction in the light transmission. There is significant danger of fire hazard.Fig.1.3.12 Polycarbonate Covering(Source: www.advancegreenhouses.com )14www.AgriMoon.Com

Design and Maintenance of Green House1.3.5 Greenhouse Type Based on Cost of ConstructionBased on the cost of construction involved;1. High cost Green House2. Medium cost Green House3. Low cost Green House1.3.6 Shading NetsThere are a great number of types and varieties of plants that grow naturally in the mostdiverse climate conditions that have been transferred by modern agriculture from theirnatural habitats to controlled crop conditions. Therefore, conditions similar to the naturalones must be created for each type and variety of plant. Each type of cultivated plant must begiven the specific type of shade required for the diverse phases of its development. Theshading nets fulfil the task of giving appropriate micro-climate conditions to the plants.Shade nettings are designed to protect the crops and plants from UV radiation, but they alsoprovide protection from climate conditions, such as temperature variation, intensive rain andwinds. Better growth conditions can be achieved for the crop due to the controlled microclimate conditions ―created‖ in the covered area, with shade netting, which results in highercrop yields. All nettings are UV stabilized to fulfil expected lifetime at the area of exposure.They are characterized of high tear resistance, low weight for easy and quick installation witha 30-90% shade value range. A wide range of shading nets (fig 1.3.13) is available in themarket which is defined on the basis of the percentage of shade they deliver to the plantgrowing under them.Fig 1.3.13 Shading net15www.AgriMoon.Com

Design and Maintenance of Green HouseModule 2.Function and features of greenhouseLesson-2 Function and Features of Greenhouse2.1. FUNCTIONS OF GREENHOUSE:Greenhouses are framed or inflated structures covered with transparent or translucentmaterial large enough to grow crops under partial or fully controlled environmentalconditions to get optimum growth and productivity. The yield may be 10-12 times higher than that of outdoor cultivation depending uponthe 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 utilization 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 propagatedplant-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 filmtechniques are possible only under greenhouse cultivation.2.2. GREENHOUSE FEATURESAlthough greenhouses look like simple structures, there's more to them than meets the eye. Areliable frame, covering, flooring and ventilation are all necessary for basic operation. Tosustain the environment, a heating system and some automated processes, like irrigation viaa dedicated water supply, may also be necessary.16www.AgriMoon.Com

Design and Maintenance of Green House2.2.1 The Frame:A sturdy frame is necessary to maintain the plastic or glass panels that let in precious lightand capture heat in the greenhouse. Larger greenhouses also need a foundation. The framecan be made of any number of materials, the most common of which are aluminum, wood,rigid PVC and galvanized steel. Aluminum lets in more light and can also support clip-onpanels, making it the most common choice.2.2.2 The Coverings:Often referred to as glazing, the panels that cover greenhouses are specially designed to let inas much of the sun's radiation as possible. Ideally, they also provide insulation, areimpervious to deterioration from ultraviolet radiation and are shatterproof. The panels canbe made of heavy glass or any of a number of synthetic materials designed to maximize lightexposure and help reduce heat loss. Glass lets in about 90 percent of the sun's radiation,helping to retain heat and hold up to ultraviolet light. Synthetics, while cheaper andsometimes stronger than glass, let in less of the sun's rays.2.2.3 The Flooring:Greenhouse floors need to have excellent drainage. Floors can be made of concrete, stoneslabs, brick, sand or even dirt. Gravel floors provide excellent drainage and can be used inconjunction with a weed barrier to keep weeds from growing up through the rocks.2.2.4 Greenhouse ventilation:Ventilation is one of the most important components in a successful greenhouse. If there is noproper ventilation, greenhouses and their plants can become prone to problems. The mainpurpose of ventilation is to regulate the temperature to the optimal level, and to ensuremovement of air and thus prevent build-up of plant pathogens (such as Botrytis cinerea) thatprefer still air conditions. Ventilation also ensures a supply of fresh air for photosynthesisand plant respiration, and may enable important pollinators to access the greenhousecrop.Ventilation can be achieved via use of vents - often controlled automatically - andrecirculation fans.2.2.5 Greenhouse heating:Heating is one of the most considerable factors in the operation of greenhouses across theglobe, especially in colder climates. The main problem with heating a greenhouse as opposedto a building that has solid opaque walls is the amount of heat lost through the greenhousecovering. Since the coverings need to allow light to filter into the structure, they converselycannot insulate very well. With traditional plastic greenhouse coverings having an R-Value ofaround 2, a great amount of money is therefore spent to continually replace the heat lost.Most greenhouses, when supplemental heat is needed use natural gas or electrical furnaces.Passive heating methods exist which seek heat using low energy input. Solar energy can becaptured from periods of relative abundance (day time/ summer), and released boost thetemperature during cooler periods (night time/winter). Waste heat from livestock can also be17www.AgriMoon.Com

Design and Maintenance of Green Houseused to heat greenhouses; e.g. placing a chicken coop inside a greenhouse recovers the heatgenerated by the chickens, which would otherwise be wasted.Electronic controllers are often used to monitor the temperature and adjust the furnaceoperation to the conditions. This can be as simple as a basic thermostat, but can be morecomplicated in larger greenhouse operations.2.2.6 Automated Watering System used in greenhouse:Water is the most important element for plant growth. Without it, plant cannot survive. Themanual system to watering is inefficient. When we water manually, the possibility to overwatering is high. Some plant can drown when we supply too much water to them.In order to overcome this problem, automatic greenhouse watering system is used. Sensorssuch as temperature sensor and soil moisture detector are used to control the wateringsystem in a greenhouseThe system also has the capability to control the water level. In Drought prone area, a tank isused that acts as a reservoir tank in case of water problem. In this tank a sensor is used toensure that water level is at its maximum level.18www.AgriMoon.Com

Design and Maintenance of Green HouseModule 3.Scope and development of greenhouse technologyLesson 3 Scope and Development of Greenhouse Technology3.1. A SCOPE ON GREENHOUSES AROUND THE WORLDThere are more than 55 countries now in the world where cultivation of crops is undertakenon a commercial scale under cover and it is continuously growing at a fast rateinternationally.The United States of America has a total area of about 15,000 ha under greenhouses mostlyused for floriculture with a turnover of more than 3.4 billion US per annum and the areaunder greenhouses is expected to go up considerably, if the cost of transportation ofvegetables from neighbouring countries continues to rise.Spain has been estimated to be around 28,000 ha and Italy 19,500 ha used mostly for growingvegetable crops like watermelon, capsicum, strawberries, beans, cucumbers and tomatoes. InSpain simple tunnel type greenhouses are generally used without any elaborateenvironmental control equipment mostly using UV stabilized polyethylene film as claddingmaterial.In Canada the greenhouse industry caters both to the flower and off-season vegetablemarkets. The main vegetable crops grown in Canadian greenhouses are tomato, cucumbersand capsicum. Hydroponically grown greenhouse vegetables in Canada find greaterpreference with the consumers and could be priced as much as twice the regular greenhouseproduce.The Netherlands is the traditional exporter of greenhouse grown flowers and vegetables allover the world. With about 89,600 ha under cover, the Dutch greenhouse industry isprobably the most advanced in the world. Dutch greenhouse industry however relies heavilyon glass framed greenhouses, in order to cope up with very cloudy conditions prevalent allthe year round. A very strong research and development component has kept the Dutchindustry in the forefront.The development of greenhouses in Gulf countries is primarily due to the extremity in theprevailing climatic conditions. Israel is the largest exporter of cut flowers and has wide rangeof crops under greenhouses (18,000 ha) and Turkey has an area of 12,000 ha under cover forcultivation of cut flowers and vegetables.In Saudi Arabia cucumbers and tomatoes are the most important crops contributing morethan 94% of the total production. The most common cooling method employed in these areasis evaporative cooling.Egypt has about 1400 ha greenhouses consisting mainly of plastic covered tunnel typestructures. Arrangements for natural ventilation are made for regulation of temperature and19www.AgriMoon.Com

Design and Maintenance of Green Househumidity conditions. The main crops grown in these greenhouses are tomatoes, cucumbers,peppers, melons and nursery plant material.In Asia, China and Japan are the largest users of greenhouses. The development ofgreenhouse technology in China has been faster than in any other country in the world. Witha modest beginning in late seventies, the area under greenhouses in China has increased to51, 000 ha. Out of this 11,000 ha is under fruits like grapes, cherry, Japanese persimmon, fig,loquat, lemon and mango. The majority of greenhouses use local materials for the frame andflexible plastic films for glazing. Most of the greenhouses in China are reported to beunheated and the use of straw mats to improve the heat retention characteristics.Japan has more than 40,000 ha under greenhouse cultivation of which nearly 7500 ha isdevoted to only fruit orchards. Greenhouses in Japan are used to grow a wide range ofvegetable and flowers with a considerable share of vegetable demand being met fromgreenhouse production.Even a country like South Korea has more than 21,000 ha under greenhouse for theproduction of flowers and fruits. Thus, greenhouses permit crop production in areas wherewinters are severe and extremely cold such as Canada and Russia. It also permits productionin areas where summers are extremely intolerable as in Israel, United Arab Emirates, Kuwait.In the Philippines gree

Quonset greenhouse. Interlocking ridges and furrow type Quonset greenhouse. Ground to ground greenhouse. 1.3.1.1 Lean-to type greenhouse A lean-to design is used when a greenhouse is placed against the side of an existing building. It is built against a building, using the existing structure for one or more of its sides