Polyhouse Cultivation Guide for Beginners:
Introduction to Polyhouse Cultivation
Polyhouse Cultivation practices can be characterized as a farming procedure wherein the microclimatic conditions around the plant body are controlled partially or completely according to the prerequisite of plants grown amid their time of growth in their natural habitat. In temperate regions, it is not favorable to grow crops in winter as also to grow crops in summer in tropical regions. Polyhouse brought a revolution in the agriculture sector to produce vegetables, fruits, and flowers in the off-season. With the progression in agriculture, different types of in-house/polyhouse cultivation practices suitable for a particular kind of agro-climatic zone have risen. Among these In-house farming practices includes, poly greenhouse, net house, shade house, plastic tunnel and mulching and so on are exceptionally valuable for high yield.
What is a Polyhouse Cultivation?
Polyhouse cultivation is a widely accepted farming method that is generally made of transparent polyethylene sheets which are thin, cheap, and flexible creating an indoor manually controlled environment. In polyhouse, a farmer can grow vegetables and any other crop in any season in the year depending upon plant requirement as temperature and humidity can be controlled. Polyethylene durability is far superior to glass polyhouse and it conserves the thermal radiation and provides enough energy to help in photosynthesis.
Why Polyhouse Cultivation?
The need to secure the harvests against unfriendly environmental conditions prompted the improvement of ensured agribusiness. Polyhouse is the simplest practical strategy for accomplishing the targets of ensured horticulture, where common habitat conditionsare altered by utilizing sound designing standards to accomplish ideal plant growth and yield.After the approach of the green revolution, more efforts are laid on quality as well as quantity in the production of agricultural products.This can be achieved when the environment for the crop growth is reasonably controlled. India is self-reliant on food grain production and stands second in vegetable production in the world. But we are lacking behind in nutritional security and vegetable per capita. Polyhouse technology has potential to deliver more production per unit area compared to conventional farming methods. If the one-hectare land is cultivated under polyhouse conditions, the yearly production will have an increase more than 85%. Young farmers have to adapt to new technology and new farming methods such as hydroponics, greenhouse cultivation, and other intensive cultivation to enhance the crop productivity giving more income per land unit area.
Difference Between Polyhouse and Greenhouse: Well, polyhouse is one type of greenhouses made out of polyethylene on the other hand greenhouse is broad term. With wood it is called as Lath house and with Glass, it is called as greenhouse.
Crops Suitable for Polyhouse: Generally, vegetables like Spinach, Green Chillies, Cucumber, Summer squash, Brinjal (Eggplant), Green beans or French Beans, Tomatoes, Bell peppers, Okra (ladies finger), and horticulture cut flowers like Rose, Gerbera etc are grown in polyhouse. Polyhouses provide more stable and controlled or suitable conditions to grow crops when compared to open field crop cultivation.
Structural Design for Polyhouse Cultivation
When constructing a polyhouse on a site, the direction of the polyhouse must be always east to west. This always plenty of sunshine come in and ensure no tree or building or any other kind of shade cover the polyhouse. The basic structure is prepared by using iron pipes for strength and durability, though its expensive compared with bamboos. One on an initial trial basis, a young farmer can go for a 560 square meter polyhouse structure which is equal to 1/4th acre land. Use ultraviolet polyethylene (UVLDPE, 200 microns)transparent sheets for covering the structure. Plastic sheet covering can be of materials such as 1501-micron thick plastic sheet or 1mm thick GI sheet or any other material that is durable and strong having no joints. Covering materials that are low maintenance, more light transmission, less heat, and with a lifespan of three to five years works well economically. For Indian climatic conditions, Quonset type, multi-span polyhouse is recommended. Size of the polyhouse can be of any size depending upon the requirement but the width should not be more than 28 meters. The overall polyhouse design structure must pass the following requirements:
- The structure must hold all permanent construction, covering/cladding, cooling, and heating equipment, solar arrays, water pipes, and other fixed miscellaneous types of equipment to the structure frame.
- The structure must be strong enough to hold people working on the roof.
- The roof structure of each member should support 45 kg concentrated load when applied at its center.
- Most importantly, the structure must withstand wind speeds about 150 km per hr and at least 50 kg per m2 of wind pressure.
The temperature inside the polyhouse can be maintained cold or hot depending upon the season. During daytime, the temperature inside polyhouse gets increased by sunlight while little energy is lost from different opening parts. In winters, the temperature can be maintained by solar driven devices. Apart from this few manual works can also be undertaken such as, covering the northern wall of the house with jute clothing and covering the entire polyhouse with jute cloth during nights. In summer, when daytime temperature rises above 40° C, cooling of polyhouse can be done by running solar energy driven devices. Running water-misting is one way to cool the inside temperature. By removing internal air and sucking external air through installed fans. Or, by installing coolers at eastern or western side walls will lower temperatures and maintains humidity also.
Components of Polyhouse Cultivation
- Roof: Transparent top cover of a Polyhouse.
- Gable: Transparent walls of a Polyhouse.
- Cladding Material: Material that is used for walls and roof of a Polyhouse.
- Gutter: Rainwater that is collected to drain at an elevated level between two spans.
- Column: The main vertical structures carrying the Polyhouse structure.
- Purlin: Parts which connects cladding supporting bars to the columns.
- Ridge: Highest horizontal section on top of the roof.
- Girder: A horizontal structure that connects columns on gutter height.
- Bracings: They support the structure against the wind.
- Arches: That supports covering materials.
- Foundation Pipe: Connection between the structure and ground.
- Span Width: Center to center distance of the gutters in multi-span houses.
- PolyhouseLength: Length of the curtain wall on the east-west side.
- PolyhouseWidth: Length of the gable in the north-south side.
Classification of Designs for Polyhouse Cultivation
Low-Cost Polyhouse Cultivation: These structures are best suitable for temperate regions. As the name suggests the polyhouse construction uses locally available cheap materials such as timber, bamboos, and UV polythene sheets for covering. No major devices for temperature controlling or environmental parameters are available. Much of the temperature is controlled with simple manual techniques as removing side walls or by covering the sheets with jute cloth.
Medium Cost Polyhouse Cultivation: In this type of construction, galvanized iron pipes, screw fittings, manual and semi-automatic control arrangements are provided. The strength of the structure is good to withstand strong winds. Inside the house, misting, cooling pads, fans, thermostat and other devices are fixed to the structure and most of the devices are semi-automatic, hence requires more maintenance and care. This polyhouse is suitable for tropical and dry regions.
Advanced Polyhouse Cultivation: As the name suggests, this polyhouse as all the features and equipment available in medium cost polyhouse but the entire environment controlling parameters and devices functions completely automatically. Some of the devices are run by solar energy.
- Low-cost polyhouse without fan and pad – Rs.350 to 600/m2
- Medium cost polyhouse with pad and fan system without automation – Rs.750 to Rs.1800/m2
- Advanced Polyhouse with fully automatic control system Rs.1950 to Rs.3600/m2
Cultivation of plants inside Polyhouse
The grower must have a definite polyhouse floor space dimensions and specifications to plan a strategy of what to grow, where to grow, and how many to grow. Prepare a place for nursery beds for seed germination, ideally should be warmer space that will be sunny or a heated propagator unit in the polyhouse. This helps seeds to germinate well especially in winters. Use clean seedbeds and trays with fresh multipurpose compost. Plant the seeds as mentioned on the backside of the seed packet. Young seedlings that are grown sturdy and well-rooted must be transplanted to the prepared soil beds for their final positions. The distance between plants to plant must be optimum, must not be too densely planting and not too far to waste the floor space. Drip irrigation is the best irrigation system in polyhouse. Water will reach directly to the root zone without much water wastage. Provide support or trellis if vine plants are planted for proper growth. Pruning activities must be carried at the right time such as pinching of side-shoots will encourage growing of side branches and leading to more fruit.
Floor space can be designed to have more varieties of crops growing simultaneously or can have single crop inside the polyhouse. Depending on the local market demand, a farmer can choose what kind of plants to be grown and how many plants are to be grown.
Soil Preparation and Fertigation in Polyhouse Cultivation
In polyhouse cultivation, top-soil is not given much preference for crop production. Soil mixes that are highly modified mixtures of soil, organic and inorganic materials mixed in particular ratios are used for cultivation. Farmers that include top-soil as a portion of the mixture must mix with other materials such as compost, or potting mix which helps to improve water holding capacity along with soil aeration.
Soil Structure in Polyhouse Cultivation: The soil used in polyhouse should be well-drained and retain soil moisture. Soils physical and chemical properties are unique and peculiar from field soils.The physical properties of soil must be porous for excellent root system growth. Salinity levels should be less than 1 MS/cm and pH should be maintained in between 5.5 to 6.5 ranges. Below table shows the soil bed material composition.
|Material||Clay Soil||Loamy Soil|
|Peat and bark||1 kg/m2||0.5 kg/m2|
Soil Pasteurization in Polyhouse Cultivation: Soil inside polyhouse must be decontaminated as the soil contains nematodes, insects, weed seeds and other disease-causing organisms. It can be controlled either by treating the soil with heat treatment or with volatile chemical treatment using methyl bromide, tear gas etc.
|Heat||Steam||3 minutes at 80° – 85° C|
|Chloropicrin||3 to 5 ml per cubic feet of soil||Sprinkle the soil with water and cover the soil for 1-3 days with gas proof. Aerate for 2 weeks or until no odor is detected before using.|
|Basamid||8 grams per cubic feet of soil||Cover the soil for a week with gas proof cover and aerate for at least a week before use.|
|Formalin||20 ml per liter||Apply 2 l/cu.ft. Cover the soil for 14 to 36 hr and aerate for at least 14 days.|
|Methyl Bromide||10 ml per cubic feet of soil||Cover the soil with gas proof cover for 1 -2 days.Aerate for 24-28 hr before use.|
Soil Disinfection in Polyhouse Cultivation: This helps soil from fungicides and harmful bacteria. Spray the soil with 2 grams of Captan in one liter of water to prevent crops from root rot, stem rot, white mold, black rot, crown rot, pythium, fusarium, rhizoctonia, and damping off.
Spray the soil with 1 gram of Metalaxyl and Mancozeb in one liter of water to prevent crops from soil-borne pathogens, pythium, phytophthora, fusarium.
Treat soil at temperatures from 46° to 90° C. This will destroy soil pests such as water molds, nematodes, worms, slugs, centipedes, plant pathogenic bacteria, soil insects, weed seeds, and plant viruses.
Fumigation in Polyhouse Cultivation: Tools that will be used for cultivation inside the polyhouse must be thoroughly disinfected. Prepare one part of formalin in fifty parts of water or one part of sodium hypochlorite in nine parts of water for disinfecting propagation room, agriculture tools, trays, knives, working surface and others. Spray dichlorvos against inside walls to destroy insects. Trisodium phosphate or potassium permanganate will help get rid off the pathogens from workers entering in when placed at the polyhouse entrance.
Problem Management in Polyhouse Cultivation
Some of the common problems that may arise when cultivating in polyhouse and that can be rectified with agriculture officer assistance are divided below:
- Carbon dioxide.
- Macro Nutrient Deficiency.
- Micro-Nutrient Deficiency.
- Excesses Fertilizer.
Indian Government Subsidies for Polyhouse Cultivation
To develop young farmers in utilize and implement modern agriculture farming techniques, the government of India in 1984 setup National Horticulture Board (NHB) for promoting integrated development of horticulture. Different states have different subsidy structures for establishing polyhouse cultivation but usually, subsidies can be availed from 50% to 80%.
Prepare a detailed project report, filled in application form, farmer details, and land records have to be submitted to the nearest or local horticulture department for permission. An individual farmer can apply up to 4000 sq/m under horticulture and 1000 sq/m under the agricultural department. A government official inspects the site to see the land, infrastructure, water resources, and climatic conditions. Based on the feasibility report, the government department sanctions to construct polyhouse along with subsidy. More details can be acquired from the government website nhb.gov.in