Greenhouse Farming FAQ:
Many people are asking questions about greenhosue farming. Here we are presenting Greenhouse Farming FAQ or Questions about Protected environment cultivation.
What is polyhouse or greenhouse farming?
A greenhouse is a transparent structure created with glass where plants are grown under regulated climatic conditions. Modern greenhouse farming uses technology to maintain its environment through computer controlled equipment such that the plants have optimum facilities for growth. Polyhouse is synonymous to greenhouse except for the structure of the house is covered with a polyethylene plastic material, which is translucent and transparent in nature.
What does a greenhouse do?
A greenhouse, basically provides light and heat (warmth) to the plants. The translucent material covering the greenhouse structure provides the plants with enough light for photosynthesis process and as it absorbs light energy, it converts it into heat, therefore making the environment warmer for the plants. The darker the surface of the greenhouse the better absorption and heating. Since the greenhouse is airtight, sufficient amount of sunlight can make it much warmer than the outer atmosphere. When there is no sunlight, the heat energy of the greenhouse is lost and plants should be protected using artificial heat sources.
What are the benefits of a greenhouse?
Some benefits associated with greenhouse farming are:
- Fresh produce
- Facility to transplant successfully
- The possibility to produce all the year around
- Ability to grow unseasonal fruits or vegetables
- Less disease and pest problems
- Facility to create an exclusive growing environment (optimization)
- Protection from adverse weather conditions
- Less pesticide and insecticide use
- Can help save resources
- Distributed light energy to all the plants
What is the best green house covering?
The material used for covering the greenhouse effect the performance and productivity of the structure. Covering materials greatly impact the quality and quantity of light entering the greenhouse. The best materials for greenhouse covering are:
- Plastic sheeting (polymethyl methacrylate, fibre glass and polycarbonate)
- Plastic films (polythene, ethyl vinyl acetate, poly vinyl chloride)
What are the materials used to make a greenhouse or what are the components of a greenhouse?
The essential things required to build a greenhouse structure are:
- Pillars, supports and reinforcements (made from wood, galvanized steel, iron or aluminium)
- Straps and beams (galvanized steel, iron or aluminium)
- Arches (galvanized steel or aluminium)
- Foundation supports and bases (concrete)
- Material for securing the cover (galvanized wire, steel or aluminium)
- Canals (galvanized steel or aluminium)
- Crop wires (galvanized steel or aluminium)
- Covering material (glass, plastic or fibre)
- Roof and ridges
- Foundation pipe
- Span width
What is the purpose of having a greenhouse?
In India, farming is highly dependent on the climatic conditions and this is the biggest challenge to every farmer. Most of the farming in India is based on the traditional ways and this is the reason why India imports many fruits and vegetables from other countries to address the food security problem. Modern techniques like greenhouse farming can improve the production and quality because the system depends less on external environmental conditions and has many more advantages over the traditional farming methods. With a good produce the income of the farmer is also expected to increase thereby making him economically stable.
How do you keep a greenhouse warm in the winter?
Heating the greenhouse through artificial heating equipment is one solution, but can be expensive. So some inexpensive ways to keep the greenhouse warm are discussed here:
- If the inside of a greenhouse structure is layered with a bubble wrap then heat loss is reduced. Wraps with big bubbles or greenhouse insulation wrap can be used for this purpose.
- With good power supply availability electric fan heaters can also be used to circulate hot air within the greenhouse.
- Install electric greenhouse heaters with an inbuilt thermostat, which can work only when the temperatures drop below the required level.
- By choosing a correct temperature, plants can be protected during the winter.
- A thermometer in the farm is essential to observe the temperature.
- Proper positioning of heaters.
- Ventilate the greenhouse to prevent diseases and moisture build up.
- A heated propagator can help germination of seeds during winter.
How does a greenhouse help plants grow better?
The mechanism of greenhouse structures can help the plants grow better such as controlling the temperature of the greenhouse, controlled air movement can help the plants with carbon-dioxide, special soil maintenance practices and humidity management. All these factors within the greenhouse contribute to better flowering and fruiting
What can be grown in a greenhouse?
Some of the plants that are best suited for greenhouse are ginseng, herbs, mushrooms, bamboo, green leafy vegetables, Microgreens, cucumbers, peppers, swiss chard, squash, lemons, oranges, grapes, strawberries, raspberries, chillies, okra, sweet potatoes, French beans, melons, cabbage, Brussels sprouts, sweet corn, broccoli, leek, pumpkins, carrots, garlic and many other varieties of flowers.
What temperature is too hot for a greenhouse and how should it be dealt with?
Temperatures beyond 35˚C within the greenhouse are not suitable for the plants. Even when the outside temperatures are around 30˚C, the greenhouse temperatures may rise beyond 38˚C. So, the temperature should be observed regularly and ventilation on the south and north walls can help remove the hot air from the greenhouse. It is also observed that when the outside temperature reaches beyond 40˚C, then natural ventilation is not useful and shade nets either on the inside or outside are used to control the high radiation.
What is the average humidity level inside a greenhouse and how do you control it?
The average acceptable range of humidity within the greenhouse is 50-80%. Sometimes the humidity requirements may be around 90%. If the desired humidity is not available, then it can be achieved by using cooling methods like fan, pad and fogging systems. During winter, humidifiers can solve the problem of low humidity. Similarly, during rainy season high humidity can be controlled by using ventilation if the ambient humidity is low, otherwise chemical dehumidification systems can be used.
What is the cost of constructing a greenhouse in 1 acre of land in India?
There are many agencies which take the contract of building the structure of the greenhouse for commercial farming purposes and it is estimated that to build a greenhouse structure the average rate is 500 per sq m i.e. for 1 acre of land this may range within 20-40 lakh rupees. This doesn’t involve the price of materials required for farming.
What are the different types of greenhouses?
- Classification of greenhouses in made on the basis of cost, structure, glazing type, no. of spans, suitability and environmental control.
- Based on cost and suitability – low cost or bamboo, semi-automatic and high-end greenhouses
- Based on structure – Quonset, curved roof, gable roof, tunnel, tropical region, ground to ground type
- Based on glazing – fibre glass, glass, plastic film, corrugated sheet, silpaulin
- Based on no. of spans – single, ridge and furrow
- Based on environmental control – natural, passive ventilated
What is a shade house?
During excessive heat and summer months, shade houses are created for the protection of plants. These are mostly constructed as a pole supported structure and covered with lath or polypropylene fabric. These nets are available in different shade percentages and farmers use them according to their requirement. They are available in black, green and white colours. Black colour shade nets provide maximum shade by retaining the heat outside the greenhouse.
What is the average height of a greenhouse structure?
The height of the greenhouse determines how effectively internal environment can be managed within it. It directly impacts ventilation and crop quality. The recommended height for a small greenhouse with proper ventilation should be around 3.5 to 4.5 m and for large greenhouse structures it should be around 5.5 to 6.5 m.
What should be the orientation of the greenhouse?
The orientation of the greenhouse structure should be properly done depending on the location, wind direction, temperature of the area. The ridge of the greenhouse should be oriented east to west for places above 40˚N latitudes such that they receive low angle light from the sides. For places below 40˚N latitudes, the orientation of the greenhouse structure should be towards north-south because the angle of the sun is high in these places.
What are the types of load the greenhouse structure has to carry?
There are basically 4 types of loads a greenhouse structure has to carry and therefore it should be designed with care. They are:
Dead load – it consists of all the weight of permanent materials like cladding, heating and cooling equipment, pipes and other frame materials.
Live load – weight due to the hanging baskets, shelves, weight of the people working on the roof. The min live load is 15 kg/sq m.
Wind load – the force of wind on the structures should not exceed 110 km/hr and the pressure should not be more than 50 kg/ sq m.
Snow load – depends on the snowfall of the region. Special arrangements are made to withstand snow in those areas.
What are different heating systems for a greenhouse?
Heating of the greenhouse structure can be provided by the following ways:
- Boiler –hot water tubes or steam pipes
- Unit heaters
- Infrared heaters
- Solar heaters
What are different plant growing structures or containers used in greenhouse?
The different types of containers used for greenhouse farming are:
- Clay pot
- Fibre block
- Fibre tray
- Single peat pallet
- Pre-spaced peat pallet
- Single peat pot
- Strip peat pot
- Plastic pot
- Polyurethane foam
- Soil band
- Soil block
- Plastic tray
Each container type has its own advantages and disadvantages.
What are the advantages of using containers in the greenhouse?
Some of the advantages of using containers in the greenhouse can be outlined as:
- Increase production capacity
- Good quality produce
- Plant growth is uniform with good vigor
- Very little transplanting shock
- Easy sanitation
- Easy to handle and shift
- Easy drainage and good aeration
- Monitoring the plant health becomes easy
- Facilitates the use of modern irrigation methods
What are the properties of the media for greenhouse farming?
The physical and chemical properties of the soil medium are entirely different from greenhouse farming and some important aspects are discussed here:
- It should have good holding capacity and porosity.
- It should be well drained.
- Should have good aeration to facilitate good root growth.
- pH level should be in the range of 5-7 and soluble salt level around 0.4 to 1.4 dS/m.
- Low pH is not suitable, so it is raised to a desired level by adding lime.
- High pH is modified by adding sulphur or gypsum.
- The temperature of the plug mix should be around 70 to 75˚F.
- Mist irrigation is used for plug mix and it should be monitored regularly.
What type of irrigation system is deployed in greenhouse systems?
Greenhouse plants are considered to use large amounts of water for growth; therefore micro irrigation system is the most suitable way for greenhouse plants. Micro sprinkler or drip irrigation arrangement has to be installed for watering the plants. Care should be taken such that water doesn’t fall on the flowers and leaves otherwise this may lead to diseases and scorching problems.
What techniques can be used to keep a greenhouse cool in summer?
During the summer, it is important to maintain the optimum temperatures within the greenhouse, otherwise extreme heat may damage the plants and could also raise productivity problems. Some ways to cool the greenhouse are:
- Damping down
- Avoiding water stress
What does damping down a greenhouse mean?
During peak summer months, to keep the plants cool inside the greenhouse the humidity of the structure is raised by wetting the hard surfaces such as paths and stages; this is called damping down. When water starts evaporating, it increases the moisture level of the air and keeps the internal environment cool for the plants.
What type of additives can be used while selecting a covering material for a greenhouse?
Other than the glass, fibre and plastic materials for covering the greenhouse some other types of additives can be used to protect the plants such as:
- Using UV absorbers and stabilizers can reduce the damage to the greenhouse, control some plant pathogens and increase the durability of the structure.
- Heat loss is minimized by using infrared absorbers because they reduce the long wave radiation.
- Using long wave absorbers one can reduce the heat loss from the objects and plants in the greenhouse.
- Diffusing the light using scatters helps to protect the plants from being burnt and facilitates light to the lower parts of the plant.
- Surface tension of water and dispersive condensation can be reduced using surfactants.
- The plastic films are protected from dust by using antistatic agents.
- Colour pigments help in plant growth by changing the proportion of wavelengths.
- Glossy material can repel insects.
Why do greenhouses need ventilation?
Ventilation within a greenhouse is the most important component of the plant growth and survival. Proper ventilation can help regulate the temperature, provides fresh air for the plants during photosynthesis, prevents the occurrence of many disease and pest infestations and sometimes encourages pollination.
How can someone increase the humidity of a greenhouse?
The respiration process of plants naturally keeps the greenhouse humid, but sometimes it may be required to maintain a higher humidity level for certain plants to grow; then if it is a commercial farm then the humidity is automatically controlled by misting the plants according to the timer. Besides this there are few simple ways to maintain the humidity within the greenhouse such as:
- Placing water buckets in the greenhouse
- Misting the plants daily or on a regular basis
- Placing the plants on pebble trays filled with water
- Using small humidifiers or cool mist vaporisers
How does low humidity affect the plant growth?
Plants take water for the process of transpiration i.e. roots absorb the water and it gets evaporated through the leaves such that the plant remains cool. When there is low or high humidity this process of water flow within the plant gets affected. High humidity slows down the transpiration and low humidity can increase the transpiration rate, thereby damaging the plant tissues.
What causes condensation in a greenhouse?
The temperature at which water begins to condense out of the moist air is generally referred to as a dew point. When the leaf surface temperature is below this dew point then condensation occurs in plants. When there is too much moisture in the greenhouse to remain in the vapour state condensation happens. Surfaces that are cooler will condense first like the pipes, door knobs, roof and then plant surface.
How does temperature affect the growth of a plant?
Varying temperature has multiple effects on plants and these depend on some factors like exposure to sunlight, moisture drain, elevation and the difference between day and night temperatures. It is found that the process of germination increases in higher temperatures. When the optimum temperature is reached the germination slows down.
What kind of subsidy assistance is available from the government for greenhouse farming and what are its details?
To help develop the horticulture zone in India National Horticulture Mission was launched under which there was subsidy assistance for greenhouse or polyhouse farming. There were different areas in which subsidy was given/allotted like the greenhouse structure, shade house, fan and pad structure, seeds for vegetables and flowers, water facilities, pack house, etc. There was 50% subsidy given on all these sectors and the percentages varied for different states. So, it is advisable to visit the horticulture department of the state or its website to get updated information regarding assistance programs because they keep changing from time to time.
What is a deep winter greenhouse?
To grow crops in winter, fossil fuel is required to maintain it. These deep winter greenhouse structures are solar operated rather than being operated by traditional methods. The orientation of deep winter structures is towards east-west with a glazing wall on the south. The air is heated by the heat of the sun and is blown by a fan to be stored in the rocks. This heated rock bed acts like a thermal mass or heat battery and is used when required. This structure is needed for exclusive winter countries and places.
What are the disadvantages of a greenhouse?
Some major disadvantages of greenhouse farming are:
- High labour
- High cost of production
- High capital investment
- Good expertise is needed
- Equipment handling capacity is a pre-requisite
- Clear knowledge and understanding of the method
- Low possibility for pollination
What is the profit associated with greenhouse farming in India?
The investment for the fixed structure is same for all types of vegetables and fruits, but the costs vary for maintenance. Similarly, every fruit or vegetable has different yield characteristics upon which the entire profit rests. For a sample greenhouse farming structure one can read this at: Greenhouse Cost and Profit.
Does a greenhouse need direct sunlight?
Yes, there should be a provision such that the greenhouse gets direct sunlight at least for 6 hours during winter. Orienting the structure towards the east – west direction one can expect good sunlight. If this is not possible, then grow lights can be used.
Do plants grow faster in a greenhouse and why?
Greenhouse provides the plants with what is actually required and there is less exposure to adverse temperatures and climatic conditions. Hence, they tend to grow faster than normal traditionally grown plants. When plants get exposed to severe climatic conditions they either stop growing or get stressed and have stunted growth. With the controlled environment within the greenhouse everything is favorable for the plant growth.