Protected cultivation structures are essential for enhancing crop productivity, quality, and income, especially in adverse climatic conditions. These structures help in creating a micro-environment suitable for plant growth by modifying factors such as temperature, humidity, and radiation. Depending on the local topography, site-specific conditions, and regional climatic zones, the following protected growing structures are commonly used:
1. Low Tunnels (Row Covers)
- Suitable for open agricultural fields located in areas with mild winter climates.
- Consist of transparent plastic sheets or non-woven fabric supported by low hoops over crop rows.
- Primarily used to protect tender crops from mild frost, wind damage, and temperature fluctuations.
- Aid in extending the growing season and promoting early crop development.
- Commonly used for crops like cucurbits, leafy vegetables, and strawberries.
2. High Tunnels (Walk-in Tunnels)
- Designed for regions with temperate to sub-tropical climates.
- Semi-circular structures with higher headroom allowing a person to walk inside.
- Offer protection from wind, heavy rainfall, moderate cold, and pest attacks.
- Improve crop quality and yields with relatively low construction costs.
- Widely used for growing tomatoes, bell peppers, cucumbers, and leafy greens.
3. Net Houses
- Best suited for hot, humid, or coastal areas with high insect pressure.
- Constructed using UV-stabilized insect-proof or shade nets supported by a frame.
- Help in minimizing pest infestation and reducing the need for chemical pesticides.
- Facilitate healthy nursery production and cultivation of off-season vegetables and flowers.
- Can also be used for hardening of tissue-cultured plants.
4. Polyhouses (Naturally Ventilated)
- Ideal for areas with moderate temperatures and stable weather conditions.
- Made of transparent or semi-transparent polyethylene film stretched over a steel or pipe frame.
- Natural ventilation is facilitated through roof vents or side roll-up curtains.
- Useful in reducing disease incidence caused by excess moisture and rain.
- Enable cultivation of high-value crops like gerbera, capsicum, and orchids.
5. Climate-Controlled Greenhouses
- Designed for extreme climatic conditions, including scorching summers or freezing winters.
- Equipped with automated systems for temperature regulation, humidity control, CO2 enrichment, and lighting.
- Ensure year-round production regardless of external weather changes.
- Used for commercial-scale cultivation of export-oriented or exotic crops such as roses, anthuriums, and lettuce.
- Require higher investment and operational costs but deliver premium returns.
Classification of Greenhouse Structures
Greenhouses are categorized on the basis of several parameters such as shape, utility, and construction materials. Understanding these classifications helps in selecting an appropriate structure based on the purpose, location, and economic considerations.
A. Based on Shape
1. Gable-shaped Greenhouse
- Features a classic A-frame design with a peaked roof formed by two sloping panels.
- Provides good drainage of rain and snow.
- Offers more vertical space for tall plants or hanging systems.
- Easy to install ventilation windows on the roof and sidewalls.
2. Quonset Greenhouse
- Comprises a semi-circular, dome-like structure typically made from bent steel or PVC pipes.
- Covered with polyethylene film, making it lightweight and cost-effective.
- Easy to construct and dismantle.
- Suited for small to medium-scale vegetable and flower cultivation.
3. Gothic Arch Greenhouse
- An improved Quonset with a pointed arch design.
- Enhances snow shedding ability and provides more vertical space.
- Steeper roof minimizes water accumulation and prevents structural damage.
- Aesthetic appearance and efficient air circulation.
4. Saw-Tooth Greenhouse
- Features a roof design with a series of ridges and vertical glazing sections.
- Allows hot air to escape naturally through vents placed on the vertical faces.
- Well-suited for tropical and sub-tropical areas with high heat load.
- Encourages passive ventilation and reduces cooling costs.
5. Skillion (Lean-To) Greenhouse
- Constructed against an existing wall or building.
- Ideal for backyard gardening or home-based horticulture.
- Reduces material costs due to shared wall support.
- Convenient for small spaces and limited-scale operations.
B. Based on Utility
1. Production Greenhouse
- Designed for large-scale commercial farming of vegetables, flowers, fruits, and medicinal plants.
- Emphasizes yield optimization, pest control, and quality maintenance.
- Often integrated with drip irrigation, fertigation, and automated climate control.
2. Research Greenhouse
- Used in academic, government, or private research institutions.
- Equipped with sensors, data loggers, controlled environment chambers, and automated systems.
- Facilitate controlled experimentation on plant physiology, genetics, breeding, and agronomy.
3. Nursery Greenhouse
- Specially structured for the propagation of seedlings, grafts, and saplings.
- Maintains optimum conditions for germination and rooting.
- Often includes misting systems and propagation benches.
- Commonly used for fruit crops, ornamentals, and plantation crops.
4. Hobby Greenhouse
- Constructed by gardening enthusiasts and amateurs.
- Used for growing ornamental plants, bonsai, vegetables, or herbs at home.
- Compact, easy to manage, and generally not intended for profit.
C. Based on Construction
1. Wooden Frame Greenhouse
- Built using timber or bamboo, making them environment-friendly.
- Suitable for temporary or small structures with low capital investment.
- Prone to decay and termites; require periodic maintenance.
2. Pipe Frame Greenhouse
- Constructed using galvanized iron, steel, or PVC pipes.
- Offers greater strength and durability.
- Common choice for naturally ventilated and semi-permanent installations.
3. Glass Greenhouse
- Employs toughened or laminated glass panels for maximum light penetration.
- Long-lasting and aesthetically appealing.
- Requires strong framing materials and precise construction.
- Higher initial cost but suitable for temperate climates and floriculture.
4. Polyethylene Greenhouse
- Most popular and cost-effective type.
- Covered with single or double layers of UV-stabilized polyethylene film.
- Lifespan of 2–5 years depending on quality.
- Easy to install, replace, and maintain.
5. Hybrid Greenhouse
- Integrates multiple construction materials and design elements.
- For example, metal or wooden frames with poly-film roofing and netted sidewalls.
- Customizable based on crop type, climate, and user preferences.
- Offers a balanced solution between cost and performance.
Conclusion: Selecting the right type of protected structure depends on site-specific factors, crop requirements, budget, and intended use. Proper planning and management of these structures can lead to increased productivity, resource use efficiency, and sustainability in agriculture.
