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Lighting in greenhouses

Lighting in greenhouses is essential for optimizing plant growth conditions. Specific lighting conditions are often created in greenhouses to promote photosynthesis, accelerate plant growth, or extend the growing season. Using the right lighting can significantly improve plant growth, especially in environments where natural light is limited, such as during the winter months or in areas with less sunlight.

Objectives of lighting in greenhouses:

  1. Improving photosynthesis : Lighting supports the process by which plants convert sunlight into energy. Greenhouses often use artificial lighting to ensure sufficient light intensity for photosynthesis, especially during low-sun seasons.

  2. Stimulate growth and development : The right light can influence the growth phase of plants, such as promoting germination, flowering, or fruiting. Light influences photosynthetic activity and can increase the rate of plant growth.

  3. Extending Day Length : In winter, adding artificial light can help extend day length , which is important for the flowering of certain plants that are sensitive to day length.

  4. Improving yield : Properly positioned lighting can ensure higher yields in terms of quality and quantity by keeping the conditions for plant growth consistent.

  5. Disease Prevention : Using lighting can help control humidity and temperature , reducing unfavorable conditions for disease.

Types of lighting in greenhouses:

  1. LED lighting :

    • Efficiency : LED lights are energy efficient, last longer and generate less heat than traditional lighting, making them ideal for use in greenhouses.
    • Specific Spectrums : LEDs can be adjusted to produce light of specific wavelengths (colors) that are best for plant growth. They can deliver the blue spectrum (for vegetative growth) or the red spectrum (for flowering and fruit production).
    • Power : LED lighting is powerful and efficient in providing the right light, even in environments with little natural light.

  2. High pressure sodium lamps (HPS lamps) :

    • These lights are often used in commercial greenhouses and are known for their ability to deliver a large portion of the red spectrum , which promotes flowering and fruit production in plants.
    • However, HPS lamps consume relatively large amounts of energy and can produce heat, which is a disadvantage in some greenhouses.

  3. Metal halide lamps (MH lamps) :

    • Metal halide lamps produce a bluish light that is beneficial for vegetative growth. They can promote the development of strong roots and leaves.
    • However, they are less energy efficient than LEDs and also produce more heat.

  4. Fluorescent lamps :

    • These lights are often used for small growing spaces or for young plants that require little light. They are relatively energy-efficient and can provide broad-spectrum light.
    • T5 fluorescent lamps are often used for growing plants because they offer high efficiency in terms of light output and efficiency.

  5. Luminous substances :

    • In some cases , phytoliths or phytolith lamps are used, which are specifically designed for plant growth and emit light in the blue and red spectrum , which are essential for photosynthesis.

Lighting strategies in greenhouses:

  1. Basic lighting :

    • Basic lighting is often used to replace daylight when it's insufficient. This is especially useful during the winter months, when sunshine hours are limited.

  2. Additional lighting :

    • Supplemental lighting is used in greenhouses to enhance natural sunlight and improve plant growth when the sun doesn't provide enough light. This helps improve photosynthesis and accelerate growth.

  3. Lighting with a controlled spectrum :

    • Greenhouse lighting can be specifically tailored to the needs of plants by manipulating the color spectrum . Some greenhouses use systems that automatically adjust the light based on the plant type and growth stage. This allows the light spectrum to be optimized for each specific application.
    • The blue spectrum promotes leaf and root growth, while the red spectrum is essential for flowering and fruit development.

  4. Dynamic lighting :

    • Dynamic lighting adapts to the plant's biological clock. This can be done by adjusting the light intensity or color depending on the time of day and the plant's growth phase. This promotes natural growth patterns and improves overall plant health.

  5. Daylight simulation :

    • Daylight simulation is a lighting system that attempts to emulate natural daylight by varying light intensity and spectrum, which can help reduce plant stress.

Benefits of lighting in greenhouses:

  1. Increased Yield : Lighting helps optimize plant growth , leading to higher yields in terms of both quality and quantity of produce.

  2. Seasonal Adaptation : Lighting in greenhouses allows for the optimization of growing conditions in winter or in areas with less sunlight, allowing crops to be grown in seasons that would otherwise be unfavorable.

  3. Precision and control : Using lighting allows growers to precisely control light levels, color temperature , and lighting duration . This allows them to fine-tune the plants' growth phase .

  4. Energy Efficiency : Using technologies like LED lighting allows greenhouses to operate more energy efficiently, reducing operating costs.

Disadvantages of lighting in greenhouses:

  1. Installation Costs : Setting up a greenhouse lighting system can be a significant expense, especially when installing energy-efficient technologies like LED lighting.

  2. Heat Stress : Some types of lighting, such as HPS lamps , can produce significant heat, which can lead to heat stress for plants if lighting is not managed properly.

  3. Energy Consumption : Some traditional lighting systems (such as HPS lamps ) can consume relatively large amounts of energy, increasing operating costs.

Conclusion:

Lighting plays a crucial role in optimizing plant growth and improving yields in greenhouses. By using the right lighting technologies, such as LEDs , HPS , and metal halide lamps , growers can tailor greenhouse conditions for a more efficient growing process. Adjusting the light spectrum and intensity can significantly improve plant health and productivity, leading to higher yields and better crop quality.