How Is The Amount Of Light In A Greenhouse Controlled?

Light and temperature are critical factors for plant growth, and optimizing the greenhouse light environment is key to increasing crop yield and quality. However, excessive light intensity can damage plants and fruit. Supplemental lighting, such as light-emitting diodes (LEDs), can provide proper timing of light to control growth (photomorphogenesis). Typical lamp types include incandescent, fluorescent, mercury vapor, high pressure sodium, and low.

Light is a key parameter in greenhouse horticulture and growth chambers, such as nursery or vertical farming. Greenhouses should provide optimal conditions for plants to perform photosynthesis. The color, intensity, and distribution of light can now be controlled with unprecedented precision, enabling light to be used as a signal for specific physiological responses in humans and plants.

LEDs are becoming a popular choice for greenhouse supplemental lighting as they can be dimmed precisely and quickly. Computer programs can control shade curtains so the plant gets just the right amount of light. When intensity is too high, the curtain closes, and vice versa. Electric lighting is used in greenhouses to regulate the photoperiod to control flowering or to increase growth to increase crop quality and yield.

Light intensity drives photosynthesis, which produces carbohydrates that serve as the building blocks for plant growth. Some primary reasons why greenhouses manipulate light levels include temperature and irrigation management, photoperiod control, minimizing crop stress, and sensing the duration of the lighting period and the relative intensities of some low intensity wavelengths. PAR is typically measured with a quantum sensor, but PAR sensors are a more intuitive method for measuring light intensity.

How can light intensity be reduced?

Dimmers can be used to control the brightness of bulbs in the range of 5-99 and lamps, allowing them to be switched on and off with a gradual onset, saving bulb energy. This can be achieved using a dimmer in combination with wireless control, allowing lighting regulation even from the comfort of a sofa. By reducing the brightness of a 60W bulb in the day for 3 hours at 50, one lamp can save up to Kc 300 per year.

Controlling the brightness of five lamps in an apartment or house can save more than Kc 1, 500 a year, with a return on investment guaranteed within one year. The price depends on the dimmer type and light intensity 0 – 100.

What are used to control the intensity of light?

Poles are employed for the purpose of regulating the intensity of light that enters through windows.

How to regulate light intensity?

Dimmers are devices that control the brightness of bulbs and lamps within the 5-99 range, allowing for gradual onset of light. They can be regulated from the comfort of your sofa using a dimmer combined with wireless control. Dimmers are categorized by light source type (conventional bulb, halogen lamp, energy-saving, or LED) and control form (classic button or wireless). The RFDEL-71B dimmer is the most versatile, designed for all loads (bulbs, halogen lamps, energy-saving lamps, LEDs).

Its main difference is its wireless control, which allows for direct placement into the light cover and remote control. The wireless switch (RFWB-40) can be placed on a table, screwed on the wall, or attached to glass. The dimmer can be easily adjusted using a switch on the front of the device, an RF transmitter (e. g., RFWB-20 wireless switch), or an existing button.

How to measure light intensity for plants?

To use a light meter effectively, turn it on and hold it close to the plant, ensuring the probes are not touching any plant elements. A number reading should be obtained immediately, and the reading should be cross-checked with the chart on the back of the light meter package. If the light meter was used to measure soil moisture or pH, wipe the probes between uses. It is recommended to take readings over the entire day to understand the light your plant is exposed to, at least once every season.

The chart number represents the minimum light needs of the plant for at least 16 hours a day. The Bond 3-Way Light Meter has a Moisture and Light Readings Chart on the back, which can be used to ensure your lighting aligns with each plant’s needs.

How light is regulated in greenhouse?

Full-sun tolerant crops like tomatoes, cucumbers, and chrysanthemums can withstand full sun power without needing shading to limit PAR levels. However, they often need shade to limit heat buildup in the greenhouse air and on leaf surfaces. Internal shade systems can partially help lower vapor pressure deficit on hot days. For low-light crops and special applications like rooting cuttings, shade is necessary to limit total solar radiation.

External shading absorbs and reflects light energy before entering the greenhouse, heating the air and enclosed objects. However, external shade methods have disadvantages such as semi-permanent coatings and expensive construction and maintenance of retractable screens.

Internal screen systems reduce light levels on plant surfaces but do little to limit heat buildup within the greenhouse enclosure. Roof-ventilated greenhouses quickly exchange light energy with cooler outside air, and warmed air can rise through screens if they are sufficiently porous or leave gaps for roof-vented air exchange.

What do you use to decrease light intensity in a greenhouse?

Shading fabrics and greenhouse shading compounds are two materials used to reduce light intensity in greenhouses, particularly during high light levels and difficult temperature control. Shading fabrics can be applied over crops and removed during low-light conditions, while shading compounds are less expensive and can be applied to benches instead of the entire greenhouse. Shading fabrics can reduce crop solar load, but are more commonly used for temperature control.

They can also serve as thermal blankets, providing additional insulation by trapping air between the crop and greenhouse roof. Both methods are effective in reducing light intensity and improving greenhouse efficiency.

How to reduce sunlight in a greenhouse?

Shading is a cost-effective method for cooling greenhouses, often applied outside over the glazing or with screen systems inside. It can result in lower electric bills if fans are used. Shading compounds, which are applied in the spring, wear off before the first frost. Some growers add additional layers of shading as the sun’s intensity increases during summer or the shade material wears off.

An alternative is woven or knitted shade fabrics made from materials like polypropylene, saran, polyethylene, and polyester. These lightweight, easy-to-apply fabrics are available in various degrees of shade and are typically custom-fabricated to fit the greenhouse. Most materials are ultra-violet stabilized and have a lifespan of about 10 years. Costs range from 10-40¢/sq ft. Polypropylene is strong, tough, and resistant to flexing, abrasion, and chemical attack.

Saran is fireproof and shrinks about 3 when installed, while lock-stitched, knitted polyethylene netting is fire and mildew resistant. Metalized materials like Aluminet (GREEN-TEK) can moderate both day and night temperatures.

What is the light intensity of a greenhouse?

In order for a plant to become light saturated due to shadowing of lower leaves, light levels of approximately 100, 000 lux may be necessary. It should be noted that the intensity of light in a greenhouse varies considerably, ranging from 130, 000 lux on a clear summer day to less than 3, 000 lux on an overcast winter day.

How to reduce grow light intensity?

LED grow lights should be placed between 24-36 inches above the plant canopy for seedlings, depending on the power of the light source. The furthest distance from the seedlings (~36″) helps maintain lower heat and light intensity levels and prevents drying out. Once roots are established and sprouting begins, the lights can be moved closer within the first 2-3 weeks. In the vegetative stage, the lights should be 12-24 inches away from the top of the canopy, as more light is needed for photosynthesis.

As plants progress through the flowering stage, their demand for intense light decreases, and the top leaves should be 18-24 inches from the light source for flower production. Adjusting the lights’ height during flowering is not necessary, especially if taller plants are not desired.

How is light measured in a greenhouse?

Horticultural researchers typically employ the unit of micromoles per square meter per second (s⁻¹), which quantifies the number of photons utilized in photosynthesis per square meter per second.

How to increase light intensity in a greenhouse?

It has been demonstrated that increasing the intensity of light in greenhouses can result in enhanced growth of crops or horticultural plants. It is recommended that glass or other materials be used for maximum light transmission, that plants be positioned for optimal light absorption, and that light intensity be maximized for photosynthesis. This will result in an extension of the plant’s growing season, allowing crops to flourish in a greater number of months within the year and to utilise additional carbon dioxide.