- What kind of lighting do plants need?
- Incandescent lamps
- Gas discharge
- For ornamental plants
- For fruit and vegetable crops
Having planted seedlings for your garden, you expect to see sprouts that have hatched in a week, and after another two a lush carpet of leaves. However, for this you need to help the plants, they need watering, fresh air, light and, most importantly, proper supplementary lighting. Let’s talk about plant seedling lamps.
What kind of lighting do plants need?
Questions about what kind of light is best for plants, including for growing seedlings, were considered in great detail at the beginning of the last century. It was then that chlorophyll and photosynthesis were discovered and their key role in plant development was established..
Photosynthesis requires visible electromagnetic waves with a length of approximately 440 and 630-660 nm. In this case, ultraviolet is not actually used, and infrared radiation is needed only as a source of heat. Green does not participate in the life of plants in any way and therefore is completely reflected. That is why all vegetation for us is rich in greenery..
Ideal illumination should include the emission of all primary colors of the spectrum of average intensity with the formation of peaks at well-defined wavelengths. In addition, it is desirable to be able to adjust the brightness and operating time of the lighting equipment and even the direction of the light..
- Color temperature – 2400-2700 K (3000 K for a halogen lamp).
- Spectrum – solid.
- Luminous efficacy – 12-14 lm / W (conventional incandescent lamp), 16-25 lm / W (halogen).
- Efficiency – 1.9-3.5%.
For growing seedlings and adult plants, they are poorly suited, with the exception of shade-loving decorative species, which, in principle, do not need high light intensity. However, if incandescent lamps, or better halogen lamps, are used to illuminate seedlings, then it is necessary to assess the state of green shoots and soil in normal familiar lighting. They are often used as a cheap and easy-to-use source of infrared radiation for heating a greenhouse for seedlings.
Easily dimmable, and a simple timer can schedule the lamp.
- Color temperature – depends on the composition of the phosphor 3000–6500 K.
- Spectrum – linear.
- Luminous efficiency – 60-100 lm / W.
- Efficiency – 9-15%.
The source of visible light is the secondary radiation of the phosphor covering the lamp bulb. In an ordinary household fluorescent lamp, against the background of uniformly low radiation of the entire visible spectrum, powerful bursts are observed in the green and blue parts of it. The color of the lamp only seems white to the human eye.
For plant growing, a phosphor is specially selected that can produce two main peaks in the red and blue regions (630 and 440 nm, respectively). The popularity was gained by standard linear flasks with G17 connectors, which are placed in a dust-proof housing with a reflector.
Luminescent lamps for seedlings are used in combination “flora” + household (marked 840). Especially for crop production, tandem induction fluorescent lamps are used, one of which predominantly produces red and the other produces blue. The timer adjusts the emission of red or blue lighting depending on the time of day, simulating the correct distribution of daylight. The brightness of the lamp itself cannot be corrected..
- Color temperature – depends on the choice of gas in which the plasma is formed, 2000–20,000 K.
- The spectrum is solid, often with one peak of a certain color.
- Luminous efficacy – 85-200 lm / W.
- Efficiency – 10-30%.
In gas discharge lamps, light is produced by a gas through which an electric current is passed. Gases such as neon, argon, krypton, xenon are used as a filler for a large number of prepared amalgams based on sodium and other metals with mercury.
For crop production, gas-discharge lamps are used where a temporary or permanent source of a narrow spectrum of a certain color is required, more often in the red range. Using them for seedlings at home is ineffective..
- Color temperature – 2000-20000 K.
- Spectrum – solid.
- Luminous efficacy – 30-50 lm / W.
- Efficiency – 4-8%.
The light source is an electric arc between two electrodes placed in an inert gas environment. They are distinguished by huge heat release and massive radiation in the red or yellow part of the spectrum. They are not in demand in crop production, it is difficult to create optimal conditions for a lamp and at the same time limit heat generation.
- Color temperature for white LEDs – 2700-6500 K.
- Spectrum – line, band.
- Luminous efficiency – 10-150 (250) lm / W.
- Efficiency – 1.5-15%.
Spot light source, by default with a specific color glow.
White light is obtained as a mixture of three primary colors (red, green and blue) or as a result of re-emission by a phosphor when it is irradiated with an ultraviolet diode.
Specialized LED lamps for indoor seedlings and cultivation are already being produced. LEDs are strictly wavelength-matched. The radiation spectrum can be monitored on one device, which greatly simplifies the dimensions of all lighting and expands the scope of application.
It should be noted that commercially available LED strips and individual diodes often have the wrong set of wavelengths that are needed for plants..
For ornamental plants
For indoor plants, lighting efficiency is important not only to maintain photosynthesis and growth, but also to look good. Preference is given to combined lighting options, in which there is a constant source of phyto-radiation in the red and blue ranges, as well as balanced white light with a predominance of green tint.
The best suited for such requirements are LED lamps and fluorescent lamps with a combination of phyto-normalized lamps with conventional.
For fruit and vegetable crops
Growth efficiency and plant development support come to the fore.
For germination and vegetative growth of plants, the light should be dominated by blue. Suitable for this:
- Metal halide lamps (from 4000 K) in combination with an incandescent or fluorescent lamp 840 or 954 (965).
- Luminescent phytolamps with a predominance of blue.
- Blue LEDs with 400-480 nm wavelength coverage.
For flowering and fruiting, more red is needed:
- Amber sodium lamps + 840 series fluorescent lamps.
- Gas discharge lamps with a glow temperature below 3500 K.
- Induction fluorescent lamps in a combination of blue and red 40% and 60% respectively.
- White LED lamps with warm glow phyto-phosphor.
LEDs and fluorescent lamps allow you to place light sources as close as possible to plants without fear of burning leaves and shoots. At the same time, the light from fluorescent lamps is easily distributed by reflectors, and the LEDs are compact and can be mounted on movable fixtures, simulating the daily cycle.
All other light sources are difficult to fit into compact germination greenhouses. It will require active ventilation and heat removal from the lighting device, as well as the use of infrared filters, preventing overheating of the soil and foliage surface.