Benefits of UV-C LED in Horticulture

According to its wavelength, UV (Ultraviolet) radiation is divided into three groups, UV-A (315 - 400 nm), UV-B (280 - 315 nm) and UV-C (100 - 280 nm). UV light is widely used in horticultural lighting for improving plant growth. For example, UV-A and UV-B can increase cannabinoids and protecting cannabis from disease and pests. UV-C light has been increasingly used for disinfection against COVID-19 in recent years. UV-C lights are effective in hospital sanitization. With the popularity of LED, the UV-C LED light is gradually replacing conventional UV-C lights, such as mercury and amalgam UV lights. Here, we would like to talk about the benefits of UV-C LEDs in horticulture.

What is UV-C

First, let’s learn about what is UV-C.

Natural UV is emitted by sun. Unlike UV-A and UV-B, UV-C cannot reach the surface of the earth. In contrast, it has the shortest wavelength (100 - 280nm), and it is almost absorbed by atmosphere. However, UV-C is powerful. It has strong ultraviolet germicidal irradiation. Compared to natural UV-C, artificial UV-C is more common in our daily life. It is well-used in disinfection application, such as air purification, water disinfection, and hospital sanitization. UV-C is broadly utilized in horticulture as well.

How does UV-C work

UV-C has a powerful disinfection effect on bacterial, fungal, pathogens, etc. How UV-C actually works? Take bacterial as an example. As known, the region of UV-C wavelength is between 100 nm to 280 nm. The peak UV absorption of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and nucleoprotein in bacteria is between 254 nm to 257 nm. The UV absorption causes DNA strands breaks, leading to cross-linking of nucleic acids and proteins, killing the biological activity of nucleic acids, and causing the death of bacteria.

How does a UV-C LED work

You should have heard that LEDs can be customized for the spectrum. That is what UV-C LEDs make sense. UV-C LEDs are manufactured with the radiation between 100 nm to 280 nm, which is can inhibit their reproduction significantly and damage the DNA or RNA of cells. The common wavelengths of UV-C LED is 275 nm and 222 nm. 275 nm UV-C LEDs have been proved effective in disinfection. Recently, researchers found that 222 nm UV-C cannot penetrate human skin but has the same disinfection effect, which means that UV-C in this region is safe and powerful. What should we keep in mind is that the effect of UV-C LEDs is strongly depends on its dose and working time.

Benefits of UV-C LED in horticulture

Regardless of growing cannabis, strawberries, cucumber, or tomatoes, pests and diseases are the common problems. Growers have to solve the problems like black spots, powdery mildew, and gray mold. UV-C can eliminate detrimental bacterial, fungal, pathogens, etc. Growers used to used traditional UV-C lights, such as mercury UV-C light for disinfection. However, UV-C LEDs are more beneficial for horticulture than mercury UV-C light. UV-C LEDs can purify the air, sterilize the surface, and disinfect the water in greenhouses, indoor vertical farms, and other horticultural applications. Here is a table about the comparison with LED UV-C and mercury UV-C.

Combined with the information from the table, we can conclude following benefits of UV-C LEDs.

• Chemical free

The main benefits of UV-C LEDs are they are chemical free and environmentally friendly. Although growers have been use fungicides for centuries to protect plants from disease, fungicides are still regarded as the burden to the natural environment. The chemical contents of fungicides increase a risk to the water and soil. Moreover, the fungicides may contaminate the plants. In comparison to mercury lights, UV-C LEDs do not contain mercury, which is harmful and hazardous. UV-C LEDs are safer than mercury lights.

• Better durability

UV-C LEDs are durable because they have robust structure, lone lifespan, and better heat dissipation. Mercury lights are composed of fragile glass. In contrast, UV-C LEDs are made of rugged semiconductor. They are less sensitive to mechanical influences like vibration and shock. The better durability enables UV-C LEDs apply for various applications. Additionally, UV-C LEDs have almost a half longer lifespan than mercury lights. Overheat can cause the depreciation of performance. UV-C LEDs emit light from front side and dissipate heat at back side, reducing heat accumulation.

• Convenient operation

Mercury lights require about 15 minutes to warm up and reach the full lighting output. UV-C LEDs react immediately instead of consuming long time for warming up. They are capable of emitting full brightness when turned on and stop instantly when turned off. This makes UV-C LEDs suited for frequent switching. In other words, frequent switching will not affect the lifespan and lighting performance of UV-C LEDs. Furthermore, because of the smaller size, UV-C LEDs allow the flexible design. In sum, the instant-on features and flexible design contribute to convenient operation of UV-C LEDs.

• Natural plant growth regulator

According to the surveys, proper UV-C irradiation can suppress diseases, regulate growth, and prolong postharvest longevity of commercial greenhouse ornamental plants. UV-C suppresses diseases through stimulating plant resistance and damaging DNA or RNA of pathogens. It can also improve branching, decline the height, and affect flowering time. It showed that impact of UV-C on plants highly depends on dosage of UV-C. Too high a dosage of UV-C will burn or even kill plants. Too low a dosage of UV-C does not have effect. Because spectrum of UV-C LEDs can be customized, we can select the most effective region to regulate plant growth based on specific needs. UV-C LEDs is a low cost and natural plant growth regulator. Especially that recent surveys showed 222 nm UV-C will not hurt human skin while remaining the same disinfection effect.