Sunlight is also called natural light, which refers to solar radiation received in an exposed outdoor environment. Sunlight is undoubtedly the most suitable for plant growth. The purpose of all artificial plant lights is to imitate sunlight and give plants photosynthetic energy, heat, sterilization and insecticide.
We have already talked about the light that provides photosynthetic energy to cannabis. Today we talk about the application of ultraviolet light in cannabis cultivation.
Ultraviolet rays are light with a wavelength of 400nm to 10nm (nanometers) in sunlight. In the solar spectrum, the frequency of ultraviolet rays is higher than that of visible rays. Can be divided into UVA (ultraviolet A, wavelength 400nm～320nm, low frequency long wave), UVB (wavelength 320nm～280nm, intermediate frequency medium wave), UVC (wavelength 280nm～100nm, high frequency short wave), EUV (100nm～10nm, ultra high frequency ) 4 kinds.
As the wavelength becomes shorter and shorter, the energy of the photon becomes higher and higher, the destructive power becomes stronger and stronger, and the penetrating power becomes weaker and weaker. UVC and EUV can cause great damage and destruction to all kinds of creatures on the earth, but because of their weak penetrating ability, they have been basically isolated by the ozone layer. In the natural environment, the ultraviolet rays received by hemp are mainly UVA and UVB.
Fruits and vegetables are sweeter outdoors, and sweeter in sunny places. This is because the outdoor can provide more sufficient light to make plants grow more vigorously; in places with strong sunlight, there is more sufficient ultraviolet light to stimulate all the potential of plants.
In nature, every autumn in the Northern Hemisphere, the sun is closest to the Tropic of Cancer and closest to the Northern Hemisphere. The sunlight will become particularly strong, because the reduction of distance strengthens the transmission ability of ultraviolet rays. This period of time is commonly called “autumn tiger”. During this period of time, animals begin to prepare for winter. Herbivores will desperately eat plants that have already blossomed and obtain large amounts of nutrients into fat, which is the so-called “autumn fat”. Cannabis itself is a weed, and they are also in danger of being eaten by herbivores. When they feel autumn, in order to increase the chance of fertilization and protect the seeds, the cannabis plants that have successfully bloomed will secrete a large amount of hallucinogenic substances, which will make the animals that eat them dizzy, and then cause the disgust of herbivores. Keep your flowers and seeds. The substance they secrete is THC.
Therefore, many cannabis with very good taste and strong energy are produced at very high altitudes or very close to the equator and the tropic. The cannabis in these places can be closer to the sun during its flowering period, and can receive more ultraviolet rays for a longer time. Of irradiation.
We have discussed various types of planting lights in the previous chapters, but none of these planting lights emit ultraviolet light. Instead, HID’s metal halide ceramic lamps emit ultraviolet light. Therefore, many experienced growers will say that the cannabis grown with metal halide ceramic lamps tastes very good. This is because metal halide ceramic lamps tell cannabis that autumn is really here. Cannabis growers will tell cannabis autumn by adjusting the photoperiod, but adding strong ultraviolet rays will make this information more complete and stimulate the potential of cannabis.
Most people can increase their THC by 20% when they first use ultraviolet light, and the most experienced growers get more than 30% higher THC. In addition, ultraviolet rays can help plants defend against insects and kill bacteria and fungi. It can also make plants secrete other types of defensive compounds. These defensive compounds include volatiles (to prevent the sexual odor of insects), hormones (to strengthen the defense of other parts of the plant), secondary metabolites (to change the color and taste of the plant) and Trichomes. These compounds make plants more harmful or toxic to insects.
The use of ultraviolet rays in the cultivation of hemp can make hemp healthier, with more THC, which greatly improves the safety and efficiency of cultivation.
It is theorized that UVB promotes the secretion of more THC in cannabis for 6 hours a day for at least 40 days. UVB rays with an intensity of 1.34 watts per square meter can increase the production of THC by more than 25%.
But the real UVB lamps on the market are very rare, and the cost of UVB ultraviolet lamps is similar to ordinary ultraviolet lamps and UVA ultraviolet lamps, which is difficult to distinguish. In addition, strong UVB rays will degrade the plastic, so both the life of the UVB itself or the life of other supporting facilities in the irradiated area will be greatly lost.
More and more indoor growers have realized this, and they have begun to use metal halide ceramic lamps for full-period planting, because the spectrum of ceramic metal halide lamps is very close to the sun and can radiate ultraviolet rays. Most of them have received huge returns!
Whether using ceramic lamps or UVB lamps, we should all be aware that ultraviolet rays can harm human retina and skin, and strong ultraviolet rays can kill plants and accelerate the aging speed of the planting environment. When using ultraviolet rays to irradiate plants, we must control the UV index not to exceed 10. The specific ultraviolet intensity can be measured with an ultraviolet measuring instrument, and the value is more suitable in the range of 400uW/cm²～800uW/cm².