LED lights in hydroponic cultivation
Anyone who has been planting for some time has probably seen a graph showing the adsorption characteristics of chlorophyll A and B. As shown in the image below, most of the light absorbed by plants has a wavelength of less than 500 nm or It is above 650 nm, so the hypothesis that plants can only grow effectively using light in these areas is very simple. The commercial answer to this hypothesis is that blue / red LED light gives the plant energy that is suitable for absorbing the “best” and prevents energy from being “wasted” in producing unabsorbed light. However, these blue and red lights have so far been a loser, and the vast majority of the industry has now turned to full-spectrum LED lights.
When the cost of red / blue lights was low enough, significant research was done to evaluate them in the scientific community to determine how they affect plant growth. It quickly became clear that plants could be grown with these new lights, and that products could be as healthy as products produced in normal full-spectrum light. However, some problems arose as these red / blue lights began to move toward larger commercial applications. Although the commercial use of these lights in large fruit plants is practically non-existent due to the high cost of supplementary lighting, their use for some small deciduous plants such as lettuce and spinach, which can be used in urban settings under high density conditions, is still their main use in space. It was cannabis cultivation, which is one of the only expensive crops grown largely under supplemental light when it is away from the equator.
Most people who did this soon realized that plant growth was not equal to what is achieved when using fuller spectrum lights, such as HPS or even metal halide lamps, even at equivalent photon flux values. Although scientific publications on cannabis are scarce, this 2016 report (1) shows that white lights generally do a better job of growing plants than blue / red lights. Other research (2) shows that blue / red lights can also affect the chemical composition of secondary metabolites, which makes the decision to move to red / blue LED growth lights affect the quality of the final product.
It has also been shown that green light is not completely unused by plants, but can actually have important functions. This study (3) addresses many of the important functions of the green light signal and why it can be important for healthy plant growth. Some researchers have also begun experiments with red / blue / green growth lights that show the positive effects of adding some green light to the composition (4). It has also been shown that other regions of the spectrum, such as far red (5), can significantly contribute to photosynthesis and the regulation of plant biological processes. Ultraviolet light can also significantly help express certain molecules in plants. An article evaluating cannabis under several different light regimes shows how light spectrum composition can manipulate the secondary metabolite composition of plants (6).
Finally, the last problem with the growth light phenomenon, especially in the case of plants such as hemp, was the fact that the plants appeared under this red / blue-black light. This means that the growers were completely unaware of the potential problems that arose, because the plants were virtually invisible to them throughout their lives. This was one of the main reasons why these lights were never widely used, as they detected nutrient issues and insect problems – which are easy to detect under full-spectrum light for a relatively experienced breeder. – It was almost impossible with these reds / water growth panels in operation, a large commercial operation relies heavily on experience and ongoing product evaluation by on-site personnel, and failure to do this useful process review is a recipe for disaster.
The LED industry has learned from these problems and has since moved to develop high-efficiency, full-spectrum growth panels for the hydroponic industry. These will surely become the future and standard in the domestic hydroponic industry, especially if prices fall as a result of mass acceptance. Having full-range bulbs, which are much more efficient than HPS and MH bulbs, gives farmers the opportunity to save a lot of money while maintaining or even improving the quality and performance of their crops.
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