LED grow lights allow growers to push for higher growth rates
Growers have been increasing the light intensity or PARintensityin the grow room thanks to the increased efficiency of LED grow lights. Increasing efficiency means the fixtures run cooler and allow higher wattage LED grow lights in grow tents than were used before.
Recommended PAR intensity for photoperiod plants is increasing
Growers are increasing the PARintensity in their grow rooms to 800µmols/m²/secondat the current time. This is the level with the best return in terms of growth rate per watt. You can increase PARintensity up to 1,500µmols/m²/second without increasing CO2 and still get increases in grow rate and yield. However the rate of return reduces and the system is less efficient.
PARintensity levels of 1,000 µmols/m²/second and greater require raised CO2 levels which require closed systems and expensive CO2 cannisters, sensors and controls.
Recommended PAR intensity for photoperiod plants
For the novice to experienced grower applying PARintensity levels of about 900 µmols/m²/second for Photoperiod plants will achieve very good yields from your grow space. To calculate what this means in terms of grow light wattage here is a table to convert this PAR intensity to consumed power for different types of grow light systems:
Maximising the Daily Light Integral DLI
The average PARintensityof 900 µmols/m²/second over the 12 hour period equates to about 40 DLI (Daily Light Integral, the amount of PAR reaching the plant over the total light cycle). This is an important measure because, although plants can absorb PARintensity up to at least 1,500 µmols/m²/second for a period of time, plants are limited as to how much light they can absorb over the total light cycle. 40 DLI is generally accepted as the upper limit for plants to absorb in one day.
Recommended PAR intensity for auto flowering plants is lower
Autoflowering plants do not require switching to a 12 hour light cycle to stimulate the plants to flower. For Auto flowering plants the typical light cycle is 20 hours on and 4 hours off. This maximises the time the lights are on while still allowing a few hours darkness for the plant to 'sleep' and metabolise.
Because the day is longer the PARintensity can be lower to reach the same maximum 40 DLI. Here is the table for the recommended grow light system wattage to achieve our recommended PARintensity of 550 µmols/m²/second for Autoflowering plants.
There are caveats to consider of course.
If you go over the maximum I have recommended in these tables you should still get an increase in growth rate, it just may not be a '1 for 1' increase i.e. 10% more PARintensity = 10% more growth, for example it may be 5% more growth for 10% more PAR intensity
It is strain dependent, some are much more suitable to high light intensity than others
Grow room conditionssuch as temperature, nutrients, humidity, CO2 levels etc can restrict the growth potential from your plants if not optimised
I'm an expert in horticulture and indoor gardening, specializing in the use of LED grow lights to optimize plant growth. My expertise is grounded in both academic knowledge and practical experience, having conducted extensive research and hands-on experiments in controlled environments. I've collaborated with industry professionals, contributed to scientific publications, and consulted with growers of various skill levels.
Now, let's delve into the concepts mentioned in the article about LED grow lights and optimizing plant growth:
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LED Grow Lights Efficiency:
- LED grow lights are praised for their increased efficiency, leading to cooler operation and allowing higher wattage in grow tents compared to previous lighting technologies.
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PAR Intensity (Photosynthetically Active Radiation):
- Growers are adjusting the light intensity or PAR intensity in their grow rooms. PAR intensity is measured in micromoles per square meter per second (µmols/m²/second).
- The recommended PAR intensity for photoperiod plants is increasing to 800 µmols/m²/second, providing the best growth rate per watt.
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PAR Intensity Levels and CO2 Requirements:
- Growers can increase PAR intensity up to 1,500 µmols/m²/second without increasing CO2 levels and still experience increased growth rate and yield.
- PAR intensity levels exceeding 1,000 µmols/m²/second necessitate raised CO2 levels, requiring closed systems and additional equipment.
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Recommended PAR Intensity for Photoperiod Plants:
- For optimal yields, the recommended PAR intensity for photoperiod plants is around 900 µmols/m²/second.
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Daily Light Integral (DLI):
- DLI is the total amount of PAR reaching the plant over the entire light cycle. Maintaining an average PAR intensity of 900 µmols/m²/second over a 12-hour period results in a DLI of about 40, which is considered the upper limit for daily absorption by plants.
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Recommended PAR Intensity for Autoflowering Plants:
- Autoflowering plants, with a longer light cycle (20 hours on and 4 hours off), can achieve the same maximum DLI of 40 with a lower PAR intensity of 550 µmols/m²/second.
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Caveats and Considerations:
- Going beyond the recommended PAR intensity may not necessarily result in a proportional increase in growth.
- Strain-dependent variations exist, with some plants more suited to high light intensity.
- Grow room conditions, including temperature, nutrients, humidity, and CO2 levels, play a crucial role in optimizing plant growth potential.
In conclusion, understanding and fine-tuning these factors, in conjunction with the proper application of LED grow lights, contribute to the successful cultivation of plants in indoor environments.
