naires themselves. Another factor to take into consideration is light uniformity. This depends on how your greenhouse is set up but in general HPS lamps will provide a broader, more uniform light output pattern and LEDs tend to have a more focused illumination. Since we manufacture and sell both HPS and LED luminaires, we do not have a bias towards either and are motivated only to sell you the best lighting system that works for your greenhouse.
Spectrum and Intensity Considerations
Plants require light in the photosynthetically active radiation (PAR) range of 400-700 nanometers for proper development – and not all lights are created equal when it comes to PAR and light quality. When thinking about adding LEDs to your growing operation we recommend starting with a trial area, so you know what to expect if you decide to adopt the lighting on a larger scale. We have worked with growers in the past who have installed a competitor’s LED system, to have them come back and buy additional luminaires from P.L. Light Systems because their existing lights did not have the full spectrum the plants needed and/or the light intensity was not enough to hasten the plant’s growth. Plant varieties will all react differently to variations in light spectrum and light intensity and it’s important to understand what these reactions and outcomes are before investing in lighting for an entire greenhouse.
Considerations for when choosing a lighting system
Many things should be taken into consideration before investing in a lighting solution. Consider how lighting might affect the environment of a greenhouse and any changes that will need to occur. Parameters such as watering, heating, nutrient uptake and humidity may be affected and need to be adjusted.
Some crop and environmental considerations to think about when choosing a lighting system:
- What is your target DLI for your crop?
- This chart from Purdue University gives recommendations of DLI based on crop. By deciding what your target DLI is you can better choose the amount of light you will need to reach your target
- What is your photoperiod for your crop?
- You may need day extension (photoperiod) lighting depending on what you are growing and their photoperiod requirements (long day, short day or day neutral plant varieties).
- What is your temperature range for growing your crop? In general, temperature helps drive the plant development rate.
- Are you growing cold tolerant crops like greens or heat loving crops like tomatoes? Figuring out your target temperature for plant growth can help decide what lighting solution works best for your space
- Where are you growing your plants? How far will the lights be to your plants? This information can help decide light distribution and uniformity over the crop
- Are they on benches?
- Are you growing plants on the floor or in hanging baskets?
- Are they being grown in a vertical system?
- What materials are the greenhouse made of? How much light gets emitted and absorbed by the plants?
- How are you watering your plants? The type of lighting you chose will affect your irrigation schedule. In general, plants grown under HPS lamps require higher amounts of water. Using flood tables or drip irrigation can help control watering and prevent water loss.
- Are you injecting CO2?
- Natural winter CO2 levels can drop in the greenhouse. In general, CO2 enrichment will increase the photosynthesis rate in plants and will have a positive effect on quality and yield.
- Are you using energy curtains in the winter to save on heating costs?
- While a good way to save on heating costs, the curtains can decrease the amount of light being transmitted and should be considered when calculating winter DLI and creating a light plan.
- In some cases, lighting may affect nutrient uptake and may lead to deficiencies or excess amounts of certain macro- and micro-nutrients.
- Keeping an eye on pH, EC and getting timely nutrient analysis’ done may be helpful in figuring out a nutrient management program under some artificial lighting
How P.L. Light Systems can support you
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