LED grow lights are revolutionizing the way we grow plants indoors. They provide a more efficient and targeted way to deliver the light that plants need for photosynthesis. But to optimize plant growth, you need to understand some essential terms and concepts related to the artificial lighting of plants. Let's dive into PAR, PPF, PPFD, and DLI to help you make the best decisions for your indoor gardening.
What is PAR ? PAR refers to the range of light wavelengths that are useful for plant photosynthesis. This spectrum ranges from 400 to 700 nanometers and it’s the same band of visible light that our eyes can see. The photosynthetic process uses these wavelengths to convert carbon dioxide and water into glucose,
Understanding the PAR spectrum helps you choose LED grow lights that produce the correct wavelengths for your plants. Some lights might focus on the blue or red part of the spectrum, beneficial for different growth stages.
PPF is a measure of the total amount of PAR that a lighting system produces per second. It's measured in micromoles per second (µmol/s) and tells you how many photons in the PAR band are emitted by the LED grow light.
The PPF provides a raw measure of the total light produced within the PAR spectrum, helping to gauge the efficiency and potential effectiveness of the grow lights. It is an absolute number for any grow light fixture and would largely depend on its wattage and Efficiency.
PPFD measures how many photons in the PAR range fall on a given surface each second. It's measured in micromoles per square meter per second (µmol/m²/s). Unlike PPF, which tells you the total amount of light produced, PPFD tells you how much of that light reaches the plants.
Different plants and growth stages require different PPFD levels. Understanding the PPFD allows growers to adjust the lighting system to provide the optimal amount of light for the plants' specific needs.
DLI measures the total amount of PAR received by a plant in a single day. It's calculated by taking the PPFD and multiplying it by the number of seconds the light is on during the day, giving a total in micromoles per square meter per day (µmol/m²/d).
DLI helps growers understand how much light a plant receives throughout the day, ensuring that they are neither under-lighted nor over-lighted. Different plants and growth stages require different DLIs, so understanding this value can help optimize growth.
Multiply the PPFD by the number of seconds in your photoperiod, then divide by 1,000,000 to convert from micromoles to moles: DLI=(PPFD×number of seconds in photoperiod)/1,000,000DLI=(PPFD×number of seconds in photoperiod)/1,000,000 Here's an example calculation: • PPFD = 500 µmol/m²/s • Photoperiod = 16 hours • Number of seconds in photoperiod = 16 hours × 60 minutes/hour × 60 seconds/minute = 57,600 seconds DLI=(500×57,600)/1,000,000=28.8 mol/m²/dDLI=(500×57,600)/1,000,000=28.8mol/m²/d.