What Plants Need with a Lighting focus
What Plants Need to be Successful
Plants basically need 9 things. At some point I will make a drawing but for now:
- Light for Energy!!
- Above the Ground
- Proper temperature, windspeed, humidity and carbon dioxide.
- windspeed
- Humidity
- Carbon Dioxide
- Below the Ground (roots)
- Temperature
- Water
- Nutrients,
- Oxygen
In addition, plants need to be anchored.
If you are working in soil or non soil systems the plants requirements are the same.
Lighting: What you need to know.
The sun sends out energy in the form of magnetic radiation. Part of this energy we can see (visible spectrum). visible light (energy we can see with our eyes) is between 300 and 700 nm. Shorter wavelengths are referred to as UV radiation and are at wavelengths less than 300 nm. Over 750 nm is referred to as infrared radiation.
Plants can use the energy from wavelengths very similar to the wavelengths we see.
Solar energy (complete solar spectrum) is measured in Watts/m2 and in direct sunlight this can be a maximum of 1600 Watts/m2 . This is great for solar panels but plants can't make use of the total light spectrum.
For plant growth, we want to know what is wavelengths are used by the plant. This is referred to as Photosynthetically Active Radiation or PAR. It turns out the plants make good use of the same energy wavelengths that we can see, about 400 to 750 nm.
We measure this PAR energy not in Watts/m2 but in a photon flux density that has units of micromoles/s/m2. It is commonly referred to as Photosynthetic Photon Flux Density or PPFD.
Each plant responds differently to PPFD with some, like lettuce having a response only up to 500 PPFD while other plants, like corn, having a growth response with as much as 2000 PPFD (about the max from the sun). (Tomatoes and cucumbers can get by with about 200, Peppers need 400. But I am not sure what their response curve looks like.)
Daily Light Integral.
The last thing to think about with lighting is the Daily Light Integral or DLI. While PPFD tells you how much light is coming per second, your plants really need a quantity of light energy (think about PPFD as inches of rain per hour and DLI as total inches of rainfall in a day). Think about it, do they just need 500 PPFD for one hour or do they need 500 PPFD for 24 hours? This DLI is plant specific. For instance, a corn plant requires a DLI of 42 (about 42 moles/m2/day) In Utah you can get a DLI as high as 60!!
To calculate the DLI you multiply the PPFD by the time (umoles/s/m2) x how many seconds the plant is exposed to this light. So twelve hours per day of light shining on a plant providing 500 PPFD provides a DLI of 21 mole/m2/day.
What is the difference between Lumens and PPFD?
Lumens is the total energy coming from the light in the visible spectrum.
PPFD is the amount of energy that strikes a certain area over a given period of time. The light bulb gives off the same amount of lumens but as you move away from the light the PPFD will change because the light energy is dispersed.
How does K value of a light fit with all this?
K value is a measure of the light spectrum of a bulb. Higher K values (5000) look more white (tending to the shorter wavelength end of the spectrum). Lower K values 2500-3000 show up more yellow having a higher percent of light that are longer wavelength.
Why is this important?
When you start plants you need abut 50 PPFD for about 12 hours per day. When you get your plants home they will require more and more light as they grow bigger. Each plant species will be different. Getting the plants into the sunlight as much as possible will really help. But even so, you may need to provide more light. We have a light meter in the makerspace. You are welcome to bring your light in and test your PPFD at different distances.
For MORE INFORMATION check out these videos:
Lighting by Bigleby https://www.youtube.com/watch?v=ID9rE5JewVg
Links to an external site.