Light cycle vs light intensity. How do these relate to each other when setting up your grow lights? What is DLI? In today's video, we focus on hydroponic lettuce grown under some small 15w SANSI LEDs.

Watch PART 1 of this series for further context:
   • Preventing Tip Burn: Hydroponic Lettu...  

TEST OBJECTIVES: To compare the growth of hydroponic lettuce grown under a daily light integral of 16 delivered through varying photoperiods (12/12, 16/8, 24/0). Also, to determine if continuous light on a lettuce plant will induce flowering or elongated growth.

KEY TERMS:

PHOTOPERIODISM: The physiological growth or reproduction response of a plant when exposed to a specific photoperiod or day length and the corresponding period of darkness.

DLI: Daily Light Integral refers to the total number of PAR photons, delivered to a square meter area through the course of a 24hour period. It is expressed as moles of light (mol) per square meter (m−2) per day (d−1).

PPFD: Photosynthetic Photon Flux Density as measured in micromoles per second, per square meter(μmol/m2/s) is a snapshot of all PAR light falling on a surface within a single second.

TEST BED PRODUCT LINKS (# CommissionsEarned):
Lettuce Tom Thumb: http://shrsl.com/bzt8 (Botanical Interests)
SANSI White LED Light: http://amzn.to/2zEUQzT (Amazon)


My PPFD Meter (Apogee Instruments):
► https://amzn.to/3ebJiHZ




Test Setup:
Lettuce 1: 10.25" Distance 370 PPFD @ 12hr = 16 DLI
Lettuce 2: 12.5" Distance 278 PPFD @ 16hr = 16 DLI
Lettuce 3: 21" Distance 185 PPFD @ 24hr = 16 DLI

Fresh Weight (tops only):
Lettuce 1: 77g
Lettuce 2: 81g
Lettuce 3: 93g No Bolting Occurred

SLIDE CORRECTION (6:59):
I showed the remaining solution & failed to convert that number to solution consumed as labeled. Here is the replacement slide:
http://albopepper.com/images/Photoper...
Lettuce 1: 1125mL
Lettuce 2: 1252mL
Lettuce 3: 1341mL

SUMMARY:
There is a direct relationship between light intensity and photoperiod. DLI is a measurement that accounts for both parameters. Light intensity (as measured in PPFD) is documented and then converted to a 24 hour period, adjusting for the dark cycle as well.

When plants receive insufficient light, light intensity can be boosted by placing the light closer to the plants. However, increasing the duration of the light cycle is also a possible option. Both approaches effectively raise the DLI and boost plant growth.

Of course, when plants are getting too much light the reverse applies. Raising lights might solve the problem. But reducing the light cycle is advantageous due to the reduction in power consumption. Thus plant may yield more mass per watt consumed.


#Horticulture #GrowLights #knowledge #IndoorGrow #Lettuce #UrbanGardening #GrowingTips


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