Photoperiod vs Intensity: PPFD / DLI - LED Lights Lettuce Experiment (What is DLI?)

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: H...
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 24-hour 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: shrsl.com/bzt8 (Botanical Interests)
SANSI - White LED Light: amzn.to/2zEUQzT (Amazon)
My PPFD Meter (Apogee Instruments):
► 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:
albopepper.com/...
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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[@Albopepper]

*Watch PART 1* of this series for further context: kzbin.info/www/bejne/nXm6l2d-m85mnqM _Check out my other reviews:_ *"1000" LED Grow Lights Shootout pt 1:* kzbin.info/www/bejne/nWfRaYmei6x-ers *"1000" LED Grow Lights Shootout pt 2:* kzbin.info/www/bejne/jZ7NgIawiKtgfqs *Spider Farmer SF300 / SF600:* kzbin.info/www/bejne/iInFg2CemL2Yh5Y *Active Grow LoPro Max 320W:* kzbin.info/www/bejne/hnTElqaflLJoerM *Maxsisun MG3000:* kzbin.info/www/bejne/iqiZXqponN6VndE This UPS power station can backup a grow light! ► kzbin.info/www/bejne/nmTWhoh-eKqkmNU Check out my *Grow Light Cost Calculator:* kzbin.info/www/bejne/l4XSipuvhb-AjNU _Learn more about artificial lighting and plant growth:_ ► What is PAR vs ePAR Light? kzbin.info/www/bejne/oYbTdoRqoLpkapo ► The impact of Red or Blue light on plant growth: kzbin.info/www/bejne/qZfMmXhqftp5q7c ► To avoid Tip Burn: kzbin.info/www/bejne/nXm6l2d-m85mnqM

[@laultimaverdad1187]

Excellent!!!

[@erict9392]

it looks hard to do but hate the bugs outside

[@AndroidSamsung-qz9pl]

What is bolting?

[@Albopepper]

@@AndroidSamsung-qz9pl When plants flower when we don't want them to, we call that bolting. Annual cool season vegetables including lettuce and spinach will bolt as days grow longer in summer. Bolting usually brings on bitter flavors in the foliage as will the usually hot temperatures that come along with longer days. Hot temperatures also cause the flowers to come on more quickly as will dry soil. Some biennial vegetables bolting is induced by a cold snap during a plants normal vegetative stage. Prone to bolting include rhubarb, Chinese cabbage, and mustard greens. Some biennial vegetables, (those that normally produce only vegetative structures their first year, flower and seed their second year), may bolt during the first growing season in response to a cold spell. Most biennial vegetables, including onions, carrots, heading cabbage, have to reach a certain stage of growth before they are able to start the flowering process. But turnips are sensitive to cold as soon as they germinate. Bolting cannot be reversed once the flowering process has begun, so replace affected plants with heat-tolerant summer crops or wait until later summer to replant for a fall harvest.

[@AndroidSamsung-qz9pl]

@@Albopepper Wow. Thanks for the though reply! :) More power to you.

[@acolley2891]

I just love how you question things that may seem like they don't make sense at first and test it regardless. No question is a stupid question. I learn a ton from you.

[@teenaneuner3376]

you know, sometimes a person just plants their garden and lets it do its own thing ,but this experiment really makes you appreciate the true science involved in what we may take for granted. i really enjoyed the technical science, although i'll never remember the terms.

[@Albopepper]

Thank-you for your kind words! The videos are here, so you always have this resource available to you!!! xD

[@deakemarschall2992]

Another great experiment that very simply explains a complex theory. Thanks.

[@Albopepper]

Thanks so much for watching! :-)

[@Flamingpiano]

I would love to test this in the other way. Increase light intensity to a huge maximum (with matching intense cooling), and shorten the light cycle as much as possible, to increase periods of darkness and growth. Perhaps we could condense the day light cycle into a 3 hour window for example, allowing for more frequent dark cycles and as such quicker crop growth.

[@Albopepper]

You should test it out and share your results!

[@MTechOver9000]

Ps. I wanted to say that your your teaching style is great. I find that you explain complex things in a very basic manner that anyone can understand. Even as a scientist by profession who understands most of these concepts, I'm not even mad at your pace. They always told me in my studies that you only truly understand something when you can make a layman understand which I think you do great. Subbed. Keep up the good work sir and keep these interesting experiments coming!

[@kramermcjergen5711]

totally different light set ups with very similar results. thanks for the science lesson!!!

[@Albopepper]

Thanks Kramer! This was the most scientific method I could come up with to demonstrate DLI in practical terms. :-)

[@ikyitching]

So lettuce, at least the variety you grow, is not very sensitive to light cycle! Good to know! Thank you a lot for taking so much time doing this experiment!

[@Albopepper]

Thanks for taking time to watch!

[@ikyitching]

Thanks! You provide important information! These experiments should be repeat by some national labs!

[@hlorofos]

Oh, that was so useful! I'm using 24h leds and got the same picture like yours, deformed leaves and burns. I definitely knew I made something wrong, but now I'm pretty sure I understand the reason.

[@KENNETHFRANCISRODRIGUES]

You should be a Professor! I learnt many concepts of lighting which i could not understand. The experiements were well designed and the resukts were explained clearly. Have you published your data? It has all the elemnents of a high impact publication.

[@maksymkharkavyi3563]

I haven't even watch the first video to the end but a fan already

[@vonzaag4555]

Glad you did this comparison. I sure don’t put in the time/effort to find it out for myself

[@solopianoamico...6719]

Wow, he just came up with a new variable that was hided out of sight all this time... amazing!

[@arcataslacker]

Very much enjoying your process. Just getting started in indoor gardening and until now, haven't found anything this data driven. Thank you!

[@Civilsitis]

Admit it, your real name is SUPER MARIO....ISNT IT ;)

[@Albopepper]

It'sa me!

[@alexacquaah4074]

*i knew it!*

[@rexbk]

Great experiment. I am growing lettuces with NFT system myself in Indonesia. The pH level that I always maintain for lettuces is 5.5 - 6.3. You may want to consider this pH aspect as well.

[@nigelsharp4664]

Excellent presentation of all the information!! And really well thought out experiment. Very much enjoying these.

[@Albopepper]

Thanks Nigel!

[@K1ngG00mba]

I’m starting a microgreen channel soon and plan to replicate your experiments! I appreciate the science behind everything you do, reminds me of my gen bio 2 class! Well done

[@punkyroo]

I love these experiments! Thank you. During the winter I am an avid indoor grower and this info is so helpful. :)

[@grubsgarden7364]

It gets cold but we don't get snow here, every year I appreciate the winter season more and surprise myself in what I am able to grow (although there are failures, to be sure, no luck with cauliflower). I only have one north facing window though and it's not a place I can set up an indoor garden, but I do grow on my north facing balcony in winter too.

[@volvo09]

Same here, I absolutely love Albo's experiments!

[@Albopepper]

xD Thank-you for your support!

[@Albopepper]

Thanks Punky! I'm glad that this info was helpful. :D

[@punkyroo]

Grub's Garden It sounds like you are having success despite having some limitation. :) Very cool!

[@MSLBushcraftSurvival]

Good video. I asked my self about that for a while already, nice to see your experiment results. Thanks

[@Albopepper]

Thanks, I appreciate your support! :-D

[@SanGennaro83]

Very interesting experiment (ofc accounting for the limitations of the case)! Keep it up!

[@Albopepper]

Thanks for your support! :-D

[@indopleaser]

I use read a study about this , crazy your experiment matches the test

[@Ahoy123]

elo do u still remember the study name?

[@billastell3753]

In this world people who have an opinion are a dime a dozen. Those who put out the effort to find the facts are true gems. Albo Pepper... you sir are a gem! On a different note, have you ever watched my name is Earl? You could pass as his brother with that mustache. Wishing you the best Karrma for all your videos and work. Thumbs up!

[@PixelSeekingPhotography]

I just started to learn about indoor growing and lighting. I have to say this is my favorite channel I've come across. Keep up the good work, and I cant wait to learn more from you.

[@mnisarg]

Thanks a lot for explaining the complex concepts with such clarity. It will surely help my plants grow better.

[@Albopepper]

Thanks for watching Nisarg! I appreciate your positive feedback. :-)

[@Stephanbitterwolf]

I love how you are bringing science into your videos. It would be awesome if you could have triplicates of each treatment :D

[@hobesmcgee]

Great experiment, thank you for creating informative and entertaining content to share with all of us - awesome work!

[@Albopepper]

Thank-you Hobes! I appreciate it. :)

[@maxgomez8967]

What a good video, very useful thanks for sharing it. I think that if we use lights with less consumption (less lumens) and closer to the lettuce, we could get the same target DLI and with the same electric consumption per gram as lettuces 1 and 2 or maybe less.

[@Albopepper]

Thanks Max. Any little bit of extra efficiency is worth it! :)

[@belspace]

Lovely channel ! All you need to know about plant grow lighting, explained cristal clear 👍 Albo!

[@fishbone1151]

Your experiments are always appreciated so much, sharing knowledge like this is extremely valuable. Ty so much for what you do.

[@unravel523]

You were So professional in your approach, I subbed right away. Thank you! It´s winter soon, and I can´t buy commercial veggies, so this is brilliant. Let´s Grow :)

[@TheNorthwestForager]

Such a cool experiment! All the sort of things I'd love to try. Thanks for sharing. -Hank

[@Albopepper]

Thanks Hank! I appreciate your support. :-)

[@KBorham]

Thank you for serious and academic content, and for using PPFD and DLI!

[@Morpheus852]

Thanks! Helped me a lot to understand things further. I would love to see such tests with Basil, as I'm struggling with my indoor setup and I'm sure I'm not watering to much / less and ferts should be good, at least in my opinion compared to outdoor gardening :)

[@firecloud77]

I found that lettuce tip burn is greatly reduced on indoor plants by growing them in half-strength nutrients.

[@constantinwossala9926]

always, or introduce gap weeks.

[@meowmeowmeow5202]

You're videos are awesome, bro. Keep it up. Quality content. Cheers.

[@Richos_Permaculture]

That was very informative mate. Nice and straight forward.

[@robertobaldizon8206]

Great video, sir. Thank you very much. Greatings from Argentina.

[@juangracian4756]

this was quite an interesting study. I'd like to see it replicated on a larger scale.

[@Albopepper]

So would I Mr Gracian. Hmm... looks like you have a busy Winter ahead of you! Let me know how your test turns out! ;-P

[@influencer_music]

When looking at growth per watt, did you consider that with the 24 hour light cycle, the distance of the light means the coverage area is greater, so you may have been able to put more plants under the light than the other two?

[@midwestmangos2452]

Exactly, or as I mentioned in my comment just use a light that offers a dimming method to reduce the power usage instead of wasting light (as spread out light has greater chance of losses even if used for more plants like you mentioned.

[@Joni_I]

Super awesome video. Helpful for understanding my aquarium lighting a bit better too

[@mackplymale342]

The Inverse-Square Law of light This law states that for every foot below the reflector the light should loose 75 percent of it's energy due to dispersion. So 1000 lux at 1 foot is 250 lux at 2 foot. I have taken a lux meter and find that I am only loosing 50 percent per foot. I am thinking the reflective walls are keeping the numbers up. Also, if you are have multiple lights when you just below the reflector you only get light from it. As you move down you get light from multiple lights. This applies to HPS and Metal Halide due at the side bouncing of the wall is as bring as just below it. Where LED blow all their light down.

[@goonernumone8444]

Just found your channel but im hooked..... thank you from.the UK !

[@cstevens2001]

You always have exactly what I'm looking for... Thanks

[@Albopepper]

I'm glad I can help Chris. Thanks!

[@808trancast]

Very insightful, the only factor is missing is the humidity.

[@shawtop]

I dont know what you just said but I enjoyed it 😂😂😂

[@niberusky8567]

Exactly what i was searching for. Thanks

[@robs227]

This was a glorious experiment

[@srtomas]

great video! It'd be really appreciated if you put a ruller in the back of each growing box, since you're using the same pots for all of them. the difference in height would be easier to differenciate between plants, and you could use that info for further analysis. It's just a detail! Greeing from Argentina!

[@electrician5168]

I don,t know any body that has a lettuce shirt. You could be the new and improved Mr. Green Jeans.

[@forageforage3520]

Awesome Test! Thank you for doing this.

[@papablueshirt]

Cool experiment, I may dial mine back a bit. More is not always better.

[@SeamusHarper1234]

This is really awesome and I would like more of it. Although I have to say that the cost comparison is a misleading conclusion. Instead of moving the light away from the plant, you could save energy by using a dimmer light, or increase yield by growing multiple plants.

[@Albopepper]

Yes the suggestion of growing multiple plants was put forth in the 1st installment of this series: kzbin.info/www/bejne/nXm6l2d-m85mnqM The lights I was using were not dimmible and I had to make due. The focus of the test is to show the relationship between PPFD levels and Light Cycle duration in calculating the photons received by plants. It explains DLI. That's the core concept.

[@SeamusHarper1234]

@@Albopepper you did that and well by the way! I am 100% agreeing with 99,5% of the video ;-) I hope it's constructive criticism. I have seen the first video 👍👍

[@tysonmayberry1208]

you are the best mate! keep it going!

[@Shanngella]

Thanks for the 2 interesting videos. I've never had tip burn until I received an aerogarden as a gift. My kratky lettuce is fine but my aerogarden lettuce always has tio burn. I've tried over and over to experiment with same nutrients and same water and duration. The only difference is that light included on the aerogarden. So after watching your video I think my hunch is correct about the aerogarden light.

[@BogdanovFamily8]

Awesomeness work, dude! You're the best! You're considered everything! Thanks much!

[@Albopepper]

Thanks so much for watching Andrej!

[@philipripper1522]

I'd love to see a continuation where you get to shorter and shorter light periods with same DLI. For lettuce, I'm curious where the watt/oz maximum is.

[@ElderandOakFarm]

Thanks so much for this video!

[@Albopepper]

Thanks for watching Candace. I appreciate your support on my channel! :)

[@samuelgates693]

A Super Plumber turned Gardner. I dig it.

[@extendedp1]

Great video, thanks.

[@aquahydroman7623]

Great information. I also experimented with 12 varities of lettuce. Tom Thumb suffered tip burn.

[@clintongracias9981]

Hi, like your informative content. Can you please specify the climatic conditions for lettuce to grow, ie the optimum humidity and temperature. Keep up the good work. Lots of love from Goa.

[@Albopepper]

Hi Clinton. I would recommend checking out this resource from Cornell: www.cornellcea.com/attachments/Cornell%20CEA%20Lettuce%20Handbook%20.pdf

[@nfetiu]

Very informative video as usual. Thank you very much.

[@mrdkoser]

I agree with below- as I used to be a middle school science teacher.... You should be a Professor! I learnt many concepts of lighting which i could not understand. The experiements were well designed and the resukts were explained clearly. Have you published your data? It has all the elemnents of a high impact publication.

[@Albopepper]

Thanks Devin! I greatly appreciate your positive feedback. :-)

[@surronzak8154]

DLI wonderfully simple explained, new sub

[@Albopepper]

Cool! Welcome to my channel!!! xD

[@chanfred3037]

nice experiment

[@scottfoss716]

This was amazing. Thanks.

[@Albopepper]

Thanks for watching Scott!

[@chingching2607]

Great information! Love the video! Found a small typo on 7:14 with the slide title

[@johnhattingh9759]

Great video man!

[@hannesgranlund8838]

Extremely informing

[@MTechOver9000]

Thanks bro, love these experiments!

[@Albopepper]

Thanks for watching MTech! I appreciate your support on my channel! :-)

[@simplyengineering2350]

The average person isn't gonna have the fancy sensors. A test with lights at same height will be more practical for most viewers. However it's still a contribution to the community. Thanks and cheers.

[@Electronics_Edu]

Good video. Maybe you can try applying the light intermittently. Does it affect the crops quality? And does it really save electricity? Maybe you can make (10 min on / 10 min off intervals) or maybe (1h on and 1h off intervals). Does long or short intervals matter?

[@growstar6646]

Great Experiment Bro !

[@Albopepper]

Thanks man!

[@infowarsrecast4679]

Interesting, Matanuska produce in Alaska is huge, 18-22 hours of daylight.

[@Albopepper]

Good point! Thanks for watching. :-D

[@EngineerCatPyro]

And just like that! I don't know ish about growing. :) Great video. Thanks!

[@Albopepper]

LOL, thanks for watching!

[@HowToGetMoreMetal]

Wow, great job

[@StanTheMan709]

this was awesome love these vids bro!

[@Albopepper]

Thanks man!!! :-D

[@nicolastorres8327]

beautifully explained!

[@stefanstef2036]

Great experiment guys 🤗

[@dwiantony4875]

Thank you sir your content soo helpfull until this day ❤

[@GiGaSzS]

Thank you, very informative :)

[@Albopepper]

Thank-you for watching, as always!

[@mk00.01]

great video..it's so informative..well done

[@Albopepper]

Thanks for watching and visiting my channel! xD

[@ЯрославЮрчишин-з7э]

Very interesting. And how can we calculate the right distance from the light to the plant? I mean how did you get figures 10,5 and 12,5 and 21 inches? By using PAR-meter?

[@marsofearth]

Fantastic work! Thank you for your well thought out mini experiments. I am fascinated with the idea of light intensity and light period. Have you tried any experiments with periodic darkness within a 24hr period? Say 12hr with 1hr on 1hr off. Or 4hrs on 4hrs off. Would more frequent pauses help with tip burn? Or will these pauses cause a different stress reaction?

[@mk00.01]

Yeah I would like to know that aswell

[@FuelX]

Thank you, my lettuces are growing very fast and I have tipburn. I will try reducing my light cycle.

[@MrNeuroticRA]

OMG omg OMG. So I just ran my lights at 24 hours as an experiment. Deformed! 18/6 seems to be the cure. Also I agree with broad spectrum white light being better for growth. The PAR argument sounds good but LEDs makes my plants wonky unless they are already strong. Excellent novel research design.

[@Albopepper]

Good to know John! What type of plant were you growing?

[@MrNeuroticRA]

@@Albopepper Cannabis.

[@ryanbuck4569]

I like your videos thanks

[@Albopepper]

Thanks Ryan! xD

[@galihgori]

Awesome, thanks

[@mosiahparkman358]

Excellent 👍

[@davidceaser7907]

Hi, what was the starting pH and EC of your experiment ? Also, what nutrients did you use? Thanks so much for sharing this info. Also, have you done any experiments w shorter light cycles? 5 min on, 5 min off vs 5 min on 2 min off, etc ?

[@FARAJSCHOOL]

Thank you you for these information

[@wheelmanstan]

awesome, i just finally started using a grow light, i got fed up with the weather...this is exciting, first off..the led full spectrum is just a beautiful light, it makes me feel better just being in the light, haha, just feels natural, maybe I have SAD..I don't know this all makes perfect sense, I think leaving the lower intensity light on 24/7 at a greater distance, which allows for more plants to receive it, should be best, for what I'm trying at least, you proved that 12hr is ultimately the overall most sensible way to grow but I'm going to experiment first, honestly I'm more worried about constantly powering on/off the grow bulbs, should I not be?

[@jimd1617]

@3:17 I love this guy :)

[@unclearam2055]

Could you do a test on growing the same crop at 24/7 vs 18/6 vs 12/12 and compare root development between them. I want to see if the majority of plants root development happens during daylight rather than night.

[@ulraforums9009]

Great science lesson. I'm really impressed! I already have a DIY aquaponics system and I'm trying to mimic your setup #3 (24hr). Is it a good Idea to add a diffuser on LED white lights instead of bringing it up? Just like an ordinary LED bulb with white plastic that covers it to diffuse. I have limited space and I can no longer move it up. Thank you!

[@aquaponicsbackyardfarmingp2265]

very helpful,, thank you

[@juliomaruyama]

Greate video. I'm so sorry, but could you tell me how did you get those values(0.0864, 0.0576, 0.0432)? Was it with a PAR sensor? Answer: The 0.0864 factor is the total number of seconds in a day divided by 1,000,000.

[@Albopepper]

Thanks for watching Julio! This resource is a definitive reference for DLI: www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf I have a PAR sensor (Quantum Light Sensor) that I use to measure my PPFD.

[@juliomaruyama]

AlboPepper - Drought Proof Urban Gardening Thank you.

[@CurraDoo]

i believe that how much DLI a plant can take is also affected by the Co2, nutrition, temperature, humidity, airflow and oxygen to the roots. If everything is optimal a plant can use more DLI and grow even faster and produce more yield.

[@csolorio88]

Interesting exercise. What I don't understand is why people choose to move the light over dimming. Is it a grow light limitation? Moving the light keeps the electricity consumption the same, while dimming it should reduce it, right? Thanks!

[@Albopepper]

Correct, some lights aren't dimmable, especially the ones from a few years back. Also when you raise lights, you can cover more area and thus you can grow more plants. But I agree, dimming is a great option!