Daily Light Integral (DLI) Too much/ too little light daily?

[Vandenberg]

PPFD is how hard its raining at that moment while D.L.I. is how much it rained in a 24 hour period
The PPFD number multiplied by the 3600 seconds in an hour of time multiplied by how many hours the light was on will give you your daily light integral number, just lose all the zeros at the end of the calculation. .


What does Daily Light Integral (DLI) mean?

Daily Light Integral (DLI) is the amount of photons (light particles) received by a particular area in one day.

DLI greatly affects plant growth and development, and the measurement of DLI is important to many gardeners and growers. DLI can be measured, and its measurement is particularly important to commercial farmers and gardeners that use greenhouses.

Light particles, particularly those that have a wavelength between 400 and 700 nm, provide plants with the energy for photosynthesis.

DLI influences plant growth, vitality, and yield.
A rise or fall in the DLI that plants receive can affect a plant's root system, stems, and flowering stage.
Although many plants benefit from controlled DLI, specific levels needed will vary from plant to plant.

Knowing an area’s particular DLI can help gardeners in several different ways.
First, measuring an area’s DLI can help a grower decide which crop variety would grow and thrive best a particular location.
Additionally, DLI can help growers optimize use of supplemental lighting.
To measure DLI, growers will need to purchase a light sensor and record light levels throughout the day.
Light sensors and DLI meters can be purchased from specialty suppliers and do tend to get pricey fast.

In the past, biologists have used lux or energy meters to quantify light intensity.
They switched to using PPFD when it was realized that the flux of PPFD is the unit of measure, defined by ?mol/m2/s or micro-moles of photons falling on a square meter per second.
Normally, Photosynthetically available Radiation (PAR) wavelength is 400nm - 700nm.
The 400-700 m range is the important factor in driving the photosynthetic process.

Daily light integral includes both the diurnal variation and day length, and can also be reported as a mean value per month...
DLI has been shown to be better related to plant growth and morphology than PPFD at any moment or day length alone.
Some energy meters are able to capture PPFD during an interval period such as 24-hours.
PPFD is the unit of measure, defined by ?mol/m2/s or micro-moles of photons falling on a square meter per second.

Vandenberg

 

[Vandenberg]

LED Grow Light Intensity And Coverage Simplified

LED Grow Light Intensity And Coverage Simplified

Patience: currently a work in progress.
It is currently a wee-bit wordy (still editing ) but still highly informative.

To make the most of LEDs, you have to understand LED grow light intensity and coverage.
And even experienced HID growers have a bit of a learning curve when it comes to LEDs...
Top-tier LED lights require much less energy to produce the same intensity of light.
Not only that, they also emit the exact color spectrum your plants need and focus those photons directly onto the canopy.
This eliminates waste, ensuring you only consume as much energy as you need for your crop.

What LED Grow Light Intensity Really Means
When we talk about light intensity, we’re referring to the amount or strength of light produced.
With that in mind, let’s clear up one of the greatest misconceptions about grow light intensity.

Watts do not equal intensity.
A watt is simply a measurement of electric power.
It tells you the amount of energy your lights require in order to operate.
The only reason growers associate watts with light intensity is because all HID bulbs are fairly uniform in terms of wattage.
This is not the case with LED lights.

Not only are quality LEDs far more efficient than HIDs, but there is a wide range of efficiency among LED grow lamps.
A quality 100-watt LED produces much greater light intensity and higher quality light output than a cheap LED grow light of the same wattage.

Understanding the Metrics of LED Grow Light Intensity and Coverage:
When you research different LED lights, there are certain metrics you should look for.
As was said before, watts are not relevant for determining the intensity or coverage of LEDs.
Don’t worry about lumens, either.
Lumens simply refer to the visual brightness of a light; it has nothing to do with how well your plants can use that light.

Here are the metrics that do matter when determining the intensity of an LED grow light.

PAR
Grow light manufacturers engineer LED lights to provide a high intensity of usable light.
This is refer to this usable light as photo-synthetically active radiation or PAR.
Your plants only use certain wavelengths for photosynthesis.
These wavelengths all fall within the visible light range of 400-700nm.
As a grower, your greatest concern should not be the amount of light your grow light produces, but the amount of light within the PAR range.
Anything outside the range is useless to your plants.
PAR is measured in micromoles.

Coverage Area
Every LED grow light you consider should have information regarding the lamp’s footprint.
This refers to the coverage area—the square footage of canopy that will fall under the beam of the luminaire.

But there is also an important correlation between LED grow light intensity and coverage area.

This correlation is referred to as the inverse square law of light.
We’ll spare you the complicated formulas and just cut to the chase: The farther an object is from the light source, the less intense the light is when it reaches that object.
And light intensity drops off fast.

Let’s say you have a lamp hanging at a 1-foot distance from your canopy.
Then, you increase the hanging height to a distance of 2 feet.
You will now have a light intensity that is ¼ of what it was before. Major difference, right?

This is why the coverage area is essential.
Not only do the size and lenses of your LED grow light determine your coverage area, but so does hanging height. The greater the distance between your lights and canopy, the larger the footprint . . . but the lower the light intensity.

This is why it’s very important to pay attention to hanging heights and coverage area when selecting a light. These metrics tell you the conditions under which your plants receive the advertised. PPFD.

And what is PPFD?
PPFD
Thanks to the inverse square law, it simply isn’t enough to just know how much PAR your grow lights produce.
PAR only tells you how many usable photons your LED light emits. The amount of PAR that actually reaches your plants . . . that’s a whole other measurement.

PPFD stands for photosynthetic photon flux density.
Your LED grow light’s PPFD metrics tell you the number of PAR photons reaching your canopy each second.
This metric is expressed as micromoles per square meter per second (or umol/m²/s).

So what’s a good PPFD number?
It depends on what you grow.
Different plants have different needs.
Many flowering plants, for example, prefer 300—600 umols for vegetative growth and 800—1,000 umols in the flowering stage.

Uniformity in LED Grow Light Intensity and Coverage
Now that we have a better grip on LED light intensity, let’s talk a little more about your coverage area.
LED grow light intensity and coverage are related not just through hanging heights, but also through the light spread.
Depending on the specific LED lamp, you could experience a decrease in light intensity at the outer edges of the footprint. This is why it’s so important to do your due diligence when choosing the best LED grow light.

I am a big fan of the newer large bar LED' on lightrail movers to help overcome leaf shading issues and increase potential production but that's another thread.

Let’s say, for example, that you need a grow light to cover a 5’ x 5’ canopy. You find an LED lamp with a 5’ x 5’ footprint and a PPFD that falls within the ideal range for your crop. But then after a few weeks, you notice that the plants directly under your light are thriving, while those at the edges look a little weaker.
The problem is that the PPFD provided by the manufacturer only measured photons reaching a surface directly below the lamp. The manufacturer neglected to inform you that their product does not achieve an even light spread.
When evaluating LED grow light intensity and coverage, pay close attention to uniformity.

Request a PPFD map from the manufacturer.
This map shows PAR measurements for various hanging heights and across surface areas.
PPFD maps make it easier for you to compare LED grow lights and determine how many lights you actually need.

Light Intensity and Efficacy
As we previously mentioned, wattage is not a clear indication of LED light intensity because LED lights vary inefficiency. While HID efficacy is fixed, LED lights consistently advance to achieve greater intensity for less energy input.

This is why high quality LED grow lights are astoundingly cost-effective in the long run.
In addition to boasting a much longer life span, LED lights provide greater intensity at about half the energy expense.

If you’ve ever used HID grow lights, you know that achieving an even spread of light requires the use of reflectors.
This is another area where LED grow lights simplify your grow operation.
Quality LEDs are made to spread light with uniform intensity.
All light is directed.

I Thank You Cal Lightworx for the primer, well done!
Vandenberg

 

[Mars Hydro Led]

Spend me some time to read. Nice thread though.

 

[f-e]

Based on a 12 hour day, PPFD x 0.0432 = DLI


The above is boiled down from the slightly longer explaination that follows.

PPFD is light per second. We want light per day.
PPFD x 60 = light per minute. Times 60 = light per hour. Alternately PPFD x 3600 = light per hour in one sum.
Light per hour times by number of hours gives us the DLI but in umol which is a fraction of a mol. You take the umol result, and divide it by 1,000,000 to get mol. Or you can just kinda look at the calculator and forget the last 6 digiits. It's going to look something like 30,???,???

Green wants 30 DLI or more in flower. 30-50 perhaps. As high as 65 has been worked by some scientific teams, with everything in place. You can go lower than 30 DLI but no pot plant is giving it's best below 30 DLI. Conversely, some might see more than 30 DLI as just wasteful. That's about 650 ppfd.

650 x 3600 x 12 / 1000000 = 28.08

650 x 0.0432 = 28.08
^ This is presuming 12 hours. If you have 18 hours, times the result by 1.5 (it's easy to remember 432 an adjust. I could calc the 18 hour figure, but my brains not going to remember both)

 

[Ipotato]

How much DLI is the sun, its like 1500 (2000 at equator) PPFD right? That would be 65 DLI(up to 85 at equator) or so? Also I think the frequency range from OP has been disproved the above is just visible light with far red adding Emerson effect

Frontiers | Why Far-Red Photons Should Be Included in the Definition of Photosynthetic Photons and the Measurement of Horticultural Fixture Efficacy

www.frontiersin.org

 

[f-e]

I read nowhere in the states reaches 65

If we believe in 2000 PPFD, then that's mid day. The rest of the day is lower. That 2000 PPFD would be about an 85 DLI, if it was 2000 for the full 12 hours.

2000 seems calculated. 1500 used to be the figure. Over desert dust is lifted. Over sea it's water vapour. A perfect day at high altitude might see 2000 once in a blue moon, for a few minutes.

65 is a very high figure.
50 is high
40 is still rockin it.
30 is absolutely fine, and gains above this get fewer and fewer. It's 650 PPFD. About 80% of all you can expect, even with co2

 

[Desert Dan]

What about DLI in veg? I have heard others say to match DLI of bloom, so more hours and less PPFD?

I just experienced the downfall of too much DLI without a dialed in environment… plant’s couldn’t keep up and fried all my fan leaves.

-DD

 

[DARKSIDER]

Maybes this will help some of you good people if allowed then again maybes not.

https://www.apogeeinstruments.com/daily-light-integral-measurement/

 

[airplane]

It all comes down to dimming the light inlate flower by 25% before harvest - and in early veg dimming at 50% during seedling and working up to 100% in veg comes down to leaf temp's - anyone know were a person can get a leaf temp sensor to help with light intensity

 

[goingrey]

It all comes down to dimming the light inlate flower by 25% before harvest - and in early veg dimming at 50% during seedling and working up to 100% in veg comes down to leaf temp's - anyone know were a person can get a leaf temp sensor to help with light intensity

What kinda sensor, something connected to a computer/controller? You can get an infrared sensor for that from electronics parts stores... Or if just measuring manually an infrared thermometer "gun" from your local pharmacy, supermarket, DIY store, whatever... I just use the top of my hand though.

 

[Vandenberg]

This DLI Chart should be helpful when calculating appropriate amounts of light.

 

[delta9nxs]

hello vandenberg! nice thread!

the transition of the industry from hid to led lighting has created a huge amount of misinformation.

to me, it seems that most of the led manufacturers are not telling the truth about the capabilities of their lights.

dr's el-sohly of the university of misssissippi and bugbee of the university of utah have done research demonstrating that cannabis achieves the highest rate of photosynthesis at 1500 umols of flow.

photosynthesis responds linearly with increasing light up to 1500 umols.

this rate does not damage the plant. if your plants are being damaged under this level of flow it is because something else is wrong.

further, the response curve is flat and steady up to 2000 umols of flow. 2000 umols will not damage your plants if all the other factors are correct.

once you get past 2000 umols the response curve falls straight down on the graph. like a skyscraper, and plant damage begins.

yet very few of the newer led lights will achieve that at all. unless you put the light at 6" or so.

then, as you said, the light doesn't get anywhere near that at the edges.

i won't mention any specific manufacturers here but in their haste to get to market with a light within a certain price point range they are ignoring research data.

almost all are selling lights that do not perform to professional levels.

so now that i have assassinated the led grow light industry by calling them all liars i will prove my points.

i have built an experimental grow light that is 1680 watts of actual consumption. i do not recommend this kind of power level as i have proven it redundant to a degree. but the power level allowed me to quantify the maximum light level a cannabis plant can use efficiently.

this light produces 1500 umols at 26". this distance is very nice because almost none of the led's heat makes it down to the canopy. i have a fan above pulling air up through it from the canopy.

but the astounding thing is that this light then produces 1000 umols at 36". this is a major yield enhancer. what manufacturer can claim this?

we hear all the time people talking about light penetration.

there is no light penetration of a cannabis leaf.

i own a par meter and with it getting a reading of 1500 umols on the top surface of a single leaf i only get 200 umols immediately below that same leaf. barely at the compensation point.

so the only light that matters is light that gets through the gaps in the canopy.

the more powerful the light the greater the yield up to a point.

why are we all using a 12 hour light cycle? because 12 hours of dark is necessary to maintain flowering.

which brings us back to the discussion of moles per day or moles per diurnal period.

we know that 1500 umols produces the highest rate of photosynthesis in cannabis but the plant can stand up to 2000 umols without damage for a while.

what is this while? we have to look at cumulative light totals per diurnal period or moles for the answer.

it is my opinion that the cannabis plant needs 40-50 moles per period for top production.

looking at the chart above we see the 12 hour point at 1000 umols producing 43.2 total moles of light per period.

what this means is that if you have a light in the 650-750 watt range you MUST run it 12 hours to get a decent yield.

even then you will not average that 43.2 moles spread evenly over the entire canopy.

there is nothing in the scientific literature saying a cannabis plant needs 12 hours of light.

but experience and the literature say that it needs 40-50 moles per period.

ok, let's go for a while to what happens out in the field growing under natural light conditions.

in middle tennessee where i worked for the last three years we grew both indoors and out. we had 1600 acres of cbd hemp for extraction and a10k sq ft indoor facility for hemp flower.

i am including a modern dli map of the US. for reference.

you can see in tennessee that we get between 40-50 moles maximum.

but most of that light is delivered in a shorter time frame than 12 hours.

now go to the chart above and look at 8 hours at 1000 umols and we get 28.8 moles. not enough!

well, i have been delivering 40-50 moles per day with an 8 hour period.

in the center of the canopy right now the light flow is 1745 umols going out to about 1250 at the edges.

the center is getting 50.2 moles per period delivered in 8 hours.

the plants look great and are very healthy under this intensity.

so you don't need 12 hours of light, you need 40-50 moles of light per period.

and most of these led lights won't accomplish that even if you give the plants 12 hours.

most of the led manufacturers are producing lights that are barely adequate.

next, i would like to touch on the issue of photoinhibition.

if you do have powerful lights and you run the 12 hour period you are risking photodamage to the chlorophyll-producing apparatus.

my light at 1745 umols if run for 12 hours produces 75.38 moles. this exceeds any reading in nature anywhere on the planet.

for plant health and yield you are better off using the most intense light you can for a shorter period of time.

i'm seeing the greatest plant health and overall dankness i've ever seen in 25 years of continuous growing.

remember hid's running 12 hours at close proximity? at about 8 hours into the period many folks have seen "the wall".

the plants that have been standing up to address the light have now hung their leaves lower and some even twist sideways as if to diminish the amount of light hitting them.

this is photoinhibition at work.

ok now let's look at electrical efficiency.

in a commercial scenario many folks run 2 rooms off the same power supply by flipping them back and forth.

using an 8 hour period you could run 3 rooms off the same power supply.

the led manufacturers are building lights to equal the performance of 1000 watt hid's but they are missing the point that 1000 watt hid's were themselves inadequate.

the heat from them suppressed growth at the same time it was powering growth. a push me pull me type of thing. fighting itself.

so the led builders simply subtracted the percentage of power they thought was going towards heat and built the balance as an adequate light.

i would like to see led lights offered that produced 1500 umols at around 16-20" over the entire canopy.

the lack of reflectors on most led lights is the reason why the lights drop off so sharply at the edges.

they should have drop-down reflectors around the edges of the light fixture.

i operated a test drop-down type curtain around this entire light to get an idea of what happens and the results were amazing.

the average led diode projects light at 120 degrees. 60 degrees off of center in all directions.

i am including a picture i took of a 120 degree arc.

as you can see a huge amount of light is escaping to the sides. a simple drop-down type reflector brought my readings from 1500umols in the center and 1150 umols at the edge of the 4 ft canopy to 1500 in the center and 1350-1400 at the edges.

i had to remove it recently as i have the light all the way up and the reflector was causing the center to run at something above 2000 umols as that is where my meter pegs. i also noticed a bronzing of the leaves. a color i have never seen before so i removed it.

those in tents won't notice this so much as you have a lot of vertical reflective surface but those in large rooms should really take notice.

but why are the lights not offered with them? price point!

also, there is a whole discussion to be had about terpene production involving heat and light using these 8 hours of a very intense light schedule. since most actual cell growth occurs during the dark cycle i think the 16 hours of cool darkness is enhancing terps.

i guess this is enough for now! i will show some pics of the setup and close-ups of some flowers growing under 1745 umols of light. these are at 6 weeks on a 9 week strain.

This is d9's pheno of ethos genetics orange kush cake.

let me know what you think of the health. also resin production.

later d9