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RUFUS HOUND

Stumpy Autos - is my light too close? DLI, PPFDDLI

32 posts in this topic

Hi all, I need a little help and advice from those versed in using light measurement to grow autos.

 

My problem is basically, very short, squat plants and zero stretch at flower. I veg with light at 18" above canopy and when flowers appear, I drop light down 1 inch a day till it reaches about 11/ to 12"".

I was assuming that as my plants werent growing in height, that my light was too weak and so moved it closer.

Now Im beginning to think that maybe my lights are to powerful in my little tent  60x60x140 tent (only 170W) and / or Im bringing them too close to fast.

I havent had any light burn, well not up to 10" away but I havent dared go closer. 

 

Does anybody have a DLI chart or a PPFD chart for autoflowers to give me something to aim for, or give me any pointers would be much appreciated. 

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Posted (edited)

If  your light was weaker on the canopy  they would increase height with increased distance between the nodes.  You need to increase your height. Try 2-- 2.5ft. High light intensity encourages shorter plants. It works the opposite way to what you are thinking. You could also dim it to the same effect, if you have that option.

Edited by catweazle1
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Posted (edited)

If you want a more consistent measurable means of setting intensity, have a look at this migro video that shows you how to use a luxmeter. If you get one of the meters he mentions, he's done the maths on those  - they are quite cheap - and multiply the reading by the number he shows for each meter, that converts it to PAR units. I got the UNI-T version and multiply by 0.017. If the lux goes into the 1000's you will see on screen it tells you to multiply the reading by 10, do this by adding a 0. So, multiply by 10, then multiply by the conversion factor for the units he mentions to give you PAR units in umols/sec. Using one has taught me to back off on the intensity, I was using too much before.

 

 

Edited by catweazle1
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I know @Crow River had a pretty good ppfd/dli chart up somewhere recently, if I knew how I'd put the screenshot of it I took up but I don't know how

:skin_up:

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I like the "Tent buddy" app for android phones if your device supports it and the light sensor is any good.

I use the DLI metric more than anything to see where I'm at.

I  recently did a 24/7 auto run and gave them way too much light.

The squatest, densest plants you ever did see!

:-)

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Posted (edited)

22 minutes ago, Should Know Betterer said:

I know @Crow River had a pretty good ppfd/dli chart up somewhere recently, if I knew how I'd put the screenshot of it I took up but I don't know how

:skin_up:

 

Here it is... :) 

@RUFUS HOUND maybe useful? I found it really handy for the last grow.

 

large.DLI_chart_LEDTonic.png

Edited by Crow River
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Is that specifically for cannabis?

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Just now, Wacky Wardrobe said:

I like the "Tent buddy" app for android phones if your device supports it and the light sensor is any good.

I use the DLI metric more than anything to see where I'm at.

I  recently did a 24/7 auto run and gave them way too much light.

The squatest, densest plants you ever did see!

:-)

have a look at my signature for my G41 diary's , its a  whopping 9" tall 50 days in  

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Just now, catweazle1 said:

Is that specifically for cannabis?

 

I suppose the data could be used for any crop grown under artificial light. I found it on a web site about grow lights, and the info was mostly about cannabis. I have read elsewhere that optimal DLI for cannabis is in the range 30 to 45 mols. Above that, you're basically wasting electricity as the plant can't use the extra light energy. The colour coding on the chart relates to the DLI ranges for cannabis. If you're growing lettuce, you don't need anywhere near as much light. :) 

 

What that chart also usefully shows is why auto flowers don't need as powerful lighting as photoperiod strains. Because they tend to be grown entirely on the lighting schedule used for vegging photoperiods. When a photoperiod is flipped to 12/12, you need more PPFD to get the same DLI as you had on 18/6, 20/4, or 24/0. With an autoflower, there's no flip so your PPFD can be lower.

 

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@Crow River Which is auto band and photo band. Cheers.

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Just now, RUFUS HOUND said:

a  whopping 9" tall

Mine were a bit bigger but a lot tighter.

One in particular (Sweet Seeds Crystal Candy XL) had huge buds but they grew all pressed against each other.

The whole plants was just one mass of bud.

I lost a tiny amount to mould because of lack of airflow through the denseness of the plant.

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Just now, catweazle1 said:

@Crow River Which is auto band and photo band. Cheers.

 

Doesn't matter really. It's just a quick reference tool for figuring out DLI. There are also online calculators that will figure it out based on your light's wattage, colour spectrum, and distance from canopy. I just like this table because you can rapidly assess if you're giving your plants too little or too much light.

 

Within that though, yeah the DLI for a seedling might need to be lower, and for a photoperiod in flower at the upper end of the range. But I'm assuming you know that, I'm not claiming any expertise in growing. :) 

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Posted (edited)

@Crow River cheers dude - Im on 18/6 I will get my light up ntil DLI is aprox 40 in the centre of tent 

@catweazle1 thanks

@Wacky Wardrobemines like that - tonnes of budlets, just all crammed in on top of each other, I got my circ fan pointed at them to keep the air flowing.

Edited by RUFUS HOUND
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Posted (edited)

Just now, RUFUS HOUND said:

@Crow River cheers for that - is it for autos or photos

 

Neither. It's just a table showing what DLI you get for PPFD against time in hours. But, as far as I understand, whatever strain you grow you are aiming to be in the range 30 to 45 mols for DLI. I'm not an expert, but I can read... :D 

 

E2A - My light is in a fixed position, so I either have to use the dimmer or change the hours of light. You can move your light or change the hours to get to the sweet spot.

 

Edited by Crow River
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Oh I forgot to add that 45 mols DLI is for plants without added CO2. I suppose commercial growers would use CO2 injection systems, in which case they can push the DLI up to 65. @RUFUS HOUND I dunno if your yeast carton would enable such a high DLI, but you might be able to edge it over 45. Again, I haven't tried this it's just based on reading. So I can't claim direct knowledge. But most of the scientific data I've read seem to point to the same range of around 30 to 45 mols for optimal growth.

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