Side lights

Prawn Connery said:

When lights are off plants starts to reverse photosynthesis. Photosynthesis uses CO2 + H2O + light energy to produce carbohydrates. At night, it is the reverse, so carbohydrates (stored energy) + O2 are used up and CO2 and H2O are released, which is why humidity goes up at night.

I also want to reiterate that you positively do not want to give your plants 2200 PPFD for 12 hours at a time, even with CO2, because light energy accumulates. You need to do some research on DLI, or Daily Light Integral, to see the proper formula for calculating light needs for plants. 2200 PPFD might be OK for 1-2 hours, but you need to ramp it up and down either side of that – just like the sun does during the day – to give yourself an average closer to 800-1000 PPFD, or around 1500 PPFD with CO2. If you go higher, your yields will usually go backwards as the plants will be stressed.

Remember also that there are not too many parts of the world where it gets to 2200PPFD in late Autumn, whic is when short-day plants (cannabis) typically flower outside. I live in Australia where it does get to that level in summer in the middle of the day, but we are the sunniest continent on earth, so our sunlight levels are much higher than other parts of the world.

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Prawn Connery said:

When lights are off plants starts to reverse photosynthesis. Photosynthesis uses CO2 + H2O + light energy to produce carbohydrates. At night, it is the reverse, so carbohydrates (stored energy) + O2 are used up and CO2 and H2O are released, which is why humidity goes up at night.

I also want to reiterate that you positively do not want to give your plants 2200 PPFD for 12 hours at a time, even with CO2, because light energy accumulates. You need to do some research on DLI, or Daily Light Integral, to see the proper formula for calculating light needs for plants. 2200 PPFD might be OK for 1-2 hours, but you need to ramp it up and down either side of that – just like the sun does during the day – to give yourself an average closer to 800-1000 PPFD, or around 1500 PPFD with CO2. If you go higher, your yields will usually go backwards as the plants will be stressed.

Remember also that there are not too many parts of the world where it gets to 2200PPFD in late Autumn, whic is when short-day plants (cannabis) typically flower outside. I live in Australia where it does get to that level in summer in the middle of the day, but we are the sunniest continent on earth, so our sunlight levels are much higher than other parts of the world.

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medidedicated said:

What you said about humidity would be very relevant on my rh spiking concern thread, explains why I have that issue when lights shut off. I was suspecting that this activity is why that happens, I made a wild guess that that basically is why it spikes for a hour or two then goes to 37rh.

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Rocket Soul said:

Spiking humidity at lights off isnt really a consequence of plant metabolism, its more a consequence of dropping temps. RH is relative humidity which means for the same amount of water in the air RH will go up as temps goes down, since the air can contain less and less water the colder it gets. If you keep the temps up you wont see this really but it means you need some kinda he as ter in there since you remove the light as a heatsource when you turn it off.

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medidedicated said:

What makes a top tier light aside from optimal ppfd? More far reds?

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medidedicated said:

I put in DLI calculator 1100ppfd 18 hrs a day and says 77. I am thinking the lights are slightly too strong but these side buds are growing nice.

How do you calculate ppfd for a light for DLI, I thought just do an average. My light map is posted, check it out, I said 1000 and side lights are 100.

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cdgmoney250 said:

DLI values are actually a function of the total PAR values during a spot reading, averaged over the course of day. The equation is as follows:

Convert PAR to DLI. Do this by using the following equation:
PAR (μmol.m-2.s-1) x 0.0864
The 0.0864 factor is the total number of seconds in a day divided by 1,000,000 (micro moles - moles)

This value is for light over a 24 hour period. For light schedules like 12 hour days, this total DLI value would be multiplied by .50 (12hrs of light/24 hours in a day). Likewise, for an 18 hour day, you would multiply your total calculated DLI value by .75 (18 hrs of light/24hrs day). This will give you your actual DLI values.

You would really need a PAR meter or LUX meter with PPF conversions to get accurate values. You could make guesstimates based of the posted light footprint, but because you are in a tent, your readings will likely be higher due to the reflective lining.

I’m not sure there is any consensus on what DLI ranges to shoot for with cannabis, people just usually aim for tomato/pepper values since cannabis is a high light plant. For example: 1000ppfd (static) over 12 hours is 42.3 Moles. Outside during summer, certain field plants in certain regions can receive up to 70 Moles/day. The more dialed in your plant and environment are, the more DLI you can push before light stress occurs.

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medidedicated said:

I can be timid with problems I never had but I am timid with curing because one time I did it careless by probably letting it dry in minus 55rh and it gave me an ashma like attack which never happened before with other people’s weed. Still wondering wtf happened.

It grew under horrid conditions of a 90%rh green house and was basically one giant larf bush with only 3 hrs direct sunlight a day if lucky. Was not my grow so I barely did much or cared.

The underdeveloped larf bud is another possibility for sure.

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Splinter7 said:

i smoked a bud i found on the floor of my tent...i don't dry there. it was fine. i guess it just broke off or something i missed when taking out the plant. i found it a few weeks later. underdeveloped larf sound more plausible. a bad cure just makes it taste less unelss it's moldy.

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medidedicated said:

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Hello, thanks for the tip! I get heat issues but have been airing out ambient space to keep below 90F.

No problem! Ambient temps help to know, but actual leaf temperatures are more critical to know. At higher temps like that, I would just make sure your airflow across your canopy is adequate especially in the hot spot of the light foot print where you’re more likely to run into heat/light intensity issues.

Started feeding 1.5ec total max, currently 1.0 in ripen. Aside from that I wonder what to look for with too much DLI.

The calyx are swelling large! I like this light for the price. I used a DLI calculator so that makes more sense, just do that but with the calculator.

I do not see DLI come up often, is it something visual signs give that dimming/raising the LED would resolve? IE foxtails, fists? How do you know when it is due to excessive DLI.. searching now.

Yes, dimming or raising your lights would help to alleviate symptoms of light stress/photoinhibition, but at the sacrifice of decreased ppfd to the rest of your canopy. This is where having a more uniform light foot print can come in handy, especially for SCROG type grows or LST training. I wouldn’t think to tell you what’s causing what in your grow, but I would start with process of elimination if you’re seeing signs of stress. If you’re plants are watered properly, fed properly and the ph is balanced in your media, I would start looking into the entire environment for clues.

My guess is VPD/nute deficiency like signs, like grilling it with light.

You bet. Another term for damage caused to plant tissue by light saturation is “photo damage”. If you search it you can find a number of different symptoms including the ones you mentioned as well as bleaching.

(Ignoring the side lights, cannot be dimmed but are not that bright anyway.)

I think plant size matters.

I guess you are saying it is subjective and just a tool for diagnosing stunted growth and planning out grows? What you think about the light and map? Bud shot look good?

Kinda sorta not really what I’m saying. It might be subjective to us, as we’re merely observing the plants and making tweaks based on assumptions or measurements. But to plants DLI, Light Saturation, Photoinhibition, Photodamage are all very objective and measurable if you have all the right testing equipment. It’s up to us to determine what conditions we can give the plant to try to maximize yield and quality, because they can’t choose for themselves. In that sense, DLI is a tool for helping dial in your environment. The light map is pretty hot in the middle, which is to be expected by the diode spacing/layout. Plants look a little stressed, but I’m sure the bud will still be smoking good.

So it works in sections, like one spot can have too much DLI over the next square foot or half square foot?

Yes. Remember that the sun changes in position and/or intensity the entire time the plants are awake outside. In Nature, single parts of the plant are never receiving the same light intensity for 12-18 hours a day.

Feel free not to answer every question I just am throwing them out there as I might get better info than what I end up finding.

I keep the vpd dialed in with vpdchartdotcom and stay within region. Well exausted and circulated. Some swings here and there but for dialing in by hand, not bad.

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