Question about light height and PPFD during flowering using a IONBOARD S24

[SimeonToko]

So this post is for more opinions and experiences thing it is a question I don’t know how to get the answer for. I have a ionboard s24 and currently I have my light at 18 inches above canopy on level 8 or 80% which has me on average at 800 PPFD across the canopy top. I do have a lux meter on which I have done the readings and conversion so I know where my PAR is for my flowers. I also understand the amount needed and how it should kind of gradually increase but not to exceed 1000 PPFD ( which is not a problem with my light ).

Basically I just wanna know what people are having good experiences which when it come to light height and PPFD especially through flowering and if you have a IONBOARD S24 or just experience which a specific method of achieving good yields by way of a certain PPFD or Height of light through flowering.

Thanks in advance

 

[Delps8]

When I looked at your plants, my impression is that they are not getting all that much light. Two characteristics left me with that impression - the plants have signficant internodal space, they have a small number of fairly large leaves, and they are tall and slender. When cannabis plants are given "lotsa light" they have short internodal space, a larger number of small leaves and are short and compact.

Given the high percentage of blue in the spectrum, per this link, your plants should be shorter and have branches that are more stout. Those characteristics are increased by a high percentage of blue light.

After I saw the make and model of your light, that answered my question. I big fan of AC Infinity products but their lights are value-priced rather than premium-priced. In the case of that light, it's a 200 watt light so it simply cannot generate a high level of PPFD across a large area.

If you look at the PPFD map at this link, you'll see that that the manufacturer reports that the spot in the center of the light has a PPFD of 1060µmol. Once the sensor moves away from that central spot, the reading for the 6" area under the center is 864 and another 6" out, it's 682. That's a signficant reduction in PPFD and light levels continue to roll off very quickly. That's a common profile for lights from AC Infinity - hot spot in the middle and rapid rolloff once you leave center mass.

A light with that output is going to make it tricky for get good light across a grow because, per the manufacturer, much of the plant will get < 600µmol at an 18" hang height.

Given that light, I would lower the light to 12" and move the plants away from the center. The very high value for PPFD in the center spot is meaningless so I'd assume that area in the center is 1200 but 6" to 1' off center, you should get light levels in the 900µmol range. That's the PPFD value that you should be aiming for.

Re. you light readings - how are you measuring PPFD?

Re yield - "about a pound".

It's impossible to tell other than a range. Multiply the number of mols that the grow will receive over the life of the grow and multiply by 0.2 to 0.3 to get an approximate number of grams of above ground mass. That assumes that the entire grow area is covered by canopy. If not, reduce those values by the percentage of floor space coverage that you have.

 

[SimeonToko]

When I looked at your plants, my impression is that they are not getting all that much light. Two characteristics left me with that impression - the plants have signficant internodal space, they have a small number of fairly large leaves, and they are tall and slender. When cannabis plants are given "lotsa light" they have short internodal space, a larger number of small leaves and are short and compact.

Given the high percentage of blue in the spectrum, per this link, your plants should be shorter and have branches that are more stout. Those characteristics are increased by a high percentage of blue light.

After I saw the make and model of your light, that answered my question. I big fan of AC Infinity products but their lights are value-priced rather than premium-priced. In the case of that light, it's a 200 watt light so it simply cannot generate a high level of PPFD across a large area.

If you look at the PPFD map at this link, you'll see that that the manufacturer reports that the spot in the center of the light has a PPFD of 1060µmol. Once the sensor moves away from that central spot, the reading for the 6" area under the center is 864 and another 6" out, it's 682. That's a signficant reduction in PPFD and light levels continue to roll off very quickly. That's a common profile for lights from AC Infinity - hot spot in the middle and rapid rolloff once you leave center mass.

A light with that output is going to make it tricky for get good light across a grow because, per the manufacturer, much of the plant will get < 600µmol at an 18" hang height.

Given that light, I would lower the light to 12" and move the plants away from the center. The very high value for PPFD in the center spot is meaningless so I'd assume that area in the center is 1200 but 6" to 1' off center, you should get light levels in the 900µmol range. That's the PPFD value that you should be aiming for.

Re. you light readings - how are you measuring PPFD?

Re yield - "about a pound".

It's impossible to tell other than a range. Multiply the number of mols that the grow will receive over the life of the grow and multiply by 0.2 to 0.3 to get an approximate number of grams of above ground mass. That assumes that the entire grow area is covered by canopy. If not, reduce those values by the percentage of floor space coverage that you have.

Been getting a DLI of 45 and PPFD of 725 at highest cola and average of 550-650 on Lowers. I’ve read more then 700-750 PPFD or 50 DLI for a 20/4 schedule is the range needed for my autos to flower. I’ve also watched videos of MYGRO owner test the light at different ranges and the light is good enough for a decent grow from what I understand and how my grow seems to be going. I had my light closer at higher into and that caused light stress. I value your input and will take what you said with a grain of salt. I appreciate your help and thank you for pointing out your assessment of my grow.

If I did drop the light to 12 inches what would my PPFD range I would try for? I’m also compensating for the heat that comes off the light that I currently have at 75% at about 16- 18 inches from canopy top? I’m in 3rd week of flower fyi

 

[bluter]

200w should be in the adequate range for flowering two plants. the light is a platter though which isn't ideal.

i'd run 90-95% full at 18 inches and let it stretch into the 12 inch then raise the light back up. probably safe to let it finish at 12 when it stops stretch, but i'd leave it a bit higher between 15 and 18 to avoid damage on the nicest top buds.

 

[SimeonToko]

200w should be in the adequate range for flowering two plants. the light is a platter though which isn't ideal.

i'd run 90-95% full at 18 inches and let it stretch into the 12 inch then raise the light back up. probably safe to let it finish at 12 when it stops stretch, but i'd leave it a bit higher between 15 and 18 to avoid damage on the nicest top buds.

Through some lite research it’s been said that autos only need from 30-45 DLI or 600-800 PPFD. I have no problem trying out your method at 18 inch 90-95% which would probably have my light output at around 900-1050 on the canopy. I’m also assuming you have this light and have experience with that method?

 

[bluter]

I’m also assuming you have this light and have experience with that method?

naw fuck just old with a pile of growing experience, and an early adopter of white light leds before they were commercially available.

there's a few standardized things across platforms that will work regardless of mfgr as long as you are in the correct range. w/sqft has dropped per ppfd generated a little over the years but it's still the same general calculations.

edit : you can leave it a bit back on autos, but they'll run about the same as photos in flower if you're going for trichs.

75 - 80% full is the lowest i would go. they'll run a touch smoother. and longer. i normally pile it on though. ymmv.

 

[Delps8]

Been getting a DLI of 45 and PPFD of 725 at highest cola and average of 550-650 on Lowers.

Sounds about right, on both measurements. 45mol is a moderate amount of light and, at 550 you're at the bottom of the "recommended" range. Cannabis will grow at light levels >=64µmol, as best I can find but, the more light you give it, the better the yield.

I’ve read more then 700-750 PPFD or 50 DLI for a 20/4 schedule is the range needed for my autos to flower.

Per above >=64µmol is what cannabis needs to survive. Light levels to not determine when cannabis goes from vegetative to flower. Photoperiod plants will start to flower when the photoperiod is switch to 12 hours of darkness. For autos, it's a function of the number of days. My first 5 (IIRC) grows were autos. As I learned more about cannabis grow lighting, I gave my plants more light and, for my last few grows, had them in the 70-80 range for most of the grow. Yields were significant with one grow at > 700gm/m2.

I’ve also watched videos of MYGRO owner test the light at different ranges and the light is good enough for a decent grow from what I understand and how my grow seems to be going. I had my light closer at higher into and that caused light stress. I value your input and will take what you said with a grain of salt. I appreciate your help and thank you for pointing out your assessment of my grow.

Shane @ Migro is an engineer, I suspect an EE, but, with one exception, his lights are not very powerful. After a few years looking at this products and listening to his videos, I've changed my opinion about why he designs his lights. high lights have lower power inputs/lower light outputs than other lights in a given market (the 2' x 4' "market", the 3' x' 3' market, etc). I ascribed that to being a savvy business man, the idea being that he's producing a lower cost light because his drivers are not as powerful as those in competing product while understanding that his lights have lower PPF but enough to get a "good" grow. That's a valid approach. Many competing products from Spider, Mars, etc. draw more wattage and produce more light but have a higher price tag.

One reason why I took that approach is that the data shows that crop yield increases as light levels increase. All research indicates that to be so, plant biology indicates that, and, in the past year, it's hard to hide from that if you watch any YT videos on the topic or just "Google it". Once again, I assumed that if a schlub like me knew about it, a smart guy like Shane would know about it.

Going back about a year or so, I watched a couple of YT vids where he interviewed Bruce Bugbee and Bugbee laid it out for him that they run cannabis up to 2000µmol and yield goes up in an almost direct proportion to light input. In two vids that I watched, Shanre reacted as if that was news. It was odd.

I've changed my opinion to think that him selling moderately powered lights was 100% business savvy. I still think it's a very defensible business move but, based on how he was, apparently, gobsmacked by Dr. B citing research that's been available for a few years, I also believe that he just didn't know.

Shane does sell a light that I'd buy. He calls it a CO2 light, or somesuch, because it gets the canopy >1000µmol. There's no need to be running CO2 to give you grows 1lµmol (I do that routinely) but, unfortunately, that light is a 4' x 4' light (I think) so it won't fit in my little 2' x 4' space. :-(

In short, people on YT are selling something. Bugbee is broadcasting a lot of info but he pitches his instruments. Shane repackages info and he sells, mainly, grow lights. The videos by de Bacco are mainly repackaging Bugbee and he's "selling" his consulting services.

My take is to ask a source for citations. Shane doesn't offer those and the folks at growlightmeter.com don't offer them. Well, when I wrote them and asked, they had nothing and since their recommendations were "lame", I recommend that growers disregard their recommendation of 45 mols for autos.

If your grow environment is sound, your plants should be able to handle 800-1000µmol. The advantage of giving your plants that much food is that you'll get a plant that's easier to harvest and you'll get a larger harvest. If your grow can't tolerate that level of light, it might be worth it to find out why. Or not. Many growers are quite happy with modest yields. It certainly is a lot less hassle.

One nice thing about getting a large crop is that you build up inventory. I've had two grows go bad - one got bud rot and, for this last one, I stepped on my metaphorical dick. Fortunately, I've got about 8 oz from a grow in 2022 so I've still got some herbal refreshment.

If I did drop the light to 12 inches what would my PPFD range I would try for? I’m also compensating for the heat that comes off the light that I currently have at 75% at about 16- 18 inches from canopy top? I’m in 3rd week of flower fyi

Dropping the light to 12" will get more light and, IIRC, it's about 1k in the center. If your grow is baulking at, say, 800 you'll need to address that. The big issue with that light is that it's got a hot spot in the center so the light cast is not even. If you drop the light to 12", just move the plants away from the center//arrange them around the hot spot in the middle.

A couple of years ago, Mitch Westmoreland did a video on "hemp" research, the low THC version of cannabis. He said, paraphrasing, that secondary metabolites went in the toilet when ambient temps were in the 80's. I noted that but, for a variety of reasons, didn't change my growing processes to accommodate it. About three months ago now, he released two videos in which he shared info from his PhD dissertation, one topic being about temperature. Sure enough, he expounded on the impact of hear on secondary metabolites and heat is a bitch.

You're wise to be concerned about heat and, if you watch the video on YT, he'll explain it. In short, run your grow at up to the mid-80's to get the canopy as large as you can but, soon after the plant goes into flower (about 2 weeks?), the temperature of the buds should be kept <=78°. As a good scientist, he warns that strains will tend to be different but, my takeaway, is that 78° is the max for the tops of the flowers.

With that in mind, we've got to keep temps down in the area around the grow space//tent and then make sure that we have plenty of cool air flowing into the tent. We also need to keep our LED's well away from the canopy because LED's do generate heat.

I don't know what part of the country you're in but we're heading into summer so anything you can do to get your temps down will help. You don't have to have temps <=78 but if you can get the temp down at the tops of your flowers, your plants will tend to have higher levels of all the good stuff.