How many umols for fllowering?
- Thread starter Porky101
- Start date
Airwalker16
Well-Known Member
That'll do.Hi All!
How many umols for flowering? Im using Cree CXB 3590's and I range from 500-900umols at the canopy.
Thanks for any advice!
Randomblame
Well-Known Member
Hi All!
How many umols for flowering? Im using Cree CXB 3590's and I range from 500-900umols at the canopy.
Thanks for any advice!
I would say 600-900μMol/s/m² without extra CO² and 1000-1200μMol/s/m² with. 700-800 is the sweet spot and probably the range with the highest grams per watt rating. With 1000 you will yield more but it will be less efficient because above 800μMol/s/m² the profits are getting smaller and smaller. You need 20% more energy for 1000μMol/s but the profit in yield is probably only 5% more. See below..
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Porky101
Well-Known Member
Wow thank you so much for this!!!
Rocket Soul
Well-Known Member
Also factor in strain, sativas seem to like more light than indicas. With higher intensities you have to factor in nutrient uptake, for 1000+ par you need to have kick ass roots and nutes to supply photosynthesis. Getting enviroment right as well: with the right temps you can grow efficiently with less par. Im pretty sure @Randomblame has a chart on that, hes like the frigging library around here 
Randomblame
Well-Known Member
Yeahehe, I even have two for you.
This one shows that a plant getting 500μMol/s/m² at 30°C grows faster as the same plant getting 1500μMol/s/m² at only 20°C.
And this one shows that the profits from more light gets smaller and smaller with increased intensity. The sweet spot for highest gram/w performance is lrobably around 700-800μMol/s/m².
In my 10sft cabinet I'm using up to 320w LED +39w UVB and it's pretty easy to keep temps and humidity in check(~30°C/60% RH with lights on). If I use more light I need something like a humidifier because my exhaust fan has to run faster to keep the temps around 30° and I can not hold the RH where its needed. Keyword: VPD
This one shows that a plant getting 500μMol/s/m² at 30°C grows faster as the same plant getting 1500μMol/s/m² at only 20°C.
And this one shows that the profits from more light gets smaller and smaller with increased intensity. The sweet spot for highest gram/w performance is lrobably around 700-800μMol/s/m².
In my 10sft cabinet I'm using up to 320w LED +39w UVB and it's pretty easy to keep temps and humidity in check(~30°C/60% RH with lights on). If I use more light I need something like a humidifier because my exhaust fan has to run faster to keep the temps around 30° and I can not hold the RH where its needed. Keyword: VPD
Randomblame
Well-Known Member
Do you like charts? Here is another one. You see the green area..? This is the humidity you need for healthy growing plants. It's already calculated for white LED(2°C less leaf temps) so you can use it 1:1.
Porky101
Well-Known Member
ooohhh
The Famouse VPD Chart!
I do love charts, this one is super important, I do my best too encourage the correct amount of evaporation otherwise the water potential in the plant goes out of balance and you get all sorts of issues. Your my chart hero!!!
nachooo
Well-Known Member
There are a lot of vpd charts..but this one is exactly the one I use
Randomblame
Well-Known Member
There are a lot of vpd charts..but this one is exactly the one I use
Yea, lots of VPD charts available but this one is already calculated with LED's in mind. Most of them are older and created with HPS in mind, like this one here..
show me ONE led room where the leaf temperature is 2° cooler than ambient.
usually the leaf temperature is less than 1° cooler with led
Randomblame
Well-Known Member
To keep the RH where its needed can be a sisyphean task. To hold 60% I often have to close all doors and windows in the room where the box is, especially when it's dry outside. The RH in this room must be atleast about 70% to hold 60% inside the tent. With closed doors this value is reached quickly but without fresh air I have to set up a few CO² bottles just to make sure there is always enough CO².
This is really annoying and I am already considering to buy a 2l bottle with CO² (these are used for inert gas welding) and a timer controlled regulator. There are also small CO²-setups with 2l bottles for aquariums one can get for around $150.(e3ay)
With a hydro setup it's much easier to adress a not optimal VPD's simply by changing the nutrient strength. If it's 20% too high lower the nutrients by 20%. This is not so easy to manage when you grow in organic soil like I've done in the past.
I'm building currently a coco dtw setup for my small 50x 30" area.
Instead of closing doors and windows and adding CO2 bottles all I have to do is adjust the nutrient strength according to the RH/VPD.
Not only is it much less effort it will also deliver much better results.
This is really annoying and I am already considering to buy a 2l bottle with CO² (these are used for inert gas welding) and a timer controlled regulator. There are also small CO²-setups with 2l bottles for aquariums one can get for around $150.(e3ay)
With a hydro setup it's much easier to adress a not optimal VPD's simply by changing the nutrient strength. If it's 20% too high lower the nutrients by 20%. This is not so easy to manage when you grow in organic soil like I've done in the past.
I'm building currently a coco dtw setup for my small 50x 30" area.
Instead of closing doors and windows and adding CO2 bottles all I have to do is adjust the nutrient strength according to the RH/VPD.
Not only is it much less effort it will also deliver much better results.
Randomblame
Well-Known Member
Nope! It's -2° with white CRI80 LED's and even -3° with blurples. Compared with HPS it's +2-3° because of the high amount of IR radiation. With CRI90 the difference could be a bit lower because it already has twice as much far red like CRI80.
When my thermometer shows 30°C ambient and I check the canopy temps with my IR thermometer(measured with 45° angle to the canopy) it's always shows between 27-28°C and I use a mix of 3000°k/CRI80 and 90 and a 39w T5 UVB bulb.
BUT that you only measure 1° difference could also be due to the thermometer. I do not have two thermometers that show exactly the same temperature even if they stand in the exact same place...
I once had a scientific paper about far-red where leaf temperatures under LED were discussed too. If I still have it I'll upload it for ya later.
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nachooo
Well-Known Member
Is very important what you are noticing...some people cant change the temps or RH for several reasons and their plants suffer a lot...and they dont know that they can avoid some issues just changing their nutes concentrations
I knew that if I had a wrong vpd situation..with high transpiration rate...lets say 30 C and 50 % RH I have to low nutes concentration to avoid nute burn… But my question is: Will it work with low transpiration rates..I mean if I have 23 C and 75 % RH.. should I have to raise nutes concentration accordingly to allow the plant to get nutes at good rates?
Will be nice a chart that includes some kind of vpd, temp, rh chart with PPM concentrations suggestions,, in veg/flower …
diyled
Well-Known Member
Rocket Soul
Well-Known Member
Heres the Vpd calculator, you can set how much hotter/colder your leaftemps are.
http://opennlabs.com/vpd/VPD_calculator.php
http://opennlabs.com/vpd/VPD_calculator.php
Rocket Soul
Well-Known Member
I think youre correcTt but there would allways be an upper limit on how much you can raise nutes before the nute solution starts sucking water out of your plant. Afaik
nachooo
Well-Known Member
Also it should be keep in mind that at low temps, photosynthesis rates go down...so the plant use less nutes..so a kind of equilibrium much be reached….
Rocket Soul
Well-Known Member
Like allways its a try and see, we got rid of calcium deff by raising temps when the initial reaction was to add more calmag.