New Grower Word of advice for new LED growers ...

[steelrat]

Hi LED noobs !

I'm an LED noob too, but i have done six CFL grows.

Thought i'd post this as a warning to people with less or roughly equivalent experience.

Because my light (Prakasa 120W) generates very little heat, this one difference has had a domino-effect and ended up with the plants in my current grow not having enough Nitrogen in veg phase, stunting growth and will now lead to a smaller harvest

Sequence of events :

1. Less heat in the growbox.
2. Plants drink a LOT more slowly.
3. You feed them less often.
4. Nutrient uptake is slow.
5. Yellowing of lower leaves.

Because i'm used to CFL-growing i was slow to spot what was happening, also i'm not used to plant deficiencies so didn't spot it in time.

So now, at 1 month the plants are shorter than they should be and only just starting to get pistils, and eventual yield will be lower :

https://www.autoflower.org/f138/gro...r-one-critical-cheese-26571-5.html#post531575


hope this helps someone,

steely

 

[Power.P]

Get a regulation for your outtake fan, this will keep your temps at where you want them to be

 

[astronomy420a]

simple fix...run cfl's with your new light! increasing lumen's and temp!:smokebuds:

 

[Red eyed c]

Some of what you say is correct mate,LEDs do give off less heat,and if the temps drop a lot it will effect nute uptake,but looking at the last pic in the linked thread your temps look to be 24.5C,which is plenty warm enough for growing & nute uptake. I'd say your shallow 3L pots are keeping your plants smaller.

 

[Muddy]

While I agree with some of what you are saying, I also think some of it is a bit misleading and could potentially lead to new LED growers being misinformed. Yes, LEDs do give off less heat, which is the primary reason many of us have switched them. But that lower heat does not necessarily lead to other issued in and of itself. How fast plants drink is directly related their transpiration rate. Transpiration is the plants equivalent to sweating. They take up water and release it through the leaves. High heat will cause this to slow down, as will low temps. With HPS lights the recommended temp and humidity has always been 78 - 80 degrees and 60% humidity in veg, 45% in flower. With LEDs the humidity levels are still the same, but with less heat temps can be a bit higher. Optimum temps under LEDs can be in the 82 - 85% range. This will increase transpiration, which in turn means the plants will drink more and you can feed them more often. This will increase nutrient uptake.

Your soil mix also plays into this. When I grew with HPS lights I always used Pro Mix BX. With LEDs, I use Pro Mix HP. The reason being is that BX holds a bit more moisture than HP, so the HP dries out faster under LEDs. It's often desirable with LEDs to mix a bit more perlite into the mix to make it a bit lighter so it will dry faster.

Yellowing lower leaves isn't a symptom of using LEDs. Usually when lower leaves yellow early in the grow it's either a nutrient or pH situation, with the pH being the most common. Out of range pH can cause some of the nutrients to be locked out and unavailable to the plants, causing the plants to feed off it's leaves, turning them yellow.

 

[steelrat]

Some of what you say is correct mate,LEDs do give off less heat,and if the temps drop a lot it will effect nute uptake,but looking at the last pic in the linked thread your temps look to be 24.5C,which is plenty warm enough for growing & nute uptake. I'd say your shallow 3L pots are keeping your plants smaller.

Thanks Red, yes the temps are ok at the canopy but they are 5 degrees or so lower around the bottom of the pots. I've grown AKR in 2L pots before and they were bigger than this at 30 days, which leads me to think it's lack of N that has held back their vegetative growth rather than pot size/shallowness.

While I agree with some of what you are saying, I also think some of it is a bit misleading and could potentially lead to new LED growers being misinformed. Yes, LEDs do give off less heat, which is the primary reason many of us have switched them. But that lower heat does not necessarily lead to other issued in and of itself. How fast plants drink is directly related their transpiration rate. Transpiration is the plants equivalent to sweating. They take up water and release it through the leaves. High heat will cause this to slow down, as will low temps. With HPS lights the recommended temp and humidity has always been 78 - 80 degrees and 60% humidity in veg, 45% in flower. With LEDs the humidity levels are still the same, but with less heat temps can be a bit higher. Optimum temps under LEDs can be in the 82 - 85% range. This will increase transpiration, which in turn means the plants will drink more and you can feed them more often. This will increase nutrient uptake.

Your soil mix also plays into this. When I grew with HPS lights I always used Pro Mix BX. With LEDs, I use Pro Mix HP. The reason being is that BX holds a bit more moisture than HP, so the HP dries out faster under LEDs. It's often desirable with LEDs to mix a bit more perlite into the mix to make it a bit lighter so it will dry faster.

Yellowing lower leaves isn't a symptom of using LEDs. Usually when lower leaves yellow early in the grow it's either a nutrient or pH situation, with the pH being the most common. Out of range pH can cause some of the nutrients to be locked out and unavailable to the plants, causing the plants to feed off it's leaves, turning them yellow.

Thanks Muddy, yes my soil (Plant Magic) has fytocell so holds on to moisture for far too long, will definitely add some perlite next grow, thanks for that.
I hope i wasn't misleading but i didn't say yellowing leaves is due to LED's, but that the lack of N was the eventual result of a chain of events started by me not being used to LED's.

I've just foliar fed them and i ahve the heat turned up in the room in order to hasten the next watering/feeding.


Thanks for advice all,

steely