How much light (PAR) before problems?

  • Thread starter phxazcraig
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steamroller

steamroller

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How old are your LED lights? I have four Mars SP-3000 LEDs and keep it at 14 inches too :-). My PAR is about 1200 on top. LED lights are suppose to weaken over time. I only had mine for 6 months now and the SP-3000s are operating very well.
I am running the TSL 2000. They are 6 months old aprox .
Right now they are 16" from highest bud .
With warmer weather my room may get up to 86 so I keep the light safely away .
May turn on AC for daylight and get closer for last couple weeks [week 4 1/2 flower now ].
Many say over 800 is not doing much without co2 ?
 
phxazcraig

phxazcraig

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Yesterday I spent some minutes looking closely at the leaves under the PAR 1300 area. I think I might have seen the first signs of stress - leaf edges curling up - and so I reduced the power on the light. Plants in the center are now at about PAR 1000, but the corners are now a bit under 500. This is the biggest issue with not having enough height for the light. I'm debating trying to raise the light some more, by taking out the ratchet hangars, and directly attaching the leads from the light together with a carabiner. I did that before I swapped the tent, and I should have simply set the light up that way when I set the tent up. The problem now is that it is very difficult to get inside the tent to raise the light. The top leaves are 6 foot above the ground, and they are higher than the tent door. The plants are too entwined in the trellis net to move out of the way, and I think at this point it's just going to be a lesson learned. I'll keep watching leaves and try to skirt the edge of too much light.
 
phxazcraig

phxazcraig

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Without CO2 enhancement, you'll start to see light burn around 1200-1300 PPF. You want yourPPFD to be in the 700-900 range. Above 1000 PPFD your plant start using light avoidance mechanisms without additional CO2. If you have a meter or an app to measure PPF, use that to adjust your light via dimming.
Based on the experience from this grow, I think this is correct. Don't go above PAR 1000. I definitely got burnt leaves from PAR 1300 after several days or a week, and things didn't really settle down on the bud sites involved until I got PAR down to 1000. Which means PAR is low in the corners, but that's that. I may end up harvesting the top of the canopy and let the rest grow another couple of weeks. In which case I can turn the light up again and have better coverage!
 
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