Is there any benefits or negatives with mixing these two different spectrums during vegetation. Say...four 26w 6500k bulbs and 2 26w 5500k bulbs per plant?
Well, both the 6500k and the 5500k are both Veg bulbs --- the 5500k is actually a little bit better than the 6500k. There is no harm in mixing these spectrums during veg. In fact, you could even mix in a few of the 2700k (flowering spectrum) bulbs during the veg stage, and vice versa.... just try to keep more veg bulbs during veg, and more flowering during flower does that make sense? yes you can mix those, no problems.
Thanks for the reply. What makes the 5500k better than the 6500k? Do plants do more photosynthesis at that spectrum?
The 5500k is a bit more like daylight -- checkout this chart - can be found in the HID LIGHTGUIDE -- there is a similar CFL GUIDE
so really 5500k would be best for veg and 2200k for flower? why would 6500k and 2700k be suggested if they both have lower readings according to this chart?
It's somewhat debatable as to what constitutes the "exact" perfect spectrum. On one hand you can look at what the sun gives off, on another hand you can look at what the plant utilizes, and overlay all of this with an understanding that no HID or CFL bulb gives off only its rated spectrum but rather that represents an average or midpoint for what that bulb gives off. I've always heard that 6500k is more the optimum spectrum that the plants can use for vegetative growth, but know that 6500k and 5500k bulbs will have a lot of overlap in their spectrum output.