I do think they need some blue too. I think
@Tolerance Break mentioned earlier the suns almighty, and she pumps out a fair amount of uv and hidden light/energy. As did MH/HPS. Here's one conundrum I'm having on spectrum tho, this mint green EVO hype, supposed to deter pest and sanitize, (like uv) does, but I thought herb took in less light from green than any other color on the visible spectrum. Very curios to see those minty grows tho. I only know that i know nothing
I'm pretty sure Bugbee has said at least 4% blue in flower so I suspect that any grow light will have at least that amount. I use Growcraft veg and flower lights and I'm sure it's >=4%.
Re the spectrum of the sun - I don't buy into the "it's nature, it's optimal". We have a really good handle on the radiation that plants use, so much so that there's even a name for it.
Based the new research that Westmoreland has laid down, I'm probably going to end up retiring my two year old Growcraft and replacing it with a Spider SE4500 or a 500 watt Growcraft (if they ever get their head out of their ass and publish PPFD values).
Re pest - the research that I've read (vs the marketing BS) it's UV C that is very effective against nasties and UV-C is very expensive and is, itself, nasty shit. What data are there on UV A or B that retard or eliminate the bad stuff?
Cannabis absorbs green very well.
Bugbee has been saying, for at least three years, light quality (spectrum) shapes plants, light quantity drives yield. Between the Frontiers paper and the research that Westmoreland did for his PhD thesis, there's little question that's the case. Full disclosure - Mitch Westmoreland is/was a PhD student under Bugbee at Utah State.
I agree that PPFD is way more critical than spectrum tho. Interesting note, I don't plan to CO2,but there's a vid i mentioned earlier where Shane and Dr. Bugbee talk about co2 and the doc says absolutely every single grow benefits from co2 even at very low wattages. I think it took Shane by surprise.
That
was pretty funny - "deer in the headlights".
Did you also see Shane's reaction when Bugbee laid out going to 1kµmol? That was a come to Jesus moment for Shane but it all fits. Check out the Migro array lights. They're a great design but those little 240 watt drivers poop out at 900 or so vs the offerings from Mars, Spider, etc. which go over 1k. I figured Shane was doing that to keep price down, giving him a price advantage, but, after seeing how he reacted to Bugbee on that point, I get the feeling he actually didn't know about it.
Re. CO2 - no doubt. 25-30% increase in photosynthesis. I've attached the Chandra paper. It's been out for years so Shane should have read it a long time ago.
Below a chart from the paper.
One thing to keep in mind about the Chandra paper is that the data are based on removing leaves from the plants and testing them in a small chamber, about the size of a big shoe box. Also, the paper looks at net photosynthesis. When I read that, it irked me because I'm not harvesting "net photosynthesis", I want to harvest lots of weed. That issue is addressed in the Frontiers paper, attached, in a not very subtle way.
Open the document and do a "Find" for "plastic". It's in the Discussion paragraph. That was a big f'ing deal for me when I read it because Chandra shows that the net P curve rolls off pretty quickly above 500µmol but the Frontiers paper shows why that's misleading. I was pretty psyched when I read that and, since then, I jumped on the high light bandwagon.