[oregon bob]

Hi all, just found this chart that had written out when first went vertical. Mr Jones got me thinking about this again as never had really resolved this in my head. This relates to the maximum footprint one can accommodate within the verti set-up. The push seems to be put the lights as close as possible to the plant tops to maximize the total lumen count... seemingly w/o much consideration to the effort required balanced against the actual benefits. What are the benefits of say 40k lumens?

Essentially, it appears to me that the conventional wisdom of the more the lumens the better, is wrong. The estimates I find for summer sunlight is between 10-15000 lumens, with appx 2000mMol/m2/s. This latter figure was referenced to PAR & PPF, where the two have been used interchangeably depending on source. Maybe someone can help with the difference here...?

Related to the mMol fig, it has been stated that 15 PAR watts is the minimum required by plants per m2. The max usable is 85 PAR / m2. Also related, found another source stating 1200mMol/m2/s is the most radiation that the plant can use w supplemented co2, where 800 to 1000 is suggested for healthy mj growth.

Not all of this makes complete sense to me, but it is what i could reliably find from at least one other source, preferably 2 or more. The lumen counts have been stated to reach diminishing returns at 6500 lumens per sq ft... w supplemented co2. The maximum necessary is listed at 10000, though it appears the advocacy of a shit load more is common...

My logic has been to keep the lights as far away from the plant tops as possible while maintaining canopy saturation. This almost seems contrary to the prevailing trends... liquid lumens, air cooling, chillers, movers, etc. What are your thoughts on this issue?

Would like to try to resolve this a little better within the verti forum...

Here's the hand chart... just scanned it, so hope it is clear enough to make out. Just to reference to picture my contention a little better. It's basically the lumen chart by HGO but drawn out for our application. Peace everyone!

Originally Posted by oregon bob

Related to the mMol fig, it has been stated that 15 PAR watts is the minimum required by plants per m2. The max usable is 85 PAR / m2. Also related, found another source stating 1200mMol/m2/s is the most radiation that the plant can use w supplemented co2, where 800 to 1000 is suggested for healthy mj growth.

Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions

https://www.icmag.com/ic/showthread.p...04#post2469004

The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m−2s−1 PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m−2s−1 and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m−2s−1. In view of these results, temperature and light optima for photosynthesis was concluded to be at 25–30 °C and ∼1500 μmol m−2s−1 respectively.

You want the lamps as close as possible to the canopy without blasting the canopy with so much heat that photosynthesis is slowed.

[oregon bob]

LJB, you're the man! Talk about addressing my question head on... perfect... even w the data charted out for me. Thank you.

Okay, upon a cursory overview of the article, will go back & reread, but a few quick questions...

1. Noticed that fig 5 shows marginal differences in water use (transpiration i'm assuming) where there is marginal differences between 500-1300 mMol (where is the mu key?). Temp has the largest overall impact where 25-30c is "ideal". Is this your interpretation as well? I see marginal differences in metabolic activities as long as you have in excess of 500mMol.

2. How does the mMol measurement convert to the ratings of the bulb? I couldn't find a clear, concise, understandable explanation. I get PAR, but PPF is still a little unclear. Regardless, how would you take the ratings for the Hortilux super hps & determine mMol availability? Also, this is measured in m2, correct? Is the 1/d2 applicable?

Thank you so very much for taking the time to get this to me! Peace brother.

[oregon bob]

Just went to the pdf link, just read through the original post & found my answers. Thank you brother.

1k hps @ 11.5k lumens/sq ft appx to reach saturation point of 1500 mMol.

Shit dude, you even showed me how to convert in addition to the listings of SM! On the ball...

Thank you once again & the greenest of vibes.

[maddr101]

So guys what is the minimum requirements of light/lumen in a grow box per sq ft to allow proper growth or acceptable growth?

[Hydro-Soil]

Originally Posted by maddr101

So guys what is the minimum requirements of light/lumen in a grow box per sq ft to allow proper growth or acceptable growth?

It really depends on the lights you're using. Different lamps put out different PAR qualities and lumens don't measure that.

For working in a grow box with flat white paint or other reflective coating.... I can tell you that if you're talking about the PL-L CFL lamps I use, anything over about 7,000lm/sqft is a waste without CO2 being added. For anything else you'll have to consult those that are familiar with that particular lamp.

[maddr101]

Originally Posted by Hydro-Soil

It really depends on the lights you're using. Different lamps put out different PAR qualities and lumens don't measure that.

For working in a grow box with flat white paint or other reflective coating.... I can tell you that if you're talking about the PL-L CFL lamps I use, anything over about 7,000lm/sqft is a waste without CO2 being added. For anything else you'll have to consult those that are familiar with that particular lamp.

Thanks for the help man you guys know your stuff

My pleasure, Bob.