Experimental idea - switch back to MH in last week of flower for yield boost?

[Ian Singerdale]

So I know that MH produces a ton of UV, and if used in flowering can help produce a ton of extra resin / weight.

I have a 400W MH/HPS convertible ballast and a very fancy 7200k MH veg bulb. I have a grower friend who knows a SHITLOAD about light absorption etc and he told me a few things. sorry if this is not explained very well, I only got the gist of what he said. Here are the key points

- dual-arc mh / HPS bulbs are worthless. There is a reason why commercial grows never use them; if they worked, EVERYBODY would use them.
- for a 1000 W dual-arc you are essentially getting one 600 hps and one 400 w mh for more than the electricity consumption of either
- for plants, light sources DO NOT ADD. For example, two 400W lights DO NOT equal one 800W. it simply covers more area
- Even worse, if there is a higher power light, the photonic absorption is completely dominated by it. This means that the 400W MH isn't contributing AT ALL to plant development, because the plant only "sees" the 600W

All of these are reasons why dual-arc bulbs are worthless.

However, I was thinking to get both the lumens of the HPS and resin production of the MH, what if I switched bulbs towards the end of flowering? My ballast supports both anyway.

Has anyone done this? I intend to find out

And does anyone know if my friend is completely full of shit?

 

[mared juwan]

I know peeps who flower exclusively with MH. Is supposed to be better for resin production but sacrifices some yield. I haven't tried it myself but I've sampled some finished buds by these growers and they were definitely super potent. That being said I never tried any buds they grew with HPS to compare so who knows whether the extreme potency was due to their lights or something else.

 

[MtHEMoNSTAR]

one of these dudes I know run both HPS & MH religiously. Seems like the plants closer to the MH have more of a oily resinous look to them.

I run dual spectrum t5's from start to finish. I'm lovin it
GL

 

[Ian Singerdale]

one of these dudes I know run both HPS & MH religiously. Seems like the plants closer to the MH have more of a oily resinous look to them.

I run dual spectrum t5's from start to finish. I'm lovin it
GL

interesting, how many lumens / bulbs are you getting with those t5s? what your usual yields? I have a small clone tent with 10k lumen t5's that I could probably flower in and get some extra strains or something...

I also heard the smell was less with flouros, true?

 

[goleboy]

i have done a side by side room comparison with same strain/medium/feed schedule and we replaced the HPS in the last weeks with MH...the UVB radiation prduced by MH causes resin process to go into overdrive because that late in the flower cycle you are forcing the plant to produce more resin to defend itself from transpiration. DEFINATELY noticeable resin increases if the last 7-10 days is switched to MH

 

[Pipe Dream]

As for increasing the yeild by switching to MH...probably not. For increased resin output because of UV possibly. I have heard that their are many advantages with using MH including better tasting but I cannot verify this. As for using 2 lights, I doubt that the light would be useless because of the HPS light more light = more bud in general. I'm not sure what dual arc MH bulbs are are these MH to HPS conversion bulbs? I have read that they suck and that agrosun gold bulbs have increased spectrum in red and are great for flowering. I am going to get some when I upgrade my MHs.

 

[Ian Singerdale]

I'm not sure what dual arc MH bulbs are are these MH to HPS conversion bulbs?

No, it is literally both types stuffed into a single bulb, usually powered off of an HPS ballast. So essentially the MH filament is a 400W conversion-bulb, with a 600W HPS tacked on, seen here. I still doubt it would produce as much or as nice as a single 1000W HPS

linky

 

[captain chronizzle]

- Even worse, if there is a higher power light, the photonic absorption is completely dominated by it. This means that the 400W MH isn't contributing AT ALL to plant development, because the plant only "sees" the 600W

so, all smaller wattage lights in room are not "seen" it doesn't make sense friend. any and all light adds to the overall light. this is what your plant uses to complete photosynthesis. heavy, on the photo, meaning light.

i have heard of MH emiting higher amounts of uv light, thus increasing levels of resin to act like a sunscreen. also, in the last few weeks, your buds have already grown to full size. it is then, that they pack on wet weight when the seed bracts swell with resin.

i was actually googling results with MH, for the last month and just decided to try it myself to find out. found this thread

i am actually planning a future grow using MH in the last 2 weeks. got the bulb on friday, still waiting for the ballast components. gonna try this shit and figure it out.




here is a photo of my big ol' bulb. fucker is huge!

 

[kappainf]

The whole UV debate is very interesting. I haven't done a comparison yet but I will, I know that mercury vapor lamps emit a ton of UV, so I may try experimenting with those as well. When I switch over to the 12/12 light cycle I always stick with the MH bulbs for the first 7 to 14 days, this technique seems to help decrease the plants stretching. The current grow will get some MH halide action during the last 7 to 14 days as well, however, if you are using a glass air cooled fixture, then I think the glass may be blocking the beneficial UV.

 

[MtHEMoNSTAR]

interesting, how many lumens / bulbs are you getting with those t5s? what your usual yields? I have a small clone tent with 10k lumen t5's that I could probably flower in and get some extra strains or something...

I also heard the smell was less with flouros, true?

I just have a 2 foot 4 bulb t5 fixture with 2 "6500k" and 2 "3000k" spectrum bulbs.
And then 3 68w "2700k" CFL's.

usual yields depend on veg time, strain, technique, etc.

the smell is less because its overall, less heat. you get more smell when you have high heat intensity essentially "baking" your plants.

 

[Dougiefresh2011]

Why would the glass block uv? Thats weird never heard of that.