HPS only or HPS and MH

Countryfarmer

Countryfarmer

Active Member
I have read a number of threads on a number of sites and instead of helping me out I am just even more confused. I turned to the experts (those who have written books widely read and promoted by growers) and find just as much confusion and contradiction.

For example, Ed Rosenthal stated the following:

Using Metal Halide (MH) lamps in any stage of growing is a waste of time and money. More total light useable by the plant is produced by High Pressure Sodium (HPS) than MH lamps, so plants grow faster using HPS lamps alone.

Jorges Cervantes gives the standard advice of using MH for veg and HPS for flowering.

And then of course you have those who promote a mix of both lights during veg and flowering, but with a 2:1 emphasis on MH in veg and the same ratio with the emphasis changed to HPS during flowering.

So guys, mind helping me out? What is the best answer? HPS only? Veg with MH and flower with HPS? Or a mix of both lights during both veg and flower?

Truly stumped.
 
woodsmaneh!

woodsmaneh!

Well-Known Member
IMHO

Ok you need both for flowering, the reason is plants still need blue and green to truly take advantage of photosynthesis a and b. You can buy compo lamps but they are 2 to 3 times the cost of a regular lamp. I have been looking into LEDs so have found out some intresting info like the attached.

The real measurement you should be using is PAR.

Photosynthesis Basics
To understand why LEDs are so well-suited to growing plants, let’s
review a bit of plant biology. Then we can compare LED lighting
solutions to HID lamps to determine which is better for plants.
Plants perform photosynthesis using two types of chlorophyll:
Chlorophyll-A, with peak response at 430nm and 680nm, and
Chlorophyll-B, with peak response at 450nm and 660nm.
While blue light in the mid-400nm range can activate photosynthesis,
plants mostly use red light in the 650 to 700 nm range. But pure red
light produces abnormal plants, indicating that blue light is required for
proper growth. Blue light also tells the leaves to open their stomata and
allow CO2 in.
Notice that green light produces no response in the chlorophyll curves.
Plants look green because their leaves reflect the green light. Human
vision, however, is most sensitive to green light—an advantageous
adaptation for a species that evolved in the forest.
Measurements of an air-cooled HPS lamp show that more than 60
percent of the electrical energy is turned into heat and ultraviolet light,
and only 32 percent of the electrical energy used is turned into light
energy (MacLennan, 1994). HID lamps produce light that’s useful for
humans, meaning that most of their light energy output is in the green
part of the spectrum, with less than 10 percent of that output in the red
and blue regions where plants use light.
Therefore, we see that the typical HID output spectrum is actually the
opposite of what plants really need. HID grow lights work only because
they are using so much energy that their 10 percent output in the
photosynthesis region is enough to grow plants.


Target the Spectrum Plants Need
LEDs allow us to take a targeted approach to horticultural lighting by
converting electricity into only the light energy that plants will use.
Instead of wasting energy producing the broad emission spectrum of an
HID lamp, the LEDs create very narrow emission spectra: 20nm to
40nm spread compared to several hundred nm for an HID lamp.
Meanwhile, LEDs are very efficient at creating light from electricity. At
least 20 percent of the electrical energy put into an LED turns into light,
and all this light is usable for photosynthesis. For the HPS noted above,
only 10 percent of the 32 percent conversion efficiency is in the
photosynthesis region, meaning that the HPS is only 3 percent efficient
at creating light usable by plants.

Peace
 
T

twistedwords

Well-Known Member
Go get yourself a ceramic metal halide bulb and dump them both. This bulb provides you the full spectrum of light and it fits in a HPS ballast.
 
Countryfarmer

Countryfarmer

Active Member
twistedwords said:
Then get a Son Agro bulb HPS as it is the next best thing. I have used them before with great results, just trying to help.
Click to expand...
I appreciate that. I really do. But we are back to the same question of HPS only, MH and then HPS or a mixture of both in a ratio throughout the grow.

I fully understand that the MH bulb is supposed to give more in the blue spectrum and the HPS more in the red. But as you can see from my quote, Rosenthal, who is one of the standard bearers on indoor growing says to use HPS only. As a matter of fact, the quote that interview comes from has him going on to say to leave the metal halides at the ballpark where they are supposed to be.

Cervantes, another great in the world of marijuana growing gives the standard MH then HPS spiel.

And then we have those who recommend using both throughout the grow.

At this point I have read enough to have a layman's understanding of lumens, PAR, PAR flux and a host of other terms and measurements of lighting, but I really only want to know what people have used that is successful and what they have settled on. I am quite sure I can grow with only HPS, or for that matter only MH. I'm sure if I really wanted to I could grow with a bunch of 20 watt incandescent bulbs if I wanted to do so.

But without having to go through the process of multiple grows using the various combinations of HPS and MH lighting, can someone who has already done so tell me what they use and why? Basically I am attempting to short cut the process with someone else's hard won knowledge.
 
Countryfarmer

Countryfarmer

Active Member
Bumping this back to the top in the hopes that someone who has done some experimenting on lighting answers my question. I know someone has to have done this experiment. I guess at this point it is just a waiting game to see if they read this post and choose to respond to it.
 
jamNburn

jamNburn

Active Member
IDK but I just finished 2 weeks veg with cfl and will continue veg with hps so watch and see its in my sig.
 
Wudaheo

Wudaheo

Active Member
If you want to keep your plants short and dense use MH for vegg stage. Then HPS for flowering. This will optimize your grow space.

If you have room and don't care if plant stretches out and grow all long. Then use HPS. But your plants will take up more space.
 
jamNburn

jamNburn

Active Member
Ya if mine start to stretch Ill switch to cfl or mh.. But Im gonna run a week or two and see what happens.. My grow room has a/c so they are only a foot away from the light.. we'll see.....
 
Countryfarmer

Countryfarmer

Active Member
I guess if no one has ever done this experiment (growing with HPS, then MH, then one for veg and another for flower, and then a mix), I will end up having to do it myself. I am fairly sure someone, somewhere has done this type of experiment. I'm fairly positive as large as this site is, someone on it has already done the experiment, or at least a majority of it. So, I'll keep bumping this up in the hopes they see it and answer my question.
 
jamNburn

jamNburn

Active Member
I dont know of any scientific proof but I've seen grows done with one or the other only ... and they seem pretty comparable... Just search the site for mh grows or hps grow and make your own decision..
 
Countryfarmer

Countryfarmer

Active Member
jamNburn said:
I dont know of any scientific proof but I've seen grows done with one or the other only ... and they seem pretty comparable... Just search the site for mh grows or hps grow and make your own decision..
Click to expand...
You see, I have done that. And the search tells me I should:

(1) Grow with CMH (not an option as I do not have magnetic ballasts, mine are digital)
(2) Grow with HPS only (Rosenthal agrees with this)
(3) Veg with MH and grow with HPS (Cervantes agrees with this)
(4) Veg with a 2:1 ratio of MH to HPS and then flower with a 2:1 ratio of HPS to MH
(5) Grow with LED (not an option)

So I am hoping someone has already done the various combinations surrounding metal halide and high pressure sodium and care to share their knowledge.
 
G

gobbly

Well-Known Member
woodsmaneh! is giving you good info!

Though I respect ed, I don't really agree with his conclusion on this one. Photosynthesis peaks at several wavelengths, and though you want to cater to chlorophyll A more, it still peaks at similar ends of the spectrum, and I am a believer in giving a wider spectrum opposed to a more narrow targeted spectrum (though I do believe in going for peaks around where chlorophyll peaks). The red spectrum has been shown to be slightly more efficient at producing sugars, but it's actually a minor difference in everything I have read. I still think variety is the spice of life :)
 
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