S
Südhang
thats an interesting thread!
-
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MH vs HPS in bloom
- Thread starter the gnome
- Start date
FreedomFightr
Member
HPS uses the weakest colors out of the color spectrum. HPS is cheapest bang for your buck. If u want to win go with a mixed spectrum. One of my 4x8 tables I have a 1000watt Hps and a 1000watt MH over it. The ones under the MH are always better IMO
I do not have time to read this thread, but I have done a lot of work on this, and I love MH, but never use them in bloom any more. Mary loves the blue more... but she yields better for all yellow than blue or mixed.....for most strains, high end sativas are a different gal, they need the blue.
I proved this to myself over and over again. All yellow is not enough light, so they produce more to try to catch more light, the result is increased yield.
H
I proved this to myself over and over again. All yellow is not enough light, so they produce more to try to catch more light, the result is increased yield.
H
produce more to try to catch light? I can imagine that you see they are more leafy but I don't see why a plant would develop better or try harder than a plant getting a correct spectrum. You might have more yield with a HPS lamp than the same power MH, but that is not because of the worse spectrum, but because of the more photons.
Just curious to see if anyone has tried the new hortilux's that burn both at the same time?
Now there is an idea for an interesting side by side....?
http://www.eyehortilux.com/products/High-Pressure-Sodium#sblue
Have A Great Day
Mr Wags
Now there is an idea for an interesting side by side....?
http://www.eyehortilux.com/products/High-Pressure-Sodium#sblue
Have A Great Day
Mr Wags
And Digilux says they have more red in their MH bulbs. Works the other way around in veg too (more complete spectrum) - adding a few 3000 k T5s in an 8 bulb fixture. Some are using the aquarium T5's (like UV Lighting Red Sun) but I like the Plantmax 3000ks or GE Starcoat (cheaper and still very good T5s).
J
Javadog
That is a very interesting reference. Thank you for taking the time.
I must lag behind the "bleeding edge" but will look forward to some product
researcher posting a side-by-side comparison of how these new bulbs perform.
I am stuck at 600W for the foreseeable future, but I can upgrade my bulb.
Thanks again,
JD
I must lag behind the "bleeding edge" but will look forward to some product
researcher posting a side-by-side comparison of how these new bulbs perform.
I am stuck at 600W for the foreseeable future, but I can upgrade my bulb.
Thanks again,
JD
this is what you get when you grow this strain
this is what you get when you grow this strain
I dropped into the advanced nutes love it or hate it state your claim thread last year and saw a pic of a very frosty bud and this was said
you can read my response in the link,
here's a quickie of my edited reply with a pic of an equally frosty cola
lots of similarities between that thread and this one.
hash, you said in posts a few pages earlier things like this
not bashing on ya hash
don't take this the wrong way,
but *that* is skewed science
Ive been comparing which of my strains prefer what lite since i started this thread last year and if you run a cloned strain with HPS and 1 with MH, at the end of the grow you'll know which lite that cloned strain prefers
where's the scientific proof in knowing those particular 3 strains prefer HPS over MH???
then doing it over and over 7 times or even 177 times???
lol, you know the strain will do better under hps after
the 1st side x side run, or surely by the 2nd, i know, ive done it.
its a repetetive procedure with a known outcome and applying it blanket fashion
over all strains.
again.. that is skewed science
so its a pretty loooong stretch to say HPS is better for cannabis in bloom based on your 7 time hps gro with the same 3 strains.
what your science proved is those 3 strains perform better in HPS in bloom
1st 3 pages of this thread,
look at vapedg13s all MH gro's with $21 bulbs.
he runs many differing strains and killing it with MH.
and others have said the same with their Mh gro's
why? its the strains he selected for that purpose.
they are every bit as good as the best HPS plants Ive seen
same with me, my SR clone did well under HPS,
but under MH it was tons more weigh, tighter buds!
i knew what bulb i was growing that one under from now on,
and i have again under both hps and mh.
same results every time, MH outperforms MH *with that strain*
whats to be taken from this thread, at least the 1st 15-20 pages
is that some strains prefer MH over HPS and vice versa.
after that it started getting mucked up.
by a few of the usual shit stirrers that turned it into
hps is the only bulb for bloom because i know it etc etc etc
that's complete BS
all one has to do is look at vapedg13s pics
and other MH growers buds, like mine.
I know now which of my strains do well with what bulb which can only be a a tool and an asset for growing better
and that's what we all strive for in our gardens, right
I didn't start this thread to prove HPS is better or MH is better,
although unfortunately the few of the usual suspects have taken it to that that place,
but what there is to be taken from this thread is this.
its the strain people.... its the strain
some like frankie gets it,
and put into words aptly.
this is why i started this thread
this is what you get when you grow this strain
I dropped into the advanced nutes love it or hate it state your claim thread last year and saw a pic of a very frosty bud and this was said
you can read my response in the link,
here's a quickie of my edited reply with a pic of an equally frosty cola
lots of similarities between that thread and this one.
hash, you said in posts a few pages earlier things like this
not bashing on ya hash
don't take this the wrong way,
but *that* is skewed science
Ive been comparing which of my strains prefer what lite since i started this thread last year and if you run a cloned strain with HPS and 1 with MH, at the end of the grow you'll know which lite that cloned strain prefers
where's the scientific proof in knowing those particular 3 strains prefer HPS over MH???
then doing it over and over 7 times or even 177 times???
lol, you know the strain will do better under hps after
the 1st side x side run, or surely by the 2nd, i know, ive done it.
its a repetetive procedure with a known outcome and applying it blanket fashion
over all strains.
again.. that is skewed science
so its a pretty loooong stretch to say HPS is better for cannabis in bloom based on your 7 time hps gro with the same 3 strains.
what your science proved is those 3 strains perform better in HPS in bloom
1st 3 pages of this thread,
look at vapedg13s all MH gro's with $21 bulbs.
he runs many differing strains and killing it with MH.
and others have said the same with their Mh gro's
why? its the strains he selected for that purpose.
they are every bit as good as the best HPS plants Ive seen
same with me, my SR clone did well under HPS,
but under MH it was tons more weigh, tighter buds!
i knew what bulb i was growing that one under from now on,
and i have again under both hps and mh.
same results every time, MH outperforms MH *with that strain*
whats to be taken from this thread, at least the 1st 15-20 pages
is that some strains prefer MH over HPS and vice versa.
after that it started getting mucked up.
by a few of the usual shit stirrers that turned it into
hps is the only bulb for bloom because i know it etc etc etc
that's complete BS
all one has to do is look at vapedg13s pics
and other MH growers buds, like mine.
I know now which of my strains do well with what bulb which can only be a a tool and an asset for growing better
and that's what we all strive for in our gardens, right
I didn't start this thread to prove HPS is better or MH is better,
although unfortunately the few of the usual suspects have taken it to that that place,
but what there is to be taken from this thread is this.
its the strain people.... its the strain
some like frankie gets it,
and put into words aptly.
this is why i started this thread
Last edited:
I'm on a quest for horticultural truth - a lot of new growers will be starting up in the next 5 years with legalization. I hate to see the rampant misinformation and hype steering people wrong.
I actually just converted over to electronic ballasts - Lumatek. So far I love them. They are smaller, lighter, and silent, and more versatile (diff. wattages and MH or HPS).
But then you're repeatedly subjected to hype about e-ballasts being better all these other ways....doesn't match the data I've seen. If you change your capacitor on time it's just as bright and the bulbs last just as long.
Hortilux was supposed to come out with a full line of US-made e-ballasts, but according to them it's not going to happen until next year. Their 1000 watter looks great though. P.L. Lighting also makes nice 600 and 1000 watt lights w/e-ballast available through commercial sources.
I've flowered plants under MH and they came out great, but if someone's just starting out I would say go HPS all the way. (btw I do believe the MH plants are very potent, but mine came out leafier which shows the trichomes on the leaves more.) One of my favorite things about HPS is the higher calyx-to-leaf ratio vs. outdoor light.
there is something I noticed with MH that doesn't occur, that Ive seen yet.. is that MH plants stack closer internodes in veg and later the 12/12 stretch is way less than hps, but there's still many variables with that, ive seen plants in 12/12stretch then fill completely, but that seems to be the exception and not the rule.
other misconception imo, such as leafier buds with MH
other misconception imo, such as leafier buds with MH
BS leafy buds are a genetic trait..... look at these buds... all bud MH the entire grow
Excellent info whazzup. I got info from Solis-Tek which states plants use the spectrum of the full sun, not just selective PAR wavelengths or "nature doesn't have 2 brick walls that say 400 and 700 nanometers".hmm.. I'm not going to pick on details but there certainly is a big difference in par measurements and lux measurements. Any lamp with a high amount of green in the spectrum will give you a much higher lux reading. In general when you use MH you need 30-50% more lamps/wattage to obtain the same ppf a good horti HPS will give you. Though a MH will look very bright to the human eye, it's not that it actually outputs more photons in the PAR spectrum, and that's what drives photosynthesis: the number of photons in the right spectrum.
Now there is a lot of difference in HPS lamps when it comes to efficacy. Some HPS lamps do just over 1.6 umol/W, while the best do 2.1 umol/W. MH usually doesn't go any further than 1.2 - 1.5 umol/W (and have a really bad light maintenance). The new CMH do 1.7-1.9 umol/W but are only medium wattage, so it will be interesting to see what the new high wattage lamps do you see pop-up sometimes.
But anyways, if you replace a bad HPS lamp with a good MH I think you can have a better yield and a better quality because of the improved spectrum. However, if you are going to replace a really good HPS with a bad MH then you could lose about 30-50% of your total ppf easily. That amount you can't make up with a better spectrum.
That's another reason why you should measure umol instead of lux: there is more than enough scientific evidence that there is a very strong correlation between the photosynthesis and the amount of par light. That's scientific.
I did numerous side by side tests (yeah I enjoy a good scrog) where I made sure that the plants received the same amount of PAR light, but from different light sources. In all the different grows I saw mostly quality/health/morphogenetic differences, yield differences were minor at the same PPFD with comparable reflectors (also important). Now that I don't call science, but experience.
(ps the white sensors you see once in a while are the RH/T/CO2 dataloggers)
DE STRAIN BOSS, DE STRAIN!its the strain people.... its the strain
wow, they make a lot of very silly mistakes in that document. Most silly is that they say that the light efficiency curve they show (not the plant efficiency curve btw) was made for the human eye sensitivity and this is not correct, they show the McCree curve. For the human eye the lux scale has sensitivity peak at 555 nm and drops on either side.
The McCree curve that has bee around since the beginning of the 70's has since been adjusted under other circumstances than the used 100 umol s-1 m-2. There is much research done about efficiency of light and plant responses, even green light is very efficient in high intensity white light. In fact it might be more efficient than red or blue in high intensity white light. But the general response in photosynthesis indeed is between 400 and 700 nm (or a bit wider).
Many people forget that though there is a photosynthetic response from a plant, the morphogenesis of a plant is also greatly influenced by the spectrum.
The McCree curve that has bee around since the beginning of the 70's has since been adjusted under other circumstances than the used 100 umol s-1 m-2. There is much research done about efficiency of light and plant responses, even green light is very efficient in high intensity white light. In fact it might be more efficient than red or blue in high intensity white light. But the general response in photosynthesis indeed is between 400 and 700 nm (or a bit wider).
Many people forget that though there is a photosynthetic response from a plant, the morphogenesis of a plant is also greatly influenced by the spectrum.
Thanks again very much whazzup.
Some info from Jorge Cervates on blue light, MH and morphogenesis along with lots of other lighting info (he's referencing the Gavita site and that link seems to be broken so here's the .pdf link too @ Plasma spectrum for use in combination with HPS lighting for the generative phase):
"Here is a good piece on the new Light Emitting Plasma (LEP) lights to get this thread off to a good start!
Here is a direct link to the pdf: http://www.gavita-holland.com/index....-lighting.html
Plasma spectrum for use in combination with HPS lighting for the generative phase
Introduction
Many studies have shown that full continuous spectrum with sunlight qualities is the best spectrum for healthy plant development. For this purpose Gavita manufactures a light emitting plasma (LEP) luminaire with a high CRI of 94, the Gavita pro 300 LEP. Though it is lacking some red spectrum it is the best suitable lamp for continuous vegetative development or high intensity sunlight simulations in climate rooms.
A different application for plasma lighting is the quality improvement of HPS light. A combination of LEP and HPS provides a much better spectrum because the HPS is lacking blue spectrum, and generally most spectrum below 560 nm (see fig 1). Additional advantage is the UVA and UVB light that the plasma adds to the spectrum. Blue light and a continuous spectrum is very important in any development phase of the plant, be it vegetative or generative, as the full spectrum contains colors that define photosynthetic rate, morphogenesis and high energy (blue) photons that help maintain the photosynthetic system in the plant during the generative phase.
Fig 1: Typical High Pressure Sodium spectral diagram
This paper describes our recommendations for a more efficient plasma spectrum for use in combination with HPS lighting, using an alternative emitter: The STA 41.01.
Efficiency of light
Most plant response curves such as the famous Keith McCree curve (fig 2) show a lower relative photosynthetic efficiency for blue and yellow/green light. This is correct for low PAR levels. Recent studies however have shown that even the green light, which is most abundant in sunlight, is very efficient when used in high intensities. In fact, at high irradiation levels the green light is equally or more efficient than other colors.
Fig 2: Efficiency of light in the PAR spectrum– McCree ’73 – P curve is plant sensitivity curve, V curve is human eye sensitivity http://www.keithmccree.net/Biographi...oProf/PAR.html
In horticultural greenhouses there is mostly enough quality sunlight available, even in the low light season when HPS assimilation lighting is used. The most efficient technology for creating photons in the PAR region at this moment is High Pressure Sodium light. The disadvantage of the bad quality HPS spectrum is compensated in the greenhouse by the available sunlight. In recent years though we have seen an increase in used HPS PAR levels in the greenhouses, which may be accountable for a less than usual quality in the winter. It is suggested that this is a result of the lacking blue light. In Scandinavia, where the daytime light is even shorter and so the DLI provided by the sunlight is totally inadequate this is compensated by using supplemental Metal Halide lighting.
The effect of blue light
Light spectrum is one of the factors that define how a plant develops. There are many mechanisms in a plant that are responsible for stretching, photosynthetic rate and morphogenesis. One effect of blue light is the development of sun leaves which have higher rate of photosynthesis per unit leaf area. Another very important factor is the morphogenesis: Leafs develop in a better position to intercept the light, which results in a higher photosynthesis and faster vegetative development. It also puts the plant in a favorable position for generative development.
Research indicates a requirement for 7% blue light spectrum as a good balance with the HPS light for quality plant development. The highest measurable increase in quality of added blue light was found within the 0-10% more blue light. Above that level blue light still increases the quality and yield of the crop, but it doesn’t increase as much as within the 0-10% range. Below that level plants can suffer from the imbalance in the spectrum, as in a deterioration of their photosynthetic system, more compact growth, vulnerability for disease and fungi and a less efficient morphogenesis.
Fig 3: Increase of photosynthetic rate with the addition of blue light (data from Hogewoning et al. 2010)
Another important factor in the applied spectrum is the continuity of the spectrum: Research indicates that plants develop best under a full continuous spectrum. Plasma light provides a continuous spectrum.
Light color and stretching
The phytochrome fotoreceptors are responsible for the stretching of a plant. They have an action spectrum from ~350-800 nm, and the far red color is an important signaling color. Generally a more blue spectrum leads to less stretching, but it is important to take all colors and factors into account, including the leaf positioning and photosynthetic rates. Plasma light will not influence the stretching of the plant much when used in combination with HPS. Other effects, such as light interception of the plant by a better leaf position when plasma is used in the vegetative phase and a higher rate of photosynthesis per unit leaf area have a much bigger influence. The faster development of the plant under just plasma light is only for a small portion due to stretching.
Adding quality spectrum to HPS
Analysis of the HPS spectrum shows a start of the effective spectrum at about 560 nm (yellow to red). Below that wavelength there are a few small spikes, but not a balanced continuous availability and not enough blue spectrum. For that reason Philips recommends to use MH to accompany her GreenPower HPS lamps when used in climate rooms, as these have very low levels blue light. In climate rooms therefore you see many combinations of MH and HPS.
Adding MH however has some disadvantages:
1. The lifetime is very short (6-8 months)
2. MH is not very efficient (much less than HPS)
3. The spectrum is not continuous but has many spikes
4. The color temperature stability is low
5. MH lamps either need a closed fixture or they need to have protection against shattering of the outer bulb in case of a failure. They are very dangerous to look into when they are broken as they provide very high amounts of UVC radiation
6. MH lamps emit a lot of IR radiation (heat)
With the introduction of CMH (Ceramic Metal Halide, arc tube made of ceramic material) better color rendering and longer light maintenance have become available, but only in the low to medium watt ranges, and it still isn’t a continuous spectrum and lacks UVA and UVB.
Tests have shown that lacking quality spectrum in HPS lighting in climate rooms can be compensated by LEP, as the sunlight does in the greenhouses. Plants stay greener and healthier, while the available UVA and UVB triggers defense mechanisms in the plant that harden the leafs. UVA and UVB also cause increased levels of flavonoids, essential oils and terpenoids in many different strains. They have a long life (30.000 – 50.000 hours), a stable spectrum with very low levels of infrared and a high CRI of 94. So plasma technology is well suited for this task.
However, some of the spectrum of the plasma lamp overlaps with the HPS lamp which has an abundance of light in wavelengths above 560 nm. HPS technology is currently the most efficient way to generate red photons. So it would be better to have a plasma lamp that supplements the HPS lamp under 560 nm instead of overlapping in the higher bandwidth radiation. The full spectrum version of the plasma lamp is still superior in situations without HPS where you need to only grow vegetative or in sunlight simulations in climate rooms.
Choosing the right emitter
The wide continuous spectrum of a plasma lamp is caused by the emission of molecular light of a specific mixture of chemicals in the plasma cell which is brought into a high temperature plasma state. Changing the combination of the chemicals will change the spectrum. In our first Gavita Pro 300 LEP fixture we use the STA 41.02 emitter, which has the highest quality light output, ideal for simulating sunlight. It is regarded best suited for continuous vegetative growth and sunlight simulation. But there is another emitter available: The STA 41.01 emitter has less red in its spectrum, and shifts more to the spectrum below 590 nm while maintaining the same blue spectrum. (fig 4: plasma spectrum):
Fig 4: spectrum of the STA 41.01 and STA 41.02 emitter
As you can clearly see the spectrum of the STA 41.01 drops steep as from 590 nm, and it just overlaps for a small bandwidth with the HPS light. Energy is shifted from the red spectrum to a bandwidth below 590 nm. This makes the 41.01 better suitable to complement HPS light, as there is more supplemental light and less overlap.
The STA 41.01 module has other generic advantages:
- Increased life time 50.000 hours versus the 30.000 hours for the STA 41.02
- Much better output in lumen, but this is of no significance to the plant
- Slightly higher PAR output (PPF, photons per second)
We have tested the 41.01 lamp for vegetative development as well. Though it does not perform as well as the 41.02 lamp, for a short vegetative phase (<4 weeks) the differences were not significant. Under the 41.01 lamp at very high intensities we see a slight V shape of the top leafs, which disappears when transplanted to a combined HPS/LEP environment or when the leafs move to the lower parts of the plant. Plant development and photosynthesis were not significantly different.
The 41.01 emitter therefore is a better alternative for the 41.02 for situations where it is used in combination with HPS for generative development. For pure vegetative use the 41.02 emitter is still the lamp of choice, and it still is a proven valuable addition to the HPS spectrum as for the blue light.
How much plasma to complement HPS?
Our calculations and research show that for a climate room the combination of one 300W plasma light with 1000-1200W HPS light provides enough blue spectrum (>7%) for a healthy development of the plant. For the HPS light we calculate with the horticultural HPS light, which offer an efficiency of almost 2 μmol W-1.
It can be used in higher intensities to provide a higher blue ratio which will result in a higher photosynthetic rate, but the biggest increase in quality and yield can be obtained with up to 10% blue light. We recommend to use only plasma in the vegetative phase to optimize the photosynthetic rate and harden the plants.
So in conclusion:
- We recommend the 01 version as most efficient to complement HPS light during the generative phase and suitable for short vegetative cycles
- The 02 version is also suitable for a combination with HPS, but has a better quality than the 01 for vegetative development, so it is best utilized in a pure vegetative environment or for sunlight simulations
- Use one Gavita Pro 300 LEP in combination with a maximum of 1200W HPS lighting for a better color spectrum which results in healthier plants, higher quality and a better yielding crop
Gavita Holland bv Oosteinderweg 127 1432 AH Aalsmeer The Netherlands
www.gavita-holland.com [email protected] T +31 297 380450 F +31 - 297 380452"
And to take out a few paragraphs from above pertinent to this thread:
"The effect of blue light
Light spectrum is one of the factors that define how a plant develops. There are many mechanisms in a plant that are responsible for stretching, photosynthetic rate and morphogenesis. One effect of blue light is the development of sun leaves which have higher rate of photosynthesis per unit leaf area. Another very important factor is the morphogenesis: Leafs develop in a better position to intercept the light, which results in a higher photosynthesis and faster vegetative development. It also puts the plant in a favorable position for generative development.
Research indicates a requirement for 7% blue light spectrum as a good balance with the HPS light for quality plant development. The highest measurable increase in quality of added blue light was found within the 0-10% more blue light. Above that level blue light still increases the quality and yield of the crop, but it doesn’t increase as much as within the 0-10% range. Below that level plants can suffer from the imbalance in the spectrum, as in a deterioration of their photosynthetic system, more compact growth, vulnerability for disease and fungi and a less efficient morphogenesis."
Some info from Jorge Cervates on blue light, MH and morphogenesis along with lots of other lighting info (he's referencing the Gavita site and that link seems to be broken so here's the .pdf link too @ Plasma spectrum for use in combination with HPS lighting for the generative phase):
"Here is a good piece on the new Light Emitting Plasma (LEP) lights to get this thread off to a good start!
Here is a direct link to the pdf: http://www.gavita-holland.com/index....-lighting.html
Plasma spectrum for use in combination with HPS lighting for the generative phase
Introduction
Many studies have shown that full continuous spectrum with sunlight qualities is the best spectrum for healthy plant development. For this purpose Gavita manufactures a light emitting plasma (LEP) luminaire with a high CRI of 94, the Gavita pro 300 LEP. Though it is lacking some red spectrum it is the best suitable lamp for continuous vegetative development or high intensity sunlight simulations in climate rooms.
A different application for plasma lighting is the quality improvement of HPS light. A combination of LEP and HPS provides a much better spectrum because the HPS is lacking blue spectrum, and generally most spectrum below 560 nm (see fig 1). Additional advantage is the UVA and UVB light that the plasma adds to the spectrum. Blue light and a continuous spectrum is very important in any development phase of the plant, be it vegetative or generative, as the full spectrum contains colors that define photosynthetic rate, morphogenesis and high energy (blue) photons that help maintain the photosynthetic system in the plant during the generative phase.
Fig 1: Typical High Pressure Sodium spectral diagram
This paper describes our recommendations for a more efficient plasma spectrum for use in combination with HPS lighting, using an alternative emitter: The STA 41.01.
Efficiency of light
Most plant response curves such as the famous Keith McCree curve (fig 2) show a lower relative photosynthetic efficiency for blue and yellow/green light. This is correct for low PAR levels. Recent studies however have shown that even the green light, which is most abundant in sunlight, is very efficient when used in high intensities. In fact, at high irradiation levels the green light is equally or more efficient than other colors.
Fig 2: Efficiency of light in the PAR spectrum– McCree ’73 – P curve is plant sensitivity curve, V curve is human eye sensitivity http://www.keithmccree.net/Biographi...oProf/PAR.html
In horticultural greenhouses there is mostly enough quality sunlight available, even in the low light season when HPS assimilation lighting is used. The most efficient technology for creating photons in the PAR region at this moment is High Pressure Sodium light. The disadvantage of the bad quality HPS spectrum is compensated in the greenhouse by the available sunlight. In recent years though we have seen an increase in used HPS PAR levels in the greenhouses, which may be accountable for a less than usual quality in the winter. It is suggested that this is a result of the lacking blue light. In Scandinavia, where the daytime light is even shorter and so the DLI provided by the sunlight is totally inadequate this is compensated by using supplemental Metal Halide lighting.
The effect of blue light
Light spectrum is one of the factors that define how a plant develops. There are many mechanisms in a plant that are responsible for stretching, photosynthetic rate and morphogenesis. One effect of blue light is the development of sun leaves which have higher rate of photosynthesis per unit leaf area. Another very important factor is the morphogenesis: Leafs develop in a better position to intercept the light, which results in a higher photosynthesis and faster vegetative development. It also puts the plant in a favorable position for generative development.
Research indicates a requirement for 7% blue light spectrum as a good balance with the HPS light for quality plant development. The highest measurable increase in quality of added blue light was found within the 0-10% more blue light. Above that level blue light still increases the quality and yield of the crop, but it doesn’t increase as much as within the 0-10% range. Below that level plants can suffer from the imbalance in the spectrum, as in a deterioration of their photosynthetic system, more compact growth, vulnerability for disease and fungi and a less efficient morphogenesis.
Fig 3: Increase of photosynthetic rate with the addition of blue light (data from Hogewoning et al. 2010)
Another important factor in the applied spectrum is the continuity of the spectrum: Research indicates that plants develop best under a full continuous spectrum. Plasma light provides a continuous spectrum.
Light color and stretching
The phytochrome fotoreceptors are responsible for the stretching of a plant. They have an action spectrum from ~350-800 nm, and the far red color is an important signaling color. Generally a more blue spectrum leads to less stretching, but it is important to take all colors and factors into account, including the leaf positioning and photosynthetic rates. Plasma light will not influence the stretching of the plant much when used in combination with HPS. Other effects, such as light interception of the plant by a better leaf position when plasma is used in the vegetative phase and a higher rate of photosynthesis per unit leaf area have a much bigger influence. The faster development of the plant under just plasma light is only for a small portion due to stretching.
Adding quality spectrum to HPS
Analysis of the HPS spectrum shows a start of the effective spectrum at about 560 nm (yellow to red). Below that wavelength there are a few small spikes, but not a balanced continuous availability and not enough blue spectrum. For that reason Philips recommends to use MH to accompany her GreenPower HPS lamps when used in climate rooms, as these have very low levels blue light. In climate rooms therefore you see many combinations of MH and HPS.
Adding MH however has some disadvantages:
1. The lifetime is very short (6-8 months)
2. MH is not very efficient (much less than HPS)
3. The spectrum is not continuous but has many spikes
4. The color temperature stability is low
5. MH lamps either need a closed fixture or they need to have protection against shattering of the outer bulb in case of a failure. They are very dangerous to look into when they are broken as they provide very high amounts of UVC radiation
6. MH lamps emit a lot of IR radiation (heat)
With the introduction of CMH (Ceramic Metal Halide, arc tube made of ceramic material) better color rendering and longer light maintenance have become available, but only in the low to medium watt ranges, and it still isn’t a continuous spectrum and lacks UVA and UVB.
Tests have shown that lacking quality spectrum in HPS lighting in climate rooms can be compensated by LEP, as the sunlight does in the greenhouses. Plants stay greener and healthier, while the available UVA and UVB triggers defense mechanisms in the plant that harden the leafs. UVA and UVB also cause increased levels of flavonoids, essential oils and terpenoids in many different strains. They have a long life (30.000 – 50.000 hours), a stable spectrum with very low levels of infrared and a high CRI of 94. So plasma technology is well suited for this task.
However, some of the spectrum of the plasma lamp overlaps with the HPS lamp which has an abundance of light in wavelengths above 560 nm. HPS technology is currently the most efficient way to generate red photons. So it would be better to have a plasma lamp that supplements the HPS lamp under 560 nm instead of overlapping in the higher bandwidth radiation. The full spectrum version of the plasma lamp is still superior in situations without HPS where you need to only grow vegetative or in sunlight simulations in climate rooms.
Choosing the right emitter
The wide continuous spectrum of a plasma lamp is caused by the emission of molecular light of a specific mixture of chemicals in the plasma cell which is brought into a high temperature plasma state. Changing the combination of the chemicals will change the spectrum. In our first Gavita Pro 300 LEP fixture we use the STA 41.02 emitter, which has the highest quality light output, ideal for simulating sunlight. It is regarded best suited for continuous vegetative growth and sunlight simulation. But there is another emitter available: The STA 41.01 emitter has less red in its spectrum, and shifts more to the spectrum below 590 nm while maintaining the same blue spectrum. (fig 4: plasma spectrum):
Fig 4: spectrum of the STA 41.01 and STA 41.02 emitter
As you can clearly see the spectrum of the STA 41.01 drops steep as from 590 nm, and it just overlaps for a small bandwidth with the HPS light. Energy is shifted from the red spectrum to a bandwidth below 590 nm. This makes the 41.01 better suitable to complement HPS light, as there is more supplemental light and less overlap.
The STA 41.01 module has other generic advantages:
- Increased life time 50.000 hours versus the 30.000 hours for the STA 41.02
- Much better output in lumen, but this is of no significance to the plant
- Slightly higher PAR output (PPF, photons per second)
We have tested the 41.01 lamp for vegetative development as well. Though it does not perform as well as the 41.02 lamp, for a short vegetative phase (<4 weeks) the differences were not significant. Under the 41.01 lamp at very high intensities we see a slight V shape of the top leafs, which disappears when transplanted to a combined HPS/LEP environment or when the leafs move to the lower parts of the plant. Plant development and photosynthesis were not significantly different.
The 41.01 emitter therefore is a better alternative for the 41.02 for situations where it is used in combination with HPS for generative development. For pure vegetative use the 41.02 emitter is still the lamp of choice, and it still is a proven valuable addition to the HPS spectrum as for the blue light.
How much plasma to complement HPS?
Our calculations and research show that for a climate room the combination of one 300W plasma light with 1000-1200W HPS light provides enough blue spectrum (>7%) for a healthy development of the plant. For the HPS light we calculate with the horticultural HPS light, which offer an efficiency of almost 2 μmol W-1.
It can be used in higher intensities to provide a higher blue ratio which will result in a higher photosynthetic rate, but the biggest increase in quality and yield can be obtained with up to 10% blue light. We recommend to use only plasma in the vegetative phase to optimize the photosynthetic rate and harden the plants.
So in conclusion:
- We recommend the 01 version as most efficient to complement HPS light during the generative phase and suitable for short vegetative cycles
- The 02 version is also suitable for a combination with HPS, but has a better quality than the 01 for vegetative development, so it is best utilized in a pure vegetative environment or for sunlight simulations
- Use one Gavita Pro 300 LEP in combination with a maximum of 1200W HPS lighting for a better color spectrum which results in healthier plants, higher quality and a better yielding crop
Gavita Holland bv Oosteinderweg 127 1432 AH Aalsmeer The Netherlands
www.gavita-holland.com [email protected] T +31 297 380450 F +31 - 297 380452"
And to take out a few paragraphs from above pertinent to this thread:
"The effect of blue light
Light spectrum is one of the factors that define how a plant develops. There are many mechanisms in a plant that are responsible for stretching, photosynthetic rate and morphogenesis. One effect of blue light is the development of sun leaves which have higher rate of photosynthesis per unit leaf area. Another very important factor is the morphogenesis: Leafs develop in a better position to intercept the light, which results in a higher photosynthesis and faster vegetative development. It also puts the plant in a favorable position for generative development.
Research indicates a requirement for 7% blue light spectrum as a good balance with the HPS light for quality plant development. The highest measurable increase in quality of added blue light was found within the 0-10% more blue light. Above that level blue light still increases the quality and yield of the crop, but it doesn’t increase as much as within the 0-10% range. Below that level plants can suffer from the imbalance in the spectrum, as in a deterioration of their photosynthetic system, more compact growth, vulnerability for disease and fungi and a less efficient morphogenesis."
B
BasementGrower
has anyone noticed if its strains bred for outdoor growing better under mh orhps.. or strains bred inside under mh better under mh ? or what? is there anything to it ? or is it just completly random?
(that paper is still on the gavita site under documents and download - white papers)
Question to your answer: "more like indica or sativa strains?" the gnome and others may have a better answer.
Personally I go with indica dominant & mix 600w MH & 600w HPS in early flower then 600w MH & 1,000w HPS in late/finish flower. I use bare bulb so also have some UVB from MH lights. I'm willing to trade off yield for better quality/potency using some MH in flower. Indica dominants more bushy so I keep the HPS lights lower in canopy where especially the HPS could penetrate better.
Bingo! This from the .pdf link you gave as well, same or very similar graphs it seems (p=plant response, v=human eye response):
it's old news basically, about ten years ago researchers already didn't take the McCree curve as a holy grail anymore, as it is only the chlorophyll response to light. There are many other pigments in a plant that take an active part in the photosynthesis, which works in two systems.
The 2004 (old) article is funny as it misspells our name (Garita instead of Gavita). We introduced the first horticultural electronic HID ballasts back in 2003 (now ten years ago), before Philips did.
Since then a lot more research has been done.
oh yeah, one other thing: chlorophyll is most sensitive to orange light, not red.
The 2004 (old) article is funny as it misspells our name (Garita instead of Gavita). We introduced the first horticultural electronic HID ballasts back in 2003 (now ten years ago), before Philips did.
Since then a lot more research has been done.
oh yeah, one other thing: chlorophyll is most sensitive to orange light, not red.
Swampwater
Member
Here's a trick I've learned for increasing yield with MH.
When I move my plants under the flowering lights (1k hps), the norm is to give em 7 days veg(give or take) before flipping to 12/12.
By using a MH bulb instead of hps during this veg time, I can double the veg time to 14 days & still get the same height. But I get double the root mass. Mo roots= mo yield. I keep the mh in for the first week of flower to help with the stretch on taller plants as well. I used to do 2wks but now only one.
When I move my plants under the flowering lights (1k hps), the norm is to give em 7 days veg(give or take) before flipping to 12/12.
By using a MH bulb instead of hps during this veg time, I can double the veg time to 14 days & still get the same height. But I get double the root mass. Mo roots= mo yield. I keep the mh in for the first week of flower to help with the stretch on taller plants as well. I used to do 2wks but now only one.
J
Javadog
I did one week of Vegging too.
My SOG is at 8 weeks from flip tomorrow.
It seems to have worked great for me.
Onward and upward,
JD
My SOG is at 8 weeks from flip tomorrow.
It seems to have worked great for me.
Onward and upward,
JD
