Rahz' notes and observations

I've been slipping some observations into other threads because they didn't seem to warrant their own topic. Thought I would start a thread for those things.

First item, 3000K 70CRI beside 2700K 90CRI. Both samples exhibit a lot of vertical stretch along with overall plant size being notably larger. The primary differences between this grow and the previous grow with 3000K 70CRI:

Nutrient strength: previous grow was 10 gallon (1 gallon per square foot of canopy space). This one is 20 gallon (2 gallons-sq/ft). In both cases reservoir was/is topped off daily with full strength solution. Because of the extra volume it seems reasonable that the overall TDS remains higher in the 20 gallon system. Possible solution for boosting TDS levels throughout the week in the smaller system would be to top off with a stronger mix than the initial level. Because TDS readings can be somewhat unreliable after the changeout I've been hesitant to do this, but it may warrant some testing.

Reservoir size and circulation: Again, comparing the system volume, the 10 gallon system uses 3 5gallon buckets (2 plants + gravity fed rez). Root ball is restricted to about 3.5 gallons. With the 20 gallon system I'm using a 30 gallon tub. Each plant has about 10 gallons of space for the root ball and about 2-3 x the footprint. In addition it's a RDWC so better water movement through the root system along with more space for the roots to spread out.

Just a guess but between those two items I suspect the extra space and water movement has more to do with the observed differences than TDS. Yield with the 10 gallon system was fairly dense, best yield per foot yet. Whether the larger rez will support higher yield remains to be seen... more plant mass doesn't necessarily mean more yield. But, it would allow a shorter veg period. This was a 24 day veg (final plant footprint is 28"x28") and all other things being equal I could easily have knocked off a week, assuming I got the same stretch after 12/12. Another tricky proposition because less veg time means starting 12/12 with a smaller root ball.

Takeaways:

At start of 12/12 2700K 90CRI was taller, but not by nearly as much as I would have predicted.

In both instances we have very healthy plants, both under 3000K 70CRI. Stretch and plant mass notably higher with the larger rez. Suggests size of root ball is at least as much a determinant of potential stretch as light source. Plant height can be limited by using less solution per square foot, OR possibly supporting shorter veg times via more solution per square foot.

Anyway, these plants are going hog wild. I wouldn't be surprised if yield is slightly higher, but would be surprised if it was substantially higher. If you want to grow giant plants, or perhaps shorten veg time it would be good to experiment by ditching the grow buckets and try tubs... and/or a recirculating system provides obvious benefits in regard to nutrient uptake.

Finally, there could be some discussion about getting a similar effect with less volume via shallow water culture (3.5 gallons spread out over several square feet rather than being confined to a 3.5 gallon bucket. SWC is generally used for SOG, but I don't see why it wouldn't work with fewer, larger plants.

Not exactly scientific, and nothing new really, just wanted to draw attention to the importance of the water culture design and it's effect on growth rate. It's not all about the lights.

In other news, the 3500K 80CRI vs 3000K 90CRI challenge is happening in the bubble buckets. High CRI has a 5-8" jump on the 80CRI lamp, week 2 of 12/12. Hard to tell exactly because they're being trained on a screen. Previous test was 3500K 80CRI vs 3000K 70CRI, final yield of the two was almost exactly equal. Will the mighty 3000K 90CRI lamp be able to edge out the time tested 3500K 80CRI lamp? Or will yield results again be similar?

Takeaway: Worth mentioning here, when utilizing a SCROG method, higher CRI should support shorter veg times as that extra vertical growth can translate into extra width as the plants are trained. Put it all together and the shortest veg time for SCROG should happen with high CRI and oversized recirculating rez. Whether this translates into same yield with shorter veg time is TBD. In a couple months I'll put both of my 90CRI lamps over the 20 gallon system and test this out, flipping to 12/12 at 14 days regardless of whether I think they're ready.

What's going on brother I hope all is well. I wanted to ask a question actually as I was perusing your website for info the other day in some un scientific testing of my own.

IS there a conversion factor yet for "LED" light to calculate Lumens to par to get PPF/PPFD etc yet? Or are we still guesstimating a number that has been agreed upon etc? I ask you this because of all the research you have done. I'm glad to see that 70CRI did well I remember picking it out in one of your threads and people looking at me like an alien LOL

So the reason I ask about the conversion factor is I have been messing with distance to canopy lately to try and better my results with my current COB's now that we have gotten to know each other some. I do not have a par meter and downloaded a Lux app on my phone (I know) but I am simply using this as a tool for trying to get even numbers across the canopy. Thing is at the distances I have found "optimal" for my plants, my Lux readings are no where near where the recommended ranges are.......?

Also, have you guys mixed COB spectrum yet when growing? I am considering mixing my 6500K/3000K COB's in my 3x3's would there be any benefit to this?

Good to see you about again and thanks in advance for any answers you may provide. Hope all is well

My run comparing 3000k 80 and 90 CRI ended up in a draw. The 90 CRI started flower earlier but the 80 caught up during late flower. Same quality in end product, couldn't tell the difference between them.

No reason not to mix them up or go with either in my opinion. 90 CRI provides a better light on the eyes is about all I can think of as a benefit.

I too have seen similar results. I still recommend the 3000k/90cri in most cases. I like the extra stretch I get for indicas, while still stacking nicely. My side by side also had the growth density and stretch with a SFV OG were nearly the same.
@Evil-Mobo The 3000k/90cri next to a DE fixture ( in my case) still looked like a MH bulb. If you want to add the 6500k, have it kick on for 2-4 hrs mid day during flower. Simulating high noon.

Hi @Evil-Mobo, things are good, hope all is well with you. The Bridgelux sim comes with PPF figures now. I had been estimating 3000/90 at 2.8umol/j(700ma) and 3umol/j(500ma). The spreadsheet is indicating 2.7 and 2.9 respectively so the estimates weren't far off. They are only using one decimal place so it's probably 2.7something and 2.9something.

There are Lux to PPFD formulas out there but because cheap meters aren't going to give perfect readings and will vary from brand to brand there's no perfect formula, plus of course it will depend on spectrum but... Reported by @BuddyColas in '16 is LUX reading/1000 * 15 = PPFD. Might be worthwhile to compare that result to projected result with the sim if you're using Vero. The sim doesn't account for reflective loss so it should be somewhat higher than actual. Also, Apogee and perhaps others provide conversion formulas specific to their LUX meters.

Playing around with my meter, I've found it's possible to get very close to the projected PPFD numbers depending on light spread and area. For instance, the T22 I produced gave really nice readings in a 2x2 but unable to reach the projected #s due to all the light hitting the tent walls. However, in a 3x3 the projected PPFD and measured PPFD were both 600 +-5 points. The trade off of course is that when you minimize reflectivity this way it's because light levels are concentrated toward the center. The best strategy IMO is to let the canopy levels be a little "lumpy". If you're picking up (PPFD) readings of 700-1400 at the canopy because the emitters are spread out and down low on the plants, to me that seems like a better unevenness than a hotspot in the center and low readings around the outside. Trying to even things out more by using more emitters at lower power is not a bad idea (which is why I tend to do that and have been using 45-50 watts per cob max).

There of course is a fine science to it, but not at all unreasonable to suggest aiming for 15-25 par watts per foot and keeping the individual cob wattage low is 95% of the solution. From there it's just a matter of spacing out the available cobs as evenly as possible. I like to keep the 30w cobs about 6" from the wall and 45-50w cobs 12" from the wall. After that's done, forget about canopy evenness. Just get that lamp as low down on the plants as possible. Cause some damage, raise the lamp 1 inch. That's where the ideal spot is IMO.

The very first lamp I built was a 3000/4000K mix. It was a good idea in that I was able to use all the 4000K cobs in veg and turn on the rest of the 3000K cobs at 12/12. It's been said before that the mean result will tend to be the average, IOW 3000 and 4000 will come out to 3500. Whether this is a perfect analogy or not I can't say but it does make sense. Maybe it's a little different when talking about 6500K spectrum because it's going to be blue/green heavy but in practice I don't see it making much difference. I should state that I've never used anything over 4000K so not the best person to ask.

thanks, subbed!

Up to 12 Vero 29 c per square meter now. 400w max for only 6 hours per day in peak flower. PAR meter is an absolute necessary tool.

@Rahz maybe you can shed some light on something I have wondered for a long time. If a "Par" meter is measuring all photons with the "par" range, why do companies like Apogee have different calibrations? Sun, Metal Halide, Fluorescent, etc.
Shouldn't one meter be able to be taken from sunlight straight to the artificial source and give a true reading under each with accuracy for "par"??

OneHitDone said:

@Rahz maybe you can shed some light on something I have wondered for a long time. If a "Par" meter is measuring all photons with the "par" range, why do companied like Apogee have different calibrations? Sun, Metal Halide, Fluorescent, etc.
Shouldn't one meter be able to be taken from sunlight straight to the artificial source and give a true reading under each with accuracy for "par"??

Click to expand...

The response curve typically will drop off on the high end and low end so correction can be different depending on what the SPD of a light source looks like. The older Apogees, 50% at 400 and nothing over 670. You can see here with Apogees newest meter a much better response on the ends. They claim this new version is pre-calibrated for all light sources... mostly true in the 400-700nm range.

Probably took a hint from HydroFarm

I allways subb to your threads, theyre the bomb. Better than growmau5 , no offence meant either way

Info on grows in first post isnt posted in its own thread, just around? Looking forward to what you got cooking this time.

subbed, but to upgrade, good info

nevergoodenuf said:

I too have seen similar results. I still recommend the 3000k/90cri in most cases. I like the extra stretch I get for indicas, while still stacking nicely. My side by side also had the growth density and stretch with a SFV OG were nearly the same.
@Evil-Mobo The 3000k/90cri next to a DE fixture ( in my case) still looked like a MH bulb. If you want to add the 6500k, have it kick on for 2-4 hrs mid day during flower. Simulating high noon.

Click to expand...

You say the DE and 3000K 90 CRI are similar but how the look or we talking yield as well? If yield how many watts of LED vs the DE and what wattage on the DE a thouie? Sorry just want to make sure we are all clear man I'm not looking for an argument genuine questions. I know you were doing a side by side before but haven't been in here much except to try and keep up with my own thread health has been kicking my ass lately.

My 3000K are 80 CRI Citizen 1812's, and my 6500K are Citizen 1212's. I have (5) of each respectively in their own 3x3 tent and was considering mixing them up between the two to see how that "combo" would compare to the 3500K 1812's running in my 4x8..........

I'm a former HID guy so this is all interesting to me. And honestly what I am doing with COB's right now was/is more out of necessity than anything else.

Rahz said:

Hi @Evil-Mobo, things are good, hope all is well with you. The Bridgelux sim comes with PPF figures now. I had been estimating 3000/90 at 2.8umol/j(700ma) and 3umol/j(500ma). The spreadsheet is indicating 2.7 and 2.9 respectively so the estimates weren't far off. They are only using one decimal place so it's probably 2.7something and 2.9something.

There are Lux to PPFD formulas out there but because cheap meters aren't going to give perfect readings and will vary from brand to brand there's no perfect formula, plus of course it will depend on spectrum but... Reported by @BuddyColas in '16 is LUX reading/1000 * 15 = PPFD. Might be worthwhile to compare that result to projected result with the sim if you're using Vero. The sim doesn't account for reflective loss so it should be somewhat higher than actual. Also, Apogee and perhaps others provide conversion formulas specific to their LUX meters.

Playing around with my meter, I've found it's possible to get very close to the projected PPFD numbers depending on light spread and area. For instance, the T22 I produced gave really nice readings in a 2x2 but unable to reach the projected #s due to all the light hitting the tent walls. However, in a 3x3 the projected PPFD and measured PPFD were both 600 +-5 points. The trade off of course is that when you minimize reflectivity this way it's because light levels are concentrated toward the center. The best strategy IMO is to let the canopy levels be a little "lumpy". If you're picking up (PPFD) readings of 700-1400 at the canopy because the emitters are spread out and down low on the plants, to me that seems like a better unevenness than a hotspot in the center and low readings around the outside. Trying to even things out more by using more emitters at lower power is not a bad idea (which is why I tend to do that and have been using 45-50 watts per cob max).

There of course is a fine science to it, but not at all unreasonable to suggest aiming for 15-25 par watts per foot and keeping the individual cob wattage low is 95% of the solution. From there it's just a matter of spacing out the available cobs as evenly as possible. I like to keep the 30w cobs about 6" from the wall and 45-50w cobs 12" from the wall. After that's done, forget about canopy evenness. Just get that lamp as low down on the plants as possible. Cause some damage, raise the lamp 1 inch. That's where the ideal spot is IMO.

The very first lamp I built was a 3000/4000K mix. It was a good idea in that I was able to use all the 4000K cobs in veg and turn on the rest of the 3000K cobs at 12/12. It's been said before that the mean result will tend to be the average, IOW 3000 and 4000 will come out to 3500. Whether this is a perfect analogy or not I can't say but it does make sense. Maybe it's a little different when talking about 6500K spectrum because it's going to be blue/green heavy but in practice I don't see it making much difference. I should state that I've never used anything over 4000K so not the best person to ask.

Click to expand...

Ok thanks for the info. See because everywhere I looked the conversion factors were based off of HPS, Metal Halide, T5, etc..........so what I had found with all the LUX/PAR stuff was that the most recent info out there was re written by another person/company but still based off of the old conversion numbers so then for LED they would not apply. So I would look at your charts with the PPF/PPFD and they were close in the curves of what amount is optimal for what stage of growth to the older LUX/PAR charts. If I would go by those older numbers now in flower I would be wanting around 70-80K Lux (off the top of my head) for optimum growth, and my readings are even across the canopy around 15-17K and that's a huge difference. But this run is my healthiest and largest "cob" run to date at the new spot since moving here......

So there has to be something we are missing??? Because how could I possibly be on top of my best looking girls going into flower using a lot less watt/sq ft than normally recommended, feeding lighter EC than ever before (saves money too), and at double the normal distances recommended? I mean the grow is not over I'm only like 2 weeks into flower but......just ccrazy to see this all happening and it's technically "wrong" according to word of mouth info.

When I tested the COB's vs the QB's last year and stuck to the higher watts/sq foot and closer distance to canopy my plants were smaller than usual yielded less and were problematic throughout the grow always something to adjust. Now I back off on everything and it's cruise control, just trying to make sense of this LOL.........

Rocket Soul said:

I allways subb to your threads, theyre the bomb. Better than growmau5 , no offence meant either way

Info on grows in first post isnt posted in its own thread, just around? Looking forward to what you got cooking this time.

Click to expand...

Thanks. The results of the previous test I snuck into the 1200$ budget for 4x8 thread.

"3500K 80CRI: 12.81 oz
3000K 70CRI: 12.85 oz

Highest yield/ft yet at about 73 g/swft.
GPW by output 1.8. GPW from wall, 1.7

Interestingly the GPW is only about 5% better than what I got from the Vero29g5 setup. GPPW is actually worse. There could be a variety of reasons for this so I'm not going to spend too much time thinking about it, but I think I can do a bit better with this lamp.

Done with CLU058-1825 at 1050ma. Not bad for 50w emitters."

To provide a bit more detail, each lamp is 4x CLU058-1825s at 50w each. Lamp draw including the two DC fans is about 220 watts per lamp. Each lamp over 5 sq/ft (28"x28"). That grow was done in the bubble buckets with gravity feed rez. Maxibloom/Maxigrow powder, 2.5/2.5g per gallon up to week 5 then 4/2g gallon through to week 8. I was using 2ml per gallon 0-0-4 silica and 5ml per gallon Hydroguard. Also each bucket uses 2 air stones coming in on opposite sides of the net cup. Very simple and effective design, easy to change and top off, roots don't block the lines. I'm currently playing around with dropping the PH in the third bucket. The bubble buckets will go from 5.5 to 6.4 over night. Also kind of a pain to take PH measurements from the grow buckets once the plants get large so I'm thinking that if I adjust the rez to the right PH it will provide a slow drip of PH down as the plants drink water. This setup uses about 2 gallons a day (1 gallon per plant and 5 square feet) once the canopy is full.

The only negative (besides possibly space for the root ball) is that it's not recirculating and therefore no chiller. As long as the room is 72 the solution is 72, but it might become an issue in the Summer if the AC can't keep up.

Evil-Mobo said:

Ok thanks for the info. See because everywhere I looked the conversion factors were based off of HPS, Metal Halide, T5, etc..........so what I had found with all the LUX/PAR stuff was that the most recent info out there was re written by another person/company but still based off of the old conversion numbers so then for LED they would not apply. So I would look at your charts with the PPF/PPFD and they were close in the curves of what amount is optimal for what stage of growth to the older LUX/PAR charts. If I would go by those older numbers now in flower I would be wanting around 70-80K Lux (off the top of my head) for optimum growth, and my readings are even across the canopy around 15-17K and that's a huge difference. But this run is my healthiest and largest "cob" run to date at the new spot since moving here......

So there has to be something we are missing??? Because how could I possibly be on top of my best looking girls going into flower using a lot less watt/sq ft than normally recommended, feeding lighter EC than ever before (saves money too), and at double the normal distances recommended? I mean the grow is not over I'm only like 2 weeks into flower but......just ccrazy to see this all happening and it's technically "wrong" according to word of mouth info.

When I tested the COB's vs the QB's last year and stuck to the higher watts/sq foot and closer distance to canopy my plants were smaller than usual yielded less and were problematic throughout the grow always something to adjust. Now I back off on everything and it's cruise control, just trying to make sense of this LOL.........

Click to expand...

By optimal I think you mean optimal growth rate, and what you're saying is true but the chart also suggests 75% growth rate at 50% of optimal light intensity, so it makes sense to limit the veg intensity to around 700 or so until we're all getting fusion powered electricity at pennies on the dollar, and honestly even a PPFD of 450-500 is going to provide a fantastic veg if all other parameters are keeping the plant healthy. As far as yield some suggest it's close to linear but my own efforts haven't proven that out yet. Keep in mind I just recently upgraded my equipment and prior to that never used over 800 PPFD in flower. So far, jumping from 800 to 1250 has resulted in an increase from 58-60 to 72 g/sqft. I think I can do better than 72 g/sqft but for the curve to be linear I would need to pull over 90 g/sqft. I know it's been done before but probably beyond my skill level even with these nice lights. And you know, getting 60 g/sqft from a light that isn't quite hitting 800 PPFD ain't too bad.

I've always argued that it's not the most practical thing to grow with +1000 PPFD. Better to use same wattage with more space. But efficiency goes up and price goes down, and I was curious. I'm doing it for science

@Evil-Mobo we had done a couple different ways, the biggest difference was a 4000k/70cri fixture, then the 3500k/80cri, and the 3000k/90cri over a 4'x8' tray. After 2 or 3 weeks, it looked like a staircase of plants about 6" tall every color change, but the 4000k lack canopy density. This was all to long ago for me to remember what wattages we were using, since we changed it up everytime and I only made it there 2 or 3 times per test.

Oh, the 2 DE were on high, and we did almost half the wattage, 20% less, and about the same, but again I was so busy at this time and my friend was gone most of that time and none of these runs were his better runs (lazy helper let problems get out of hand). We weren't running the COBs for efficiency either. It was 12 CLU058 3618 over the 4'x8' tray on some 20 pound 600w heatsinks

Also, I never run ppm over 1000. I do want to experiment one day, but you don't need outrageous TDS to pull good yield. In the past I kinda winged it based on recommendations, but after digging a bit deeper I've got to the point where I measure out nutrients by elemental ppms. General rule of thumb is 100-150 ppm Nitrogen for best vegetative growth. I've been shooting for 100 over the last couple grows but would like to play with bumping up closer to 150 during veg, could be especially helpful for getting bulk in the first two weeks if I'm going to shorten my veg period and maintain root ball size going into flower... but I wouldn't be surprised if going from 100 to 150 didn't produce a lot of difference.

As far as the P and K, range for P seems to be 20-100 and for K 150-250. In these hydro systems I've been keeping P at around 20 using CocosAB formula and then switching to 50 ppm at the start of week 3. I've been doing this because P (typically cited at +70 ppm) inhibits various beneficial microbes and I had some root rot issues and the rot doesn't seem to care what the P levels are. Now that I've got the situation under control I'm getting less paranoid and thinking 50 ppm P will be fine to start with, and again if I want a 2 week veg it makes sense to kick the P up ASAP.

I know less about potential min/max of K. I base my 250 ppm figure on adjusting nitrogen of various brands of vegetable fertilizer to 100 ppm and see what the K comes out to. If I bump the N up to 150 that can put the K as high as 375... but for perspective these are fertilizers intended for soil so it's going to get watered down to some degree as soon as it's applied. Analyzing hydro specific nutes at suggested rates, K can be as high as 275-320 and P as high as 150-185. Like a lot of people I have my doubts about running those numbers because I've had good success running much lower, but it's worth testing out right?

Anyway, I think it's worthwhile to work out the formulas for elemental NPK and base the fertilizer plan on NPK ppm rather than TDS. I like the Maxibloom/Maxigro dry combo because I can get just about any reasonable n/p/k ratio I want with a 2 part formula, it contains cal and mag which a lot of dry "complete" fertilizers do not, and it's cheap compared to liquid nutes. I have attached a simple NPK calculator I whipped together in Excel. The pic should explain everything, but you can also copy/paste or delete rows. If you add rows you will need to double click the elemental PPM cells and adjust the sums to include the new rows. For different ferts, just change the names and the guaranteed analysis values. You can load in a whole nutrient line or just check the elemental values for a one part formula.

is your rez size altering/buffering root temps?