Help dialing in for higher yield: 1 gram per watt

[DontEvenAsk]

Hi. I've had a few grows under my belt. I guess I'm just trying to figure out some questions I have on how to get a higher yield. GOAL: 1 gram per watt. ANY OPINION IS APPRECIATED!

Type of light: Double Ended Gavita / Phantom Fixtures
Veg time: 3-4 weeks (14-20" height) 18/6
Flower Time: 8-9 Weeks 12/12
Plant count: 10 plants per light - 20 plants per tray (3x6 trays, 2 lights per tray)
Light wattage: 825 watts per fixture, 3' canopy clearance
Medium: Rockwool 6" Cubes
Feed System: Once every other day at 1 minute during Veg, Once per day at 2-3 minutes during flower. TOP FEED RECIRCULATING SYSTEM
Flushing: I replace my res once a week, so they only recirculate for that week. I top off a few times when the res run out during each week.
Feed PH: 5.8 - 6.2, I fluctuate between the two every other feed.
Feed PPM: 1000-1300
Nutrient Used: Advanced Nutrients, Dyna-Gro, Hygrozyme, A&B, Cal Mag, Big Bud, Vitamax, Sweet Raw
CO2 PPM: 1000-1300
Temperature: 80 degrees during lights on flowering, 82 degrees lights on veg
Humidity: 40-50% during lights on. Higher when lights go out.
Strain: Gorilla Glue


My questions:

1. My AC isn't strong enough to bring the temperatures down to 75-78 while lights are set to 825 watts.
2. Is 825 watts too strong for canopy clearance of 3 feet away from bulbs?
3. I always feed at 5.8-6.2 PH, but my run off sometimes comes out at a low PH (4.5-5.0) .. what's going on?
4. Should I turn on dehumidifer when the lights go out? Does humidity matter during the night time?
5. Is the CO2 okay?
6. If everything is dialed in, what else do I need to know to hit 1 gram per watt?
7. Should I lower my light wattage down to 600 watts? or set all of them to 750? as opposed to 825 watt.

 

[TorturedSoul]

1. My AC isn't strong enough to bring the temperatures down to 75-78 while lights are set to 825 watts.

If you are giving your plants sufficient light-energy - and you are obviously supplementing CO₂ - then not only is this less of a concern, you'll most likely benefit from a higher lights-on temperature. There is a relationship between these three things. If you notice that you've increased your light and/or CO₂, but the rate of plant development does not seem to have quite kept up, your (relatively) low temperature range is probably why.

BtW, there are insulated covers for many air-cooled HID fixtures that'll further help keep the lights' heat from the grow room. They do help a little but, again, I don't feel that your temperature is too high (if anything, I'd guess the opposite to be the case, to some extent). Unless you're growing a strain known for performing at lower temperatures, of course. But, oft times, it seems like "my grow room is too hot" ends up meaning "I am not able to provide enough light-energy to my plants for the temperature that they're living in." Again, "IMHO."

"Best temperature" for a strain is kind of like "minimum hours of uninterrupted darkness required for flowering" - it varies (somewhat) from strain to strain. Most such recommendations are, therefore, of the "one size fits all" type. And as the obese and anorexic can tell you, one size doesn't actually fit all.

2. Is 825 watts too strong for canopy clearance of 3 feet away from bulbs?

I shouldn't think so; people have run higher-wattage lights even closer, with air-cooled fixtures and proper ventilation (I'm a big fan of having the lights and room ventilated separately, although my setups do not currently allow this). If you happen to notice any minor bleaching effect, consider one of those (improperly named) "light spreader / diffuser" things that clip onto the socket. Basically a reflective piece of metal with lots of holes in it, to block (actually, reflect back up to your fixture's reflector, where it'll get redirected to the greater canopy area) some percentage of the light from reaching the plant(s) directly underneath the bulb.

3. I always feed at 5.8-6.2 PH, but my run off sometimes comes out at a low PH (4.5-5.0) .. what's going on?

You mean your immediate runoff is that different from your nutrient solution's pH? If my pH tanks, I tend to think "unwanted microbial life," but that's in a DWC situation. And there are, of course, other possibilities. I'm about wiped out from exhaustion, but plants consuming one part of a nutrient can cause a marked shift in pH. Again, I wouldn't think this would be immediately measurable, though.

Some pH meters are pretty sensitive to interference from nearby electric/electronic devices. Are you measuring both in the same physical location? If so, I wouldn't think this would account for your observations, even if your meter is being affected in this way - but I suppose it's within the realm of possibility, and I'd do some testing with things temporarily shut off.

Aeration can affect pH to some degree. This could be a factor here. It seems counterintuitive, I'd guess, but if you are sufficiently aerating your nutrient solution, try doing the same to your runoff for a period of time (IDK, an hour? Somewhat less but at least 15 minutes?) so as to approximate the same amount of dissolved oxygen in both sets of samples.

4. Should I turn on dehumidifer when the lights go out? Does humidity matter during the night time?

I would. Remember the term "relative humidity." If it's 86°F during your "day," and you have the amount of moisture in the air to equate to a 40% RH... If you allow the temperature to drop to 72°F without removing any moisture from the air, your RH is going to go way up. That's how you get dew outside overnight - the air cools to the point where it is no longer capable of holding (all of) the moisture that it did when it was hotter the evening before.

Plants transpire moisture that they take up via their roots as a matter of course, via the stomata in the undersides of their leaves. That's a basic biological process, it's pretty much a given. You really don't want "dew" on and in your buds.

5. Is the CO2 okay?

Okay by me . If you get your temperatures up a bit. Otherwise, you're not really taking full advantage of it, IMHO. And assuming, as mentioned, that you are providing enough light-energy to your plants.

Yield is determined by many factors, including strain (and even phenotype) choice. Smooth walls, high reflectivity (ultra-bright flat white paint is great), making sure you've got sufficient watts per square foot (there can be some give and take here, where you might get the same - or even conceivably - slightly higher gross yield by increasing your space and, thus, somewhat decreasing your watts per square foot... but bud density will, therefore, suffer), et cetera. When you're chasing numbers like that, things have to be working pretty well and even relatively minor issues/inconsistencies (such as having your nutrient ratio being slightly sub-optimum) can cause you to miss your goal. Keep your DO (dissolved oxygen) level as high as you can (and this can end up causing you to, in practice, not need to have your nutrient concentration as high as you otherwise would, due to the plants' generally increased efficiency.

If you really want to chase yield, consider an integrated vertical setup (multiple lights in a vertical orientation, spread throughout your room). Do a search for Heath Robinson's grows. He's a member here, but has rarely posted (and not for a long time), so you'll find a lot more via a general web-search than searching this forum, but this will give you some idea of his yields:
Heath's Latest Tree Grow
1.77 grams per watt enough for you, lol?

Also, do remember that there's "grams per watt" and then there's "grams per watt per day." You can often increase your gross yield to one degree or another by lengthening your vegetative phase. But this obviously has the side-affect of allowing you less grows per year. The result of this could be a net gain or a net loss when one considers the year (or other time period) as a whole. In other words, gross yield per grow and grams per square watt are not everything that should be considered.

 

[DontEvenAsk]

If you are giving your plants sufficient light-energy - and you are obviously supplementing CO₂ - then not only is this less of a concern, you'll most likely benefit from a higher lights-on temperature. There is a relationship between these three things. If you notice that you've increased your light and/or CO₂, but the rate of plant development does not seem to have quite kept up, your (relatively) low temperature range is probably why.

BtW, there are insulated covers for many air-cooled HID fixtures that'll further help keep the lights' heat from the grow room. They do help a little but, again, I don't feel that your temperature is too high (if anything, I'd guess the opposite to be the case, to some extent). Unless you're growing a strain known for performing at lower temperatures, of course. But, oft times, it seems like "my grow room is too hot" ends up meaning "I am not able to provide enough light-energy to my plants for the temperature that they're living in." Again, "IMHO."

"Best temperature" for a strain is kind of like "minimum hours of uninterrupted darkness required for flowering" - it varies (somewhat) from strain to strain. Most such recommendations are, therefore, of the "one size fits all" type. And as the obese and anorexic can tell you, one size doesn't actually fit all.



I shouldn't think so; people have run higher-wattage lights even closer, with air-cooled fixtures and proper ventilation (I'm a big fan of having the lights and room ventilated separately, although my setups do not currently allow this). If you happen to notice any minor bleaching effect, consider one of those (improperly named) "light spreader / diffuser" things that clip onto the socket. Basically a reflective piece of metal with lots of holes in it, to block (actually, reflect back up to your fixture's reflector, where it'll get redirected to the greater canopy area) some percentage of the light from reaching the plant(s) directly underneath the bulb.



You mean your immediate runoff is that different from your nutrient solution's pH? If my pH tanks, I tend to think "unwanted microbial life," but that's in a DWC situation. And there are, of course, other possibilities. I'm about wiped out from exhaustion, but plants consuming one part of a nutrient can cause a marked shift in pH. Again, I wouldn't think this would be immediately measurable, though.

Some pH meters are pretty sensitive to interference from nearby electric/electronic devices. Are you measuring both in the same physical location? If so, I wouldn't think this would account for your observations, even if your meter is being affected in this way - but I suppose it's within the realm of possibility, and I'd do some testing with things temporarily shut off.

Aeration can affect pH to some degree. This could be a factor here. It seems counterintuitive, I'd guess, but if you are sufficiently aerating your nutrient solution, try doing the same to your runoff for a period of time (IDK, an hour? Somewhat less but at least 15 minutes?) so as to approximate the same amount of dissolved oxygen in both sets of samples.



I would. Remember the term "relative humidity." If it's 86°F during your "day," and you have the amount of moisture in the air to equate to a 40% RH... If you allow the temperature to drop to 72°F without removing any moisture from the air, your RH is going to go way up. That's how you get dew outside overnight - the air cools to the point where it is no longer capable of holding (all of) the moisture that it did when it was hotter the evening before.

Plants transpire moisture that they take up via their roots as a matter of course, via the stomata in the undersides of their leaves. That's a basic biological process, it's pretty much a given. You really don't want "dew" on and in your buds.



Okay by me . If you get your temperatures up a bit. Otherwise, you're not really taking full advantage of it, IMHO. And assuming, as mentioned, that you are providing enough light-energy to your plants.

Yield is determined by many factors, including strain (and even phenotype) choice. Smooth walls, high reflectivity (ultra-bright flat white paint is great), making sure you've got sufficient watts per square foot (there can be some give and take here, where you might get the same - or even conceivably - slightly higher gross yield by increasing your space and, thus, somewhat decreasing your watts per square foot... but bud density will, therefore, suffer), et cetera. When you're chasing numbers like that, things have to be working pretty well and even relatively minor issues/inconsistencies (such as having your nutrient ratio being slightly sub-optimum) can cause you to miss your goal. Keep your DO (dissolved oxygen) level as high as you can (and this can end up causing you to, in practice, not need to have your nutrient concentration as high as you otherwise would, due to the plants' generally increased efficiency.

If you really want to chase yield, consider an integrated vertical setup (multiple lights in a vertical orientation, spread throughout your room). Do a search for Heath Robinson's grows. He's a member here, but has rarely posted (and not for a long time), so you'll find a lot more via a general web-search than searching this forum, but this will give you some idea of his yields:
Heath's Latest Tree Grow
1.77 grams per watt enough for you, lol?

Also, do remember that there's "grams per watt" and then there's "grams per watt per day." You can often increase your gross yield to one degree or another by lengthening your vegetative phase. But this obviously has the side-affect of allowing you less grows per year. The result of this could be a net gain or a net loss when one considers the year (or other time period) as a whole. In other words, gross yield per grow and grams per square watt are not everything that should be considered.

That's a very very helpful and informative reply. Thank you. I guess what I need to do is check off everything suggested one by one.

 

[TorturedSoul]

As always, don't treat ol' ~TS~' words as Gospel, lol. But, yes, a few things to think about.

I'm guessing you've got all the basics well and truly nailed down by this time. Much of what you'll be doing now probably falls under the heading of fine-tuning. That's when it's doubly important to consider the relationships between the various things that make up a cannabis grow, and how changing one may require (for best results) some minor(+/-) changes in one or more other things to keep the plants' efficiency level as high as possible.

Good luck with your quest!

 

[HigherTheHigh]

Hello buddy!

If it were me that were doing this garden grow i would change only 1 thing and that would be using only 4 plants per 3x3, 10 plants in that space is far to dense, most of your canopy will be overgrown and out of control.

If you only plant 4 then this means you have more breathing space for your plants with a better environment, i veg for 4-6 weeks and harvest around 20+oz with only a 600w so you should be able to easy break that target of 1g per watt.

The main man @TorturedSoul pretty much covered everything but in all honesty 600w per 3x3 will get great results, some strains hate the heat, im running super and because the temper were at 29 for a few weeks its made them very airy, but the northern lights iv got are dense, mature and so pretty.

As for your humidifier i run mine from around week 5 when buds are stating to stack i leave it running 24/7, it does lower the humidity a little more than it should but having said that it really controls the night time HM.

 

[No Pain]

I agree . fewer plants per light , longer veg and scrog those ladies . Depending on weather or you are recirculating the air or exhausting the air you might not even need co2 to achieve your goal. Also I would look up and follow a vpd chart as close as I could .

 

[HigherTheHigh]

Yeah fewer plants works so much better, im actually growing 9 at the moments in 12L pots in a 4x4 tent, i would usually only do 4 with the same results, but i cant strecth to 6 weeks veg and only 3, i would say if you only have lets say 12 weeks to get it done i would, do the same as myself, 9 plants 3 weeks veg should get you a fairly decent sea of green if you bend and fold the main cola stems.