Quality but no Quantity due to environment or strain?

[ITryToGrow]

Like the topic says:

The past year has yielded me sub par grows when it comes to quantity.

When trying to figure out what could be wrong I asked myself this:

Is it possible to get excellent quality but below average yield (way below) IF there's something wrong with the environment?

With environment I mean:

Light
Humidity
Heat
Air circulation

Info about the latest grow:

10 Sour Jack clones vegged for ~2 weeks.
Clones came off of a 2 month old mother.

Light: 600W HPS (semi-electronic ballast)

4'x4'x6.5' tent (120x120x200 cm) (secret jardin)

Ample air-circulation (2 fans) and air-extraction

Grow-method is NFT

Metrop nute regimen

They looked beautifully green all thru the entire grow

No pests or diseases

Day temps ~82F (28C)
Night temps ~68F (20C)

rH: perhaps too low during veg, around 30-40%.
Better as they grew bigger.

Result was a TOTAL of ~4 ounces (120 grams) !?


I've probably missed something, so let me know if you need to know anything else.

My initial thought was that it has to be the strain.

It goes against my common sense that I could get excellent quality with something in the environment wrong.

But what do the experts say?

 

[habeeb]

something is off

food - feeding wrong? not enough? to much and stunts? boosters? to many products? to few?
temps-there getting high, you wanna lower it, is 82 even the tops or just the tent? I'm sure the tops are getting it bad as all that radiated energy is hitting the tops
light- 600 is fine if it's a HPS, new bulb? old bulb?
veg time- did clones get enough time to root? when you flipping them? maybe more veg time?


don't worry though, as we can only learn through "mistakes" , and what fun is it when your at the top? people don't know, but we like "problems" more then we can imagine.. stick in there, start fine tuning your methods and you'll get bigger harvests each time..

 

[LJB]

Is it possible to get excellent quality but below average yield (way below) IF there's something wrong with the environment?

I tend to think so.

However, it seems that lower RH = more cannabinoids.

Chemical ecology of Cannabis

Experimental evidence is accumulating that reinforces these notions. Sharma (1975) reported a greater glandular trichome density on leaves of Cannabis growing in xeric circumstances. Paris et al. (1975a) have demonstrated a marked increase in the cannabinoid content of Cannabis pollen with decreased humidity. Murari et al. (1983) grew a range of Cannabis fiber cultivars in three climatic zones of Italy and found higher THC levels in those plants grown in the drier "continental" (versus "maritime") climate. Hakim et al. (1986) report that CBD-rich English Cannabis devoid of THC produced significant amounts of THC and less CBD, when grown in the Sudan. This trend was accentuated in their next generation of plants.

 

[cannabowl]

Could be the the selected mother was a low yielder. It seems you have things dialed in. I'm not to keep on your feeding regimen, but I'm sure someone that is will pop in. Just for comparision, I recently finished up 6 plants done organic in 2 Earthboxes in a 3 x 4 area under a 600 and yeilded 9 oz. You definatly should have yielded more than 4.


Peace,
Canna

 

[LJB]

temps-there getting high, you wanna lower it, is 82 even the tops or just the tent? I'm sure the tops are getting it bad as all that radiated energy is hitting the tops

We know that above 30c and approx. up to 35c, leaf surface temp. is higher than air temp.

And we know that 25-30c is not necessarily harmful and 30c is probably the limit for maximizing growth.

more questions for ITTG:

What kind of reflector do you use?

During flowering, what was the distance from the bulb to various parts of the canopy?

Ample air-circulation (2 fans) and air-extraction

What type of fans and what was the placement? What specifically where they aimed at? Did the fans induce a lot of movement, some, just a light flutter?

Container size?

They looked beautifully green all thru the entire grow

Even up until the very end?

 

[Lazyman]

Old bulb? Uh, not enough plants or veg time? That was what hurt my yields, I didn't have enough plants/veg time to fill my trays, so this time I of course overcompensated:

 

[ITryToGrow]

thanks habeeb for a quick response.

Food:

As far as what the plants where telling me, everything was tip top! No signs of nute-burn, just a healthy looking canopy. And the resin, OMG, hello frosty the snowman! Unfortunately I have no pics, so you'll just have to take my word for it!

Perhaps it wasn't enough tho. I did keep pH and EC in check during the entire grow and followed the nute manufacturers recommendations.


Temps:

I measure the temp in the dark above the reflector, not directly above it tho, and since heat rises the temp should be the highest where I measure it. At least the ambient (air) temp.

As far as radiant heat, I don't know - how do I measure it?

What I do have is one of the fans directed to circulate the air between the tops and the bulb/reflector.

I keep the reflector at a distance of ~20" (50cm) from the tops.

No signs of heat-stress on them either.


Light:

Bulb is not more than two grows old...
I exchange bulbs every two or three grows. I usually use Sylvania GroLux.


Veg time:

Nice little root-ball on them before I put them in the tent. I have a special clone "station".

Someone told me that some strains aren't suited for cloning, could this be the case?

Sour Jack is a cross of Sour Diesel and Jack Herer.


Yeah, I totally agree! BUT, for that to work I have to first figure out WHAT went wrong!

And I've had more than a few 11-14 ounce grows in worse setups than my current one.

HOWEVER, that was from seed. 2 weeks of veg tho.

 

[ITryToGrow]

I tend to think so.

However, it seems that lower RH = more cannabinoids.

Chemical ecology of Cannabis

Great info!

But could the low RH be such a big benefactor to the sub par yield?

 

[ITryToGrow]

Could be the the selected mother was a low yielder. It seems you have things dialed in.

Yes, that was something I was thinking of aswell. Especially since the method I used for selecting a proper mother was heavily flawed.

And perhaps the age of the mother was a factor?

 

[ITryToGrow]

Old bulb? Uh, not enough plants or veg time?

Bulb, see my post below. Don't really know the definition of new vs. old bulb.

Well, as far as canopy, it DID NOT cover the entire 4x4 area. Maybe 70-80%.

Veg time could very possibly be a factor.

New to the cloning, 2-3 weeks was always more than enough when I grew from seeds.

 

[LJB]

Temps:

I measure the temp in the dark above the reflector, not directly above it tho, and since heat rises the temp should be the highest where I measure it. At least the ambient (air) temp.

Most important to know the leaf surface temps, but scientists use crazy sensors for that. I like to use a digital thermometer with a sensor wire and lay that sucker right on top of a leaf to get as close as possible. And than add a little bit, because it's not perfect and we know (see my previous post) that the true leaf surface temp is higher than the air temp. Leaf surface temp is going affect rates of photosynthesis and transpiration.

I keep the reflector at a distance of ~20" (50cm) from the tops.

No signs of heat-stress on them either.

I would argue that the bulb was too far away and that you should get that 600w as close you can without causing photon and/or heat stress. You can probably cut that in half to 10" or even slightly less with proper ventilation. Photon and/or heat stress is going to be visible immediately in the form of bleaching and the leafs curling up.

 

[ITryToGrow]

What kind of reflector do you use?

Ecotechnics Diamond reflector.

During flowering, what was the distance from the bulb to various parts of the canopy?

See my post below. That was the minimum distance. Canopy was evenly distributed both height-wise and width-wise.

What type of fans and what was the placement? What specifically where they aimed at? Did the fans induce a lot of movement, some, just a light flutter?

Circulating 10" (25cm) fans (2 speeds). One hung and blew air between the reflector and the tops. Highest speed-setting. Not oscillating.

The other was on the "floor" blowing upwards on the grow. Lowest speed-setting. Oscillating.

Container size?

Hydrogarden DualFlow system.
Table is 19" (48 cm) by 39" (100cm).

Even up until the very end?

No, at then end they turned into what I like to call "fall-colors".

Thanks for all the input!

I think I love y'all!

 

[LJB]

Great info!

But could the low RH be such a big benefactor to the sub par yield?

I think so, but only if you weren't feeding them enough to keep up with their increased needs due to the low RH and it doesn't sound like you had problems with chronic underwatering or feeding.

 

[Lazyman]

If you're changing your bulb ever 2-3 grows you're fine, and if the quality was good it's just not enough plants or too short a veg time. Make sure that if any light is hitting the floor, that you put a plant there next time. Even if it's not under direct light they will still yield something.

 

[LJB]

Bulb, see my post below. Don't really know the definition of new vs. old bulb.

Well, as far as canopy, it DID NOT cover the entire 4x4 area. Maybe 70-80%.

How many hours has the bulb been turned on for in it's lifetime?

I think you tried to cover a little too much space. Your ventilation system sounds good. Reason I asked that question is that too much wind blowing on the plants can slow them down.

In my experience and based on a growing, but still limited knowledge base, a 4' x 4' area with a 600w bulb at 20" from the middle of the canopy (and more from the sides) is going to be detrimental to efficiency and yield.

 

[ITryToGrow]

Most important to know the leaf surface temps, but scientists use crazy sensors for that. I like to use a digital thermometer with a sensor wire and lay that sucker right on top of a leaf to get as close as possible. And than add a little bit, because it's not perfect and we know (see my previous post) that the true leaf surface temp is higher than the air temp. Leaf surface temp is going affect rates of photosynthesis and transpiration.

I can get a hand on of these.

Could I use that to somewhat accurately measure surface temps?

 

[cyberwax]

How large is your grow space? Key factor

 

[LJB]

I can get a hand on of these.

Could I use that to somewhat accurately measure surface temps?

That looks $$$$$ and not necessary.

Some might say that with more experience you won't need meters unless they're hooked up to an automated ventilation system. After a while you will get a feel for inside temps and RH % and the big changes.

However it helps to have one of these:

I'll sit the "outside" wire on top of leaves to get the closest area temperature.

http://www.sunleaves.com/detail.asp?sku=SDMHT600

 

[quest]

Of all the plant

 

[DiscoBiscuit]

Keep it up, ITry. You're bound to get better with every grow. If there's anything more frustrating than having trouble dialing in a certain aspect, it's getting things perfect and not knowing what you did different to get the results you're looking for, lol.