Spots on leaves?

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bobbjoedope

Member
Garlic Jam auto. Been feeding masterblend 5gal formula (12MB, 6 Epsom, 12calnit) running sterile (pool shock).

Been feeding full strength for several weeks now. Rez changes once a week or when Rez gets down to 1ish gallons. Always keep ph 5.8-6.5 usually around 6. Ec is always less each reading. Today for example, I changed the reservoir at 11:00 a.m. *I did half strength today* and phd to 5.8. Starting EC was 1691. Checked around 6:00 p.m. tonight And pH was up at 6.5 and EC was 1630.

First thing that's coming to mind is magnesium deficiency. Maybe I should raise the epsom levels?

The leaves are dark green but I don't see any burning. Thanks!
 

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Billy the Mountain

Billy the Mountain

Well-Known Member
bobbjoedope said:
Garlic Jam auto. Been feeding masterblend 5gal formula (12MB, 6 Epsom, 12calnit) running sterile (pool shock).

Been feeding full strength for several weeks now. Rez changes once a week or when Rez gets down to 1ish gallons. Always keep ph 5.8-6.5 usually around 6. Ec is always less each reading. Today for example, I changed the reservoir at 11:00 a.m. *I did half strength today* and phd to 5.8. Starting EC was 1691. Checked around 6:00 p.m. tonight And pH was up at 6.5 and EC was 1630.

First thing that's coming to mind is magnesium deficiency. Maybe I should raise the epsom levels?

The leaves are dark green but I don't see any burning. Thanks!
Click to expand...
An Mg deficiency will look lighter green between the leaf veins, i.e. interveinal chlorosis.

Rust spots are indicative of a Ca deficiency.
 
D

Delps8

Well-Known Member
You're at EC 3.2 which is very high.

Per @Mr. Mohaskey, that could be the issue which is causing nutrient burn.

I ran my grows at 5.8 but saw a recent Bugbee video where he recommends 6.0.

[sees that VPD is 1.08]

That's a tiny bit higher than "optimal" so your plants are transpiring slightly more than at 1.0. My take is that they're just getting too many nutrients.

Have you run that high in the past?

Rising pH and dropping EC that quickly makes me think that you're in buckets or (from the pictures) totes? Is that the case?
 
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bobbjoedope

Member
Where do you get 3.2 from?

First time running full strength. I figured because I wasn't seeing any nute burn and that the ec kept dropping that it was still hungry and wanted more.

I am growing in 16 gallon totes using 5 gallon mixtures. I ph to 5.8 and let it rise. The next day it's like 6.3 and I then ph daily to 6.0. she's on an every 3 day res change now. I let it go down to about 2 gallons.

I grown in an unfinished basement. The only thing I can control (somewhat) is the humidity.
 
Mr. Mohaskey

Mr. Mohaskey

Well-Known Member
Your VPD is in range, but I would shoot for higher Temps in the low 80s if using a LED. Then adjust your humidity to get your VPD where you want it.
 
Mr. Mohaskey

Mr. Mohaskey

Well-Known Member
bobbjoedope said:
Where do you get 3.2 from?

First time running full strength. I figured because I wasn't seeing any nute burn and that the ec kept dropping that it was still hungry and wanted more.

I am growing in 16 gallon totes using 5 gallon mixtures. I ph to 5.8 and let it rise. The next day it's like 6.3 and I then ph daily to 6.0. she's on an every 3 day res change now. I let it go down to about 2 gallons.

I grown in an unfinished basement. The only thing I can control (somewhat) is the humidity.
Click to expand...
I too grow in a basement. Had to invest in oil filled heater, dehumidifier for summer, and humidifier for winter to help dial everything in.
 
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bobbjoedope

Member
Mr. Mohaskey said:
I too grow in a basement. Had to invest in oil filled heater, dehumidifier for summer, and humidifier for winter to help dial everything in.
Click to expand...
I'm not quite sure those VPD numbers are accurate anyway since I am not measuring leaf temperature.

I looked into ways to climate control the basement but it just seems impractical. It's about 1800 square feet. Any type of conditioning that I create inside the two tents is just going to get sucked out by the exhaust fan. Essentially everything will be running Non-Stop trying to condition the entire basement space. This is how I see it anyway. The final product ends up being satisfactory anyway.

This is my second dwc grow. The first one was vidamints by 2020 Mendocino and that I ran half strength the entire time. The only time I had spotting was when I wasn't changing the Rez and just topped off for a few weeks.. that grow was in 5 gallon buckets with 3 gal mixtures.

This grow currently was started with the same 5 gallon bucket (3 gal mix) but I switched to this larger tote with the front flap (5 gal mix) 2 weeks ago, pretty much when these problems started. As I'm typing this I'm wondering if it's a coincidence or not.
 
Billy the Mountain

Billy the Mountain

Well-Known Member
bobbjoedope said:
I'm not quite sure those VPD numbers are accurate anyway since I am not measuring leaf temperature.
Click to expand...
A healthy transpiring leaf will be ~ 3-5 °F below ambient temp under LED lighting. That's from actual measurements and not speculation.
Use that value for calculating your VPD. Lower VPD for seedlings and veg, higher VPD during flowering is the general rule.

For the curious, using the simplified Tentens formula for VPD:

vpsat = .61078 * 10**((7.5*leaftemp)/(237.3+leaftemp))
vpair = .61078 * 10**((7.5*airtemp)/(237.3+airtemp)) * (humidity/100)
vpd = vpsat - vpair
 
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bobbjoedope

Member
I'd be into VPD but since I'm not able to control the temperature it seems futile so I don't bother. I can adjust my dehumidifier (in the open basement) in the summer by 5ish % (or else it runs 24/7) and I can manipulate the tent/exhaust fans for another 5% humidity but that's it. In the winter I raise the plants all the way up toward the lights and lower them as they grow.
 
Mr. Mohaskey

Mr. Mohaskey

Well-Known Member
Do you have a tent? Keep heater in tent along with humidifier and dehumidifier. Run both at preset levels the do not counteract each other or based on relative humidity levels of time of year. Run heater and exhaust fan through a temp controller. Wallah, you have a controlled environment in a tent without controlling the whole basement.
 
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bobbjoedope

Member
Mr. Mohaskey said:
Do you have a tent? Keep heater in tent along with humidifier and dehumidifier. Run both at preset levels the do not counteract each other or based on relative humidity levels of time of year. Run heater and exhaust fan through a temp controller. Wallah, you have a controlled environment in a tent without controlling the whole basement.
Click to expand...
But what happens when my exhaust fan blows out the conditioned air into the basement? And it's going to pull in the unconditioned air....
 
Mr. Mohaskey

Mr. Mohaskey

Well-Known Member
bobbjoedope said:
But what happens when my exhaust fan blows out the conditioned air into the basement? And it's going to pull in the unconditioned air....
Click to expand...
Your fan shuts off more than it is on, and the environment inside the tent stabilizes. The exhaust acts as a cooling function and only turns on when Temps get too hot. The rest of the basement acts as a lung room, and should be kept cooler than the tent.
 
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