Nutrient burn during 5th week of flowering

[shortnweak]

Hi guys, I am a long time lurker, post time poster and first time grower.

 

Indoor/Outdoor: Indoor (4x2x6 tent)
Growing Medium: Osmocote seedling mix with 30% perlite
Growing Style: LST + topping + trellis
Watering/Feeding Frequency: 3L once a day
Nutrient Strength (PPM/EC): varies aiming for 800ppm
PH Levels: aiming for 6.5, was using Sydney tap @ 7-8ph
Temperature/Humidity Levels: 25-31c  / 50-60RH (Sydney summer)
Air Flow/Fans etc.: 3 x 5” fans, 8” exhaust fan
Lighting Type (CFL/HPS/MH etc.): 240w LED HLG 3000K
Total Wattage: 240w
Growth Stage: 7 weeks veg, 5^th week of flowering
Plants Age: 12 weeks
Cannabis Strain:Sativa

 

Wanting any advice, I was making a tea for the plant based on fertilizers + molasses. I started using the TDS meter and realised in was way too hot. I hate to say run off was measured at 5000ppm. I noticed this 9 days ago. Roots are everywhere, probably needs a larger pot. Sometimes I didn't have runoff or if I did, the pot would sit in the water.

 

I flushed maybe 30L for a 14L pot. PPM in (tap water) is 150, and the lowest PPM out was 200. Growing in soil and perlite. 1st grow

.

The photo maybe doesn't show it that good, but maybe 30% of the leaves are yellowing with dark spots, the edges of the leaves are burnt.

Flowering looks good, a few brown pistols emerging now. Try to feed <800 PPM at 6.5ph. Last feed was 400 PPM in and 540 PPM out.

 

How should I proceed? I was thinking off cutting off the yellowing / rusty / dying leaves and going easy on the nutes with just potassium/calcium/magnesium.

 

Is it too late to repot into a 25L container? It would be hard / awkward to move with the screen there.

 

Guy I got the seed off thought I have 4 weeks of flowering left.

[Porky 1982]

What’s the air movement in your tent like?

The tips of the plants look burnt from over feeding but the plants look very pale which is usually a sign of low N.

 

 

 

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[shortnweak]

Hi mate, air movement is very good, I have 2x5" fans on either side above the canopy, and one 5" fan underneath the plant.

 

On the 30/1/20, a few days ago, all the leaves were healthy and green. After flowering I was given them powerfeed green but in lower amounts compared to vegging stage.

 

What’s the air movement in your tent like?
The tips of the plants look burnt from over feeding but the plants look very pale which is usually a sign of low N.



Sent from my iPhone using OZ Stoners

 

[Porky 1982]

Hi mate, air movement is very good, I have 2x5" fans on either side above the canopy, and one 5" fan underneath the plant.

 

On the 30/1/20, a few days ago, all the leaves were healthy and green. After flowering I was given them powerfeed green but in lower amounts compared to vegging stage.

To me the spots on the leaves look like rust mould spots from the pics

Have you pulled of any of the effected leaves and looked underneath them for any signs of bugs.

As for the burn on the tips it looks like burn from over feeding but the colour of the rest of the plant makes it look hungry. Maybe that’s just the lights making them look pale.

 

How often do you water them with plain water??

 

 

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[Porky 1982]

When you look at your plants are all the leaves moving from the fans or are there dead spots where the leaves never move??

 

 

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[shortnweak]

Hi mate, yes I have pulled the dying leaves aleady. There are no bugs on the leaves, I am sure of this.

 

Maybe the lights make them look a bit pale, however the leaves are yellowing  / dying (about 30% of them).

 

Until about 10 days ago, I would rarely do plain water. Now, since the really high TDS meter reading, i have been flushing for 2 days, then I added nutrients again (no nitrogen) and am getting a higher PPM out then in reading.

 

This is what I am getting

 

PPM in PPM out 1000 360 - 24 hours later measued 1200 1278 1200 600 1000 250 220 400       700 800 400 540

 

To me the spots on the leaves look like rust mould spots from the pics
Have you pulled of any of the effected leaves and looked underneath them for any signs of bugs.
As for the burn on the tips it looks like burn from over feeding but the colour of the rest of the plant makes it look hungry. Maybe that’s just the lights making them look pale.

How often do you water them with plain water??


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[shortnweak]

There are a few dead spots as the fans are not oscillating, however I wasn't having this problem during vegging.

 

When you look at your plants are all the leaves moving from the fans or are there dead spots where the leaves never move??


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[Old fox]

I don't think a TDS meter provides an accurate PPM measure for runoff in a soil medium. I think the soil particles can give an inaccurate PPM runoff reading. Not sure if an EC measurement for runoff is accurate in soil ?? Can anyone confirm ?

 

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[Porky 1982]

There are a few dead spots as the fans are not oscillating, however I wasn't having this problem during vegging.

Ya need all the air moving in flower.

Veg it does not matter.

Are the spots on the leaves mainly where the air is not moving as much??

 

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[Porky 1982]

You say at the top its in seedling mix and perlite. Seedling mix has very few nutes in it and perlite has none.

If the plant is yellowing from the bottom up its usually a sign of it being hungry. As the plant goes into flower it wants far less nitrogen and more phosphorous and potassium.

 

 

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