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Is This A Potassium Deficiency?


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The pH turned out to be pretty low, initial runoff around 5.8 or so. That's been a constant battle the last few weeks, but as the pH situation improved the leaves started yellowing like that. Wasn't sure if it was normal or not, as they ARE at about the 20th day of flowering (all of my plants have lost a fair number of fan leaves, with more getting lime green or yellow and dropping.

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I would totally cut out the nitrogen. Your plants don't need it at that stage anyway.

Cannabis needs at the very least small amounts of Nitrogen almost all the way through flowering (until you start your flush). Your plant will stop up-taking Nitrogen when they are no longer genetically able to and start to yellow. If you stop giving Nitrogen during flowering your yield will suffer badly. Nitrogen fuels new growth. Too much is not a good thing either as your flower cycle will last longer than you expect, or your end results will be very harsh if harvested at the regular time unless cured for a long time. Too many times I see a plant yellowing too soon. More often than not, on 8-10 week strains the plant shouldn't be starting yellow unless you are a minimum 5 weeks into the cycle, and it will start from the bottom up with the complete leaf yellowing, veins and all.

To be honest, a runoff PH of 5.8 is not that bad and shouldn't cause a lockout (could be better though, you're on the border and should probably give a good flush).

A picture showing more of the plant would help.

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Guest Happy Guy

I have run into a some growers using the guano type fertilizer and having it build up in veg and causing lock out after a few weeks of flower. Those leaves look burnt and locked out to me. But, of course, it's just a guess. When I guess I go with less until things straighten out. Most nute manufacturers advise to cut way back on nitrogen in flower.

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I have run into a some growers using the guano type fertilizer and having it build up in veg and causing lock out after a few weeks of flower. Those leaves look burnt and locked out to me. But, of course, it's just a guess. When I guess I go with less until things straighten out. Most nute manufacturers advise to cut way back on nitrogen in flower.

Never use the same soil you used in veg. Always transplant your girls into fresh soil before flowering and you won't have to deal with those issues and there will be sufficient Nitrogen for your cycle.

You may be correct as there is a slight burning happening, but that also tells me they are not locked out and getting too much of something, possibly Nitrogen like you said but it could be any of the nutrients. Either way flushing is the starting point. A picture of the whole plant will help too.

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I've been giving that plant very low ppms for a while, trying to bring them up. I didn't have a ppm meter and had no idea I was feeding so little. The last feeding, yesterday, I brought it up to 666 ppm (I didn't round that, LOL)... 5ml of a 3-1-2 formula, 5ml of a 2-2-3 formula, 2ml calmag, 5ml of some 0-0-3... pH balanced to around 7, I think... hopefully that does some good.

 

Temperatures in the tent have hovered around 80, though usually lower (mid to high 70s). It may be warmer at the tops, but the leaves I posted pictures of were near the bottom of the plant. The very very tops, the leaves coming out of the buds, are a good deep green, but the ones immediately below are lime green. I'll get some more pictures soon, thanks for the help.

 

I didn't repot - they're in 3 gallon smartpots right now.

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