Potassium deficiency?

JHake

Well-Known Member
Hello RIU.

I've been dealing with these symptoms.

A little bit of context and info first:

Strains:

A)
2 sativa dominant hybrids (Moby-D and Super Lemon Haze) from BSF Seeds, a spanish "breeder". 4-5 gal pots.
Moby-D is soon to be harvested; SLH still has a weeks to go.
B)
2 unknown strains which seem to be Indica dominants. 2,5 gal pots.
They are on a early bloom stage, something like day 21 after photoperiod change compared to a indoor.

Medium and pots:

Potting soil mixed by myself: 50% peat moss, 30% perlite, 20% earth worm castings. Amended with dolomite lime (4 cups for 60 gallons of soil).
All plants are on root prunning system pots; one airpot and three made here in my country (although im sure the design was stolen from somewhere)

Nutrients and feeding regime:

Both sativas:
I fertilize with an organic nutrient line. The products lack of technical data on the labels, just a brief description. But i know the products at least are okay; i've used them a few times and a few friends also used them.
The only problem i found with these nutrients is the very low concentration or total lack of N on the bloom base, also confirmed not only by other uses experience, but a friend of mine was told by the owner of the brand to use Grow/Veg base in conjuction with the Bloom one.
Normally, nutrients are applied once a week. Maybe i just mix the base nutrient with some additives, sometimes i applied them in different waterings.
The only addition i made to the guidelines of the brand:
I add a little bit of a 25-6-15 salt, to bump the N ppm's. And i also give some Epsom salts/magnesium sulfate. Maybe Magnesium is not needed; N definitely is.

Indicas:
These ones are being fertilized mostly with salts. I own a 25-6-15 and a 16-6-27 NPK ratios. I also have chelated micros in salt/powder form. And magnesium sulfate. I also own a liquid Calcium additive, and humic acids and kelp extracts.
These plants were a little unattended. They are just there to harvest a little more and i also used them to test some things related to transplants, rooting, etc.
I've used these salts on a DWC system with good results, only needing to add Calcium to the nutrient solution.

So...where is the problem and why i make this thread?

All the plants are showing signs of what i understand as a Potassium Def (deficiency i haven't had on other crops using the same nutrients, both the salts and the organic line).
And it's not very clear for me why this could be.

With the sativas i am only concerned with the SLH, Moby-D is about to go...

1) At first i thought i needed to bump up feeding frequency due to plant size, root mass, etc. I already did that, waiting on the results.
2) I also have a little suspect about light penetration...leaves showing signs were the more "peripheral" ones, those you can cleary see the petiole coming out of the branch. They also are on the lower part of the plant. I though that maybe the plant was starting to "neglect" those lower peripheral leaves.
But today i found the signs on leaves of a bud that is exposed to sunlight.

But the indicas are clearly on another stage/phase of their lives and they have a structure where sunlight can reach the whole plant. Anyways, summer has ended here and the hours of sunlight are not as much as weeks before.

I started to think about elements both plants share, since genetics and nutrients are different:
1) Potting mix. Is the first time i use this potting mix "made" by myself. Although is a pretty straight forward mix of peat moss, perlite and ewc with dolomite lime.
2) Maybe going somewhat too heavy with Nitrogen doses: as an addition on the late flowering sativas, and as base nutrient for the little indicas. I believe an excess of N can lead to problems with Pottasium intake.

Anyway...i leave some pictures here and willing to read your answers. Sorry for the long thread but i wanted to be as detailed as possible.

Pics 1-2: leaves i was talking about; first picture are lower ones; second picture is a sunlight exposed bud
Pic 3: same plant but to show the leaves that are nearer the branches and buds
Pics 4-5: leaves on the indica plants

Thanks to everyone.
 

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JHake

Well-Known Member
White stuff is diatomeacus earth, forgot to say.
I stopped paying attention to pH a few crops ago. Tap water is about 6,9-7,2. I use water that i let sit for 24-72hs most of the times, but more than a few times i use it straight as it comes.
 

Renfro

Well-Known Member
First I want to say thank you for a very well presented post, this could easily have become a wall of text that makes for a migraine.

What is the pH of your medium sitting at? Thats the only reason I can see that potassium could be available (I assume it is) and isn't being used.

Really I am out of my comfort zone here, I just feed with bottles alone so I can instantly change a feed and I know exactly whats available.

One thing I will note is that this could actually be more of a phosphorous issue presently, perhaps potassium in the past.
 

JHake

Well-Known Member
Hello Renfro.

I don't have a soil pH tester. I know it's not wise to mix my own soil and not being able to check it's pH.
pH of peat moss is 4 and EWC and perlite i believe are around 6-7.

I was also confused if it was P or K; i leaned toward K because of the necrotic spots. I believe that P def is kind of a dark colored zone, but i may be wrong.
 

polishpollack

Well-Known Member
Too much of one thing, not enough of another. You're controlling it to death. Best to do research, find recipe for super soil. Or learn how to bottle feed properly. Nice try on your soil but it's not enough. You'll keep killing plants this way unless you make significant changes to your knowledge of how to grow. Stop spraying/coating with anything.
 

polishpollack

Well-Known Member
All that white stuff is interfering with photosynthesis. Maybe if you just spray it with water it will wash off. Yeah it looks bad.
 
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