Potassium Deficiency?

Discussion in 'Marijuana Plant Problems' started by algebraist, Mar 13, 2017.


    BuD_DizZLe Member

    If its one of the pen looking ones and was a cheapie, chances are its shiet lol :X and if it came from china might need to grab 3-4 of em before u get one thats somewhat accurate!

    https://www.amazon.co.uk/gp/product/B001EHAZGW/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 this is the one I got and have hooked up to my DWC buckets, not sure it will suit your setup but might do and imo is better than all the other cheap ones.

    EDIT: Those weird plug looking things on the end are separate in a little pack, when removed they expose a probe, thats how I use it anyways.

    OldMedUser Well-Known Member

    It's more the carbonates and alkalinity you want to look at. Do they list their ppm? Town water here is around 400ppm so really crappy for plants, coffee makers and tastes like crap to boot. Really high in iron and sodium as well. At least they stopped using fluoride about 6 years ago tho we have only drank or used RO water ever since we moved here in 2001.

    I hear you on the costs. I've been scrounging and making my own grow room equipment since we got here. I recently blew almost 2G on goodies and could easily blow another grand. Finally got the light mover I've wanted and a trimmer to help with the harvest and that was $600 for both. Just setting up to grow my first larger crop and looking at 2lbs at least. In the meantime will be building an addition to my grow room to give me another 8x4' grow space for flowering.

    Once you start smoking lots of your own buds you'll make that money back and lots more. I haven't run low on smoke for 20 years and always have at least 6 different strains to sample along with kief, hash and lots of cocobudder. Getting into hi-CBD strains as they seem to work so much better for my arthritis than the sativa dominants I usually do.

    I found a great spot to download FREE POT BOOKS. I downloaded a grow bible first and got lots more. Books look great and complete like the real ones I have here. No web site but just a page of links. Just right click on what you want and then "Save Link As" to download so they don't open first as some are 50+ megs. They got lots. Enjoy.

    BuD_DizZLe likes this.

    algebraist Active Member

    Yup, got a cheapo. Probably better than nothing; we'll see...

    @OldMedUser -- They don't list the ppm; will check that myself this weekend (okay, with questionable accuracy) and will report back.

    Thanks for the great list of books -- that ought to keep me busy for a decade or so...
    OldMedUser likes this.

    OldMedUser Well-Known Member

    Most ppm pens work fine when new. Much easier to deal with than pH pens and a lot cheaper. You should get some calibration sol'n for both and some storage sol'n for your pH pen to keep it properly hydrated.

    I have a 20 year old Hanna ppm pen and it has never drifted off more than 50ppm. I bought a cheap one that reads in single digits for checking my colloidal silver while it's cooking. A TDS EZ by HM Digital that I calibrate with 20ppm I make by diluting 1000ppm calibration sol'n. I've gone thru 5 or 6 pH pens in the last 20 years.

    It was great to stumble on that cache of books. I have a few hard copies of ones on that list but it never hurts to have more. :)

    Dr. Who

    Dr. Who Well-Known Member

    This is what I see.....

    #1: It's not your water. (sorry OMU)
    DO NOT "flush" to lower "salts"! This fucks with pH.

    The real problem is the lack of Ca and Mg in the FFOF in proper amounts for one thing...and low N.

    When using FFOF - mix a good heaping 1/2 cup of Dolomite lime into the whole bag of soil. Mix well. For years and years FFOF has been light on Ca and Mg over the long run. Sometimes it runs short fast....Sometimes later.

    Now in your case. Here we are going for plant Available Ca and Mg over a better buffering Ca. I also see you should have a higher N - The Botanicare bloom at 1-4-5 is way to low in N.....
    So, to help there....Lets look for a Calcium Nitrate based Ca and add some N back while fixing the other issue.

    Botanicare Cal-Mag plus is 2-0-0 and that should put your N level up to acceptable levels. USE that.

    The tap's pH is basically good - You'll add the Ca/Mg and the pH of your feed solution will drop again...

    So then, final solution is to kill 2 birds with 1 stone. Add the Cal-Mag plus and that should stop the problem for you. It'll pick up the N to better feeding levels and your leaves will green up some more a bit. You and your plants will be happy..

    Good Luck!

    PS - just to note. It's been a "rule of thumb" to go to RO (you have to use a Ca/Mg with RO) if your base water ppm's are over 150 ppm....There are many who don't but, you'll see all sorts of improvement, including yields - if you do.
    I would use a Cal - Carbonate based Ca/Mg with RO (for the better buffering qualities).....G&H CAli MAGic is good for that...(always in any hydro)....If the soil is properly built - you may not need to..

    I build my own soils and amend properly for Ca. I never use a Ca/Mg with them. I use RO too....
    travisw and coreywebster like this.

    algebraist Active Member

    Thank you, last of the time lords. I will get some Cal Mag Plus this afternoon.

    One thing that keeps bothering me: Two plants, only one showing this problem. I've been saying they were both treated the same, but there is one small incident to describe that I used to think was not worth mentioning; now I'm not so sure.

    The first day (out of twice) that I applied FF Big Bloom (which was March 6th, one week before I noticed the first signs of trouble), I shook the bottle, did a little something (20 or 30 seconds?), then measured out the quarter cup, mixed it into the gallon of water, and watered the plant (the one that is now having trouble). Then I did the same for her sister, except that I shook it and immediately measured out the 1/4 cup. Big difference! It seems Big Bloom settles out very quickly. So I've been reasoning that I just gave the first plant a little less nutrients, and maybe that's what's going on -- that one fewer feeding made the difference. But maybe when it settles the stuff that floats to the top has a higher concentration of something soluble -- no idea what... And maybe instead of just getting a little less P and K, that plant got more of something that did some damage.

    Anyway, if anyone has any thoughts on that, I'd be happy to hear them. In the meantime, I'm headed to the hydro store, and thank you all for your help.

    algebraist Active Member

    Tested my tap water this weekend: 396 ppm. Ugh. Guess there is an RO filter in my future; going to have to get these through without it.

    algebraist Active Member

    Although it is not included in my town's water report, I just found a note on the town's water department website that says the concentration of calcium carbonate is 5.5 grains per gallon. This equates to 94 ppm, which is "moderately hard" according to the "Cannabis Encyclopedia" (Jorge Cervantes).

    So my latest theory is that I have an excess of calcium (not helped by my recent Cal-Mag application -- oh well) which is inhibiting the uptake of potassium. I also definitely have a nitrogen deficiency going on as well. I guess I'll be buying a few jugs of distilled water in the short term.

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