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Thread: HELP... Yellow Leaf Edges! Potassium deficiency?

  1. #1
    steeltownstoner's Avatar
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    Exclamation HELP... Yellow Leaf Edges! Potassium deficiency?

    So i noticed the first signs of DRAMATIC leaf colour change yesterday on two of my Mystery Seed/Juicy G plants. My inital reaction was that the 42w CFL bulbs i am using are too close to the plants and burning the leaves, but this discolouration effect only happened on 2 of my 8 plants and of those two only one or two lower leaves were affected.

    To compensate i raised the lights another 4" from the plants, but when i returned today the yellowing edges have carried to another set of lower leaves on the same plant! I would usually reference my grow guide, but its currently on loan to a friend.

    If this were a potassium deficiency over fert burn wouldn't all of my plants be showing signs of this? I have 4 Jack Herer plants that have not shown any signs of discolouration...

    What could be causing this? Any remedy suggestions?

    In the meantime... i'll be reading endless threads till i find out...

    Thanks.

    http://i494.photobucket.com/albums/r...r/IMG00608.jpg

    http://i494.photobucket.com/albums/r...r/IMG00610.jpg

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    You're going to need to fill-out the Troubleshooting Form at the top of the Plant Problems section. Copy and paste the form, and give all the answers asked for, if they apply. Pictures would help, too.

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    Pics showing the whole plant, and its pot, less blurry, in better light.
    Looks so far like overfert but you gotta give some info. That's not a straight K def.

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    Exclamation HELP... Yellow Leaf Edges! Potassium deficiency?

    So i noticed the first signs of DRAMATIC leaf colour change yesterday on two of my Mystery Seed/Juicy G plants. My inital reaction was that the 42w CFL bulbs i am using are too close to the plants and burning the leaves, but this discolouration effect only happened on 2 of my 8 plants and of those two only one or two lower leaves were affected.

    To compensate i raised the lights another 4" from the plants, but when i returned today the yellowing edges have carried to another set of lower leaves on the same plant! I would usually reference my grow guide, but its currently on loan to a friend.

    If this were a potassium deficiency over fert burn wouldn't all of my plants be showing signs of this? I have 4 Jack Herer plants that have not shown any signs of discolouration...

    What could be causing this? Any remedy suggestions?

    In the meantime... i'll be reading endless threads till i find out...

    Thanks.


    http://i494.photobucket.com/albums/r...r/IMG00610.jpg

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    One thread per topic please. Merged. Not K def.

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    Post Plant Problem Form

    Hey Stinky/ Rusty,

    Yeah, sorry about the carry over from my log, figured it might help if anyone was following my progress there.


    H=Answer if you grow hydro or aero
    C=Answer if you grow coco
    S=Answer if you grow traditional soil
    L=Answer if you grow soilless other than coco (Promix, Hyponex, SunshineMix)
    R=Answer if you grow in RockWool
    T=Answer if you grow in HydroTon
    D=Answer if you run any type of automatic drip system, including into soil or soilless
    E= EVERYONE needs to answer lol!


    E-indoor
    E-hydroponic
    E- rockwool cubes, 4"
    CSL- Fibrgro
    HCL-Ebb & Flow table
    SCL- N/A
    SCLR- 6.5 pH
    E- Tap water in black rubbermaid res
    E-7 to 8 pH
    HRT-Source water EC (if hydro) (??? - not sure what this means)
    E- 25 days in veg
    E-Dutch Nutrient Formula Grow A + B (seperate bottles)
    E- 1 mL each A & B to approx. 20 L of res water ( 20 mL total of each)
    E-4 x 42w CFL bulbs (2 x 5600k, 2 x 4100k), distance from plant 4-6"
    E- 88 F during light cycle, 68.5F during night
    HD-Room Temperature (approx 71.6f)
    E-70% RH
    E-18/6
    E-Pillar fan suspended from roof of frame, loose cover opening in rear to allow for air intake without daylight coming in
    TR- Yes, all cubes were presoaked in pH balanced water before sowing seeds

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    steeltownstoner's Avatar
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    opps, think i filled out more than i was suppose to. Definitely need to learn to read instructions next time...

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    Sorry, I'm not a hydro guy.

    Just a guess...but possibly too high ph, and slight overnute...?
    What's your nutrient schedule?
    Temp swing is marginal. If possible, keep within about 15 degrees f. high/low. The wider the swing, the more it can stress the ladies.
    Do you use any other additives, sprays, goops or gels? (micronutes, CalMag Plus, Liquid Light...)

    Again, I'm a soil guy, but answering these may help others to help you.

    Good luck.

    Edit:
    I just saw your pix...and nothing looks at all drastic. Matter of fact...they look pretty good so far.
    Last edited by Rusty Trichome; Nov-07-2008 at 14:04.

  10. #10
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    pH way too high. EC unknown- you need to read the chemistry link in my sig a couple times through. It says 'soil chem' but relates to water chem.
    Correct pH for hydro is centered at about 5.8-6.0

  11. #11
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    thanks stinky.... cleaning my res and going to try to rebalance the pH... will let you know how it goes

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    Update

    So, i flushed each plant individually with approximately 1L of pH balanced water earlier today. Since i was out the rest of the day, i set my res timer for my ebb & flow table to run once in the afternoon (figured i should kept the babies well watered, but did not add feeding solution).

    Upon returning I noticed that my once drooping leaves were now angled upwards towards the lights (definitely a good sign of returning vigour, right?) and so rebalanced my res pH to 6, adding my feeding solution at 75% (didn't want to shock them bring it back full strength right away). I will closely monitor their progress over the next few days and flush again as necessary.

    This is probably a noob question, but how often should i flush my plants? Do i do this on a regular basis (ie. with every change of my res water = once a week) or should I only be concerned with doing it when noticing major plant problems and before harvesting my bud?

    In an added note... my run-off is running a pH of 7.5, which seems way too alkaline to me. I can't say i've measured it in the past so i have nothing to compare too. I know that rockwool has a tendency to make water more basic as opposed to acidic, and considering my run-off drains back to my res i know i may very likely run into the same problems i've just had.

    Now to the question: Should i risk running my res water a little higher on the acidic side (5.5 or more acidic) in the hopes that my run-off will balance somewhere in the range i want it to be (5.8-6 pH) ?

    OR

    Am i just detecting the remnants of the Neutral pH solution i flushed with earlier today?

    I've been getting conflicting info from different threads i've read, so a little reassurance is greatly appreciated as i get ready to prep for cloning at the end of this week. Thanks again for all your help!

  13. #13
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    If your runoff is still high, you can hand-water the slab with pH 5.5 until you get it down around 6, and then preferably change your res. IF you don't want to do this, just drop your res pH to ~5.6-5.8 and you may notice it rising gradually back up. Continue to adjust it to slightly lower than your target until the drift stops.

    You don't need to flush unless there is a problem. But change the res every 1-2 weeks to prevent nutrient imbalances.

    Next time, pre-treat your RW by soaking it down to pH 6 and then shaking out excess water before introducing plants. And when you stack some paper, grab yourself an EC meter. These things are REALLY useful to hydro growers. You may not NEED one sicne you are good about res changes, but when the time comes that you want to dial-in a strain perfectly, an EC meter and a log book are your 2 best friends!

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