PH issues - Need Experienced Grower's Help!

Discussion in 'Growing Marijuana Indoors' started by 420forPrez, Sep 7, 2010.

  1. Hope someone can help me. I've always took my grow through with FoxFarm Oceanic soil, which is a neutral soil @ 7.0. I use FoxFarms BigGrow while vegging, and I am starting my 6th week of veg this week. I've been topping and supercropping the plants for the last 3 weeks, so they aren't tall, but they have a lot of growth on them, so I'm pleased with progress.

    However, on this grow, I'd really like to have the PH between 5.5 - 6.0 during flowering because I am vegging these plants longer than usual since I have a taller grow space now :). I'm concerned that with the extra time added that the soil will need to be leeched from salt buildup during flowering, and I don't want that to happen. I am going to be vegging another 2 - 3 weeks while I add a ScrOG to it. The suggestions of local gardeners have not helped, and I've resorted to using Iron & Soil Acidifier, which I've only added once between my last two waterings. My nutrient solution is at 5.5 when I water.

    A few questions:

    The instructions on the Sulfer say to dilute 1 teaspoon per quart of water and apply 1 cup of mixture for trees with 1 to 5-inch trunk diameter.

    1. Can I add the sulfur to my nutrient solution when I water, or do I water my plants with the nutes and then add the cup of sulfer? Should the sulfer be applied on a different day than I am fertilizing?

    2. How often do I need to add the sulfer to the soil (I water every 3-4 days) and how long should it take to see a drop in the PH?

    3. Are there any questions I'm not asking that you would think I need to know about?

    Thanks for everyone's help in advance!
  2. You can totally have a ph of up to (and should be) near 7.0 in your soil without much effect. You shouldn't need to adjust the ph so early into using good soil. If anything, add hydrated or dolomite lime to keep the ph hovering around 7. If anyone disagrees speak up.

    Are there any specific problems you are having where its making you think you need to adjust ph? I thought I had ph problems for the longest time, and it turned out to be micro nutrients and not so good water. Have you been testing with a soil ph meter directly into the soil? Many people tend to think they have ph problems but its just a misdiagnosis.

    Also, with your water ph being so acidic, you're going to want to flush once a month with a flushing solution to get rid of those excess salts and help drive the ph back up.

  3. For soil, you want your pH 6.5-6.8.

    5.5-6.0 in soil will give you all kinds of lockout, so I would do a bit more research on soil pH before you screw up your grow.

  4. I can keep the PH at 7.0 throughout - I've done it before with this setup. If it won't yield any noticeable benefits to get it closer to 6.5, then I won't mess with it.

    I can change the PH of my water and bring it up closer to 6.5. And yes I have a digital soil tester that I use periodically, especially a day or two after feedings. I've only give then plants the sulfur mixture once, and it was a week ago. No change in the soil PH yet...I'm guessing it takes a few weeks of regular treatments.

    Ok. I'll leave it alone. Just trying to perfect another part of the process and avoid any pitfalls that could potentially occur. The plants are healthy and doing well :smoking:
  5. You want your pH lower "because I am vegging these plants longer than usual."

    I don't understand the logic there...

    I completely, 100%, suggest against adding sulfur to your mix. Sulfates can be -2 or -3, and they lock up your positively charged cations. By adding the electrical charge of sulfates to the present ions in the soil you cause two notable chemical reactions. Firstly, Calcium, Magnesium, and Potassium become in short supply as they are now locked up as Calcium Sufate, Magnesium Sulfate, and some kind of Tripotassium Sulfite. These are salts and they will need to be leached. In addition, if you took high school biology you know enough about osmosis to understand this part. The roots establish electrical equilibrium with the media. As the plant uses elements an electrical "shortage" in the plant, and abundance of that element in the soil, allows the plant to draw that element in to the cell walls of the roots via osmosis. This process can be reversed though. If the media is abundant with the wrong kind of elements (toxicity) then the plant will be forced to lose the opposing elements to establish the electrical equilibrium again.

    Thus, adding sulfates which lock up positive elements from absorption will force the plant to replace the missing positive elements from itself. Further deepening any deficiency.

    If you want to drop the pH of your media use a Nitric Acid or Phosphoric Acid pH down solution designed for plants. There are many available and they sell small bottles for less than an extra value meal.
  6. Nice! This does make sense. Thanks for all of your time! Do any of you leach your soil on a regular basis to avoid problems caused by salts, or do you wait until there is a problem, and leach the soil then? Obvsiously preventative maintenance is preferred, but when should I leach the soil? I've never done this, but I feel it may be necessary since it is a longer grow than what I usually do. Thanks again!
  7. I personally leech every other watering, like you said, to avoid any future problems.
  8. sorry to butt in... but does leach=flush?
  9. yes sir it is when you flush the soil.
  10. Flight96,

    What do you use to flush the soil, if you don't mind me asking? Just curious. Treated water, tap water, flush solution?
  11. #11 Flight96, Sep 8, 2010
    Last edited by a moderator: Sep 8, 2010
    I use either Ph distilled. Or tap. And its not so much a 'flush', it's more like just a neutral water feed.
  12. I grow in coco so my method might not be the same.
    What I do is begin alternating 10% feedings with regular strength feedings after my plant has been in a planter for more than 30 days. I transplant to a 3 gallon planter around day 25, so sometime around days 55 to 60 is when that starts.

    Not every other watering. More like every 3rd or so. When I see a plant is having a problem I'll flush it with water, I don't care much for the pH just RO water, about 6 gallons water through 3 gallons of coco. Then I give it a full strength watering of my macro nutrients and some cal-mag.

    In soil, you'd need to replace food for the organics, maybe some carbohydrates and humics. I think that soil really doesn't require much in the way of flushing, just keep your pH in range with waterings and everything runs pretty smooth.
  13. Man that is really cool. What made you decide to use coco as a growing medium? Do you have any good resources to share regarding your method of growing? I'm interested!
  14. thats pretty much what i do, but with fox farm ocean forest. i dont pay too much attention to PH. i have a cheap meter in case i need it for something serious, but i usually flush with double to triple the ratio of water to soil for any problems. followed by 2 tbsp earth juice grow and the same for earth juice bloom, per gallon of tap water. i have good tap water so i don't worry much. every once and a while i'll water with molasses to give the soil a little somethin somethin. but i dont add anything but water for the first month and a half from seed, or the first 3 weeks from clone, making sure i get a decent run out the bottom of the pots.

    4 grows down and no big problems. nothing i couldn't solve with a flush and correct dosing of nutes for the issue. the weed has just been getting better and better.:)

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