What amendments do you add to reduce soil ph?

Discussion in 'Growing Organic Marijuana' started by Toyboy, Mar 21, 2024.

  1. What amendments do you add to reduce soil ph?
     
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  2. That's what a lot of growers have to fight. Especially in no till containers. Constant irrigation with water at an higher pH level than the optimal range will do that.
    (Hope you're not asking because too much lime was added to your mix)
    Don't play with Aluminium sulfate in cantainer.
     
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  3. #3 Toyboy, Mar 21, 2024
    Last edited: Mar 21, 2024
    By have to fight, you mean growers struggle to keep the soil slightly acidic. is it?
    Don't understand the irrigation part you mentioned, why add higher PH water to reduce the soil PH?

    You are not aware of any organic dry amendment/liquid that can reduce soil pH?
     
  4. Yes growers (including me) struggles to keep soil slightly acidic. Tap water is usually higher than 7, most people would still use it that's what I meant with irrigation.
    The best way to lower your soil pH is to add more peat moss. In the long run you can slightly lower soil pH with gypsum and sulphur. But relaying on these two to lower your soil of a full point or 2 would be fantasies. But if you know by your water source that you are at risk (in the long run, after reusing your soil for a few plant) to slowly raise your soil pH you can use gypsum and product like potassium sulfate as a part of your mineral content in your soil blend or top dress with them at needs and between each plant.
     
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  5. Got it. Thanks.
    Add more peatmoss, you mean top dress with peatmoss?
    Gypsum already has sulphur. Why add both?
    Of a full point or 2, you mean from pH 7 to 6 and 6 to 5?

    Heard of pine needles before?
    Pine needle humus soil is rich in organic nutrients, and the nutrients are higher than other soils.
    It is a happy soil for acid-loving plants.
     
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  6. You can't really top dress with peat moss and hope it will pour down the container into the whole soil like it would with dry amendments in powder form. Adding peat moss means you'll have to fully till it in.
    Gypsum have other properties than plain sulphur like it's calcium content. Same for Potassium sulfate. I add both for their other benefits than plain sulphur.
    Correct with the full point thing. 1 point of pH is a lot.
     
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  7. oh yeah, about pine needles. I am sure they do the job just nicely outdoors. But I learned the hard way more than once the risk of bringing elements from outside in a controlled environment with no predators. Got infested with aphids, thrips, and white flies so I would kindly advised to think twice before you bring stuff inside.
     
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  8. You can water for years with water that has a pH of 8 and it won’t raise the soil pH - so long as alkalinity of the water is below 100ppm. Gypsum does not lower soil pH. Calcium becomes a problem in soils with a high pH because most of the calcium is in carbonate form and requires acidity to break that bond which makes the calcium available to the plant. Gypsum contains calcium that is not in carbonate form which allows a plant to tolerate a higher soil pH but it doesn’t lower soil pH.

    Potassium sulfate doesn’t lower soil pH and I don’t remember the chemistry behind it. It’s easy enough to look up. At 0-0-50 it should really be used with caution since it’s easy to overdo. Oddly enough this would have been awesome for me to use on this run since I have a full blown K deficiency going on. I moved to a new area and I’m experimenting with bagged mixes I’m unfamiliar with. Hoping to dial in an easy, no frills mix for autos. Autos always give me a hard time!

    I do agree that peat moss can help lower soil pH. Iron sulfate is probably my top choice and starts working in 2-6 weeks. Elemental sulfur can take months, a little goes a long way and is best suited for outdoors or beds but it just takes so damn long.
    RD
     
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  9. I’ve mentioned this before but it’s far better to understand the quality of your water so there’s no need to be in the situation where you will have to lower soil pH. Really need to find a water report or rely completely upon collecting rainwater.

    If I remember right you are somewhere in the Middle East or North Africa? These regions are infamous for the salinity of the water supply - if so it can only be corrected by altering the water itself.
    RD
     
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  10. #10 Toyboy, Mar 22, 2024
    Last edited: Mar 22, 2024
    Noted. Will make some calls soon to see who has the report and if they will share it with me. I will know within a week if can obtain it. I drink the same filtered water I give the plants without boiling it. But I let it rest 48 hours before feeding the plant. I am in south east asia.
     
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  11. This potassium sulfate?

    Potassium Sulfate or Sulphate of Potash is an inorganic crystalline salt. In mineral form it is known as arcanite. Potassium Sulphate is a white crystal or powder, odorless, bitter tastes, and is nontoxic.
     
  12. Noted. They sell it here online. Anyway it's expensive.
     
  13. #13 Toyboy, Mar 22, 2024
    Last edited: Mar 22, 2024
    Can I add and mix gypsum 1 week later, after I have mixed everything up in the no till recipe and let it to cook?

    Amended per cuF with:

    1/2 - 1 cup Neem or Karanja
    1/2 - 1 cup Kelp
    1/2 - 1 cup Crab/Crustacean meal
    1 cup MBP (Malted Barley Powder)

    1/2 cup Gypsum (nice sulphur source)
    4-6 cups Basalt
    6-8 cups Biochar
     
  14. Yep
     
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  15. Thank you
     
  16. in addition to everything already mentioned add using food grade citric acid to your irrigation water to reduce the ph to the desired level. this is another tool for the kit bag. i reuse one gallon jugs filled with municipal water and i’ve learned to check my water before use as i found that my municipal water ph will change frequently. during late veg and most of flowering i’ll use ~1+ gpd in a 1 cf container and adjust as needed with citric acid. :confused_2:

    something to think about.
     
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  17. #17 Toyboy, Mar 24, 2024
    Last edited: Mar 24, 2024
    Are you growing fully organic? What is ~1+ gpd?
    According to RD, water ph will not effect soil ph.
    You can water for years with water that has a pH of 8 and it won’t raise the soil pH - so long as alkalinity of the water is below 100ppm.
     
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  18. I'm struggling with high alkalinity water. Using 5gal grow bags, which probably doesn't help. Anyhow, doing research on formulating a mix that will help to compensate for my conditions and still provide all the essentials. One thing that I've come across is the potential for both biochar and basalt affecting soil pH in an upward direction. If anybody has direct experience with these as it relates here, that would be useful. The rock dust I have been using has been referred to as 'alkali olivine basalt' in USGS survey documents covering the area that I collect it from. It consists if fine volcanic cinders and ash (1/8" to powder consistency) and contains a good array of the minerals/trace elements we look for in a rock dust, but as the name suggests is quite basic (vs. acid) by nature. I can provide supplemental info if anybody's interested. So, if addition to this material is heaping insult on top of injury, what might be a better more neutral option? Also, the amount listed in the no till recipe seems a little excessive (4-6 cups per ft^3?). Anyhow, I'm eventually going to start a thread to try and address these and other issues, but it would be nice if I can piggyback here for the time being. So far, every mix I have made has gone high pH/alkaline faster than convenient and would be great to get the problem solved once and for all. Thanks!
     
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  19. #19 puffnstuff1960, Mar 24, 2024
    Last edited: Mar 24, 2024
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  20. #20 Toyboy, Mar 24, 2024
    Last edited: Mar 24, 2024
    I grew my plant up to week 4 flower. It was large and healthy. It was my first grow and I never checked the pH.
    My soil mix was super simple with just few fertilizers, but it went south because 5g pot was too small for organics and I over did with the fertilizers.
    Anyway, I will test pH in my next grow and will use many nutes this time.

    Ignore the 4-6 cups per cf. It has to be much less.

    This is how much rock dust I will use in next grow. You can use more.
    Dosage based on 16g/60l of soil mix (Perlite+ewc+peatmoss (4:3:3 ratio) 6.4:4.8:4.8 gallons).

    Mineral amendments:
    Azomite 1/3 cup
    Biochar 16 cups
     
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