Raising Soil PH

Discussion in 'Growing Marijuana Indoors' started by MnMbuds420, Jul 27, 2017.

  1. My soil PH is low right now it's about 5.7 and I'm trying to figure out the best way to raise it.. I've been feeding them with just water this week that is PH'd at 6.8.. I also bought hydrated lime but am nervous about applying it.. can anyone give me any advice on a way to raise my soil ph?
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  2. add it to a measured water sample

    so you keep a good track of the volume and quantity

    and do note the temp too

    good luck
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  3. On the bag of hydrated lime it says to add a tablespoon per gallon of water.. you think maybe I should try half of that?
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  4. I thought I read hydrated lime was a big no-no in one of Jorge Cervantes' books, but I don't have it in front of me and can't be sure. Sorry for adding zero value to this thread.
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  5. It's quicklime that he's referring to brotha

    Attached Files:

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  6. Okay so I added 3 teaspoons of hydrated lime to 3 gallons of water and fed my plants, which is less than half of the recommended usage on the bag.. I'm going to check the PH tomorrow and see how it was affected.

    I'm guessing the hydrated lime being dissolved in water works its way into the soil to provide more of a permanent solution to balancing out the soil's PH?
  7. You're awesome, thanks :)
  8. The last thing you want to use is Hydrated Lime, aka Calcium Hydroxide. I hope you haven't used it already.Hydrated lime is caustic and unless used super sparingly and mixed perfectly it can and will burn your plants. It will also burn your skin, eyes, throat.

    What you want is Calcium Carbonate - simple Ag lime, or Calcite Lime. If you can't find Calcite Lime then you can use Dolomite Lime but the Calcite Lime is the best choice.

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  9. You're absolutely correct.

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  10. Quicklime is just another name for Hydrated Lime, or at least it WAS Hydrated Lime to which water has been added.

    Hydrated Lime = Calcium Hydroxide
    Quicklime = Calcium Oxide

    For gardening purposes neither should be used. They are more industrial agents and are too caustic (strong/powerful & extremely alkaline) to be used in a soil garden.


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  11. Turns out it is actually Quicklime that I was thinking of. See above. Hydrated lime can be useful, but one needs to exercise caution when using it.
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  12. Quicklime IS Hydrated Lime - to which water has been added, and which changes the chemical composition from Ca Hydroxide to Ca Oxide - but is so similar it's not even worth separating the two. Both are just too strong to be useful in the garden IMO.

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  13. I appreciate all you're advice but this is what I took from "The National Lime Assosiation on QuickLime vs. Hydrated Lime

    Terminology & Specifications
    Q: What is lime? What are the differences between quicklime and hydrated lime, high calcium lime, and dolomitic lime?

    A: Lime is a generic term, but by strict definition it embraces only the manufactured forms of lime — quicklime and hydrated lime. It does not include limestone, which is the feedstock for lime manufacturing (click here for a short description on how lime is produced). Quicklime, the product of calcination of limestone, consists of the oxides of calcium and magnesium and, in the United States, it is available in three forms:

    • High calcium quicklime -- derived from limestone containing 0 to 5 percent magnesium carbonate.
    • Magnesian quicklime -- derived from limestone containing 5 to 35 percent magnesium carbonate.
    • Dolomitic quicklime -- derived from limestone containing 35 to 46 percent magnesium carbonate.
    Hydrated lime is a dry powder manufactured by treating quicklime with sufficient water to satisfy its chemical affinity for water, thereby converting the oxides to hydroxides. Depending upon the type of quicklime used and the hydrating conditions employed, the amount of water in chemical combination varies, as follows:

    • High calcium hydrated lime -- high calcium quicklime produces a hydrated lime containing generally 72 to 74 percent calcium oxide and 23 to 24 percent chemically combined water.
    • Dolomitic hydrated lime (normal) -- under atmospheric hydrating conditions only the calcium oxide fraction of dolomitic quicklime hydrates, producing a hydrated lime of the following chemical composition: 46 to 48 percent calcium oxide, 33 to 34 percent magnesium oxide, and 15 to 17 percent chemically combined water.
    • Dolomitic hydrated lime (pressure) -- this lime is produced from dolomitic quicklime under pressure, which results in hydrating all of the magnesium oxide as well as all of the calcium oxide, producing the following chemical composition: 40 to 42 percent calcium oxide, 29 to 30 percent magnesium oxide, and 25 to 27 percent chemically combined water.
    Q: What about physical specifications for lime?
    A: Hydrated lime is available only as a fine powder or a slurry. Normal grades of hydrated lime suitable for most chemical purposes will have 85 percent or more passing a 200-mesh sieve, while for special applications, hydrated lime may be obtained as fine as 99.5 percent passing a 325-mesh sieve. Quicklime, however, is commercially available in a number of sizes (the following definitions are derived from ASTM Standard C51):

    • Large lump lime -- a maximum of eight inches in diameter.
    • Crushed or pebble lime -- ranging from about ¼ to 2½ inches.
    • Ground lime -- ¼ inches and smaller.
    • Pulverized lime -- a typical size is substantially all passing a No. 20 sieve.
    • Pelletized lime -- one inch sized pellets or briquettes, molded from fines.
    Q: What are the differences between Type N, NA, S, & SA hydrated lime used for mortar and other building applications?
    A: A short fact sheet on hydrated lime for masonry purposes is available. Hydrated limes used in building applications are divided into four types, as described in ASTM Standard Specification C207 (Hydrated Lime for Masonry Purposes):

    • Type N – normal hydrated lime
    • Type NA – normal air-entraining hydrated lime
    • Type S – special hydrated lime
    • Type SA – special air-entraining hydrated lime
    Types S and SA are differentiated from Types N and NA principally by the unhydrated oxide content and their water retention value. Type S must meet a water retention value of 85%, while Type N hydrate lime must have a water retention value of 75%. No distinction is made based on the nature and source of limestone. The maximum air content of cement-lime mortar made with Types NA and SA is 14%; with Types N or S lime, 7%.

    Q: Is aglime the same as lime?
    A: The term agricultural lime, or "aglime," usually refers to crushed limestone. Limestone (calcium carbonate) is not the same as hydrated lime (calcium hydroxide).

    Q: Do you have a listing of the specifications for lime in various industrial uses?
    A: A complete list of standards is available at Lime Standards.

    Q: What procedures should I use to test lime?
    A: ASTM has Standard Methods for testing chemical (C25) and physical (C110) properties. These standards can be purchased directly from ASTM at www.astm.org.

    Handling & Transport
    Q: Do you have technical advice on how to design lime storage and conveyance systems? What type of lime handling equipment should I buy?
    A: NLA’s "Lime Handling, Application & Storage" publication includes information on the handling and storage of lime, equipment for application of lime, lime slaking and slurry handling, and factors affecting the selection of lime. Contact your lime supplier for more specific technical assistance and advice on equipment vendors.

    Q: Are there any handling or safety precautions that workers should follow?
    A: Please see "Fact Sheet: Lime Safety Precautions."

    Q: What regulations apply to transporting lime?
    A: Lime is generally not regulated as a hazardous chemical when transported. The one exception is airborne shipments of quicklime. A fact sheet on shipment of quicklime by air is available.

    Soil-Related & Agricultural Applications
    Q: How much lime should I use to stabilize soils?
    A: A fact sheet on soil stabilization is available under Technical Information. NLA offers several free downloads on soil stabilization with lime.

    Q: Can’t lime be used to dry up mud — for short-term soil modification to expedite construction?
    A: Yes, a fact sheet on using lime to dry up mud called “Lime Dries Up Mud” is available.

    Q: How much lime should I use on my garden?
    A: Hydrated lime can be used to raise the pH of acidic soils. This is also referred to as soil "sweetening." Hydrated lime is available from garden centers and should be applied in the amounts and using the procedures recommended on the packaging.

    Lime Suppliers
    Q: Where can I obtain lime?
    A: A list of U.S. and Canadian lime suppliers by state/province is available under Find a Lime Plant.

    Q: Where can I obtain food grade lime?
    A: W e are aware of one company that makes food grade lime: Mississippi Lime (www.mississippilime.com).

    Q: Where can I obtain lime for masonry and other building applications?
    A: Building lime can be obtained from Carmeuse, Graymont, Lhoist North America, and Mississippi Lime.

    Other Topics
    Q: How do I use lime to make whitewash?
    A: NLA has no current publications that address whitewash. Other references include:

    If you have a question concerning lime, please email us or contact us at (703) 243-5463 ext. 226.
  14. That's all fine - but I've seen people ruin crops with both. Neither are meant for the garden - my opinion of course. Straight Dolomite or Calcite (Ag) Lime is what you're looking for.

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  15. Listen to Jerry
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  16. Is that best just mixed into the soil before the plants are potted?
  17. I threw out the hydrated lime and just flushed each of my 5 gal pots with 6 gal of water PH'd 6.7-6.9 and my soil PH is up to 6.5-6.6 throughout each of my plants... I'm going to wait until they all dry out some and flush again at 6.8 until the soil is the same then start back to feeding
  18. Lime in general can take some time to break down sufficiently to actually change the pH of the soil - it is after all, crushed, powdered rock. It requires both microbial action and Sulfuric Acid (naturally in soil) to break down and become part of the soil. For best results in the future it should be added directly into the potting soil well in advance.

    Calcium Carbonate (CaCO3) is what you're really looking for to increase the pH of Acidic soil. It is gentle and long lasting vs Hydrated or slaked lime which is fast and powerful but dangerous unless used very sparingly.

    Other options to safely increase soil pH are Oyster shell powder (90+% Calcium Carbonate), any of the crustacean meals (Lobster, shrimp, crab shell) which also not only contain high amounts of CaCO3 but also contains Chitin which inadvertently acts as a pesticide as well.

    Then there's simple worm castings which many folks just don't realize acts as a pH buffering agent - as the castings pass through the digestive tracts of the worms they are coated in a slime that is pure CaCO3...

    I guess my point here has been that there are gentle pH buffers that work well and there are others that work fast but in the long run nowhere near as well.

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  19. Cool. How did you learn about the worm castings acting as a ph buffer?

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