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pH up Or Down For Soil: Lowering or Raising pH


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    Importance of Soil pH

    You might have bought top-shelf seeds or clones, the best led lights, and the best grow tent that you can afford. However, all the above will go to waste if your garden soil is either too acidic or too alkaline. The acidity or non-acidity of soil is measured in Ph, which will be explained below.

     Soil pH Scale 101

    Water PH Scale

    Soil’s pH is measured on a scale of zero to 14. One to seven is considered to be acidic, and seven and above are classified as alkaline.

    Some plants thrive in more acidic soil, and others thrive in more alkaline soil. For example, acid loving plants will likely only thrive in sandy soil.

    Remember that lowering soil P.H. means that you are making the soil more acidic. Raising soil P.H., on the other hand, makes it less acidic or alkaline.

    Usually, You Should Not Have To Worry About pH Level Changing

    If you apply the correct natural fertilizers (I.E., mulch compost, bone meal, and worm castings), you should not have to worry about the soil pH going up or down. The reason is that proper plant nutrients help your soil develop healthy soil bacteria and fungi.

    Why Should You Care If You Have A Ph Imbalance?

    A nutrient deficiency will occur with soil that is either too acidic or alkaline. The reason is that either situation will make it harder for your plants to absorb essential nutrients.

    Too Little Acid

    Soil with a pH level above 6.5 will have a hard time absorbing the vital nutrients, phosphorus, nitrogen, and potassium.

    Too Much Acid

    Acidic soil below 5.5 will also have a hard time absorbing vital plant growth, nutrients. (Phosphorus, Magnesium, Potassium, molybdenum, and Calcium) Additionally, with acid soil, plants are more likely to suffer from heavy metal toxicity.

    What Should Cannabis‘ pH Level Be?

    For optimum plant growth, the cannabis‘s pH should be between 6.0 to 7.0.

    How To Change P.H. Levels In Cannabis

    You did a soil pH test and found out that your pH level is either too acidic or too alkaline. Now, what are you going to do? How are you going to fix this problem? Well, don’t worry. It is not that hard to either raise or lower your pH levels to acceptable levels in most cases.

    For your reference, the top chart illustrates the various pH levels and how raising or lowering them will make ether more alkaline or more acidic soil.

    Hydroponic And Other Growth Mediums-If you have a hydroponic system or using other soilless mediums like coco coir, you will also need to check the pH. These will not be addressed in this article.

    Soil pH Testing Options

    First Things First-Test Soil: The two most common DIY methods for testing a soil sample are the following:

    Test Strips: These are simply strips of paper that turn a particular color when the soil sample reaches a certain pH level. pH test strips are the least accurate way to measure the alkalinity or acidity levels.

    Garden Tutor Soil pH Test Strips Kit (3.5-9 Range) 100 Tests


    Handheld pH Meter-Are used directly in your grow tent. All you do is place the probe’s electrodes into the soil and read the meter. The handheld meters resemble either a pen or a bike tire pump and vary significantly in price.

    Soil Test Kit, Soil Tester for Moisture, Light & pH Meter for Plant, Vegetables, Garden, Lawn, Farm, Indoor/Outdoor Plant Care Soil Tester

    Click the following link to find out how to choose the best pH Testers and Meters.

    Other Testing Options

    You can have your soil testing done professionally by a lab. Your local university or community college may have this service, or you can use a private company for your soil test.

    How To Raise pH In Soil Using Organic Matter

    For cannabis If the soil’s pH is less than 5.5, you will need to raise the soil pH to above 6.0. Adding limestone to your soil is the most common method of making the soil less acidic.


    The two types of limestone most commonly used for raising pH are calcitic limestone (primarily calcium carbonate) and dolomitic limestone.

    Both work well. However, it also adds magnesium. To use limestone, you simply work it into the soil.

    Limestone can be bought in the following forms: pellets, hydrated, granular, and crushed. The following is an overview of the various type of lime available.

    Crushed Or Pulverized Limestone

    Natural Pulverized Limestone (5 Pound)

    Crushed limestone is the preferred choice for newbie cannabis growers, as it works quickly, and is also safer for your plants. The main downside to crushed limestone is that it tends to clog fertilizer spreaders more easily. However, most indoor growers of cannabis will not need to worry about using a fertilizer spreader. For quickest results, look for the finest grounded limestone that’s available.

    Pellets Or Granular Limestone– Pellet limestone is spread more efficiently with a fertilizer spreader. The limestone pellets also take a long time to break down into the soil. Since spreading your limestone via a fertilizer spreader is not needed for a smaller indoor marijuana growing operation, granular limestone should not be your first choice for raising soil pH.

    Pro Pelleted Dolomitic Limestone - 50lb

    Hydrated limestone-(QUICKEST METHOD)Hydrated limestone is the fastest method for making the soil more alkaline. The downside to using hydrated lime is that too much can ruin your plants. Therefore, be sure to strictly follow the directions.

    Voluntary Purchasing Group Fertilome 33371 Horticultural Hydrated Lime, 5-Pound

    Other Organic Soil Amendment Methods For Lowering Acid Levels

    • Wood Ash
    • Potassium Carbonate
    • Phosphoric Acid

    How To Lower Soil pH

    Soil pH levels that are more than 6.5 will need to be lowered. This can be done by adding chemical fertilizer or organic material to your soil.


    Elemental Sulfur

    Monterey NLG7122 Dr Soil Acidifier Granules Iron and Elemental Sulfur Acidic Fertilizer, 21 lb

    (“Plain”)-Elemental Sulfur is the most commonly used method for lowering pH. Sulfur is inexpensive, spreadable, and moderately safe to handle. A significant drawback of elemental sulfur is that it takes a long time for the sulfuric acid to work.

    The time at which sulfur will start working to lower pH depends upon multiple factors. ( It even can take up to a month for the sulfur to start working)

    The following are a few factors concerning how quickly it will work:

    • How small are the sulfur grains?
    • How much soil moisture is present.
    • The temperature of the soil and bacteria that may be present.

    Aluminum and Iron Sulfate

    Aluminum and iron sulfate are preferred by most growers as it works quicker than plaint sulfur to lower soil pH. Aluminum and iron sulfate soil can be damaging if it is overused. Additionally, if it comes into direct contact, it is damaging to plants.

    So, be extra careful to make sure that any aluminum or iron sulfate does not come into direct contact with your plant leaves. If they do come in contact, you need to be sure to wash off the leaves thoroughly.

    Fertilizer Containing Acidifying Elements

    To lower the pH, add fertilizers contain elements, such as ammonium nitrate, amino acids, or ammonium sulfate. However, this is not a quick fix, and it will take time for the pH levels to decrease.

    General Hydroponics pH Down Liquid Premium Buffering For Stability, 1-Gallon


    Final Thoughts

    Proper soil acid levels are essential for optimizing plant growth. Usually, this should not be a big issue for indoor gardeners as you will likely be using purchased garden soil that is optimized for plant growth.

    You should, though, on a set basis, schedule a soil test; and then fix the issue if the garden soil is either too acidic or alkaline.



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