Why Does Soil pH Matter?

    Importance of Proper pH
    If you don’t have the proper soil pH, say, “Good-bye” to a great-looking lawn! In fact, you can be wasting between 20% and 70% of your lawn fertilizer if your pH is imbalanced. Remember, lawn fertilizers acidify turf grass every time they are applied. Fortunately, there are ways that you can balance your soil pH to optimize the lawn’s growth.

    The Role of Soil pH in the Health of the Lawn
    The pH level of the soil is an important consideration in growing lawns. Most of us have a basic understanding of pH as a way of measuring how acidic or alkaline a soil may be. If you own a swimming pool, you know that correcting and balancing the pH of the water you swim in is important. On a scale of 1 to 14, a pH of 1 is very acidic and a pH of 14 is very alkaline, also called basic, while a pH reading of 7 would be neutral. Lawns grow best in a soil that is neutral to slightly acidic between a 6.5 and a 7 reading.

    Seemingly small changes in pH readings can mean big changes for lawn grass plants. That is because the pH scale is logarithmic not arithmetic. This means that a pH reading of 6 is ten times more acidic than a pH reading of 7, while a pH of 5 is one hundred times more acidic.

    Soil Chemistry and the Importance of Maintaining a Balanced pH
    All tiny particles in the soil including minerals, organic matter, (humus) and microbial life carry electrical charges. These charges are called ions. Ions with a positive charge are called cations and particles with a negative charge are called anions. Positively charged particles are electrically attracted to negatively charged particles. This is what happens when opposite ends of magnets attract each other. Even microorganisms in the soil carry electrical charges. If it wasn’t for the operation of this weak electrical charge in holding mineral nutrients on the surface of clay and humus particles, the mineral nutrients would be quickly leached away by water. Why does this matter? The surfaces of plant root hairs carry their own negative electrical charges. Grass plant root hairs use this electrical attraction to increase their ability to attract and absorb positively charged nutrients from the soil. The pH reading indicates the concentration of hydrogen ions in the soil solution. The more hydrogen ions, which are positively charged particles or cations, the lower the pH level of the soil, making the soil more acidic. The organic acids, produced from organic decay in the soil, drive the soil pH lower. Lawn fertilizers are acidic and contribute to lowering the pH level of the soil too. It is the pH level that influences the quantity and type of microorganisms that live in the soil, and these microorganisms have a great influence on the health of grass plants.

    Not All Plants Want the Same Soil pH
    Different plants thrive at different pH levels. Among your turf grasses, Bluegrass does better in the higher range of 6, whereas Fescues will do better closer to 6.0. Typically if your soil pH is 6.3 or higher, we will not recommend applying lime.
    In the vegetable garden, different crops have varying levels of ideal pH. Rhubarb, for example, can tolerate a wide range of 5.0 to 7.0, whereas Raspberries prefer a more narrow range of 6.0 to 6.5. In general, your tomatoes and potatoes do better in a slightly more acidic soil with a pH around 6.0, while most of your other vegetables prefer a pH of about 6.7. Another acid loving plant is Blueberries, who thrive in soils with a pH of 4.8 to 5.5.

    How to Determine Soil pH
    In addition to offering simple do it yourself pH tests, we can also test your soil here at the store. Go to at least 6 - 8 different locations on your lawn. Using a garden trowel or spoon dig down into the soil 1 - 2 inches and take a small sample. Follow the same procedure at the other testing sites. When you have your samples mix the soil together in a bag or bucket, combining them to get a representative or average sample. Then bring the sample to us! It only takes a few minutes for us to determine the pH of your soil. If you would like a more complete analysis of your soil that also measures calcium, magnesium, phosphorus and potash levels you can bring us a pint of soil, and we can send it out to a lab.

    How to Correct Soil pH
    If your soil test shows that the pH in your soil is too low then it is time to add some lime. Lime not only neutralizes soil acidity, but also provides other benefits to the soil. There are two types of lime: Calcite lime and Dolomite lime. Both dolomitic and calcitic lime can be bought in a powder or pellet form. Pelleted lime is powdered lime that is bound together with a water soluble binder that makes it easier to spread.

    Dolomite Lime: Contains Magnesium, which is the center of a chlorophyll molecule and is considered a necessary secondary nutrient. Magnesium helps with seed germination, nutrient absorption and growth in the lawn. Dolomitic lime contains both calcium and magnesium.

    Calcite Lime: Contains very little magnesium, and is mainly composed of calcium compounds. Calcium is essential in raising soil pH and is vital to many grass plant functions. Some of which are: proper cell division, and elongation, proper cell wall development, and nitrate uptake. Calcitic lime works much faster than dolomitic lime in raising the pH, and with its higher level of calcium, it also helps strengthen your lawn and improve the efficiency of your fertilizer.


    Information Sourced from Jonathan Green.

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