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How to Correct the pH of Soil for a Healthy Garden

written by: BStone•edited by: Tania Cowling•updated: 8/8/2010

Acidity and alkaline levels can have a detrimental impact on the well-being of a garden. Learn about the pH effect on plant life and how to correct the pH of soil.

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    pH Levels

    garden soil pH What is a healthy pH level? What effect does pH have on plant life? What can be done to create a state of balance, in order for the garden to thrive? The soil pH is an important factor of a healthy garden. It is the measured value of either the acidity or alkalinity of the earth. A pH reading of 7 indicates neutral soil. While this is technically the value of balance, it is not necessarily the ideal state for all plants. Some do well in a slightly acidic soil, others prefer a pH that is slightly alkaline in nature.

    The wrong pH level can affect the nutrient content of the soil, and be deadly to plants in extreme cases. It can cause a consistency that is difficult for plants to grow in, leading to too much clay content, poor drainage, and poor oxygen flow. Also, beneficial microorganisms may not be able to survive in imbalanced soil. Highly acidic soil, with pH levels below 4.5, can lead to heavy concentrations of aluminum and manganese. This would be toxic to most plants. To manage this problem, gardeners need to know how to test, and how to correct the pH of soil.

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    pH Testing

    Checking the pH levels of the earth is easy. Simply buy a pH test kit, found at any garden store. Kits are generally inexpensive and efficient. They usually involve taking a soil sample to make a reading. Once the soil pH is known, it is then important to check the desired levels for individual plants. Some plants, such as azaleas, prefer acidic soil, as the dirt is usually high in iron with lower pH levels. A neutral range, from 6.5 to 7.2 will cater to the majority of plants, and some favor the nutrients available with higher values. For example:

    • Rosemary, fennel, and coreopsis 5.0 to 6.0
    • Basil, sage, primrose, viola, soybean, and watermelon 5.5 to 6.5
    • Ginger, marjoram, leeks, and asparagus 6.0 to 8.0
    • Mint 7.0 to 8.0

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    Correcting Soil Levels

    If the acidity-alkalinity levels are off, how then to correct the pH of soil? Altering the value to cater to specific vegetables, herbs, or flowers, is as simple as adding substances to the soil. If the earth is too alkaline, adding either Peat Moss or aluminum sulphate can help. If too acidic, Dolomitic Lime should be added. In either case, it is important to read the directions for which ever substance is being used. As a general rule, only use a small amount at first, and then do another soil test to make sure the pH level is correct. Add the lime or Peat Moss about one week before planting to allow the earth to properly adjust.

    Understanding the pH effect on plant life, and how to manipulate levels to find balance, will help plants not only grow, but reach their fullest potential. Take the time to care for the soil, the foundation, and reap the results of properly nourished plants.

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    Resources

    Primary Industries Agriculture http://www.dpi.nsw.gov.au/agriculture/resources/soils/acidity

    The Gardener's Network http://gardenersnet.com/atoz/ph.htm

    Bluegrass Gardens http://www.bluegrassgardens.com/soil-ph-test.htm

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    Photo Credit

    photo by: Aussie Gal (CC/flickr) http://www.flickr.com/photos/aussiegall/521281074/