Soil pH is a measure of the acidity or basicity of your soil. Besides providing suitable light, water and temperature, it's also important to control the pH of a plant to ensure proper growth.

Soil pH affects the activity of the enzymes in the plant. If the pH of your soil is outside the appropriate range for that plant, the plant will not be able to absorb an optimal amount of nutrients and growth will be stunted, halted or worse.

Most plants prefer a pH range between 5.5 and 7.5 (where 5.5 is ideal), and most plants are somewhat tolerant of pH. Consider testing the pH of your soil. Knowing it will help you choose suitable plants at, where we allow you to search for and compare plants that match your soil pH.

Many local cooperative extensions will test your soil for free or a nominal charge. Alternatively, or you can purchase a test kit at most garden centers or However, these home test kits do not measure the buffering capacity of the soil. For example, two different soils with a pH of 4.0 may take entirely different amounts of lime to raise the pH to 6.0. To change identical pH's in different soils it is not unusual to need amounts from 10 pounds to 200 pounds. So, you may need several applications to get the soil adjusted to the proper pH. For optimal results, check, and, if necessary, adjust the soil pH every couple of years.

If your pH is outside the ideal range for the plant(s) you choose, your local garden center can provide additives for your soil to adjust the pH.

To reduce the acidity of soil, powdered agricultural lime is most commonly added. Be sure to apply lime carefully and in the amount recommended on the package. Pelleted lime takes longer to work than powdered lime. Over liming soil can create more problems. Another safe and organic way to correct an overly acidic soil is to add compost. The more organic matter and compost added to soil, the better.

To reduce the alkalinity of soil, powdered sulfur (usually used in the form of ammonium sulfate) is most commonly added. Adding lots of compost, manure or other organic matter naturally brings the pH into balance too. Great additions to alkaline soils include shredded oak leaves, ground bark, aged sawdust, peat moss and pine needles.

Test your soil again after adding amendments. The pH can vary within one plot, so test several sections to get an accurate assessment.

Testing your soil for levels of Nitrogen, Phosphorous, and Potassium can help you choose an optimal fertilizer (these are the three numbers across the front of each bag of fertilizer). If your soil is deficient in one or more of these elements, consult your garden center or local cooperative extension for advice.

See also:
  Details on soil pH
  Local cooperative extensions

Back to: Ground preparation and fertilizing


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