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How to Correct the Soil pH

By Mark Pendergast
Rhododendrons grow best in acidic soil.

Soil pH measures the amount of hydrogen ions in a soil -- the term pH stands for "potential hydrogen." The pH scale goes from 0 to 14, indicating whether the soil is more acidic or more alkaline. A reading of 7.0 is neutral and means that the soil is balanced between acidity and alkalinity. Readings above 7.0 indicate a more alkaline soil; readings below 7.0 indicate a more acidic soil. Different plants thrive in soils with different pH factors. In certain cases, you may want to change the pH of your soil so you can grow certain types of plants.

Determine pH

Test your soil with a kit to identify its current pH level. Follow the specific instructions for your kit.

Identify the soil pH that is best for the plants you want to grow. Determine whether your garden's soil is too acid or alkaline for these plants.

Change your soil's pH slowly over several seasons to avoid over-correcting, which is easily done. Test your soil each year before applying amendments to make your soil more acidic or alkaline.

Raise pH

Add hydrated lime or agricultural limestone to your soil to make it more alkaline. Follow the directions on the bag or container to determine the correct amount to add per square yard.

Apply the lime or limestone with a spreader or rototiller. Avoid applying it on grass that is wilted or covered with frost.

Water the soil after applying the additive. Make sure no limestone is left on the top of the grass, if you applied it there.

Lower pH

Add sulfur to your soil to make it more acidic. Sulfur may be sold as rock sulfur, farm sulfur or dusting sulfur.

Add 1.2 oz. of sulfur per square yard if you have sandy soil. Add 3.6 oz of sulfur per square yard for other soils. Mix it thoroughly into the soil with a tiller.

Wait for the sulfur treatment to take effect. This might takes months, because the microbes in the soil must first break down the sulfur before any change in pH can take place.

 

Things You Will Need

  • Soil test kit
  • Hydrated lime or agricultural limestone
  • Spreader
  • Rototiller
  • Sulfur

Tips

  • You can purchase a soil test kit at a hardware store or garden center.
  • Consider having your soil tested by a lab. Though this method is more expensive than testing it yourself, the results are more detailed.
  • Sulfur is available at garden centers or feed stores.

About the Author

 

Mark Pendergast has worked as a freelance writer since 2007, focusing on topics such as health, sports and finance. He has worked as a newspaper reporter and librarian and has written for the "Northside Sun" and "Jackpot," among other publications. Pendergast holds a Bachelor of Arts from Millsaps College.