Different plant species need different types of soil, with varying degrees of acidity. Some plants are more sensitive to soil pH than others. PH is a measurement of the amount of lime or calcium in your soil. Heathers and rhododendrons, for example, cannot grow in soil that has lime in it. Most plants thrive in a slightly acidic pH of 5.8 to 7.0. Too much acid, however, can kill other plants. Soil must be adjusted to meet the needs of the plants you want to grow. The best way to reduce acid in soil for plants is to add hydrated lime.
Call your local nursery or garden center and ask them if they do soil testing. Many will accept a sample and test its pH, saving you the trouble.
Buy a pH test kit if your nursery doesn't test soil. They can be found at garden centers and hardware stores. The test kits come with a test tube, solution and color chart.
Collect a small sample of soil from your planting site. Put it in the tube, add a few drops of the solution and shake it. Allow the solution to settle for an hour and check the color change against the chart provided. Get the exact pH (number) of your soil.
Add hydrated lime to the soil to increase the pH and make it more alkaline. Each type of soil requires a different amount of lime, so you need to know if you have clay, sandy, peaty or loamy soil.
Add 4 oz. of hydrated lime per square yard to increase sandy soil's pH by 1.0 point. Double that amount if you're dealing with loamy soil. For clay soil, add 12 oz. of hydrated lime per square yard. Peaty soil needs the most to become more alkaline--add 25 oz. of hydrated lime per square yard.
Work the hydrated lime into the soil to mix it thoroughly. Use garden tools like a hoe or rototiller to a depth of at least 6 inches.
Expect the soil to have better nutrients after the addition of lime. Not only does it increase the soil pH, but it provides calcium and magnesium to the dirt. It also makes phosphorus, which enhances plant growth.
Consider that fixing overly acidic soil is a long-term project. It's not something you can fix in one season. Test your soil each year and make adjustments as needed.