by Michael Harman, WVU Extension Service Agent – Agriculture and Natural Resources
What is soil acidity and why does it occur?
Soil pH is a measure of the acidity of the soil. When pH is below 7.0, the soil is said to be acidic. Soils become acidic when calcium and magnesium are leached from the soil. Leaching generally occurs in regions that receive in excess of 24 inches of precipitation per year. As calcium and magnesium are leached and replaced by exchangeable hydrogen and hydrated forms of iron and aluminum, the soil acidifies. Typically, most West Virginia soils are acidic, with a pH between 5.3 and 5.8. If you intend to grow acid-loving plants like azaleas, rhododendrons, gardenias, blueberries, heath, and heather you may need to acidify your soil.
How can I determine how acidic my soil is?
Before acid-loving trees and shrubs are planted, the pH of the soil should be determined with a soil test. Test results will detail how to adjust your soil pH to the desired level. When possible, naturally acidic soil material, preferably rich in organic matter, should be used for backfill (the soil material placed around new plantings to fill the hole back in). When pH is too high, acidic or sulfur-containing materials should be mixed with the backfill material. If at all possible, modify pH before planting, since modifying pH post-planting requires more caution and is less successful. Also, avoid situations where you need to make large changes in pH.
Before changing the pH, consider the texture of your soil.