Acidification of Sensitive Soils: pH Information
WHAT IS pH?
Soil pH refers to the level of acidity in a soil. The pH is a measure of the number of hydrogen (H+) ions in the soil, and is reported on a logarithmic scale going from 0-14. A pH of 7 is considered neutral. However, most crops do best in slightly acid soils (pH of 6-7). Many forested soils are naturally acidic (pH 4-6), but vegetative growth is often limited when pH levels decrease below 4.
Soil pH is measured on soil samples mixed with water or a weak calcium chloride solution. This indicator uses pH measured in calcium chloride because it is less variable than pH measured in water. Soil pH is usually about half a unit lower when measured in calcium chloride than in water.
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