Utah State University Extension
PH is a measure of the acidity or alkalinity of a material. The pH scale ranges from 0 to 14, with 7 being neutral. A pH value below 7 indicates the soil is acidic, while values above 7 are alkaline. Each unit change in the pH scale is a 10-fold difference in acidity or alkalinity. For example, soil with a pH of 8 is ten times more alkaline than soil with a pH of 7.
Cox, Loralie and Koenig, Rich, "Solutions to Soil Problems: II. High pH (Alkaline Soil)" (2010). All Current Publications. Paper 955.