pH are symbols used by chemists for describing the degree of alkalinity or acidity of soils. There is a scale of values centred around a central point pH7 which is neutral. The scale is divided into 14 units. Values between 7 and 14 are alkaline and those from below 7 to 0 are acid. For example, a soil with a reading of pH9 would be very alkaline, whereas pH4 would be very acid. The greater majority of plants succeed best in a soil that is slightly acid, between 6.5 and neutral. The better soil-testing kits now available will accurately measure the pH of soils when that information is required.