Acid soil | A soil type described by Tom Stevenson as ‘any soil that has a pH of less than 7 (neutral). Typical acid soils that are acidic due to their parent rock include brown or reddish-brown, sandy loams or sands, volcanic soils, and any igneous or silicate-rich soil. Neutral soils can become acidic from too much humus or acid rain. Acid soils are low in calcium and magnesium, with negligible amounts of soluble salts and reduced phosphorus availability.’
Tom Stevenson (2011) The Sotheby’s Wine Encyclopedia 5th Edition by Tom Stevenson (Dorling Kindersley, 2011), p.17.