The
soil pH is a measure of the
acidity or alkalinity in
soils.
pH is defined as the negative
logarithm (base 10) of the
activity of
hydronium ions ( or, more precisely, ) in a
solution. In water, it normally ranges from -1 to 14, with 7 being neutral. A pH below 7 is
acidic and above 7 is alkaline. Soil pH is considered a master variable in soils as it controls many chemical processes that take place. It specifically affects
plant nutrient availability by controlling the chemical forms of the nutrient. The optimum pH range for most
plants is between 5.5 and 7.0, however many plants have adapted to thrive at pH values outside this range.