pH: Soils

Soil pH measures the acidity or alkalinity of a soil. Acid soils have a pH less than 7 and alkaline soils a pH greater than 7. Soils formed on acidic parent materials (see soil), such as granitic rocks or highly weathered sandstones, generally have acid pH values, whereas those formed on basic parent materials, such as limestone, basalt, or dolerite, generally have alkaline pH values. The optimum pH range for grapevines is from 5.5 to 8, although the grapevine is one of the domesticated plants most tolerant of soil pH outside this range. Soil pH is of some relevance to the resultant wine, although the effect is not direct. See also soil acidity and soil alkalinity.