Delphinidin

The pH (acidity or alkalinity) of a soil affects both the soil and the plants growing in it in various ways. Cranberries, for example, thrive under acidic conditions, but a soil that is unusually acid or alkaline may be toxic to the roots of other plants, and mycorrhizae do not survive in soils having pH extremes. These conditions, however, do not normally directly affect plants nearly as much as they affect nutrient availability.
For example, alkalinity causes minerals, such as copper, iron, and manganese, to become less available to plants, while acidity, if high enough, inhibits the growth of nitrogen-fixing bacteria. Acid soils tend to be common in areas of high precipitation where significant amounts of bases are leached from the topsoil.

It is a common agricultural practice to counteract soil acidity by adding compounds of calcium or magnesium in a process known as liming. Alkaline soils can be made more acidic by the addition of sulfur, which is converted by bacteria to sulfuric acid. The addition of some nitrogenous fertilizers may have the same effect.