A soil may be called as alkaline when the pH of the soil is more than

A soil may be called as alkaline when the pH of the soil is more than "7.0". The pH of a soil is a measure of its acidity or alkalinity, with a pH of 7.0 being neutral. Soils with a pH greater than 7.0 are considered alkaline, while soils with a pH less than 7.0 are considered acidic. Soils with a pH greater than 7.0 have a higher concentration of basic (alkaline) ions, such as calcium and magnesium, and a lower concentration of acidic ions, such as hydrogen. These soils can be challenging for some plants to grow in, as they can limit the availability of certain essential nutrients, such as iron and manganese. However, some plants, such as alfalfa and sweet clover, are well-adapted to growing in alkaline soils. Soils with a pH less than 7.0, on the other hand, have a higher concentration of acidic ions and a lower concentration of basic ions. These soils can be ideal for growing certain crops, such as blueberries and cranberries, but can also present challenges for other plants, such as lilacs and hydrangeas.