There are four principal contributors to acidic soil: rainfall and leaching, the decomposition of organic materials, the introduction of high-acidity materials into the soil and the harvest of abundantly yielding crops. The more time that passes, the more likely a soil becomes acidic and the less easily plants grow. One way the acidity of soil can be neutralized is to add lime to the soil.
The acidity of soil is measured using the pH scale. A level of seven is considered neutral, while zero is most acidic, and 14 is most alkaline. Alkaline substances are called “bases”. When rainwater leaches calcium, a base, out of the soil, it becomes more acidic. Rain can also add acidic hydrogen to soil, which further decreases its pH. Furthermore, adding fertilizers, which often have a low pH, to soil can make it more acidic. Another way fertilizers indirectly contribute to acidity is by creating a higher crop yield. This, in turn, lowers soil pH.
Adding limestone or calcium carbonate is the most common method used to raise pH levels in soil. Because water is necessary for the lime to react with the soil, this method works best in wet climates. It can take up to a year before the soil is less acidic and again ready to grow new plants or crops.