In order to change the pH of a soil it is necessary to neutralize both the active and the reserve soil acidity. Liming materials Liming materials react with acids in the soil. This is called neutralization. Liming materials usually contain the oxides or carbonates of calcium and magnesium. Crushed limestone is the most widely used liming material because of its low cost.
Limestone is mainly calcium carbonate.
Some limestones, particularly dolomitic limestone, also contain magnesium. Other forms of liming materials do exist. The effectiveness of liming materials When comparing different liming materials, it is important to know the neutralizing value and the lime particle size. When comparing the costs of liming materials, make sure you determine the cost per ton of effective neutralizing value. Neutralizing value is expressed in two ways, calcium carbonate equivalent or percentage oxides.