Calcium carbonate equivalent is a measurement to determine how effective a material is at neutralizing acidity. Calcium carbonate is used as the standard to compare all liming materials to since it is the primary component of limestone. In the laboratory, the CCE of a material is measured by reacting equal amounts of each the material in question and pure laboratory-grade calcium carbonate with a set amount of hydrochloric acid. The amount of remaining acidity in each of the two solutions is then determined through a process called a titration. The CCE is then calculated by dividing the amount of acidity neutralized by the material in question by the amount neutralized by the pure calcium carbonate. This result can then be reported as a percentage.
So, what does this mean in the real world for agronomic applications? Knowing the CCE of a lime can help determine the appropriate rate to apply to our soils to raise and/or maintain the pH in a desirable range for the particular crops being grown. Most recommendations for pH correction assume that the CCE of lime is 90%. In reality quarry derived lime can often range from 75% to 110%. This means that it may take 20 to 30% more or less material to achieve the desired result. The CCE of the lime from a single quarry does not change much over time. However, the lime from different quarries can vary quite a lot. While CCE is an important property to consider when choosing a lime source, there are other factors that go into determining the overall quality of the lime and whether it is a good fit for your operation. These factors will be discussed in future articles.