OVERVIEW
Different agricultural liming materials have different values. The value of agricultural limestone varies with the geological source of the limestone and how the limestone is processed. The geological source of the limestone determines how much calcium carbonate and magnesium carbonate is in a ton of lime. The amount of these two carbonates determines the total neutralizing value (TNV) of the limestone. The processing of the limestone determines the fineness of the particles in the finished product. The lime's fineness determines how fast the limestone will react with the acids in the soil to increase the soil pH. The combination of the neutraliz-ing value and reaction rate is the effective neutralizing value (or Effective Calcium Carbonate).

The TNV is the percentage of the limestone capable of neutralizing an acid and is expressed as CCE. If a limestone has a TNV of 80 percent it means that 1 kg of it will neutralize the same amount of acid as 0.8 kgs of pure calcium carbonate. Limestones differ in TNV since they all contain impurities which do not react with acid; the more impurities the lower the TNV. Also some limestones contain magnesium carbonate, which has a greater neutralizing value than calcium carbonate per unit of weight. One kg of pure magnesium carbonate will neutralize the same amount of acid as 1.2 kgs of calcium carbonate. Therefore, dolomite limestone (also called high magnesium lime) often has a higher TNV than calcium limestone.

When a soil tests low to medium in magnesium the use of high magnesium limestone is recommended to meet the needs of plants for magnesium.

Fineness of a ground limestone (sieve size) determines how fast the lime reacts with an acid. As a ton of limestone is ground finer there is more surface area. This increased surface area gives more places where the lime can react with the acids in the soil. The fineness of limestone is measured by how much will pass through different mesh screens or sieves. The larger the number of the mesh means the more wires per inch which results in smaller holes in the sieve. Soil and management conditions will affect how fast the different particle sizes react with your soil.