Several common agricultural practices can lead to increased soil acidity. These practices include repeated use of ammonium-based nitrogen fertilizers and harvest and removal of plant material without fertilization. Long-term applications of some organic materials or composts can also acidify soil. The most common soil amendments for increasing soil pH are called agricultural liming materials. Several liming materials are available including burned lime, hydrated lime, marl, and industrial byproducts such as slag and flyash.
Coralline limestone found on Guam and on many Pacific islands is also a potential liming material.
The effectiveness of liming material is determined by its chemical composition and the fineness of the particles. The chemical effectiveness of a liming material in neutralizing acidity is often expressed in relation to the effectiveness of calcium carbonate. In addition, the finer the particle size of a liming material, the faster it will reduce soil acidity. The neutralizing index is a measure often used for evaluating the effectiveness of a specific liming material. This index is the product of the calcium carbonate equivalence and the particle size distribution of the liming material.