||The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. (April 2012)|
Agricultural lime, also called aglime, agricultural limestone, garden lime or liming, is a soil additive made from pulverized limestone or chalk. The primary active component is calcium carbonate. Additional chemicals vary depending on the mineral source and may include calcium oxide, magnesium oxide and magnesium carbonate.
The effects of agricultural lime on soil are:
- it increases the pH of acidic soil (the higher the pH the less acidic the soil); in other words, soil acidity is reduced and alkalinity increased
- it provides a source of calcium and magnesium for plants
- it permits improved water penetration for acidic soils
- it improves the uptake of major plant nutrients (nitrogen, phosphorus, and potassium) of plants growing on acid soils.
Lime may occur naturally in some soils but may require addition of sulfuric acid for its agricultural benefits to be realized. Gypsum is also used to supply calcium for plant nutrition. The concept of "corrected lime potential" to define the degree of base saturation[clarification needed Explain] in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement" of soils.
Other forms of lime have common applications in agriculture and gardening, including dolomitic lime and hydrated lime. Dolomitic lime may be used as a soil input to provide similar effects as agricultural lime, while supplying magnesium in addition to calcium. In livestock farming, hydrated lime can be used as a disinfectant measure, producing a dry and alkaline environment in which bacteria do not readily multiply. In horticultural farming it can be used as an insect repellent, without causing harm to the pest or plant.
Spinner-style lime spreaders are generally used to spread agricultural lime on fields. Several companies such as Stoltzfus Spreaders manufacture spreaders for this purpose.
Determining the need for agricultural lime 
The primary reason to apply agricultural lime is to correct the high levels of acidity in the soil. Acid soils reduce plant growth by inhibiting the intake of major plant nutrients (nitrogen, phosphorus and potassium). Some plants, particularly legumes, will not grow in highly acidic soils.
Soils become acidic in a number of ways. Locations that have high rainfall levels become acidic through leaching. Land used for crop and livestock purposes lose minerals over time by crop removal and become acidic. For example when a 600 pound calf is removed from a pasture, 100 pounds of bone is also removed, which is 60% calcium compounds. The application of modern chemical fertilizers is a major contributor to soil acid by the process in which the plant nutrients react in the soil.
Aglime, which is high in calcium, can also be beneficial to soils where the land is used for breeding and raising foraging animals. Bone growth is key to a young animal's development and bones are composed primarily of calcium and phosphorus. Young mammals get their needed calcium through milk, which has calcium as one of its major components. Dairymen frequently apply aglime because it increases milk production.
The best way to determine if a soil is acid or deficient in calcium or magnesium is with a soil test which can be provided by a university with an agricultural education department for under $30.00, if you live in the United States. Farmers typically become interested in soil testing when they notice a decrease in crop response to applied fertilizer.
The quality of agricultural limestone is determined by the chemical makeup of the limestone and how finely the stone is ground. To aid the farmer in determining the relative value of competing agricultural liming materials, the agricultural extension services of several universities use two rating systems. Calcium Carbonate Equivalent (CCE) and the Effective Calcium Carbonate Equivalent (ECCE) give a numeric value to the effectiveness of different liming materials.
The CCE compares the chemistry of a particular quarry's stone with the neutralizing power of pure calcium carbonate. Because each molecule of magnesium carbonate is lighter than calcium carbonate, limestones containing magnesium carbonate (dolomite) can have a CCE greater than 100 percent.
Because the acids in soils are relatively weak, agricultural limestones must be ground to a small particle size to be effective. The extension service of different states rate the effectiveness of stone size particles slightly differently. They all agree, however, that the smaller the particle size the more effective the stone is at reacting in the soil. Measuring the size of particles is based on the size of a mesh that the limestone would pass through. The mesh size is the number of wires per inch. Stone retained on an 8 mesh will be about the size of BB pellets. Material passing a 60 mesh screen will have the appearance of face powder. Particles larger than 8 mesh are of little or no value, particles between 8 mesh and 60 mesh are somewhat effective and particles smaller than 60 mesh are 100 percent effective.
By combining the chemistry of a particular product (CCE) and its particle size the Effective Calcium Carbonate Equivalent (ECCE) is determined.The ECCE is percentage comparison of a particular agricultural limestone with pure calcium carbonate with all particles smaller than 60 mesh.Typically the aglime materials in commercial use will have ECCE ranging from 45 percent to 110 percent.
See also 
- Tankersley, Wayne, http://www.penningtonseed.com/UploadedDocs/KnowledgeCenter/Newsletters/Soil%20Test%20to%20Determine%20Lime%20Needs-%20revised%20May%2005.pdf
- corrected lime potential (formula)
- "One Hundred Harvests Research Branch Agriculture Canada 1886-1986". Historical series / Agriculture Canada - Série historique / Agriculture Canada. Government of Canada. Retrieved 2008-12-22.
- Syed Manzoor Alam, Syed Shamshad Mehdi Naqvik and Raziuddin Ansari. 1999, Impact of Soil pH on Nutrient Uptake by Crop Plants, Nuclear Institute of Agricultural Tanso Jam, Sindh, Pakistan http://www.crcnetbase.com/doi/abs/10.1201/9780824746728.ch3
- Bell, Jeff. 1999, Understanding and Correcting Soil Acidity, The Samuel Roberts NOBLE Foundation http://www.noble.org/ag/Soils/SoilAcidity/index.htm
- Kurtural, S. Kaan and Gregg Schwab, Acidification of Vineyard Soils by Nitrogen Fertilizers, University of Kentucky http://www.uky.edu/Ag/Horticulture/acidification.pdf
- Hathaway, Milicent L. and Ruth Leverton. 2010, Food Part 1,Part of the Yearbook of Agriculture Series http://science-in-farming.library4farming.org/Food-Nutrition-Allowances/NUTRIENTS/Calcium-and-Phosphorus.html
- Young, J. Leon. 2010, The Soils, Plant & Water Analysis Laboratory, Stephen F. Austin State University http://www.docstoc.com/docs/37721511/The-Soil-Plant-and-Water-Analysis-Laboratory-Stephen-F
- Mamo, Martha, Charles S. Wortham, and Charles A.Shapiro. 2009, Lime Use for Soil Acidity Management, University of Nebraska http://elkhorn.unl.edu/epublic/live/g1504/build/g1504.pdf
- What is Calcium Carbonate Equivalent?, Clemson University http://hubcap.clemson.edu/~blpprt/bobweb/BOBWEB2.HTM
- Jennings, Dr. John and Mr. Shane Gadberry. 2006, Forage and Pasture Limestone Quality calculator, University of Arkansas http://www.aragriculture.org/forage_pasture/limestone.htm
- Buchholz, Daryl D. 1993, Missouri Limestone Quality: What is ENM?, University of Missouri, http://extension.missouri.edu/publications/DisplayPub.aspx?P=G9107
- Mesh(scale)by Wikipedia Mesh (scale)
Further reading 
- Right Use of Lime in Soil Improvement at Project Gutenberg Transcription of 1919 text by Alva Agee.
- "A Study of the Lime Potential, R.C. Turner, Research Branch, Canadian Department of Agriculture, 1965