Editing Fertilizer (section)

==Classification==
Fertilizers are classified in several ways. They are classified according to whether they provide a single nutrient (e.g., K, P, or N), in which case they are classified as "straight fertilizers". "Multinutrient fertilizers" (or "complex fertilizers") provide two or more nutrients, for example, N and P. Fertilizers are also sometimes classified as inorganic (the topic of most of this article) versus organic. Inorganic fertilizers exclude carbon-containing materials except [[ureas]]. Organic fertilizers are usually (recycled) plant- or animal-derived matter. Inorganic are sometimes called synthetic fertilizers since various chemical treatments are required for their manufacture.<ref>J. Benton Jones, Jr. "Inorganic Chemical Fertilisers and Their Properties" in ''Plant Nutrition and Soil Fertility Manual'', Second Edition. CRC Press, 2012. {{ISBN|978-1-4398-1609-7}}. eBook {{ISBN|978-1-4398-1610-3}}.</ref>

===Single nutrient ("straight") fertilizers===
The main nitrogen-based straight fertilizer is [[ammonia]] (NH<sub>3</sub>) [[ammonium]] (NH<sub>4</sub><sup>+</sup>) or its solutions, including:
* [[Ammonium nitrate]] (NH<sub>4</sub>NO<sub>3</sub>) with 34-35% nitrogen is also widely used.
* [[Urea]] (CO(NH<sub>2</sub>)<sub>2</sub>), with 45-46% nitrogen, another popular source of nitrogen, having the advantage that it is solid and non-explosive, unlike ammonia and ammonium nitrate.
* [[Calcium ammonium nitrate]] Is a blend of 20-30% [[limestone]] CaCO<sub>3</sub> or [[Dolomite (mineral)|dolomite]] (Ca,Mg)CO<sub>3</sub> and 70-80% [[ammonium nitrate]] with 24-28  % nitrogen.
*[[Calcium nitrate]] with 15,5% nitrogen and 19% calcium, reportedly holding a small share of the nitrogen fertilizer market (4% in 2007).<ref name="ETE">{{cite book |last=Smil |first=Vaclav |title= Enriching the Earth |publisher= [[Massachusetts Institute of Technology]] |page=135 |url= https://books.google.com/books?id=G9FljcEASycC&pg=PA135 |isbn=978-0-262-69313-4 |year=2004 }}</ref>

The main straight phosphate fertilizers are the [[superphosphate]]s:
* "Single superphosphate" (SSP) consisting of 14–18% P<sub>2</sub>O<sub>5</sub>, again in the form of Ca(H<sub>2</sub>PO<sub>4</sub>)<sub>2</sub>, but also [[phosphogypsum]] ({{chem2|Ca[[SO4]] * 2 H2O}}).
* [[Triple superphosphate]] (TSP) typically consists of 44–48% of P<sub>2</sub>O<sub>5</sub> and no gypsum.

A mixture of single superphosphate and triple superphosphate is called double superphosphate. More than 90% of a typical superphosphate fertilizer is water-soluble.

The main potassium-based straight fertilizer is [[muriate of potash]] (MOP, 95–99% KCl). It is typically available as 0-0-60 or 0-0-62 fertilizer.

===Multinutrient fertilizers===
These fertilizers are common. They consist of two or more nutrient components.

;Binary (NP, NK, PK) fertilizers
Major two-component fertilizers provide both nitrogen and phosphorus to the plants. These are called NP fertilizers. The main NP fertilizers are 
*[[monoammonium phosphate]] (MAP) NH<sub>4</sub>H<sub>2</sub>PO<sub>4</sub>. With 11% nitrogen and 48% P<sub>2</sub>O<sub>5</sub>.
*[[diammonium phosphate]] (DAP). (NH<sub>4</sub>)<sub>2</sub>HPO<sub>4</sub>. With 18% nitrogen and 46% P<sub>2</sub>O<sub>5</sub> 

About 85% of MAP and DAP fertilizers are soluble in water.

;NPK fertilizers
{{Main|Labeling of fertilizer}}
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NPK fertilizers are three-component fertilizers providing nitrogen, phosphorus, and potassium. There exist two types of NPK fertilizers: compound and blends. Compound NPK fertilizers contain chemically bound ingredients, while blended NPK fertilizers are physical mixtures of single nutrient components.

[[NPK rating]] is a rating system describing the amount of nitrogen, phosphorus, and potassium in a fertilizer. NPK ratings consist of three numbers separated by dashes (e.g., 10-10-10 or 16-4-8) describing the chemical content of fertilizers.<ref>{{cite web |title= Summary of State Fertilizer Laws |url=https://www.fda.gov/ohrms/dockets/dailys/03/dec03/121503/02N-0276_emc-000107-02.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.fda.gov/ohrms/dockets/dailys/03/dec03/121503/02N-0276_emc-000107-02.pdf |archive-date=2022-10-09 |url-status=live |publisher= EPA |access-date= 14 March 2013}}</ref><ref>{{cite web |title=Label Requirements of specialty and other bagged fertilizers |url= http://www.michigan.gov/mdard/0,4610,7-125-1569_16993_19405-49343--,00.html |publisher= Michigan Department of Agriculture and Rural Development |access-date= 14 March 2013}}</ref> The first number represents the percentage of nitrogen in the product; the second number, P<sub>2</sub>O<sub>5</sub>; the third, K<sub>2</sub>O. Fertilizers do not actually contain P<sub>2</sub>O<sub>5</sub> or K<sub>2</sub>O, but the system is a conventional shorthand for the amount of the phosphorus (P) or potassium (K) in a fertilizer. A {{convert|50|lb|adj=on}} bag of fertilizer labeled 16-4-8 contains {{cvt|8|lb}} of nitrogen (16% of the 50 pounds), an amount of phosphorus equivalent to that in 2 pounds of P<sub>2</sub>O<sub>5</sub> (4% of 50 pounds), and 4 pounds of K<sub>2</sub>O (8% of 50 pounds). Most fertilizers are labeled according to this N-P-K convention, although Australian convention, following an N-P-K-S system, adds a fourth number for sulfur, and uses elemental values for all values including P and K.<ref>{{cite web|title=National Code of Practice for Fertilizer Description & Labelling |url=http://www.fertilizer.org.au/files/pdf/regulation/National%20Code%20of%20Practice%20for%20Fertilizer%20Description%20&%20Labelling%20March%2011%202011.pdf |publisher=Australian Government Department of Agriculture, Fisheries and Forestry |access-date=14 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150228200433/http://www.fertilizer.org.au/files/pdf/regulation/National%20Code%20of%20Practice%20for%20Fertilizer%20Description%20%26%20Labelling%20March%2011%202011.pdf |archive-date=28 February 2015 }}</ref>

===Micronutrients===
[[Micronutrients]] are consumed in smaller quantities and are present in plant tissue on the order of [[Parts-per notation|parts-per-million]] (ppm), ranging from 0.15 to 400 ppm or less than 0.04% dry matter.<ref>{{cite web|url = http://aesl.ces.uga.edu/publications/plant/Nutrient.asp|title = AESL Plant Analysis Handbook&nbsp;– Nutrient Content of Plant|publisher = Aesl.ces.uga.edu|access-date = 11 September 2015}}</ref><ref name="Mills and Jones, 1996">{{cite book|author1=H.A. Mills |author2=J.B. Jones Jr. |year=1996|title=Plant Analysis Handbook II: A Practical Sampling, Preparation, Analysis, and Interpretation Guide|publisher=Micro-Macro Pub. |isbn=978-1-878148-05-6}}</ref> These elements are often required for enzymes essential to the plant's metabolism. Because these elements enable catalysts (enzymes), their impact far exceeds their weight%age. Typical micronutrients are [[boron]], [[zinc]], [[molybdenum]], [[iron]], and [[manganese]].<ref name=Ull/> These elements are provided as water-soluble salts. Iron presents special problems because it converts to insoluble (bio-unavailable) compounds at moderate soil pH and phosphate concentrations. For this reason, iron is often administered as a [[Chelation|chelate complex]], e.g., the [[Ethylenediaminetetraacetic acid|EDTA]] or [[EDDHA]] derivatives. The micronutrient needs depend on the plant and the environment. For example, [[sugar beet]]s appear to require [[boron]], and [[legume]]s require [[cobalt]],<ref name=Ullmann1>{{Ullmann|doi=10.1002/14356007.a10_323.pub3|title=Fertilizers, 1. General|year=2009|last1=Scherer|first1=Heinrich W.|last2=Mengel|first2=Konrad|last3=Kluge|first3=Günter|last4=Severin|first4=Karl}}</ref> while environmental conditions such as heat or drought make boron less available for plants.<ref>{{Cite web|url=https://www.aspireboron.com/formula|title=Boron Deficiency|access-date=4 March 2019|archive-date=6 March 2019|archive-url=https://web.archive.org/web/20190306044328/https://www.aspireboron.com/formula|url-status=dead}}</ref>