Editing Fertilizer (section)

==Application==<!--need timing of application, methods for applying-->
[[File:Farm fertilizer.jpg|thumb|Fertilizer [[sprayer]]]]
[[File:Drone crop fertilizer.jpg|thumb|[[Agricultural drone|Drone crop fertilizer]]]]
[[File:7252 Hand top-dressing of super phosphate on Banks Peninsula.jpg|thumb|Applying [[superphosphate]] fertilizer by hand, New Zealand, 1938]]
Fertilizers are commonly used for growing all crops, with application rates depending on the soil fertility, usually as measured by a [[soil test]] and according to the particular crop. Legumes, for example, fix nitrogen from the atmosphere and generally do not require nitrogen fertilizer.

===Liquid vs solid===
Fertilizers are applied to crops both as solids and as liquid. About 90% of fertilizers are applied as solids. The most widely used solid inorganic fertilizers are [[urea]], diammonium phosphate and potassium chloride.<ref name="IFA2017">{{cite web|title=About Fertilizers Home Page|url=https://www.fertilizer.org/En/Knowledge_Resources/About_Fertilizers/About_Fertilizers_Home_Page.aspx?|archive-url=https://web.archive.org/web/20140330225212/http://www.fertilizer.org/En/Knowledge_Resources/About_Fertilizers/About_Fertilizers_Home_Page.aspx|url-status=dead|archive-date=30 March 2014|website=fertilizer.org|publisher=International Fertilizer Association|access-date=19 December 2017}}</ref> Solid fertilizer is typically granulated or powdered. Often solids are available as [[prill]]s, a solid globule. Liquid fertilizers comprise anhydrous ammonia, aqueous solutions of ammonia, aqueous solutions of ammonium nitrate or urea. These concentrated products may be diluted with water to form a concentrated liquid fertilizer (e.g., [[UAN]]). Advantages of liquid fertilizer are its more rapid effect and easier coverage.<ref name=Ull/> The addition of fertilizer to irrigation water is called "[[fertigation]]".<ref name=FertEncyl/> Granulated fertilizers are more economical to ship and store, not to mention easier to apply.<ref>{{cite book |doi=10.1002/14356007.n10_n03.pub2 |chapter=Fertilizers, 4. Granulation |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2016 |last1=Kiiski |first1=Harri |last2=Dittmar |first2=Heinrich |pages=1–32 |isbn=978-3-527-30673-2 }}</ref>

====Urea====
{{Main|urea}}
Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN), e.g., in 'foliar feed' fertilizers. For fertilizer use, granules are preferred over prills because of their narrower particle size distribution, which is an advantage for mechanical application.

Urea is usually spread at rates of between 40 and 300&nbsp;kg/ha (35 to 270&nbsp;lbs/acre) but rates vary. Smaller applications incur lower losses due to leaching. During summer, urea is often spread just before or during rain to minimize losses from [[ammonia volatilization from urea|volatilization]] (a process wherein nitrogen is lost to the atmosphere as ammonia gas).

Because of the high nitrogen concentration in urea, it is very important to achieve an even spread. Drilling must not occur on contact with or close to seed, due to the risk of germination damage. Urea dissolves in water for application as a spray or through irrigation systems.

In grain and cotton crops, urea is often applied at the time of the last cultivation before planting. In high rainfall areas and on sandy soils (where nitrogen can be lost through leaching) and where good in-season rainfall is expected, urea can be side- or top-dressed during the growing season. Top-dressing is also popular on pasture and forage crops. In cultivating sugarcane, urea is side dressed after planting and applied to each [[ratooning|ratoon]] crop.

Because it absorbs moisture from the atmosphere, urea is often stored in closed containers.

Overdose or placing urea near seed is harmful.<ref>{{cite journal|title=Biuret in Urea Fertilizers|url=http://forum.ipni.net/ppiweb/bcrops.nsf/$webindex/AFE7446D8AF92F988525732D0038FDCE/$file/07-3p06.pdf|pages=6–7|journal=Better Crops|volume=91|year=2007|issue=3|author=Mikkelsen, R.L.|access-date=2015-05-02|archive-url=https://web.archive.org/web/20151222132413/http://forum.ipni.net/ppiweb/bcrops.nsf/$webindex/AFE7446D8AF92F988525732D0038FDCE/$file/07-3p06.pdf|archive-date=2015-12-22|url-status=dead}}</ref>

===Slow- and controlled-release fertilizers===
{{excerpt|Controlled-release fertilizer}}

===Foliar application===
[[Foliar feeding|Foliar fertilizers]] are applied directly to leaves. This method is almost invariably used to apply water-soluble straight nitrogen fertilizers and used especially for high-value crops such as fruits. Urea is the most common foliar fertilizer.<ref name=Ull/>
[[File:Fertilizer-Burn.jpg|upright|thumb|Fertilizer burn]]

===Chemicals that affect nitrogen uptake===
[[File:N-butylthiophosphoryltriamide.svg|thumb|left|N-Butylthiophosphoryltriamide, an enhanced efficiency fertilizer.]]
Various chemicals are used to enhance the efficiency of nitrogen-based fertilizers. In this way farmers can limit the [[nitrogen pollution|polluting effects of nitrogen run-off]]. [[Nitrification]] inhibitors (also known as nitrogen stabilizers) suppress the conversion of ammonia into [[nitrate]], an anion that is more prone to leaching. 1-Carbamoyl-3-methylpyrazole (CMP), [[dicyandiamide]], [[nitrapyrin]] (2-chloro-6-trichloromethylpyridine) and 3,4-dimethylpyrazole phosphate (DMPP) are popular.<ref name="YangFang2016">{{cite journal|last1=Yang|first1=Ming|last2=Fang|first2=Yunting|last3=Sun|first3=Di|last4=Shi|first4=Yuanliang|title=Efficiency of two nitrification inhibitors (dicyandiamide and 3, 4-dimethypyrazole phosphate) on soil nitrogen transformations and plant productivity: a meta-analysis|journal=Scientific Reports|volume=6|issue=1|pages=22075|year=2016|issn=2045-2322|doi=10.1038/srep22075|pmid=26902689|bibcode=2016NatSR...622075Y|pmc=4763264}}</ref> [[Urease inhibitor]]s are used to slow the hydrolytic conversion of urea into ammonia, which is prone to evaporation as well as nitrification. The conversion of urea to ammonia catalyzed by enzymes called [[urease]]s. A popular inhibitor of ureases is ''N''-(''n''-butyl)thiophosphoric triamide ([[NBPT]]).

===Overfertilization===
Careful use of fertilization technologies is important because excess nutrients can be detrimental.<ref>{{cite web |url=http://hubcap.clemson.edu/~blpprt/nitrofer.html |title=Nitrogen Fertilization: General Information |publisher=Hubcap.clemson.edu |access-date=17 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120629000817/http://hubcap.clemson.edu/~blpprt/nitrofer.html |archive-date=29 June 2012 }}</ref> [[Fertilizer burn]] can occur when too much fertilizer is applied, resulting in damage or even death of the plant. Fertilizers vary in their tendency to burn roughly in accordance with their [[salt index]].<ref>{{cite book|last1=Garrett|first1=Howard|title=Organic Lawn Care: Growing Grass the Natural Way|date=2014|publisher=University of Texas Press|isbn=978-0-292-72849-3|pages=55–56|url=https://books.google.com/books?id=UEHTAwAAQBAJ&pg=PA55}}</ref><ref>{{cite web|url=http://www.soils.wisc.edu/extension/wcmc/2008/ppt/Laboski1.pdf |title=Understanding Salt index of fertilizers |access-date=22 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130528143421/http://www.soils.wisc.edu/extension/wcmc/2008/ppt/Laboski1.pdf |archive-date=28 May 2013 }}</ref>