Editing Ammonium (section)

== Biology ==
{{Main|Excretion}}
[[File:Nitrogen Cycle 2.svg|thumb|293x293px|Ammonium exists as a result of ammonification and [[decomposer]]s. Ammonium is eventually nitrified, where it contributes to the flow of [[nitrogen]] through the ecosystem. Human impacts are not shown here, but can impact the global [[nitrogen cycle]].]]
Because [[nitrogen]] often limits net [[primary production]] due to its use in [[enzyme]]s that mediate the biochemical reactions that are necessary for life, ammonium is utilized by some microbes and plants.<ref name=":03">{{Citation |last1=Schlesinger |first1=William H. |title=Chapter 12 - The Global Cycles of Nitrogen, Phosphorus and Potassium |date=2020-01-01 |work=Biogeochemistry (Fourth Edition) |pages=483–508 |editor-last=Schlesinger |editor-first=William H. |url=https://www.sciencedirect.com/science/article/pii/B9780128146088000128 |access-date=2024-03-08 |publisher=Academic Press |doi=10.1016/b978-0-12-814608-8.00012-8 |isbn=978-0-12-814608-8 |last2=Bernhardt |first2=Emily S. |editor2-last=Bernhardt |editor2-first=Emily S.}}</ref> For example, energy is released by the [[Redox|oxidation]] of ammonium in a process known as [[nitrification]], which produces [[nitrate]] and [[nitrite]].<ref name=":1">{{Cite journal |last=Rosswall |first=T. |date=1982 |title=Microbiological regulation of the biogeochemical nitrogen cycle / Regulación microbiana del ciclo bíogeoquímico del nitrógeno |url=https://www.jstor.org/stable/42934020 |journal=Plant and Soil |volume=67 |issue=1/3 |pages=15–34 |doi=10.1007/BF02182752 |jstor=42934020 |issn=0032-079X}}</ref> This process is a form of [[Auxotrophy|autotrophy]] that is common amongst ''[[Nitrosomonas]]'', ''[[Nitrobacter]]'', ''[[Nitrosolobus]]'', and ''[[Nitrosospira]]'', amongst others.<ref name=":1" />

The amount of ammonium in soil that is available for [[nitrification]] by microbes varies depending on environmental conditions.<ref>{{Cite journal |last1=Barsdate |first1=Robert J. |last2=Alexander |first2=Vera |date=January 1975 |title=The Nitrogen Balance of Arctic Tundra: Pathways, Rates, and Environmental Implications |url=https://acsess.onlinelibrary.wiley.com/doi/10.2134/jeq1975.00472425000400010025x |journal=Journal of Environmental Quality |language=en |volume=4 |issue=1 |pages=111–117 |doi=10.2134/jeq1975.00472425000400010025x |bibcode=1975JEnvQ...4..111B |issn=0047-2425}}</ref><ref>{{Cite journal |last1=Nadelhoffer |first1=Knute J. |last2=Aber |first2=John D. |last3=Melillo |first3=Jerry M. |date=1984-10-01 |title=Seasonal patterns of ammonium and nitrate uptake in nine temperate forest ecosystems |url=https://doi.org/10.1007/BF02140039 |journal=Plant and Soil |language=en |volume=80 |issue=3 |pages=321–335 |doi=10.1007/BF02140039 |bibcode=1984PlSoi..80..321N |issn=1573-5036}}</ref> For example, ammonium is deposited as a waste product from some animals, although it is converted into [[urea]] in mammals, sharks, and amphibians, and into [[uric acid]] in birds, reptiles, and terrestrial snails.<ref>{{Cite book |last1=Campbell |first1=Neil A. |url=http://archive.org/details/biologyc00camp |title=Biology |last2=Reece |first2=Jane B. |date=2002 |publisher=San Francisco : Benjamin Cummings |others=Internet Archive |isbn=978-0-8053-6624-2}}</ref> Its availability in soils is also influenced by [[Mineralization (soil science)|mineralization]], which makes more ammonium available from organic [[nitrogen]] sources, and [[Immobilization (soil science)|immobilization]], which sequesters ammonium into organic [[nitrogen]] sources, both of which are mitigated by biological factors.<ref name=":1" />

Conversely, [[nitrate]] and [[nitrite]] can be reduced to ammonium as a way for living organisms to access [[nitrogen]] for growth in a process known as assimilatory nitrate reduction.<ref name=":2">{{Cite journal |last1=Tiedje |first1=J. M. |last2=Sørensen |first2=J. |last3=Chang |first3=Y.-Y. L. |date=1981 |title=Assimilatory and Dissimilatory Nitrate Reduction: Perspectives and Methodology for Simultaneous Measurement of Several Nitrogen Cycle Processes |url=https://www.jstor.org/stable/45128674 |journal=Ecological Bulletins |issue=33 |pages=331–342 |jstor=45128674 |issn=0346-6868}}</ref> Once assimilated, it can be incorporated into [[protein]]s and [[DNA]].<ref>{{Cite journal |last1=Llácer |first1=José L |last2=Fita |first2=Ignacio |last3=Rubio |first3=Vicente |date=2008-12-01 |title=Arginine and nitrogen storage |url=https://www.sciencedirect.com/science/article/pii/S0959440X08001541 |journal=Current Opinion in Structural Biology |series=Catalysis and regulation / Proteins |volume=18 |issue=6 |pages=673–681 |doi=10.1016/j.sbi.2008.11.002 |pmid=19013524 |issn=0959-440X|hdl=10261/111022 |hdl-access=free }}</ref>

Ammonium can accumulate in soils where [[nitrification]] is slow or inhibited, which is common in hypoxic soils.<ref>{{Cite journal |last1=Wang |first1=Lixin |last2=Macko |first2=Stephen A. |date=March 2011 |title=Constrained preferences in nitrogen uptake across plant species and environments |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2010.02260.x |journal=Plant, Cell & Environment |language=en |volume=34 |issue=3 |pages=525–534 |doi=10.1111/j.1365-3040.2010.02260.x |pmid=21118424 |issn=0140-7791}}</ref> For example, ammonium mobilization is one of the key factors for the [[Symbiosis|symbiotic]] association between plants and fungi, called [[mycorrhiza]]e.<ref>{{Cite journal |last1=Hodge |first1=Angela |last2=Storer |first2=Kate |date=2015-01-01 |title=Arbuscular mycorrhiza and nitrogen: implications for individual plants through to ecosystems |url=https://doi.org/10.1007/s11104-014-2162-1 |journal=Plant and Soil |language=en |volume=386 |issue=1 |pages=1–19 |doi=10.1007/s11104-014-2162-1 |bibcode=2015PlSoi.386....1H |issn=1573-5036}}</ref> However, plants that consistently utilize ammonium as a [[nitrogen]] source often must invest into more extensive root systems due to ammonium's limited mobility in soils compared to other [[nitrogen]] sources.<ref>{{Cite journal |last1=Raven |first1=John A. |last2=Linda |first2=Bernd Wollenweber |last3=Handley |first3=L. |date=May 1992 |title=Ammonia and ammonium fluxes between photolithotrophs and the environment in relation to the global nitrogen cycle |url=https://nph.onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1992.tb01087.x |journal=New Phytologist |language=en |volume=121 |issue=1 |pages=5–18 |doi=10.1111/j.1469-8137.1992.tb01087.x |issn=0028-646X}}</ref><ref>{{Cite journal |last1=Bloom |first1=A. J. |last2=Jackson |first2=L. E. |last3=Smart |first3=D. R. |date=March 1993 |title=Root growth as a function of ammonium and nitrate in the root zone |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.1993.tb00861.x |journal=Plant, Cell & Environment |language=en |volume=16 |issue=2 |pages=199–206 |doi=10.1111/j.1365-3040.1993.tb00861.x |issn=0140-7791}}</ref>