Editing Crop rotation (section)

=== Nitrogen fixing===

Rotations can add nutrients to the soil. [[Legume]]s, plants of the family [[Fabaceae]], have nodules on their [[root]]s which contain [[nitrogen fixation|nitrogen-fixing]] [[bacterium|bacteria]] called [[rhizobium|rhizobia]]. During a process called nodulation, the rhizobia bacteria use nutrients and water provided by the plant to convert atmospheric nitrogen into ammonia, which is then converted into an organic compound that the plant can use as its nitrogen source.<ref>{{Cite web |url=http://www.public.iastate.edu/~teloynac/354n2fix.pdf |title=Nitrogen Fixation by Forage Legumes |last=Loynachan |first=Tom |date=1 December 2016 |website=Iowa State University |publisher=Department of Agrology |access-date=1 December 2016 |archive-url=https://web.archive.org/web/20130503221208/http://www.public.iastate.edu/~teloynac/354n2fix.pdf |archive-date=3 May 2013 |url-status=dead}}</ref> It therefore makes good sense agriculturally to alternate them with cereals (family [[Poaceae]]) and other plants that require [[nitrate]]s. How much nitrogen made available to the plants depends on factors such as the kind of legume, the effectiveness of rhizobia bacteria, soil conditions, and the availability of elements necessary for plant food.<ref>{{Cite web |url=http://www1.foragebeef.ca/$Foragebeef/frgebeef.nsf/all/frg90/$FILE/fertilitylegumefixation.pdf |title=Nitrogen Fixation and Inoculation of Forage Legumes |last=Adjei |display-authors=etal |first=M. B. |date=1 December 2016 |website=Forage Beef |publisher=University of Florida |access-date=1 December 2016 |archive-url=https://web.archive.org/web/20161202170130/http://www1.foragebeef.ca/$Foragebeef/frgebeef.nsf/all/frg90/$FILE/fertilitylegumefixation.pdf |archive-date=2 December 2016 |url-status=dead}}</ref>