Editing Clover (section)

== Cultivation history ==
[[File:A drop of dew on a clover.jpg|thumb|A clover with a dewdrop in the middle|alt=A clover with a drop of dew in the middle]]
[[File:Clovers & Zrebar.jpg|thumb|Colorful flowers of clovers beside [[Zarivar Lake]] in [[Iran]]]]
[[File:Trifolium dubium RF.jpg|thumb|Lesser hop trefoil]]
[[File:Trifolium alpestre RF.jpg|thumb|Owl-head clover]]
[[File:2017-07-12 1655 clover.png|thumb|White clover]]
Clover was first domesticated in Spain in around the year 1000. During European urbanization, [[crop rotation]]s involving clover became essential for replacing the [[fixed nitrogen]] exported to cities as food.<ref name="world"/> Increased soil nitrogen levels from the spreading use of clover were one of the main reasons why European agricultural production in 1880 was about 275% of the production in 1750.<ref name="agri"/> Fields of clover, used as [[forage]] and newly-invented [[silage]], became an important part of the rural landscape;<ref name="world"/> adding clover made livestock feed more nutritious. Honey production also rose drastically, and clover remained the main nectar source for bees until the mid-twentieth century. Clover was carried around the world as a crop by [[European colonization|European colonists]], and some clover species became [[invasive species|invasive]] in some areas.<ref name="agri"/>

Imports of [[guano]]<ref name="agri"/> and the development of the [[Haber-Bosch process]] in the 20th century substantially displaced clover as a crop, with negative effects on pollinators,<ref name="world">{{cite journal |last1=Kjærgaard |first1=Thorkild |title=A Plant that Changed the World: The rise and fall of clover 1000-2000 |journal=Landscape Research |date=January 2003 |volume=28 |issue=1 |pages=41–49 |doi=10.1080/01426390306531 |bibcode=2003LandR..28...41K }}</ref> but in the 1990s and 2010s, the cost of industrially-fixed nitrogen rose substantially, approximately doubling, and reviving interest in forage mixes that include clover. As the fixation process is energy-intensive, prices are closely tied to energy prices. The 21st century has also seen interest in clover as a countermeasure to fight the global [[pollinator decline]].<ref name="agri">{{cite journal |last1=Harris |first1=Ciaran |last2=Ratnieks |first2=Francis L. W. |title=Clover in agriculture: combined benefits for bees, environment, and farmer |journal=Journal of Insect Conservation |date=June 2022 |volume=26 |issue=3 |pages=339–357 |doi=10.1007/s10841-021-00358-z |doi-access=free |bibcode=2022JICon..26..339H }}</ref>