Editing Hay (section)

== Fertilization and weed control ==

Modern hay production often relies on artificial fertilizer and herbicides. Traditionally, [[manure]] has been used on hayfields, but modern chemical fertilizers are used today as well. Hay that is to be certified as weed-free for use in [[wilderness area]]s must often be sprayed with chemical herbicides to keep unwanted weeds from the field, and sometimes even non-certified hayfields are sprayed to limit the production of [[noxious weed]]s. Organic forms of fertilization and weed control are required for hay grown for consumption by animals whose meat will ultimately be certified organic. To that end, compost and field rotation can enhance soil fertility, and regular mowing of fields in the growth phase of the hay will often reduce the prevalence of undesired weeds. In recent times, some producers have experimented with human [[sewage sludge]] to grow hay. This is not a certified organic method and no warning labels are mandated by EPA.<ref>{{cite web|url=http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELDEV3004446|title=Certified Organic Requirements|access-date=2012-01-02|archive-date=2015-07-06|archive-url=https://web.archive.org/web/20150706231920/http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELDEV3004446|url-status=dead}}</ref> One concern with hay grown on human sewage sludge is that the hay can take up heavy metals, which are then consumed by animals.<ref>{{cite journal|doi=10.1016/0048-9697(91)90377-Q | pmid=2063180 | volume=100 | title=The behaviour of heavy metals in sewage sludge-amended soils | journal=Science of the Total Environment | pages=151–176| year=1991 | last1=Alloway | first1=Brian J. | last2=Jackson | first2=Andrew P. | bibcode=1991ScTEn.100..151A }}</ref> [[Molybdenum]] poisoning is a particular concern in [[ruminant]]s such as cows and goats, and there have been animal deaths.<ref>{{cite web|title=Molybdenum Poisoning: Introduction|url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/212100.htm}}</ref><ref>{{cite web|url=http://www.soil.ncsu.edu/about/century/micronutrient.html|title=Metal uptake by plants|access-date=2013-08-14|archive-url=https://web.archive.org/web/20121122122956/http://www.soil.ncsu.edu/about/century/micronutrient.html|archive-date=2012-11-22|url-status=dead}}</ref><ref>{{cite web|url=http://www.sludgenews.org/resources/documents/McElmurrayTestimony.pdf |archive-url=https://web.archive.org/web/20100714050115/http://www.sludgenews.org/resources/documents/McElmurrayTestimony.pdf |archive-date=2010-07-14 |url-status=live|title=Contamination on McElmurray farm from human sewage sludge fertilizer}}</ref> Another concern is with a herbicide known as [[aminopyralid]], which can pass through the digestive tract in animals, making their resulting manure toxic to many plants and thus unsuitable as fertilizer for food crops.<ref>{{cite web|last=Pleasant |first=Barbara |url=http://www.motherearthnews.com/Grow-It/Milestone-Herbicide-Contamination-Creates-Dangerous-Toxic-Compost.aspx |title=Milestone Herbicide Creates Killer Compost |publisher=Motherearthnews.com |date=2009-07-24 |access-date=2012-02-23}}</ref> Aminopyralid and related herbicides can persist in the environment for several years.