coulter (agriculture)
{{Short description|Vertically mounted component of plow}}
A (US:) colter / (British:) coulter (Latin 'culter' = 'knife') is a vertically mounted component of many ploughs that cuts an edge about {{convert|7|in|cm}} deep ahead of a plowshare.{{cite book|last=Stephens|first=Henry|title=The Book of the Farm Vol 1|year=1854|publisher=W. Blackwood|pages=271–272|url=https://books.google.com/books?id=X15GAAAAYAAJ&q=%22coulter%22+-ann+plow&pg=PA272}} Its most effective depth is determined by soil conditions.{{cite book|last=Bacon|first=Charles Allen|title=The Oliver plow book: a treatise on plows and plowing|year=1920|publisher=Oliver Farm Equipment Company|pages=160–162|url=https://books.google.com/books?id=nAY9AAAAYAAJ&q=%22coulter%22+-ann+plow&pg=PA160}}
History
Its earliest design consisted of a knife-like blade.{{cite book|title=Our Steel Beam Rod Breakers from $6.50 to $7.70|publisher=1896 Sears Roebuck & Co. catalog}} In 2011 an early medieval coulter was excavated from a site in Kent, England.{{Cite journal |last1=Thomas |first1=Gabor |last2=McDonnell |first2=Gerry |last3=Merkel |first3=John |last4=Marshall |first4=Peter |date=2016 |title=Technology, ritual and Anglo-Saxon agriculture: the biography of a plough coulter from Lyminge, Kent |url=https://www.cambridge.org/core/journals/antiquity/article/technology-ritual-and-anglosaxon-agriculture-the-biography-of-a-plough-coulter-from-lyminge-kent/3EA15DA20A8F6153299E4561008E345C |journal=Antiquity |language=en |volume=90 |issue=351 |pages=742–758 |doi=10.15184/aqy.2016.73 |s2cid=55156730 |issn=0003-598X|doi-access=free }}{{Cite news |date=2011-04-07 |title=Anglo-Saxon 7th Century plough coulter found in Kent |language=en-GB |work=BBC News |url=https://www.bbc.com/news/uk-england-12997877 |access-date=2023-01-13}} Coulters using a flat rotating disc began being used c. 1900.{{cite book|title=Our $9.75 Walking Plow|publisher=1896 Sears Roebuck & Co. Catalog}} Its advantage was a smoothly cut bank, and it sliced plant debris to the width of the furrow.
Results
In his 1854 book, Henry Stephens used dynamometer measurements to conclude that a plough without a coulter took about the same amount of force to pull but using a coulter resulted in a much cleaner result. It softens the soil, allowing the plough to undercut the furrow made by the coulter.
Jointer
File:Coulter and Jointer Ferguson Plow.jpg
A rolling coulter has an optional accessory called a jointer. The jointer flips over a small part of the surface on top of the slice before the plowshare flips the main slice. It ensures that all of the plant debris gets covered by the flipped slice.