A (US:) colter / (British:) coulter (Latin 'culter' = 'knife') is a vertically mounted component of many ploughs that cuts an edge about 7 inches (18 cm) deep ahead of a plowshare.[1] Its most effective depth is determined by soil conditions.[2]
A (US:) colter / (British:) coulter (Latin 'culter' = 'knife') is a vertically mounted component of many ploughs that cuts an edge about 7 inches (18 cm) deep ahead of a plowshare.[1] Its most effective depth is determined by soil conditions.[2]
Its earliest design consisted of a knife-like blade.[3][1] In 2011 an early medieval coulter was excavated from a site in Kent, England.[4][5] Coulters using a flat rotating disc began being used c. 1900.[6][1] Its advantage was a smoothly cut bank, and it sliced plant debris to the width of the furrow.[2]
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.[1] It softens the soil, allowing the plough to undercut the furrow made by the coulter.[1]
A rolling coulter has an optional accessory called a jointer.[2] The jointer flips over a small part of the surface on top of the slice before the plowshare flips the main slice.[2] It ensures that all of the plant debris gets covered by the flipped slice.[2]