The bolt is from a John Deere Cultivator Implement and has sheered, losing its threaded end. It was found in the margins of the cultivated area on the West of the site. John Deere machinery is easily recognisable as its livery is a bright green and yellow, and the bolt has JD stamped on its top. The bolt is made of forged steel, and although it rusts, it would take many years to break down in the soil.
The big three Tractor makers have appropriated colours to their brands to make them instantly recognisable. Thus John Deere is green and yellow, Massey Ferguson is red, and New Holland is blue. A tractor gets its name because it was a vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds.