it's definitely a bayonet from the 20th century. you can tell by the button at the base where you press to release it from the rifle. to me it looks like a ww1 german bayonet. google search butcher blade bayonet, it was made for the gewehr 98 rifle. not sure what it was doing in a field in ohio though. maybe some vet brought it back from the great war as a trophy and his kid took it out to play and lost it.