Two northwest Iowa men have been killed in tractor accidents in the past two days. Osceola County authorities say a rural Ashton man died when his tractor overturned Thursday afternoon as he mowed a ditch in front of his house. 64-year-old Marvin Strouth was pinned under the tractor and later died. On Wednesday night, 60-year-old Rick Zieman of Hartley was killed in a similar accident while mowing the ditch near his home.