The Somme's Iron Harvest
The iron harvest is the annual harvest of unexploded ordnance, barbed wire, shrapnel balls, bullets and congruent trench supports collected by Belgian and French farmers after ploughing their fields. The harvest generally applies to the material from The Great War which is still found in large quantities across the former Western Front.
It has been estimated that, for every square metre of territory on the front from the coast to the Swiss border, a tonne of explosives fell. One shell in every four (some sources say one in every three) did not detonate. The Canadian National Vimy Memorial Site is notable for supposedly having one unexploded munition for every square metre.
Given the swamp-like conditions of trench warfare in the period, the unexploded weapons - in the form of shells, bullets and grenades - were quickly swallowed in the mud. As time passes, construction work, field ploughing and natural processes bring the rusting shells to the surface. Most of the iron harvest is found during the spring planting and fall plowing.