I remember reading Alistair Horne's excellent book on Verdun, "The Price of Glory," and he says that there was something like a ton of explosive detonated for every square yard of the battlefield, rendering the soil to the consistency of fine sand.
If you tour the Verdun battlesite, because of the huge about of nitrates/nitrites in the soil from all the explosives detonated, there are still today acres upon ares of soil where nothing grows...it looks like the surface of the moon..