Corwin once asked me how to destroy a fallow field. This was twentyish years ago and he was playing some simulation game – Civilization 17 or something – and his armies were invading farms for reasons that I didn’t pursue. He needed to destroy the farms including the fallow fields. 

I vaguely remembered farmers would sometimes leave fields unused so that the soil can rebuild nutrients. I explained this to Corwin and asked “How would you destroy an unused field – plant wheat in it?”

I later thought that there could be ways to destroy a fallow field. Maybe you could salt it?

Anyway, I prefer the image of barbarian hordes viciously weeding, tilling soil, and planting crops.