Here we’ve got a comma splice, a comma missing from a compound sentence, and wonky capitalization.
The land had been salted during a bitter war. Centuries later when it’s able to be farmed again, the crops start growing, and the farmers discover something odd.
Unless you’ve got a story with a setting literally named the Land (yes, I read those novels, too), don’t capitalize land.
(I don’t like how the second sentence begins; it sounds a bit off to me. I’m trying to address only the actual errors, though, and ignore anything that is merely awkward or unclear.)