After updating to the latest version of Agricraft (0.5.0-a6), all existing crops in the world disappeared, and new crop sticks crafted won't place into farmland, or anywhere else.

I'm having the same issue. Can't place crop sticks on wet farmland. They do place on dry farmland, however. Care to post your modlist?

Try deleting the config/AgriCraft/JSON/default directory and letting it regenerate.

Fixed it for me, thanks :)

I think that it's probably just out-of-date JSONs, so I am closing this issue.