These chests and boxes will appear occasionally after you clear weeds, trees, and other rubble.

You can get farm resources when you open Reward Chests. They will be on your farm for a limited time and will require different currencies to open. To view the items you could earn, tap on the Info button.

If you want to move the Reward Chest to another place or remove it from your farm, give it a long press. You can then either drag it to a free space on your farm, rotate it, or tap the Dollar button to sell it.