For some reason, the dwarves keep putting a lot of seeds in once specific corner. Is this supposed to happen?
The answer is that there's also a chair there. What's happening is the dwarfs are eating at that location, which creates a seed. It's then left in place, as there's no storage available for the new item.
If you want to avoid the mess, create some bags at a clothier or leatherworker's work area and your dwarfs will collect the seeds and store them in a food stockpile.