I would think around 2x2. The space i used outside is about 4x4 and container plants can usually be planted at the minimum spacing which would be 6" for sweet corn and you want at least a 4x4 planting block for good pollination.

I would think around 2x2. The space i used outside is about 4x4 and container plants can usually be planted at the minimum spacing which would be 6" for sweet corn and you want at least a 4x4 planting block for good pollination.