The Planters Bag is used for farming and very useful when farming in large quantities.
Upon use, the item will consume 25 of the crop's seeds and plants them in a 5x5 area around you. By right clicking, the item will cycle through the crops that you can plant with it. These include wheat, potato, carrot, and beetroot. As long as you have enough seeds the Planters Bag will always consume 25 even when they are unable to be planted.
Where to Get It
The Planters Bag can be found in Enchanted Chests.