Fertile Soil Pile is created by dumping a basket of soil or soil-filled backpack on the ground. Using a Clay Bowl will get 3 Bowl of Soil. It can be tilled using a hoe. A pile of 1 soil requires 2 tillings to get Deep Tilled Row. A pile of 2 or 3 soil only requires 1 tilling.
Note: It is considered a waste to till a soil pile with 3 bowls worth of soil since it gives the same as a 2 soil pile.