Fertilizer is an "upgrade" applied to regular dirt that enables plants and vegetables to produce additional items when Farming.
Fertilizer is used in conjunction with a Gardening Hoe to increase the yield planted crops produce.
Fertilizer is not used directly but must be located in the player's backpack or Toolbelt.
Players should equip a Gardening Hoe then right-click while aiming at block of dirt. If the dirt block has not been tilled, it will change color and will now yield produce from planted crops.
If the dirt has already been tilled and the player right-clicks again, the Gardening Hoe will attempt to use any Fertilizer in the player's inventory and upgrade the dirt. The newly upgraded dirt will have small white patches indicating Fertilizer has been used.
Dirt only needs to be upgraded once with Fertilizer, even after planting, harvesting, and replanting crops.
Fertilizer is most often looted from the following items: