Fertilizer makes crop yield more ingredients. This guide on How To Get More Fertilizer In Summer In Mara will tell you how you can learn the Fertilizer recipe as the free Fertilizer that spawns near your farm on your home island is in very limited supply, and takes a long time to respawn, if at all.
You can get Fertilizer for free at your home island. There’s a small patch of dirt with a sign next to where you grow your crops. Over time, Fertilizer does appear here, but it takes a very long time. For a better, more reliable source, you will need to learn the recipe for Fertilizer yourself, so you can make it on your home island.
How To Get More Fertilizer In Summer In MaraOnce you arrive at Qalis, a lot of new characters appear and a lot of new quests are unlocked. You need to speak with Pilly, the lady in the flowery dress at the Market on Qalis. Her quests are not immediately available but as you continue to help other characters on the island, her chain of quests will eventually become unlocked. They are very simple delivery quests, taking items from Pilly and handing them to other residents. Eventually you will be asked to deliver a bag of Fertilizer to the miserable banker. Once you have completed that delivery, you learn the recipe for Fertilizer.
You need 1x Herb, 1x Coal and 1x Cork. All of these can be purchased on the market. Herbs are a fern-like plant that can be found on some islands. You can get coal from setting fire to trees using a Campfire and a torch, I’ve yet to find an alternative source of Cork outside of the market. There are also some bags of Fertilizer on the garden just overseeing the port in Qalis.
Once you have the ingredients you can make the Fertilizer yourself.