Once you created the axe, you may have noticed that a villager used the axe on a tree by the crafting shack. When the tree died there is a seed by the trunk. A Master Farmer is needed to pick up the seed and bring in to the flooded field on the west East side of the map.
A Farming level 2 is needed for these following events to happen
When the apple seed is grown (give or take five hours, I took a nap and logged back on to find the field drained and tree grown) Have villager harvest the apple then bring it to the table for a future achievement.
You can use this field after a child plays in the dirt, creating holes, along with bringing four seeds from your seed bag and using Fert. Do this three times. The recipe is first with Grass and Wheat Grass to make the Mixed Herbs (10 mins). Then the Mixed Herbs and Earth (4 hours) to make the Fertilizer.