The Irrigation Flooring is great if you want to set up a system where you can automatically fertilize all your crops. You cannot craft this Irrigating Flooring yourself, but you must instead buy it.
In order to get Irrigation Flooring, head to the Church Store and talk with Nora. She sells a variety of items, including the Irrigation Flooring. Each floor tile cost 1x Data Disc instead of Gols, so make sure to bring these.
It can take a lot of Irrigating Flooring to set up a complete irrigation system, so the total cost of the set up is going to cost many more Data Discs than just the one for a single Irrigation Floor. This means that you probably won't get this set up early in the game, unless you really love mining!