The Irrigation Tower allows you to supply fertilizer to your planter boxes if you combine it with Irrigation Flooring. This makes your life in My Time At Portia much easier, but it's quite expensive to get your hands on.
It's not currently possible to craft an Irrigation Tower, but you must instead buy it. The item is sold by Nora in the Church Store, and costs a whooping 10 Data Discs per Irrigation Tower. This means that you must be willing to spend quite a good time mining to get enough Data Discs for this single item, which makes sense when you consider how awesome the tower really is.
With this automatic fertilization, all your crops will become more valuable, and it might be extra good to keep together with a fruit tree or something that keeps in giving you great produce.