One of the challenges with container gardening and using planter boxes is applying adequate fertilizer. Raised garden beds have much more soil and nutrients available to the plants than anything raised in a container garden.
I’m using a fertilizer feeding system for my drip irrigation. This unit supplies a steady diet of nutrients to the plants when water flows through the system and out to the plants in the planter boxes. One advantage, is that the nutrients are metered out on a regular basis. A disadvantage is that the amount and volume of nutrients to feed are unknown and must be determined over time based on plant health and growth.