I have that planter and it is a bit shallow compared to my earthboxes, so it doesn't take long for roots of some things (garlic for me) to have most of it's roots in water rather than soil. At that point "nutes" (nutrients) , as they say on hydroponic forums, have to come from the water. It might be similar with Earthboxes within a month of planting, but it was really visable when you look in that little overflow drawer.
Here is a good resource; especially Khang Starr and Matt Garver.
https://plus.google.com/communities/...95557843932467