All I can think of with this is how gross that is for anyone below the balcony. There's not enough soil to actually filter out the urine and doesn't contain anything to break down the urates. You're essentially washing it down onto whoever is unfortunate enough to live beneath you or anyone unfortunate enough to be walking below, and after enough time all that dog urine is going to cause damage.

Please if you're going this route build something with a tray underneath that can collect the urine and water and can be emptied into the toilet. I know the person in the blog said they didn't want to do it because it's gross, but that's really the only sanitary way to deal with it unless you figured out how to build an entire living vivarium style system with thick layers and bacteria and bugs to actually break things down and filter properly..