This thought just came to me, born out of total ignorance, but I have no shame.
I was reading about a fertilizer for vegetables that contains Calcium and other minerals, etc. that is supposed to be so good for vigorous plant grown and strength. So, what would be the problem with using juice from freshly juiced vegetables to add nutrients to the soil? You could dilute it with water. It would certainly contain vital nutrients.
The only thing that might be a problem would be attracting pests. But, diluting it should help. Also, only pouring it around the immediate base of the stem instead of all over the soil area.
We drink juiced vegetables and fruits to acquire needed nutrients for ourselves, so maybe it would work with plants. They might freak out, though, if you watered them with the juice of the same type of plant...cannibal plants.
It might be interesting to share a morning juice drink with the plants. Any thoughts?