[Zeus]

Does anyone know of a water soluble compound that would not harm grass or soil in concentrated amounts? Salt, for example, can dehydrate the roots of plants causing them to wilt.

I'm not sure if this is the correct place to ask this question.
Sorry, first post.

[Arkcon]

Does anyone know of a water soluble compound that would not harm grass or soil in concentrated amounts? Salt, for example, can dehydrate the roots of plants causing them to wilt.

No.  Not as you've asked it.  All living things are damaged by osmotic shock.  If I drank a big glass of concentrated compound that wasn't immediately toxic, I'd still need to drink some water to dilute it in my system, or I'd die.  Plants are worse off -- they can't run away and get a drink, they have to live with what is surrounding their roots.  You can very easily make a concentrated solution of water soluble plant food, and kill plants just as easily as you can with sodium chloride.

Of course, you haven't said how concentrated, so there can always be a caveat.  Yes sodium chloride is more toxic to plants than potassium nitrate.  But the basic underlying concept still applies.