How about you try working it out? What is ammonia? NH3. N = Nitrogen. H = Hydrogen, and there are three (3) of 'em.
What does ammonia break down into? Ultimately, it can be broken down to nitrogen gas and the other composite compounds after oxidation. Either way, as it is oxidized (broken down) into its different parts, the good bits such as nitrogen are released.
Look at some fertilizers. What are they comprised of..? Urea..! Ammoniacal Nitrogen, what is that? Nitrogen derived from an ammonia source. Ammonium sulfate, ammonium phosphate.
You'll burn the plants if you pee on them directly and they're not large enough, but diluted it seems to make sense.
Especially considering that root growth is enhanced in media with a pH of below 7 (neutral), no lower than 5.5 based on my research. So, for someone such as myself who can't afford filtration and has both high pH
and highly alkaline (strong buffering capacity = resistance to pH shift) water source, it makes even
more sense. To that end, I had my husband proffer some beer-laden urine to my efforts. If my son finds out what we did with his big pitcher, he'll.. he'll probably pitch a fit.
(P.S. Chemical burns can be via base; i.e. high pH value, not just acids.)