Is household ammonia okay for plants? My father-in-law claims that since plants need nitrogen to produce proteins, and since ammonia is NH3, that Ammonia should be fine for the plants, since it's just nitrogen and water and hydrogen, according to him. We were cleaning a rusty chain and a bunch of spilled into our garden. I'm talking about household ammonia. Is that true? I'm thoroughly convinced he is an utter idiot but then again he could be right since he does say he minored in Chemistry in his college days.

Okay, he's not wrong, technically speaking. Practically speaking _never ever fertilize your plants with ammonia_.

The ammonia you spilled will be converted into nitrates eventually, so it's not like you spilled lead into your garden. On the other hand the populations of nitrifying bacteria take a fairly long time to adapt to a bounty like "a bunch" of household ammonia (their idea of a banquet beyond their wildest dreams is 2-4 ppm ammonia) but they will eventually eat it all.

(Fishkeepers should know about the nitrogen cycle, because you have to set up a complete yet tiny version of the real thing, which takes at least a week to establish)

So your plants will be fine... next year. This year they might have a little bit of trouble considering ammonia is a base and can burn plants directly or indirectly. Don't fertilize your plants with ammonia. They will probably die.