You use ammonia to add nitrogen to crops. Making ammonia is an extremely energy intensive process that already contributes about 2-3% of global carbon emmissions. [1]

So you could spray ammonia everywhere to promote growth, but it's not clear that you'll offset the carbon emissions from making so much ammonia in the first place.

[1] https://m.phys.org/news/2018-07-electrochemically-produced-a...

we are already doing that aggressively to feed everyone, and we worry it might be hard to keep it up, as is.