What are some other ways N gets to our plants from the air???
Big One: Nitrogen Fixation by legumes, possibly over 100 lbs/A from clover. Or, I mean 2.32 lbs per K.
A thunderstorm can produce about 0.4 lbs N per K as well, but is usually less. Does that sound right Ric? That's why things often seem green just after a thunderstorm I think.