Science - nitrogen

In fertilizer Nitrogen is in the form of ammonia or ammonium ion.
80% of the air is made of Nitrogen.
Crops need N, O, and H.
Plants like peas, soy beans and clover can use N2 because they have bacteria on them, that automatically changes the N2 into nitrogen that can actually be used by the plants.

 Nitrogen can harm the environment by running into lakes and rivers and then out into the oceans, in that way destroying marine life, and it can reduce the amount of Ozone.
Changing the crops from annual crops, into perennial crops can reduce the amount of nitrogen use because, if we change them from annual crops, into crops that can grow for more than one year, then we don't need to use nearly as much fertilizer because, we won't have to plant the crops every year.