Nitrogen is naturally abundant in the atmosphere. why are nitrogen fertilizers added to soil, despite the dangers they produce when they enter aquatic ecosystems?

Nitrogen fertilizers are added to soil because nitrogen is very important for plant growth and most organisms can not utilize atmospheric nitrogen. Even though the percentage of nitrogen in the atmosphere is very high, yet it is not available to most living organisms for use because the energy required to break the bonds that hold the diatomic nitrogen together is very high. 

The answer is 65.3312