The interactive version shows the nitrogen flows by continent. Here is an article and diagram of the nitrogen cycle.
Managing the nitrogen cycle is one of the 21st Century's Grand Engineering Challenges. Here is what the GEC site says about the nitrogen cycle:
A further but less publicized environmental concern involves the atmosphere’s dominant component, the element nitrogen. The biogeochemical cycle that extracts nitrogen from the air for its incorporation into plants — and hence food — has become altered by human activity. With widespread use of fertilizers and high-temperature industrial combustion, humans have doubled the rate at which nitrogen is removed from the air relative to pre-industrial times, contributing to smog and acid rain, polluting drinking water, and even worsening global warming. Engineers must design countermeasures for nitrogen cycle problems, while maintaining the ability of agriculture to produce adequate food supplies.
Here is a good, brief discussion on managing the nitrogen cycle, with references.
We can thank Fritz Haber and Carl Bosch for developing artificial nitrogen fertilizer, which revolutionized agriculture. Haber developed the chemistry to produce ammonia
N2 + 3 H2 → 2 NH3 (ΔH = −92.22 kJ·mol−1) exothermic reaction
from nitrogen and hydrogen and Bosch engineered the process, now known as the Haber process or Haber-Bosch process. The engineered process is one hundred years old; 2013 is the 100th anniversary. Both Haber (1918) and Bosch (1931) won Nobel prizes for their efforts.
You can also produce explosives from the ammonia.
Who would have imagined we'd have a huge problem with too much soluble nitrogen one hundred years later. Think 'dead zones' in the ocean, water pollution...
Unintended consequences in spades.
"A lot of people ask, 'Do you think humans are parasites?' It's an interesting idea and one worth thinking about....If the biosphere is our host, we do use it up for our own benefit. We do manipulate it. We alter the flows and fluxes of elements like carbon and nitrogen to benefit ourselves—often at the expense of the biosphere as a whole." - Carl Zimmer