Compare the rate of human contributions to nitrogen fixation with the natural rate.

Nitrogen fixation is the modification of nitrogen present in the atmosphere into a combined form (e. g ammonia) via chemical and some biological action (microbes like soil rhizobia).

Human processes, e. g fertilizers production and fossil fuels consumption, have majorly affected to a high amount the level of fixed nitrogen in the Earth's ecosystems. It is believed that the level of nitrogen fixed by human process will be much more than that fixed via microbial processes involving diazotrophs such bacteria as Azotobacter and archaea as effected by enzyme nitrogenases.

The rate amounting from nitrogen fixation is believed to be 140 teragrams (Tg) of nitrogen per year (1 teragram is equivalent to 1 million metric tons). This amount is very small when viewed to the level at which human factors or means of contribution increases nitrogen amount to the environment.