1888: Nitrogen fixation - The book of science

Nitrogen fixation
Mysterious biology
Natural efficiency
Commentary

Nitrogen fixation

The practice of planting beans
to improve the next crop had been known
since the Egyptians and the Greeks.
Why this worked wasn’t known
until Daniel Rutherford isolated nitrogen from air
and Hellriegel and Hermann Wilfarth figured out
that the bacterium Rhizobium
growing in nodules on the roots of legumes
converts nitrogen gas into a soluable form
that plants can use.

Mysterious biology

Odd that all living organisms should require
the most abundant element
in only small amounts
except for the difficulty
of breaking the bonds of nitrogen gas
to render it as ammonia or nitrate
and as for that
no industrial process can compete
with the efficiency of natural processes.

Natural efficiency

Green plants generate energy from photosynthesis
more efficiently than the best solar panels.
Green plants work with bacteria to fix nitrogen
more efficiently than any industrial process.
This could explain why it’s so hard
to rid my yard of snails and weeds.

Earth’s atmosphere is 78.09% nitrogen in its diatomic form (N₂), in which pairs of nitrogen atoms are joined by an extremely strong bond. All living organisms require nitrogen in their DNA and RNA; all green plants require nitrogen as a primary nutrient. About 3% of the human body is nitrogen.

After diatomic nitrogen is broken, it can be combined with other elements into many useful forms, including ammonia (NH₃), nitrate (NO₃) used for artificial fertilizers, nitric acid (HNO₃), nitroglycerin used for explosives such as dynamite, and cyanides (which include a nitrogen atom triple-bonded to a carbon). When these compounds decompose back to nitrogen gas, they release large amounts of energy, and can, therefore, explode.

Rhizobia are not the only miracles of nature that fix nitrogen. Some non-legumes have nitrogen-fixing symbiotic associations with cyanobacteria or Frankia bacteria. All natural nitrogen-fixing processes use an enzyme complex named nitrogenase. Also, there are industrial processes to create ammonia and other nitrogen compounds including a process based on a method used by Henry Cavendish in 1784.