Nitrogen is essential for all forms of life on our planet. Although plentiful (the air we breathe contains about 80 per cent elemental nitrogen) nitrogen is fairly inactive chemically and is inactive biologically.
In order for plants to be able to assimilate the nitrogen needed for proteins, DNA and chlorophyll, nitrogen must be transformed chemically.
Having taken up nitrogen, plants are consumed by animals and human beings, who also consume animals. Thus, we are able to use nitrogen compounds obtained from our food to produce the compounds essential for human life.
The Nitrogen Cycle is a complex ecosystem which fixes nitrogen from the atmosphere and recycles nitrogen back into the atmosphere.
Nitrogen is made available to plants in a number of ways, both natural and synthetic.
Natural processes depend, in the main, on bacteria in the soil that are able to fix atmospheric nitrogen and on bacteria in the root nodules of leguminous (peas and beans) plants.
The energy in lightening causes a chemical reaction between atmospheric nitrogen and oxygen to produce nitrates, which are washed down to earth by the rain so that plants can absorb these compounds.
The use of rotting organic matter (manure) is a time honoured way of adding nitrogen to the soil.
Again, bacterial action is an essential part of this process, ammonia produced by the rotting organic matter is converted to nitrates.
The natural production of nitrates is vitally important, but this produces only about 50% the quantity of nitrates needed to grow the crops needed to feed the world’s rapidly expanding population.
The application of synthetic nitrates (and trace elements) is the cornerstone of modern agriculture, without which human life as we know it would be impossible.
Synthetic nitrates are produced in vast quantities from ammonia which is produced by combining, at high temperature and pressure, atmospheric nitrogen with hydrogen from natural gas.
This process was developed by Fritz Haber and Bosch in the early 20th century. Many people regard the energy intensive production and use of artificial fertilizers as undesirable to say the least, but in order to produce the food we need in an economically viable way it is difficult to see an alternative.
It does not seem possible to meet the demand for food by organic methods of cultivation alone, although this may be highly desirable in the longer term.
Nitrogen, fortunately for us, travels round the ecosystem, again, we are dependant on natural processes of decay, and therefore bacteria, to facilitate the return of nitrogen to the atmosphere.
The work of Haber, a Nobel Laureate, and Bosch is still of great importance today.
However Haber is a controversial figure, long after his death. There can be no doubt that Haber’s work has greatly benefited the human race, but his legacy is somewhat overshadowed by his work on poisonous gases, in particular chlorine.