The nitrogen cycle overwhelmed: fertiliser pollution and dead zones

A fertilizer truck spreads nitrogen fertilizer on a field in Texas. Image: AgriLife TodayArtificial nitrogen fertilisers are now readily available thanks to the Haber-Bosch process (invented in Germany in the early 20th century). They are made by reacting nitrogen gas (from the atmosphere, most of which is nitrogen) with hydrogen gas to make ammonia compounds which plants need to grow properly. The hydrogen comes from methane which comes from natural gas, a fossil fuel. And the process itself requires high-pressures and temperatures which uses a lot of energy and that, of course, also comes from fossil fuels.

Today these fertilisers are heavily used throughout the world because they're cheap, convenient and effective and mean more food can be grown. But there are downsides and they are big ones: pollution of the atmosphere and oceans. When farmers scatter it on their fields, soil microbes convert some of it into nitrous oxide, a powerful greenhouse gas which adds to global warming. And because these fertilisers easily dissolve in water, heavy rains can cause a lot of it to run off into lakes, rivers and the sea where it creates dead zones. Find out about these in this video from NASA: