High production on commercial farms is often closely associated with high chemical fertiliser use. The argument which I am most often presented with is that because there is such high production, we have to rely on chemical fertiliser to support it. If we do not use chemical fertiliser, we will not be able to keep up, and the crop will not grow. I am sure you have heard this argument made, or possibly even made it yourself. There are numerous other blogs and articles on the Trace & Save website explaining why this is not the case, and advocating for alternative approaches to nutrient management. For example, How we are wasting money and nutrients, and negatively impacting the environment; See your farm as a system; Further proof of the positive effect of decreased nitrogen fertiliser; and Are you wasting nutrients on your farm?. These blogs also address some of the environmental impacts associated with excessive fertiliser use.
I was recently reminded that there is a further environmental impact resulting from agriculture’s reliance on chemical nitrogen fertiliser for food production. This impact is potentially much larger than we can measure or understand. It all started in 1910 with an invention called the Haber-Bosch process. This process is an artificial form of nitrogen fixation, i.e. it uses gaseous nitrogen from the atmosphere to form ammonia. The main use of this ammonia is the production of fertiliser. While this process has greatly contributed in the ability to produce large amounts of food on a commercial scale, it has associated negative environmental impacts which are very often overlooked. We tend to focus on the localized environmental impact of nitrogen where it is applied, but what about the broader impact associated with its production?
There are, broadly, two main forms of nitrogen which occur, reactive and unreactive forms. Approximately 78% of the earth’s atmosphere is made up of nitrogen, in the unreactive nitrogen gas form. The Haber-Bosch process converts this unreactive nitrogen into the reactive, ammonia, form. Since the invention of this process, and the substantial increase in chemical nitrogen use in agriculture, there has been a continually increasing amount of reactive nitrogen in natural systems. These increased levels of reactive nitrogen result in biodiversity loss, climate change, freshwater pollution and a changed global nitrogen cycle1,2,3. Although reactive nitrogen converted by the Haber-Bosch process does actually get used effectively for agricultural production, large amounts do not end up in agricultural products. That which is not used effectively is lost to the environment. Approximately 40% of that which is lost eventually returns to unreactive forms of nitrogen in the atmosphere. The problem is the other 60%. This nitrogen continually changes forms, for example from nitrates in the soil to nitrous oxides and nitrogen gas in the atmosphere, thereby cascading through terrestrial, aquatic, marine and atmospheric ecosystems resulting in the mentioned environmental impacts1.
Over and above these environmental impacts, the Haber-Bosch process is very energy intensive, using a large amount of electricity to convert unreactive nitrogen gas into reactive ammonia. The fact that so much of this converted nitrogen actually just ends up back as unreactive nitrogen in the atmosphere again means that it is a very inefficient process1.
I think the challenge for agriculture is clear. We need to figure out how to productively and efficiently grow produce, ensuring food security, and the supply of an array of other agricultural goods and services, while not relying so heavily on chemical nitrogen fertiliser. The environmental impacts are just too large to properly understand or mitigate. We must implement innovative, sustainable and productive ways of food production which do not rely on chemical nitrogen, in order to ensure sustainable and long-term food production.
- Erisman JW, Sutton MA, Galloway J, Klimont Z & Winiwarter W. 2008. How a century of ammonia synthesis changed the world. Nature Geoscience 1(10):636–639.
- Fields S. 2004. Global nitrogen: Cycling out of control. Environmental Health Perspectives 12(10):A556–A563.
- Galloway JN, Townsend AR, Erisman JW, Bekunda M, Cai Z, Freney JR, Martinelli LA, Seitzinger SP & Sutton MA. 2008. Transformation of the nitrogen cycle: Recent trends, questions, and potential solutions. Science 320(5878):889–892.
Craig loves travelling and tries to go on an overseas adventure to new and interesting places every opportunity he gets. He loves an engaging conversation or a good book. He is a bit of a coffee snob and foodie, so be sure to let him know about any new and interesting coffee shops or restaurants he should try out. He is also a big sports fan, most notably of the New England Patriots.
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