Sunday Feature: Nitrogen is costing us all dearly


Tom Jordan takes a deep look at the role Nitrogen plays on our farms - It's Sunday feature time!

Sunday Feature: Nitrogen is costing us all dearly

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  • 3 years ago

Tom Jordan takes a deep look at the role Nitrogen plays on our farms - It's Sunday feature time!

Fertilizer costs are a major headache for farmers. After crops have been harvested and animals have been fattened or fed, the land must be replenished somehow as nutrients must be replaced. The most fundamental nutrient is nitrogen, without which nothing will grow.

As Europe's population expanded throughout the nineteenth century, there was a huge global trade in saltpetre, a mineral deposit found in the Chilean desert, and guano, bird dropping deposits found in Peru and Chile. These were shipped to Europe for the purpose of securing increased food production. Nitrogen rich guano was prized, but just as farmers mechanised their output to feed rising populations, the guano began to run out and there were similar fears that salpetre deposits were also getting depleted. Another source of nitrogen was needed.

As nitrogen comprises 78% of the earth's atmosphere, albeit in an unfixed form, scientists were challenged to come up with a method of extracting it. In 1909 a German chemist named Fritz Haber managed to show how ammonia could be synthesised from nitrogen and hydrogen gas using high temperatures (400-500 degrees C) and high pressure (200-300 atmospheres).

This achievement won him the Nobel Prize in chemistry in 1918, despite Haber having by then earned the moniker 'the father of chemical warfare', for his pivotal role in developing poison gases for use during World War I (his research group also invented Zyklon B, the infamous chemical later used in Nazi gas chambers, but first developed as a pesticide).

After the Great War, the rights to the Haber Process were bought by BASF. Its chief scientist Carl Bosch was given the task of developing Haber's discovery, so it could be used on a commercial scale. The two chemists worked together on the project, with great success.

But events overtook their intention of producing a tool for assisting peace-time food production. Shortly after BASF merged with five other companies to form IG Farben, at the time the world's largest chemical and pharmaceutical company, the Nazis came to power. Ammonia stocks were now diverted to make bombs and bullets for Hitler's attempt to take over Europe.

In the 1950s, having been accused of collusion with the Nazis, along with American successors of Standard Oil, IG Farben was broken up. Bayer, Agfa and BASF are three of its surviving parts. Scientists whose most notable achievements had been in the development of warfare now turned their attention to food production. The Haber process was finally was given the chance to revolutionise agriculture.

It is estimated that about a third of our annual global food production is today directly reliant on the Haber process. Combined with other developments in seed varieties along with pesticide improvements, the fundamental availability of nitrogen allowed food production to double in fifty years, with just a 10% increase in arable land. But this world of plenty is coming at a price and may be coming to an end.

The Haber process currently adds between 80-100 million tonnes of fixed nitrogen to the nitrogen cycle each year. Proliferation of nitrogen run-off is causing huge problems for natural systems. This is because crops only use a small proportion of the nitrogen they are fed, and research is showing that the more nitrogen is applied, the less it is absorbed.

A 2010 study from Critical Reviews in Plant Sciences found:
“While soil physicochemical properties play a significant part in these losses, there are several characteristic features of plant nitrogen transporter function that facilitate N losses. Nitrate and ammonium efflux from roots result in a reduction of net nitrogen uptake. As external nitrate and ammonium concentrations, respectively, are increased, particularly into the range of concentrations that are typical of agricultural soils, elevated rates of nitrate and ammonium efflux result.”

Run-off from agricultural production contains a rich array of nutrients including huge volumes of nitrogen. This run-off has been blamed for eutrophication of oceans and rivers leading to changing biospheres, proliferation of invasive species and dead zones.

Some of this run-off can be blamed on overzealous applications of nitrogen, but scientists are now convinced that much of it is also due to a gradual change in the composition of soil due to the increased presence of nitrogen. The role of micro-bacteria in the nitrogen cycle is crucial and the loss of nitrogen-fixing microbes seems to be a gradual result of our current tillage system.

Increased production of nitrogen has boosted levels of nitrous oxide (N2O) in the atmosphere, with potentially disastrous consequences for the ozone layer, as this gas is known to erode ozone properties. Ammonia levels in the atmosphere have tripled, leading to the creation of nitric acid, acid rain and smog. As ammonia binds with particles in the air, it has also been blamed for causing respiratory problems in people.

As soil that has been fed intensive concentrations of nitrogen for decades now begins to wilt, net yields are falling for the first time since the Haber Process came into being. On the one hand the fertilizer companies want to continue selling their products, but as knowledge of their long-term impacts on crop yields is spreading, farmers and scientists are asking big questions about how to remobilise nitrogen absorption in soil and reduce losses through run-off. Going organic is an obvious answer, but not a popular one with the companies that have led us into this mess.

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