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    Just say n2o: from manufactured fertiliser to biologically-fixed nitrogen

    Tomlinson, Isobel (2010) Just say n2o: from manufactured fertiliser to biologically-fixed nitrogen. Technical Report. Soil Association.

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    Abstract

    ‘Too much nitrogen harms the environment and the economy’ was the key message of the recent European Nitrogen Assessment which reported a study carried out by 200 scientists investigating the unprecedented changes humans have made to the global nitrogen cycle over the last hundred years.1 Through industrial processes, the cultivation of crops and the burning of fossil fuels, the supply of reactive nitrogen into the global environment has doubled.2 The biggest source of reactive nitrogen is from the industrial manufacture of nitrogen fertilisers for agriculture using the Haber-Bosch process.3 Its introduction to farms around the world during the 20th century has led to a profound transformation of agriculture. Manufactured fertilisers have contributed to the intensification of agriculture, and played a key role in increasing crop yields over the last 50 years, albeit at a decreasing output per tonne of nitrogen applied in many parts of the world.4 Our dependency on manufactured nitrogen for our food supply is, however, deeply worrying. The production of manufactured fertilisers is very energy intensive and uses natural gas, a non-renewable fossil fuel that will get more expensive as supplies get scarce, putting an upward pressure on fertiliser and food prices. This poses a long-term threat to food security. Nitrate leaching into water systems is a major problem, whilst the production, transportation and use of manufactured fertiliser contribute to greenhouse gas (GHG) emissions. Of particular concern are emissions of nitrous oxide (N2O), a powerful GHG, with a global warming potential of 298 times that of carbon dioxide.5 N2O makes up 54% of the UK agricultural sector’s GHG emissions.6 Recent research from the University of Illinois challenges conventional wisdom by indicating that in some circumstances the use of manufactured nitrogen can cause the loss of soil organic matter by stimulating the activity of soil micro-organisms.7 Where soils are not managed carefully with appropriate levels of organic matter inputs, this can reduce the ability of soils to store carbon, to hold water, as well as to store organic nitrogen and thus lead to higher nitrogen losses to the environment. Further research is needed to see if such results are replicated in other studies, but this report supports the concern that the organic movement has had for decades about the long-term sustainability of a farming system reliant on manufactured nitrogen fertilisers. Of course, all agricultural systems need a supply of nitrogen to replenish that lost when crops are harvested, and some loss of nitrogen is inevitable. So how should we best deal with the environmental consequences, N2O emissions and future food insecurity caused by our century-long love affair with manufactured nitrogen?

    Metadata

    Item Type: Monograph (Technical Report)
    School: Birkbeck Schools and Departments > School of Social Sciences, History and Philosophy > Department of Geography
    Depositing User: Sarah Hall
    Date Deposited: 19 Sep 2013 10:40
    Last Modified: 19 Sep 2013 10:40
    URI: http://eprints.bbk.ac.uk/id/eprint/8163

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