Over the last fifty years much of our farming has become dependent on manufactured nitrogen fertiliser for fertility. However, too much nitrogen harms the environment and the economy, according to the 2011 European Nitrogen Assessment, which reported a study by 200 scientists investigating the unprecedented changes humans have made to the global nitrogen cycle over the last century.
The use of manufactured nitrogen is not allowed in organic systems, so inputs of nitrogen come from nitrogen fixed by legumes, often clover leys, as part of a crop rotation that also controls pest and diseases. New evidence suggests that systems using this type of nitrogen behave differently in terms of nitrogen retention and loss, and a move away from manufactured nitrogen would also help mitigate the climate change impact of farming and guard against the increasing cost of artificial nitrogen.
Through industrial processes, burning fossil fuels and growing crops, the supply of reactive nitrogen into the environment has doubled in the last 100 years. The biggest source of this reactive nitrogen is from the industrial manufacture of fertiliser for farming. This energy intensive process produces high levels of nitrous oxide and uses natural gas, a non-renewable fossil fuel, which will get more expensive as supplies get scarce. This will put an upward pressure on fertiliser and food prices and poses a long-term threat to our food security.
Our report – Just say N2O: From manufactured fertiliser to biologically-fixed nitrogen – reviews the extent to which organic systems can meet the double challenge of reducing nitrogen losses and building stores of soil organic nitrogen in order to reduce dependency on manufactured nitrogen. Scientific evidence shows that the lower nitrogen inputs in organic farming can lead to lower N2O emissions compared to non-organic farms although more research is needed in a number of key areas. We are calling on the Government to look at the issue of reducing our dependency on manufactured nitrogen, and increasing efficiency of nitrogen use, as a matter of urgency.
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