Nitrogen fertiliser can 'impact soil and groundwater for decades'

Using nitrogen fertiliser can have a negative effect on groundwater for decades, according to new research. Researchers from the Universite Pierre et Marie Currie, France, and the University of Calgary, Canada, have found that nitrate leaks from nitrogen fertiliser and stays in soil for years, which can pollute groundwater.

The new study revealed that nitrate from fertiliser stays in soil for much longer than it was originally thought, suggesting that fertiliser is highly damaging to fresh water sources. It was found that traces of synthetic nitrogen fertiliser that was applied to crops in 1982 was still detectable thirty years later. Testing showed that around 15 per cent of nitrogen from the fertiliser was still present in the organic matter within the soil.

Around ten per cent of the nitrogen had leaked from the soil into the groundwater, with scientists concluding that this leaking will continue for around another 50 years. The continued leak of nitrate from fertiliser can severely affect groundwater and other freshwater sources and can lead to the growth of excess algae, throughout rivers and lakes.

The study, titled 'Long-term fate of nitrate fertiliser in agricultural soils', has been published in the journal 'Proceedings of the National Academy of Sciences'. It shows that although seeping of nitrate from fertiliser has at a very low level, it can continue for a matter of decades and so still be highly damaging. This means that reducing nitrate pollution in groundwater could be a longer process than originally thought. 

Within Canada and the US there are strict regulations regarding the levels of nitrates that are allowed in drinking water. Results from an Environmental Protection Agency in the US in the 1980s found that nitrate had the largest impact on drinking water sources than any other type of contaminant. The recent study suggests that the impact of nitrate in drinking water will now be more severe.

The study is further evidence that greater controls could be needed to ensure that fresh water sources remain as unaffected as possible to ensure they are still available in the future.