Nitrogen fertilizer remains in soil for decades and leaks into groundwater as nitrates much longer than previously thought, Canadian and French scientists say. Researchers at the University of Calgary in Canada and the Universite Pierre et Marie Currie in Paris said their research showed that 30 years after synthetic nitrogen fertilizer had been applied to crops in 1982, about 15 per cent of the fertilizer was still in soil organic matter. In those three decades around 10 per cent of the fertilizer seeped through the soil towards the groundwater and would do so for at least for at least another 50 years, they said. Losses of nitrogen from fertilizer towards the groundwater occur at low rates but over very long time spans, Calgary geochemistry Professor Bernhard Mayer said. The findings suggest it could take longer than previously thought to reduce nitrate contamination in groundwater in aquifers supplying drinking water in North America and elsewhere, he said. \"There\'s a lot of fertilizer nitrogen that has accumulated in agricultural soils over the last few decades which will continue to leak as nitrate towards groundwater,\" he said.