New Scientist News - Fertilisers give the lungs of the planet bad breath: "RAINFOREST soils polluted with phosphorus and nitrogen from agriculture are bad news for the climate. The presence of these fertilisers in the soil could trigger the release of disproportionately large amounts of carbon dioxide.
Cory Cleveland and Alan Townsend of the University of Colorado at Boulder added phosphorus fertiliser to a tropical forest plot in Costa Rica for two years and found the amount of carbon dioxide released per year was 18 per cent higher than in control plots. Nitrogen fertiliser raised the carbon dioxide output by 22 per cent, and a mixture of the two by 14 per cent.
Since tropical forests contain 40 per cent of the world's terrestrial carbon, the impact on global warming could be large (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0600989103).
Although no one deliberately adds fertiliser to rainforests soils, the amount of airborne phosphorus and nitrogen reaching tropical forests is increasing because of human activity, especially agriculture.
'Easterly winds carry significant quantities of phosphorus-containing dust from Africa to the Amazon basin, and are increasing due to desertification of the Sahel,' says Cleveland. Levels of nitrogen in the air are rising because of increased fossil fuel and fertiliser use. The researchers suggest that even small amounts of fertiliser can have a damaging effect.
From issue 2557 of New Scientist magazine, 28 June 2006, page 22"