Fertilizers are a unavoidable aspect of industrial farming. As Robin LeBreton said in his interview with us, “fertilizers are necessary for efficient production”. In many instances, high employment of fertilizers has led to dramatic consequences to the environment. Brazilian farmers does not have a history of employing high levels of fertilizers, however, the levels of usage increased simultaneously with the growth in the sugarcane bioethanol sector, specifically the application of nitrate fertilizers.
The use of such products has potentially massive environmental damage associated with it because of the potential of acidification. These nitrates have the potential to be converted into nitrous oxide that lead to the acidification of the soil if applied too liberally. This acidification is reversible if the farmer/cultivator of the field act quickly enough by liming. However, if this is not done (possibly due to cost-cutting or lacking education) and the acidification reaches the subsoil level, it becomes much more difficult to reverse. An additional negative impact occurs due to the biological fixation of the nitrates by bacteria in the soil. Endophytic bacteria found in the root nodules of the sugarcane convert the nitrates in the soil into nitrous oxide. This bacterial process increases air pollution since nitrous oxide is a greenhouse gas that is 300 times more potent than carbon dioxide. Therefore, if the data is valid, the use of such fertilizers is in part responsible for the rising global temperature.
Given the combination of the high application of fertilizers to the sugarcane fields and soil erosion leading to a lack of permeability, the scientific and non-governmental communities are reporting an increasing level of fertilizers being found in the water-systems of Brazil. While this mobility is an issue in other countries around the world, its a particular issue in Brazil since the tropical and subtropical climates increases the ability of the nitrate based fertilizers to enter into the water, especially if the application is poorly timed. This increased problem is due to the fact that most Brazilian nitrate fertilizers are applied as urea which, given the climate, is more easily lost in volatilisation of ammonia (the transformation of ammonia into ammonium carbonate via hydrolysis). This ammonium carbonate then enters the water-system and can result in the eutrophication of the river, when all fertility and biodiversity is lost due to a resulting algae-bloom.
While this pollution issue is endemic to nearly all riverways in high bioethanol production areas, Filoso (and his partners) discovered and publicly reported that such contamination was particularly high in the Piracicaba and Mogi rivers in his 2003 article “Land Use And Nitrogen Export In The Piracicaba River Basin, Southeast Brazil”.
Future considerations?
Given the potentially devastating impacts of fertilizers on the Brazilian landscape (both on land and water), many possible solutions have been given voice. Firstly, the level of soil erosion that encourages the leakage of fertilizers into the water-systems can be reduced by maintaining the riparian forests that run along the riverbanks. The government has instituted a conservation law that demands that the trees between 10m and 500m from the water are protected. However, for some this does not go far enough and they demand for the replanting of trees already cut down at a cost of $200 million.