Nitrogen surplus – an environmental problem of entirely new proportions

Federal Environment Agency campaigns for ambitious mitigation strategy

Drag hoses spreading slurry directly onto the field.Click to enlarge
Drag hoses spreading slurry directly onto the field.
Source: Stefan Thiermayer /

Nearly two thirds of all natural habitats in the EU are overfertilised. The main source of this nutrient surplus is nitrogen from the agricultural sector, which is spread onto fields in slurry and in chemical fertilisers. The EU Commission has repeatedly called for reductions of nitrogen inputs. Maria Krautzberger, President of the Federal Environment Agency (UBA), said: "It is important for the EU to continue to provide the impetus for nitrogen surplus reduction, but we must also take action at national level. The Fertilisers Ordinance is a critical means to guaranteeing better protection of air, soil and groundwater against excessive levels of nitrogen."

Nitrogen (N) is a vital nutrient for all living beings. However, many reactive nitrogen compounds are harmful to the environment in excessively high concentrations. They endanger the biological diversity of our forests and heaths because plant species adapted to low-nutrient soils are displaced. Excessive amounts of slurry are raising nitrate concentrations (NO3) in the groundwater above limit values in many locations. Eutrophication of the marine environment is the result of high inputs of nitrogen from agriculture. Nitrogen dioxide (NO2) from traffic emissions is harmful to human health. Nitrous oxide emissions (N2O) from overfertilised fields accelerate climate change. Four times more airborne reactive nitrogen compounds are entering the environment in Europe than only 100 years ago. In Germany, that is an annual amount of about 4.2 million tonnes, or 50 kilograms per person. According to EU data, 61 percent of natural habitats in Europe are exposed to too much nitrogen.

An UBA study shows that nitrogen loads can be reduced significantly. Since the agricultural sector accounts for two thirds of nitrogen emissions in Germany, this is where measures must be taken first. Ms Krautzberger said: "Amendment of the Fertilisers Ordinance is key to bringing down nitrogen emissions. In particular, it must regulate more efficient use of chemical fertilisers and more rapid entry of slurry into soil. Whether or not the measures will suffice to achieve good ecological status throughout Germany depends on assessment of the requirements." The use of drag hoses to spread fertilisers is a promising way to release fewer emissions and which would clearly reduce ammonia emissions to the air. Another important factor: larger distances between bodies of water and land areas used for agriculture would reduce the direct input of fertilisers into surface waters.

The Federal Environment's recommendation concerning the use of fertilisers – whether slurry or chemical fertilisers – is to apply them as appropriate for the crop concerned, spread them quickly and at adequate distances to rivers and lakes. This would reduce the share of harmful nitrogen compounds in the environment, nitrate in groundwater and ammonia in air. Hillside areas in particular must take precautions not to allow too much nitrogen run-off. Storage capacities for slurry must be increased in order to be able to better adapt its application to the requirements of crops.

Livestock husbandry must also produce lower levels of emissions; in other words, much less ammonia must be emitted from livestock housing. "Exhaust air cleaning systems must become standard in every large pig and poultry fattening farm. In terms of technology, it is entirely feasible", said Ms Krautzberger.

Air is the major pathway of nitrogen inputs, which is why it is particularly important to further reduce ammonia and nitrogen oxide emissions by 2030. These are the objectives of the "Clean Air for Europe" programme which the EU Commission launched in 2013 and which the new Commission now seeks to modify. "It would send the wrong signal if the Clean Air for Europe programme were watered down. Our common efforts to reduce the input of reactive nitrogen into the environment may not come to a halt", insisted Ms Krautzberger.

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