Nitrogen

Nitrogen (N) is an important nutrient for plant growth and essential, along with phosphate, for protein formation. For this reason, both are administered in fertilisers. In the Netherlands, very high levels of nitrogen are administered in the form of artificial fertiliser and animal manure, partly as a result of large nitrogen imports in the form of animal feed. This, among other things, leads to large emissions of ammonia (NH3) into the air. In addition, nitrogen oxides (NOx) are emitted, by transport and industry in particular. High levels of nitrogen affect biodiversity and contribute to fine particulates in the air.

Nitrogen oxides and ammonia land on natural ground, where they raise the nutrient level and contribute to soil acidification. This results in an imbalance in nutrients, including a shortage of calcium, potassium and magnesium, and a surplus of nitrogen. The diversity of plant species declines, and there are knock-on effects on birdlife and other fauna.

Nitrogen in the air leads to the formation of ozone (smog), and it also makes a major contribution to particulates, resulting in negative health effects. The nitrogen policy is aimed in part at limiting emissions of ammonia and nitrogen oxides.

The nitrogen problem has in fact existed since the start of the 1980s, when a great deal of attention was being paid to acid deposition, popularly known as "acid rain". Acid deposition occur in wet form (rain) and dry form (gases, particulates). It consists of sulphur dioxide (SO2), nitrogen oxides (NOx) and ammonia (NH3). Apart from sulphur, which has fallen by more than 80% since 1980, the issue then was the same nitrogen problem.

Since then, the Dutch government has also sought to reduce nitrogen emissions. Indeed, since 1990, nitrogen emissions have been more than halved. Nitrogen oxide emissions have been falling steadily for the past thirty years, although the decline in ammonia emissions has stagnated since around 2010.

In 2015 the Dutch government introduced the Nitrogen Action Programme (PAS) to further reduce nitrogen deposition and limit the harmful effects. In May of 2019 the Council of State (RvS) however found the PAS to be inadequate. As a consequence of this 'nitrogen ruling' the Netherlands has to take new measures to reduce nitrogen depositon on nature reserves.

In formal terms, nitrogen deposition must return to the so-called "critical deposition values" (CDV), but these values vary according to the type of nature. Wildflower meadows and marshland can, for example, tolerate less nitrogen than forest or sandy soil.

The critical deposition values vary mostly between 5 and 25 kg nitrogen per ha per year. In most cases, the range is between 10 and 20 kg nitrogen per ha per year, with a range of 5 to 10 kg nitrogen per ha per year for sensitive marshes and dunes.

Current and critical deposition values:

• The national average nitrogen deposition is around 21 kg nitrogen per ha per year (1500 mol)
• At an average deposition value of around 14 kg nitrogen per ha per year (1000 mol), a large part of the natural areas would be in the rough vicinity of the critical deposition values

The nitrogen problem nexus needs to be seen as a hydra-headed monster. Manure excess results not only in ammonia losses to the air, but also in laughing gas, which is a greenhouse gas. Nitrogen, in the form of nitrate, is also in runoff to groundwater and surface water. Apart from the Birds and Habitats Directives, we also have to comply with the Nitrate Directive, the Water Framework Directive and the Paris Accord. So, it is important to think in an integrated way, and when taking measures not to look purely at the effect on nitrogen deposition. Cutting ammonia emissions is the most effective to reach the critical deposition values, but cutting nitrogen oxide emissions has greater health benefits. In the light of this, cutting emissions in all sectors is important.

Nitrogen in livestock farming causes losses to the air in the form of ammonia (NH3). Over 80% of ammonia emissions in the Netherlands come from agriculture and particularly from manure. Ammonia is created when an animal has eaten protein and manure and urine mix in the stable and when (artificial) manure is spread on the land. Together with dairy farmers, Wageningen University & Research studied reducing ammonia emissions. Considerable cuts can be achieved without major financial consequences. Read more about the (technical) solutions that are readily available and about how WUR measures ammonia in the fold-out below.

In 2022, the Dutch government announced that the nitrogen emissions in some areas are to be reduced by as much as 70 to 80 per cent. For quite some time now, WUR has petitioned for a regionally focused, local and integrated approach to the three significant challenges for nature and agriculture: nitrogen, water and climate. This should lead to an integrated perspective for farmers and nature. Our researchers are currently calculating what combinations of measures enable farmers to meet the nitrogen, climate and water goals. Thus, we determine what packages of measures are needed for climate-neutral agriculture that spares nature and improves water quality.