Over-fertilization in agriculture - the effects

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Over-fertilization in agriculture - the effects: agriculture

Agriculture is considered to be the main cause of overfertilisation: Increased factory farming does not only cause an overproduction of animal food, but also an enormous increase of different pollutants and manure. The over-fertilization leads to a huge nutrient surplus, whereby in particular the nitrogen contained in the fertilizer has drastic effects on the entire ecosystem.


Nitrogen (N) is considered as an elementary building block of every living thing and is found both in the water and in the air and in the soil. The vital substance accounts for about 78 percent of the air, however, neither plants nor animals can use the atmospheric nitrogen. The natural cycle, however, provides that the atmospheric nitrogen of microorganisms in the soil is converted. As a result of the nitrogen for the plants usable molecules, which they need to grow.
Subsequently, animals and humans absorb nitrogen from the consumption of plant foods and excrete them through the faeces and urine. These are broken down again by the microorganisms, which closes the natural cycle. However, the balance of the nitrogen cycle is massively disrupted by human interference with nature, resulting in an excess of nitrogen in the environment.
  • around 62 percent comes from crop production
  • around 33 percent comes from animal production
  • around 5 percent comes from transport, industry and households

Impact on biodiversity

The increased supply of nitrogen has an enormous impact on biodiversity and ensures uniformity of vegetation. The reason for this lies in the individual nutrient requirements of the respective plants. Because some of them really love the nitrogen and benefit enormously from the oversupply of this substance. They spread accordingly quickly, but at the expense of those plants that have adapted to nutrient-poor conditions. Because these are subsequently displaced by the nitrogen-loving plants.
  • especially raised bogs are affected
  • Sundew is also displaced
  • Cottongrass and rosemary heath are spreading

Effects on the plants

Over-fertilization in agriculture

The excess of nitrogen leads to unhealthy, accelerated growth of the plants and the rooting remains on the track. For the plants put all their energy in the formation of new shoots, which are often soft and spongy. But not only the shoots are affected, because the cells and the tissue are not optimally formed. In trees, the accelerated growth also causes so-called crown glare. This makes them much more vulnerable to wind and dryness, which often leads to wind damage in the forests. In addition, it has been proven that factory farming and over-fertilization are directly related to forest dying. The nitrogen overload also has the following effects on the plant life:
  • Nutritional status of the plants is disturbed, thereby it can come to a Unterversorgung
  • Spread of bacteria and fungal diseases is increased
  • Plants are more susceptible to weather conditions
  • Storage of harvested products is impaired, which can lead to yield losses in agriculture

Impact on waters

Over-fertilization in agriculture leads to an increased nutrient content in the waters. Because the nitrogen compounds get with the flooding in lakes, rivers and oceans and lead to eutrophication of these. This is understood to mean unrestricted water plant growth, which results from the oversupply of nutrients. In particular, phytoplankton (unicellular algae) benefit from this nutrient surplus and form in masses. This results in so-called algae blooms, which are colored greenish and cover the water surface. These pose a particular danger to sensitive ecosystems such as stagnant water bodies and slow flowing waters. Because the algae can cause the waters to "tip over":
  • Algae cover the surface
  • less light gets into lower layers of the water
  • Photosynthesis can not take place and plant growth is impaired, thereby reducing biodiversity

Phytoplankton harms the waters

The algae have a lifespan of about one to five days. After the phytoplankton has died, it sinks to the bottom of the water and is degraded by bacteria living there. For this process, however, oxygen is needed, which in turn is removed from the water. The lack of oxygen resulting from the aerobic degradation process leads to the dying of plants and animals in the affected waters. If there is not enough oxygen left, it leads to the formation of toxic substances.In the so-called anaerobic degradation process, mainly toxins such as methane (CH4), ammonia (NH3) and hydrogen sulfide (H2S) are formed, which poison and kill the fish. In addition, these toxins are often found in seafood, allowing them to reach humans through the food chain. The algae also have the following effects:
  • phytoplankton create "dead zones"
  • About 15 percent of the seabed of the Baltic Sea is covered by dead zones
  • through the phytoplankton arise "foam carpets" on the beaches
  • this suffers the tourism industry

Effects on climate and air

Over-fertilization in agriculture

The fertilizers contain ammonium, which is converted to ammonia (NH3) during storage and application. The ammonia, in turn, enters the atmosphere and promotes the formation of particulate matter. However, this is harmful to humans and animals, as it acts directly on the upper respiratory tract and leads to respiratory diseases. In addition, the ammonia gas can cause acid rain, which is harmful to the whole environment. When it rains, the ammonia returns to the soil, where it acts as an additional fertilizer and thus promotes over-fertilization of the soil.
However, the nitrogenous fertilizers not only release ammonia:
  • nitric oxide (N2O) is produced by the mineralization of the fertilizer
  • this is about 300 times more harmful to the climate than carbon dioxide (CO2)
  • and is considered a highly effective greenhouse gas
  • In addition, methane (CH4) is released
  • this is about 25 times more harmful to the climate than carbon dioxide

Impact on the ground

The ammonia contained in the fertilizer is converted by the microorganisms in the soil to nitrate (NO3-). If the plants do not absorb the nitrate, so-called base washout occurs. Here, the nitrate is flushed out with the leachate and favors soil acidification. Although some plants prefer to grow on an acid soil, all plants generally grow at a pH below 3. However, soil acidification does not only affect the growth of plants:
  • there is a change in the soil structure
  • the living conditions for the soil microorganisms are also changing, thereby affecting soil fertility
  • the nutrients in the soil are washed out, thus the optimal nutrient supply is no longer given
  • toxic substances can be released (eg: aluminum)
  • Decline in earthworm population
Note: Did you know that earthworms are hugely important to the plants? Because they promote both the ventilation and drainage as well as the mixing and rotting of the soil.

Impact on groundwater

Over-fertilization in agriculture

Over-fertilization in agriculture is also considered to be the trigger for increased nitrate levels in drinking water. Because the mobile nitrate gets into the groundwater with the leachate, especially during heavy precipitation, and subsequently into the drinking water. Although slightly elevated levels of nitrate present only a minor health risk, persistently elevated nitrate levels can lead to inflammation of the gastrointestinal tract. In addition, the nitrate in the body can be converted to nitrite (NO2-), which is harmful even in small quantities. This reaction requires an acidic environment, which is why the human stomach is considered the ideal environment for this. When drinking drinking water with an increased nitrate content thus the formation of nitrite is favored.
  • Nitrite is particularly dangerous for infants, these can "stifle inwardly"
  • if the nitrite gets into the blood, it interferes with the transport of oxygen as it destroys the red blood pigment
  • the limit value for nitrite in drinking water is 0.50 mg / l
  • the limit value for nitrate in drinking water is 50 mg / l
Note: Plant foods may also contain high levels of nitrate. However, these are usually not consumed every day for a lifetime.

Measures to avoid over-fertilization

The EU has already responded to nitrogen over-fertilization and set the Nitrates Directive in 1991. Accordingly, all EU Member States are required to monitor surface water and groundwater, to identify vulnerable areas and to review them every four years. Furthermore, the guideline sets out rules of good agricultural practice which, however, are to be applied on a voluntary basis.
In addition to existing laws, over-fertilization with nitrogen can also be avoided by other factors:
  • Connect livestock to agricultural land so that the number of animals is adapted to the available area
  • Incorporate existing slurry directly into the soil
  • Using high-tech methods for fertilizer application, fertilizer machines with sensors and / or computer chips - nitrogen can be used selectively
  • Install air filter system in factory farming facilities, thereby reducing emissions
Note: Did you know that giving up meat has a positive effect on the environment? Because the less cattle are bred and kept, the less nitrogenous emissions and manure enter the ecosystem.

Video Board: What Are The Negative Effects Of Chemical Fertilisers On The Soil.

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