At the beginning of the 20th century, a process was discovered that we know today as this Haber-Bosch process know. During this process, the basic fertilizer building block ammonia is created from atmospheric nitrogen and hydrogen.
The resulting one mass use of artificial fertilizers made it possible to feed the enormously growing global population.
Since the beginning of agriculture, we humans have used fertilizers to increase yields. At first these were purely organic. Over time, artificially produced fertilizers replaced organic ones.
Function of artificial fertilization
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Fertilizers provide additional nutrients to the plants Nutrientssuch as nitrogen (N), phosphorus (P) or potassium (K). Plants need these for photosynthesis and growth.
Temporal incorrect and therefore unsuitable fertilization as well as over-fertilization can negative environmental impacts have.
The side effects of the use of artificial fertilizers are the pollution of groundwater, over-fertilization of the oceans, loss of biodiversity and, last but not least, an acceleration of climate change. After all, the hydrogen (H2) used in the process has so far come from fossil raw materials.
Collision with natural nitrogen cycle
The additional fertilizer input into the soil leads to a Kcollision with the natural nitrogen. This is part of a cycle of nature, a finely balanced process over millions of years in which microorganisms play the main role.
microorganisms bind molecular nitrogen from the air as ammonium and ensure that it becomes available to other microbes as well as plants and subsequent food chains.
Unabsorbed nitrogen becomes part of a series of chemical transition products such as nitrite, nitrate and nitrous oxide, before it ultimately returns to the atmosphere as molecular nitrogen.
The basic principle of these processes is known and understood. However, the enormous diversity of soils and microorganisms makes details of the dynamics difficult to understand.
More sustainable agriculture
Like the Austrian daily newspaper THE STANDARD reported, working on Center for Microbiology and Environmental Systems Science (CeMESS) the University of Vienna has several research groups in the field of the natural nitrogen cycle.
Their basic research helps ensure that agricultural food production can be made more environmentally friendly in the future. She is also part of the Cluster of Excellence “Microbiomes drive Planetary Health” of the FWF Science Fundwhich is coordinated by Michael Wagner, CeMESS founding director and head of one of the research groups.
Findings from the group around Wagner and his colleague Holger Daims from 2015 show that there are still real surprises in the researchers’ findings. They have these until then existing doctrine on nitrification – i.e. the processing of ammonia first into nitrite and later into nitrate – was completely thrown out the window.
Since the Drinking water supply often or mainly about Groundwater takes place and Nitrate has a harmful effect on health can have, a usage conflict arises between agriculture and drinking water supply. Among other things, nitrate is thought to increase the risk of cancer due to the formation of nitrosamines in the body.
Daims explained the process after fertilizer application in an interview with STANDARD
The process was already described at the end of the 19th century. It was discovered at that time that the two steps were carried out by two different groups of microorganisms, so-called nitrifiers.
It was assumed that both would obtain energy by using their raw material convert oxygen. Since then, the phenomenon has been considered a prime example of a microbial division of labor.
Daims, Wagner and colleagues questioned this process:
The starting point was an unusual sample that came from a borehole in the Caucasus. It only contained bacteria of the Nitrospira type, which were actually only supposed to convert nitrite into nitrate. Nevertheless, complete nitrification could be detected
he explained Microbiologist Deer the STANDARD.
It would have turned out that these microorganisms could carry out both steps, including the one from ammonia to nitrite. The bacteria with this ability were Comammox, which means “complete ammonia oxidizer” stands, called. The discovery was made 2015 in the renowned journal Nature presented. The findings coincided with those of a research group from the Netherlands.
It is now clear that comammox bacteria are not an exception but, like pure ammonia and nitrite oxidizers, can be found in almost all soils. The researchers are now presenting the hypothesis on that Comammox uses nutrients more efficiently and can therefore grow betterif the entry is slow and limited.
Nitrogen in abundance
The large amounts of nitrogen that hit the finely balanced microbial ecosystem in the soil as artificial fertilizer cannot be completely absorbed by the plants.
The nitrogen input into nature through human activity – for example through fertilizer, wastewater or fuels – doubles the natural input overall
Daims describes the current situation
Nitrate as the end product of nitrification become due to its negative charge easily washed out of soils or converted into atmospheric nitrogen. Above all, only about half of the nitrogen applied can be absorbed by plants and less than 20 percent ultimately contributes to human nutrition. The rest goes into groundwater, rivers and seas, or back into the air.
Molecular nitrogen is not the only end product released into the atmosphere. The Denitrification and side reactions of nitrification ensure high levels of artificial fertilizer large amounts of nitrous oxideviewed over 100 years – as a greenhouse gas almost 300 times as potent as CO2 and severely damages the ozone layer.
Gentle fertilization alleviates the problem
Due to the large input of artificial fertilizer, the conversion processes take place so quickly that the plants cannot keep up with the nitrogen uptake
Daims told STANDARD.
One Fertilization strategythat go to this Processes adapted is, the Esignificantly slow down the production of greenhouse gases. Organic fertilizers in particular, which bring or promote microorganisms with low nitrous oxide emissions, could cushion the climate-damaging effects. Comammox could also play a role here.
Alternative to synthetic materials
The researchers are also working on ways to… To stop nitrogen loss in the soil naturally. One goal is to provide an alternative to industrial nitrification inhibitors.
The health risk of synthetic substances that accumulate in plant and animal foods is not completely clear. The team at the University of Vienna is therefore investigating substances from plants that reduce fertilizer conversion and loss.
Some promising substances that plants use to slow down nitrification have already been identified. They will now be examined in more detail
reports Daims.
In the best case scenario, this would result in one natural product for adding fertilizer, that plant-available nitrogen stays in the soil longer. This could be an important step towards a more sustainable use of soil habitats with their unique microbial complexity.
