Nitrate – friend or foe?
Nitrate (NO3-) has many positive sides: It is e.g. an essential nutrient for plants as it is the source of one of the most important building blocks of plant cells: N = nitrogen. But in e.g. seawater nitrate is nutrient for algae, which in excessive amounts can lead to oxygen depletion and fish deaths.
A little is good – a lot is rubbish
In our body, bacteria convert nitrate to nitrite (NO2), which in turn can be converted into either nitrosamines that can be carcinogenic, but the bacteria can also convert nitrite into nitrogen monoixide (NO), which has positive effects on our health.
When we eat plants, we consume a certain amount of nitrate. It is inevitable and part of the natural nitrogen conversion and storage.
Nitrogen is an important nutrient for the body as it is part of our amino acids, which are the molecules of our proteins (muscles, enzymes, etc.). So we have to have a certain amount of nitrates. We should rather have it in the form of nutrients e.g. proteins.
All in all, nitrate is an essential element that we humans need to have through food, but as with so many other nutrients, it is about balance. Not too much and not too little.
Limit value easier to comply with
Therefore, for example, in drinking water introduced limit value for nitrate is 50 mg / liter. The amount corresponds to 500,000 times more than the limited value for pesticides. That means; nitrate is not very dangerous, but of course there should be limits. Over the years, the limit value has been made easier and easier by adhering to the general wells. Agriculture’s use of nitrogen has changed from a generous and tendentious to over fertilizing approach.
Nitrate is converted to free nitrogen in the soil
It has been learned that nitrate in the groundwater is converted by denitrifying bacteria when there are oxygen-free conditions, thereby making the nitrate free nitrogen (N2) completely harmless. Thus, by extracting water from the deeper parts of the soil where there are oxygen-free conditions, any excess nitrate is gone, and the drinking water is therefore well below the limit of 50 mg / liter.
Three types of nitrogen fertilizer
To get nitrogen into the nutrient cycle in the field, farmers can use three paths: they can partly as nitrogen-fixing crops as e.g. clover or pea. It “captures” the free nitrogen in the air and converts them into nitrate, which the next crop can absorb and use. They can also supply nitrogen in the form of manure, where e.g. a cow has converted grass into nitrogenous urea (urea) which in the soil is converted to ammonium (NH4 +) which can further be converted to nitrate.
And finally, farmers can supply nitrogen in the form of commercial fertilizers. They can be produced by using either urea, ammonium or nitrate, depending on the purpose of fertilization.
All in all, the most important thing for plants, nature and farmer is to give the crops in the field enough nitrogen to grow them efficiently and give a high yield. But that may result in a large nitrogen surplus leached to groundwater or marine environment. It applies to all three forms.
Leaf fertilizer is more environment friendly
As something completely new in recent years, the plants have started to fertilize the foliage with foliar fertilizers instead of fertilizers that are going to soil. Plants can also absorb nitrogen through the leaves, and by this way getting the nitrogen up directly, without the risk of contaminating the soil and water, gives a higher yields and less risk of pollution.
But it is a little more expensive and it is difficult to justify the extra price.
Green urea without climate impact
Traditionally, fertilizers are produced using the so-called Haber-Bosch process based on natural gas and nitrogen from the air. But the recent years’ progress in biogas production provides an opportunity for it to replace natural gas and thus lead to the production of so-called “green urea”. Similarly, it has been found that using e.g. wind turbine power or nuclear power to provide the energy needed to produce commercial fertilizers.
In the near future, we can therefore produce commercial fertilizer without burning climate-damaging natural gas and, by applying it in the form of foliar fertilizers, avoid leaching to the marine environment.
