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Fertilization is part of agriculture on grassland. However, it not only promotes plant growth, but probably also pollen.
Dunging is also a part of agriculture on grassland. However, it not only promotes plant growth but also pollen production.
Around 15 to 20 percent of the population in Germany suffer from hay fever, and the trend is increasing. Especially in spring and summer, many people struggle with irritated eyes, runny noses, sneezing fits, and breathing difficulties. It is often accepted with a shrug, hoping that the pollen season will quickly pass. However, a new study from Belgium shows that farmers and their farming practices may also play a role in this: Nitrogen fertilization not only changes the composition of plants but also influences the allergenicity of pollen.
Fertilized meadows had six times more pollen
The principle is common knowledge: where there is more fertilization, yields are higher. However, the pollen may also be more aggressive. Researchers from the Catholic University of Leuven reported this in the journal "The Lancet Planetary Health." This finding is relevant both in terms of health policy and agriculture. After all, the number of allergy sufferers has been increasing for years, and the reasons for this are being sought. Perhaps we are now a step closer. The Belgian researchers compared 25 fertilized and 25 unfertilized meadows, each paired in close proximity. This allowed for excluding factors such as climate or soil conditions. The result is clear: fertilized areas produced over six times more pollen than their unfertilized counterparts (3.6 mg/m² vs. 0.6 mg/m²).
Pollen significantly more allergenic
And not only that: the pollen was also significantly more allergenic. In laboratory tests, they showed a 5.1-fold stronger reaction in a so-called basophil activation test. This method measures how strongly the immune system reacts to an allergen. Blood from allergy sufferers was exposed to the pollen, showing that the levels of specific antibodies that allergy sufferers produce against certain pollen were higher in pollen from fertilized areas. The cause lies in nitrogen itself. Fertilization promotes certain nitrogen-loving grasses such as ryegrass or meadow grass, which are species that produce many and aggressive pollen. At the same time, the excess nutrients displace species-rich wildflower meadows with less allergy-triggering plants. The effect is twofold: more pollen overall and more pollen from problematic species.
New blame for agriculture?
Despite this connection, it is important to always keep in mind that fertilization is an important tool for producing food efficiently and in sufficient quantities. Especially in times of global food security, it is indispensable. However, the new research results show that long-term environmental and health consequences must be taken into account. It is not about an "either or", but rather a "how" and "where." Many farms are already investing in more precise application methods and adjusted quantities, which makes sense economically and ecologically. Now it turns out that these measures can also bring health benefits. Because less nitrogen not only means less environmental pollution but possibly also fewer allergies in the population.
