Cartoon Albert Jan Rasker
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Hassles with construction projects that are put on hold. Extra pressure on those farmers who are easy targets when it comes to exceeding nitrogen norms – thanks to their use and over-production of manure. In recent weeks, both these issues have been in the news quite a bit. That probably also led to an article from last month suddenly becoming one of the best read articles on Innovation Origins this week.

In this article, the Flemish biologist Tobias Ceulemans told us that his research shows that nutritious, much-needed fungi in tree roots and soil are dying of overly high levels of nitrogen. He also discovered that they are already dying with nitrogen values that are far below existing European norms for nitrogen levels (between 10 and 15 kilos per hectare, depending on what kind of area it is).

Norms for nitrogen levels must therefore be reduced, concludes Ceulemans. That said, the current norms are not even being upheld. Is this the only way to help soil recover from the excess nitrogen levels it contains? – That’s the question for ecologist Roos Loeb, a specialist in nature restoration at the B-Ware research center.

Are there other ways to reduce the nitrogen content that’s in soil other than preventing emissions?

“Yes, but they are not nearly as effective. One way is to remove a few centimeters off the top layer of the soil. It contains most of the nitrogen there and you’ll then be rid of these. But that’s not so great for the plants and animals that live there. They get a kind of desert in return. Dry conditions often arise as a result as well, so plants that need a little more moisture don’t do as well there anymore. And a lot of animals have a hard time because of the dry soil. However, heather, for example, grows really well there. But this is not the right way to tackle soil acidification caused by nitrogen deposition. This acidification leads to less varied vegetation. You notice that some plants die out, such as the catsfoot. You will also see fewer yellow flowers blooming in between the heather. You can sprinkle limestone or mineral-rich rockdust onto the ground in order to do something about this. This ensures that any acidification is negated. Another method is to cultivate grass that grows faster as a result of nitrogen deposition. You can mow that grass more often. And the grass clippings can be removed. These can then be used as animal feed, for instance. In that case, you will have taken the nitrogen out of the ecosystem. Though this doesn’t count for valuable vegetation. You can’t mow those very often.”

Is it also possible for acidic soil to recover naturally?

“It is possible. But the plants and animals that leave, do not just come back. If it weren’t for the high nitrogen emissions caused by human activity over the past 50 years, the soil would only have been slightly acidified by nitrogen. As minerals such as potassium and magnesium are released from clay more or less to the same extent, the composition of the soil would then have remained better in balance. But in that respect, you’ re talking about a process that will take hundreds of years.”

In that case, the only solution is to emit less nitrogen. How can we do that?

“That’s a difficult question. Most nitrogen is emitted by traffic, industry and agriculture. Agriculture not only releases NOx, but ammonia as well. This has an even stronger acidifying effect on soil. This is why I think the most effective solution is for agriculture to cut down on its production of manure.”