International Soil Classification Workshop in Mexico: Total commitment at perceived 40 degrees

In March 2022, 35 international experts met in Mexico to examine the soils of a wide range of regions and landscapes ranging from the summer-humid tropics to tropical-subtropical drylands on a global scale. The goal was to incorporate the results of these soil surveys into the World Reference Base for Soil Resources (WRB). Among the team members were Julia and Laurin, who are studying Sustainable Resource Management at TUM. They spent a semester abroad at the TEC in Querétaro respectively at the UNAM in Mexico City via TUMexchange and told us about their engagement on site.

Laurin and Julia, thank you for your time! How did you come to be invited to this workshop with some of the world's leading experts?
Laurin: We both have a strong interest in soils, and therefore deepened our studies in the fields of soil science and geology. Our lecturer, Dr. Peter Schad, who also attended the workshop, suggested that we apply to participate in the excursion – and it worked out. We were particularly attracted by the prospect of building a network with leading international scientists. In addition, we can get to know soils in different climatic zones that do not exist in our country.

Digging and analyzing a soil profile at perceived 40 degrees in the scorching sun is certainly a challenge. What motivated you in particular to expose yourselves to these conditions?
The results of the workshop will be used to adapt the WRB, i.e. the international soil classification system, and make it better. To do this, we have to scientifically interpret the properties and composition of the soils. This can only be done on site, no matter what the conditions are.

Why is a global understanding of soils so important?
Julia: In light of climate change and food security, soils play a significant role. Among other things, they store carbon and form the basis of our nutrition. Therefore, knowledge about soils beyond our own climate zone is becoming increasingly crucial.

In Mexico, for example, only about one fifth of the territory can be used for agriculture. In the arid zones, the lack of water is particularly noticeable. Water pollution from industry and agriculture further excaberates the problem. More than 75% of precious water goes to agriculture, where a large number of areas that were originally used to grow corn for human consumption are now used as cropland for the production of fodder for commercial livestock.

Based on the workshop's findings, are there any concrete recommendations for action to ensure sustainable use of the soil?
During the workshop, we looked at a soil in a region known for cereal and citrus cultivation. Based on the characteristics, it is then possible to make a recommendation for an irrigation system for example, using drip irrigation and the use of ground covers to keep the risk of erosion as low as possible.

The classification can generally be used to draw conclusions about sustainable management and use of the soil in question, e.g. with regard to erosion and salinization risks. Where we found soils with high salinity, extensive grazing with salt-resistant plants is recommended, as well as adapted irrigation management. In desert areas, these so-called halophytes are very often endemic, i.e. native plant species that can extract salt from the soil. They can be used for desalination and thus reclamation of the soil, which can be supported by certain additional measures. For example, the soil can be regularly flooded with low-ion water and by “loosening” it, we can achieve better percolation of the water.

However, the investigations also serve to identify potential crops and to make better statements about a correct liming and fertilization of the soil. Ultimately, the aim is to protect both the fertility and structure of the soil in the long term and to ensure sustainable use in the process.

"Sustainable use of soils and preservation of fertility for future generations can only be achieved together."

According to your experience report, you were able to classify 13 different soils over a distance of around 1500 kilometers during the nine-day workshop. What were the moments that impressed you the most
For me, the landscape of the white gypsum dunes in Cuatro Ciénegas was very impressive. Due to the high albedo, one was as if blinded on site and is constantly exposed to the sun while working in the field with sparse vegetation. It is really incredible how life is possible in such an extraordinary environment under such extreme conditions.

My very special moment was a sunset also in the nature reserve Cuatro Ciénegas. A truly unique ecosystem in the middle of a barren desert with scorching heat. It was a packed day and we were working on the last soil profile, when, in a happy atmosphere and after a long struggle, a final result was reached on the classification. A moment of scientific harmony in the face of the picturesque beauty of this landscape.

What did not go so well – in the truest sense of the word – was the penultimate day. My role model during the workshop was our mentor, Dr. Peter Schad. He has the nickname "the barefoot walking professor". I, too, was walking barefoot. That day, however, everything that had thorns and spines seemed to magnetically attract me. That was quite painful.

Looking back now: What special insights did you gain from the workshop in Mexico?

I learned how important the social component in science is. For example, we had to discuss the results of the soil survey in a team from ten different nations and classify the soils in a system. Being able to work in a team and being open to other views and approaches was essential here.

But we also had to deal with how we could apply the recommended actions to practical situations. This requires analyzing the results and working closely together with local authorities and farmers.

Sustainable use of soils and preservation of fertility for future generations can only be achieved together, not in isolation.

Thank you for the interview.

No matter whether you go abroad as a TUM student or want to come to TUM as an exchange student: Do it like Laurin and Julia and think about how you can make your stay as sustainable as possible. Find more information and tips on our website for climate-friendly mobility: Thinking green!​​​​​