TeaTime4Schools: Measuring Biological Activity in Soils with the Help of Schools in Austria


The decomposition of organic material is important for the growth of plants and microorganisms. Carbon dioxide is also released in the process. To better understand the global CO2 cycle, we need more information about the decomposition rates of organic material in soils. As part of the TeaTime4Schools project, students from 150 school classes worked as Citizen Scientists to collect data on the decomposition of organic material in soil. This was done using the standardized Tea Bag Index (TBI) method.

Project description

Changes in soil carbon content can both amplify and mitigate climate change. The decomposition of soil organic matter is part of the global carbon cycle and provides information about the biological activity of the soil. It is particularly important to understand the relationship with global climate change, as it can affect decomposition processes. On the other hand, the rate and circumstances of organic matter decomposition determine the release of greenhouse gases. A wide variety of factors, such as the organic feedstock, the climate, or the soil properties, influence the rate and also the amount of degradation products. However, there is a lack of globally standardized and inexpensive methods for measuring the rate of degradation.

150 school classes in Austria participated in the TeaTime4Schools project in 2018. Using a standardized method, the Tea Bag Index (TBI), tea bags were buried, dug up again after three months and weighed. The weight loss indicates how much plant material, in this case tea, has been decomposed. This method is easy to implement and therefore suitable as a Citizen Science project. The project also taught the students about soil microbiology and about decomposition in soil. The collected data was submitted to the global Tea Bag Index Initiative and presented in national and international maps.


In addition to conducting the Tea Bag Index, we asked school classes to submit a soil sample from the experimental plot for analysis of standard parameters. In total, we received both a TBI record in the global database and a soil sample from 69 school classes.

Most of the data collected in the project came from urban plots. The decomposition rate tells us how fast the decomposition of organic material, occurs. The stabilization factor tells us how much of the labile material in the soil was stabilized. Our decomposition rates ranged from 0.012 g d-1 in urban areas to 0.016 g d-1 in agricultural areas. We found that the differences between the different land uses were not significant. In some cases, we could not calculate the decomposition rate because the tea was already in the second phase of decomposition (i.e., all readily available materials were already gone). The stabilization factor ranged from 0.20 in forests and semi-natural areas to 0.24 in agriculture. These values are consistent with previous results from Austria in 2016 and make a valuable contribution to the global Tea Bag Index database and to further knowledge about organic matter degradation.

In addition, a class at HBLA Klosterneuburg analyzed the composition of the microbial community in the soil and in the tea bags using next-generation sequencing. It was shown that different specialists were involved in the decomposition of the tea depending on the soil type.


The aim of the project was to collect data from Austrian soils, to create a map of decomposition rates in Austria, and to better understand the role of microorganisms in soil. The meaning and importance of soil was to be communicated in a creative way. It was important that the students enjoy the project work and that they are made curious about the topic of soil and science. In addition, the project was intended to show interesting, fulfilling career paths for girls and to present alternatives for traditional female role models.

Benefit of the project

The Tea Bag Index projects have developed a hands-on learning opportunity for students, farmers and interested citizens. The processes in the soil can be experienced by doing it yourself and the participants are part of a worldwide scientific community. In addition, the methods and documents are available in the long term for use in school lessons.

Project details

Project acronym: TeaTime4Schools

Project Management: Taru Sandén, Department of Soil Health and Plant Nutrition, AGES

Project partners: Open Science, HBLA Klosterneuburg, University of Vienna, SOWA Institute

Funding: OeAD (Sparkling Science Project)

Project duration: 09.2017 to 12.2019


Sandén T., Wawra A., Berthold H., Miloczki J., Schweinzer A., Gschmeidler B., Spiegel H., Debeljak M., Trajanov A., 2021. TeaTime4Schools: Using Data Mining Techniques to Model Litter Decomposition in Austrian Urban School Soils. Frontiers in Ecology and Evolution Volume 9, doi 10.3389/fevo.2021.703794

Follow-up project

TeaTime4App: In this project, a Citizen Science App was developed together with the partner school Francisco Josephinum. With the help of the app, one can perform the Tea Bag Index, come into contact with soil and make observations on soil properties (e.g. texture, soil animals, pollution). The TBI app is freely available and anyone interested can use it to become a soil researcher themselves.

Last updated: 15.11.2023

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