Soil System Sciences

Will drinking tea get us thinking about soils? Yes, but only if you help us spread the word!

Taru Lehtinen
PhD candidate at the Faculty of Life and Environmental Sciences, University of Iceland


Meet Taru at EGU2014 in sessions SSS10.3 and SSS10.8.

The Tea Bag Index Project wants to create a global map on decomposition with the help of citizen scientists. We use teabags to collect vital information on the global carbon cycle. With our protocol (see our web page and our article: Keuskamp et al., 2013), citizen scientists worldwide can collect data without much effort or instrumentation.

Tea Bag Index Project developed a simple and cheap method, which anyone can use to measure decomposition in the soil, simply by burying teabags. Tea Bag Index Project want to gather data points from all over the globe through the involvement of citizen scientists.

Two main questions to be answered with the data gathered:

  1. How do environmental conditions determine the speed of decomposition?
  2. How do environmental conditions determine how much is broken down?

Eventually, a global soil map of decomposition will be created that can be used for educational purposes and to make current climate models even more accurate.

What is about?

Decomposition (the decay of organic material) is a critical process for life on earth. Through decomposition, nutrients become available for plants and soil organisms to use as a food source in their metabolism and growth. When plant material decomposes, it loses weight and releases the greenhouse gas carbon dioxide (CO2) into the atmosphere. In cold environments, breakdown is slower than in warm environments, meaning more carbon is stored in the soil and less CO2 is released. Factors like moisture content, acidity, or nutrient content of soils can also influence how quickly plant material decomposes


For better insight into global CO2 emissions from soils it is important to know more about decomposition in those different soils. Such an insight is important to improve climate models that show CO2 fluxes. To clarify the picture of global decomposition, we need a lot of information on different soil characteristics and related decomposition rates around the world. Large efforts have been taken to create a soil map of the world; however, predictions on the relations between soil an decomposition are often imprecise. It would be a great improvement if we could actually measure decomposition (rate and degree) globally.

Tea Bag Index Project developed a simple and cheap method to measure decomposition rate and degree. By burying everyday tea bags.

As tea is plant material, the weight loss of nylon teabags over time represents the decomposition of the plant material within an ecosystem. After three months buried in the soil of interest, the bags are dug up, dried and weighed. By burying two types of tea with different decomposition rates, we obtain information on how much and how fast plant material is broken down.

The importance of this research

Efforts have already been taken to map global soil and climate conditions; however an index for decomposition rate is still missing. Predictions of decomposition used in climate models are often imprecise.

The idea is to use the Tea Bag Index to collect data from around the world to feed databases in the global soil map, and to get as many citizen scientists as possible involved. This crowdsourcing approach will strengthen the dataset; due to the power-by-numbers principle; and it will increase awareness of soil science at the same time.

Soil receives very little attention in media coverage of environmental issues. Tea Bag Index Project specifically aims to involve school classes and youth groups as those have shown the highest response and most reliable data so far.

We hope to get as many school classes and youth groups as possible to get involved in the project! Tea Bag Index Project would be grateful for your help in spreading the word about this new method, and your support in making a global decomposition map reality!

If you want to discuss during EGU2014 send an email to Taru Lehtinen, and feel free to send comments to! If you want to join our mailing list and hear more from us, look for the following link:

Additional information

Our web page:

Our mailing list:

Know more

Keuskamp JA, Dingemans BJJ, Lehtinen T, Sarneel JM, Hefting MM. 2013. Tea Bag Index: a novel approach to collect uniform decomposition data across ecosystems. Methods in Ecology and Evolution 4, 1070-1075. DOI: 10.1111/2041-210X.12097.

Lehtinen T, Gísladóttir G, van Leeuwen JP, Bloem J, Steffens M, Ragnarsdóttir KV. 2014. Do aggregate stability and soil organic matter content increase following organic inputs? Geophysical Research Abstracts 16, EGU2014-905-1.

Lehtinen T, Schlatter N, Baumgarten A, Bechini L, Krüger J, Grignani C, Zavattaro L, Costamagna C, Spiegel H. 2014. Effect of crop residue incorporation on soil organic carbon (SOC) and greenhouse gas (GHG) emissions in European agricultural soils. Geophysical Research Abstracts 16, EGU2014-10278.


This post has been simultaneously published in G-Soil.


Antonio Jordán is a Senior Lecturer at the University of Seville and coordinator of the MED Soil Research Group. Antonio’s research focusses on rainfall-induced soil erosion processes, the effects of wildfires on soil properties and soil degradation in Mediterranean areas. He is an active members of the Soil System Sciences (SSS) Division of the European Geosciences Union (EGU), which coordinates the scientific programme on soil sciences.