2. IT’S CITIZEN SCIENCE What is the Tea Bag Index?
It’s citizen science …and what is citizen science?
It’s the collection and analysis of information relating to the natural world by members of the general public (like you), often as part of a big project with professional scientists.
The Tea Bag Index is an experiment that involves you guys digging holes in your school yard and burying tea bags and digging them up in 3 months time! Sounds great doesn’t it!
But why are we asking you to do this?
Because scientists in Holland have found that by burying tea bags and weighing them 3 months later we can learn about decomposition around the world. We are going to learn a bit more about this process in a few minutes but firstly we’re going to look at… why do we need healthy soils?

3. Why should we look after our soils?
Buildings all over the world, from America, England to Africa have been made using soil. ½ of the world’s population live or work in buildings made of soil.
The nutrients in our soils allow farmers to grow their crops successfully. As the number of people on our planet increases, it is important to take care of our soils as demand for food will rise.
Soils can absorb and store water like a sponge, which helps to reduce flooding. If soil becomes too solid the water will drain away more slowly, increasing the chance of flooding.
As water passes through the soil it is filtered and cleaned – protecting streams and rivers from harmful pollution.
A small patch of soil just 1 metre sq in area can hold a billion living things. These include insects, spiders, worms, centipedes, mites, fungi, and tens of thousands of bacteria. These creatures help to recycle and add nutrients to the soil, which in turn helps plants to grow. This is called decomposition.

4. What is decomposition? Bacteria Fungi & Worms
When a plant, animal, or insect dies, that plant, animal, or insect is broken into tiny pieces and those pieces become part of the soil. This is called decomposition.
Bacteria, fungi, and some types of worm are what break down dead plants, animals, and insects. The bacteria, fungi, and worms are called decomposers. Decomposers eat dead plants, animals and insects as their food/energy source. This process breaks down the dead material into smaller and smaller pieces, adding nutrients into the soil.
We get nutrients from our food – pasta and potatoes give us carbohydrates, meat gives us protein and fat, fruit gives us vitamins and sugar.
The dead and broken down material in the soil is like dinner for a decomposer!
Living plants take nutrients from the soil so they can grow. So, living plants use nutrients from the soil, as well as water, sunshine and air, to help them grow. Decomposers help provide these nutrients.
Bacteria Fungi & Worms

5. What is the Carbon Cycle?
CO2
CO2
The carbon cycle in the process where CO2 is taken in by trees and plants.
When the trees, plants or leaves die they fall to the ground and decomposition happens like we just talked about.
When decomposition happens all the CO2 that the tree, plant or leaf had breathed in gets released.
Some of this CO2 escapes back into the atmosphere (sky), some gets breathed in again by trees, plants and leaves and some stays in the soil.
Some soils store huge amounts of carbon. It is estimated that there is three times more carbon in soil than in all the vegetation and forests.
There are some other sources of CO2, what are they? Combustion (burning fuel to make energy) who has some examples of these? Animals, breath out co2, and so do we!
The tiny decomposers in the soil depend on different factors in their environment as they do not have a thick skin or clothes to help them to, for instance, have a constant body temperature. Therefore, decomposition is slower in cold climates and faster in warmer climates. This also means that in colder climates, less carbon dioxide will be released into the air and more is stored in the soil.
The decomposition rate depends on:
® Environmental conditions (humidity, acidity, the amount of nutrients in the soil, temperature). These factors affect the activity of the microorganisms; how fit they are and how much food they need.
® The chemical properties of the material that is going to be decomposed (e.g. a branch compared to a flower or plastic compared to paper). This is because microorganisms prefer some materials over other. Just like us humans, microorganisms love to eat sugar but take longer to break down harder materials, like wood, which is why you can still see dead trees for many years after they fall.
® Which decomposers are present. Mites, worms, fungi and bacteria all break down the different parts of the plant material at different speeds, as each of them has its own preferences.
CO2
Bacteria Fungi & Worms

6. What will happen to our tea bags?
Each of the tea bags we bury has leaves inside, 3 Rooibos, 3 green tea.
By weighing them before we bury them and again after they have been in the ground for 3 months we can see how much decomposition happened to the leaves.
The Rooibos tea and the Green tea may have decomposed at different rates because they are made of different kinds of leaves. This is because microorganisms prefer some materials over others, just like us humans.
The rate will also depend on what decomposers (bacteria, fungi and worms) are present.
It will also depend on things like the temperature of the soil, or how much it has rained – microorganisms will decompose the teabags quicker in warm damp soils
Rooibos Tea
Green Tea

7. Where can you do the Tea Bag Index?
School grounds
Garden
Park
Nature reserve
Allotment

8. What will we need to do the
Tea Bag Index?
Today:
3 Lipton Rooibos tea bags
3 Lipton Green tea bags
Instructions
Recording form
Sticks to mark where the tea bags are buried
Waterproof marker pen
Trowel or spoon
Metre ruler
In 3 months:
A warm and preferably sunny spot indoors where the tea bags and soil samples can dry when you have dug them up (such as a window sill)
A weighing scale

9. How do we do the Tea Bag Index?
Step 1
Collect all your equipment and the instructions
Step 2
Weigh each of your tea bags one by one and number the labels
Step 3
Choose where you will conduct your survey, remember to ask permission!
Step 4
Write down all your observations information on your recording sheet

10. How do we do the Tea Bag Index?
Step 5
Measure out a 1 metre triangle and dig an 8cm hole at each point big enough to fit 2 tea bags
1 meter
Step 6
Bury the tea bags, one of each in each hole with the labels sticking out above the ground
Step 7
Remember to mark your site so you know where to look for your tea bags in 3 months time

11. Hello! We are Taru, Joost, Judith and Mariet.
What will happen to our results?
Hello! We are Taru, Joost, Judith and Mariet.
We are SCIENTISTS!
We are asking you to take part in the Tea Bag Index and submit your results to us on our website.
Once we have lots of results from around the world we can create a global soil map to help us learn more about our climate!

12. Who else is taking part?
The TBI is being completed all over the world already, in Holland , Austria and Sweden, all the way down to South Africa and over the Atlantic in Canada!

13. What about the SDGs?
In assembly this morning we learnt about the sustainable development goals.
Who remembers what these are?
Which one do of the goals in particular do you think we are learning about when taking part in the tea bag index?
Lots of your lessons in school will connect to the sustainable development goals. Always keep an eye out to see how you and your class are working towards them.
Maybe even put them up on the wall so you can always check which ones might link into what you’re learning.
To achieve the Global Goals by 2030 we need ALL young people to know and care about them.

14. And don’t forget World Soil Day
Question Time!
And don’t forget World Soil Day
Monday 5th December!