Citizen Science – The Garden Experiment
Citizen scientists are helping us understand the dynamics of soil microbial diversity
Soil is living matter! The microbial community in soil has a big impact on how well plants grow. Certain soil bacteria interact with plant roots and provide benefits to the plant such as increased leaf size or resistance to infectious pathogens. Unfortunately, soil life is threatened globally and it is important to find ways to restore soils to a healthy, microbially diverse state.
NCCR Microbiomes is interested in studying how microbial biodiversity in soils can be restored by soil transplants. One possibility is to transplant diverse microbes from healthy soils into degraded soils, hoping that the microbes will be able to colonise the soil habitat and re-establish the equilibrium.
Unfortunately it’s not so simple. The resident microbial community is not welcoming to newcomers; bacteria that are already established may out-compete the introduced bacteria for resources like nutrients and space. To potentially improve the success of transplants, we would first like to understand what happens to the various microbes when you mix the soils together! This is where citizen scientists have an important role to play.
In September 2025, we recruited over 200 volunteers in Switzerland to help us study how microbes that are already present in their garden soil mix with those in a soil transplant. The soil transplant is a natural soil from a site here at the University of Lausanne. We have characterised it really well in terms which microbes are there and in what proportions.
Transplanting simply means mixing and waiting! We let the soil microbes develop for several weeks. At the end, we measure the community composition in the mix and compare it to the community composition of another sample of the garden soil, one that didn’t receive a transplant. We hope to see if any of the bacteria we added were able to take up residence in the soil.
The experiment is very simple, but hopefully, collectively, we can learn a lot!
We look forward to sharing the collective results at the end of spring 2026.
Science et Cité made a short video about our citizen science experiment:
All the spaces have been taken! Thank you for your enthusiasm!
How to participate
To take part in the experiment, participants registered using a designated sign-up sheet, making sure to take into account the instructions below.
Timeline
The experiment began in late September 2025. Soil samples were returned by the end of November 2025. Our lab is processing the samples through the end of spring 2026.
Important Notes
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To participate, access to a private outdoor space (such as a garden, yard, or natural patch of ground) that can remain undisturbed for six weeks is necessary.
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Please note that only natural soil can be used. Soil in pots, planters, or balcony containers (including potting mix) won’t provide usable results for this study.
Due to the large number of responses, sign ups closed early on 15th September 2025.
If you have any questions about the experiment or its outcomes, feel free to email us: contact@nccr-microbiomes.ch
Citizen scientists' role, step by step
Participants received a small tube of soil (INOCULUM) of which we characterised the microbial diversity in great detail, and 2 empty tubes (labeled SAMPLE and CONTROL). They then
- Mixed this batch of soil, with a spoon, into a 10×10 cm2 plot of bare top soil (the top 5 cm) in your garden.
- Used the markers to delimit that spot.
Then, waited six weeks. Just leaving the soil as it is and treating and watering it as normal. After six weeks it was time to:
- Take scoops of soil from the mixed plot and fill the SAMPLE tube received.
- As a control, take soil from the garden that is 50 cm away from the mixed plot, and put this in the CONTROL tube received.
- Send both tubes by post to our lab in the envelope provided – we cover the postage.
- Scan the QR code received and simply fill the description and geographic location of the experiment site.
What then happens in the lab: We…
- Extract the microbes from both the mixed and the control soil, and characterise the microbial diversity of bacteria, protists and fungi.
- Perform a simple chemical analysis of the soil to measure its nutrient content and the pH.
- Compare all samples to understand how the soil we mixed in changes the original diversity (represented by the control).
- Because all participants will receive a soil transplant with the same level of diversity, we hope to learn how soil microbes from all the various individual gardens respond to the transplant.
What participants will receive from us at the end is:
- The nutrient levels and pH of their garden soil
- The microbial composition!
- An overview of our collective results (this may take a little while, because it is quite complicated!)