Citizen Science – The Garden Experiment

Help 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 we need your help.

As a first step, we are looking for volunteers in Switzerland to help us study how microbes that are already present in your 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’ll let the soil microbes develop for several weeks. At the end, we’ll measure the community composition in the mix and compare it to the community composition of another sample of your 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 will be very simple, but hopefully, collectively, we can learn a lot!

How to participate

If you’d like to take part in the experiment, please register using our sign-up sheet. Make sure to read the instructions below carefully!

Timeline
The experiment will begin in late September 2025. Soil samples should be returned by the end of November 2025. Our lab will process the samples through the end of Spring 2026.

Important Notes

  • To participate, you’ll need access to a private outdoor space (such as a garden, yard, or natural patch of ground) that can remain undisturbed for six weeks.

  • 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.

If you have any questions about the experiment or its outcomes, feel free to email us: contact@nccr-microbiomes.ch

Sign up here

Your role, step by step

You will receive a small tube of soil (INOCULUM) of which we characterised the microbial diversity in great detail, and 2 empty tubes (labeled SAMPLE and CONTROL).

  • Mix this batch of soil, with a spoon, into a 10×10 cm2 plot of bare top soil (the top 5 cm) in your garden. 
  • Use the markers to delimit that spot.

Now, wait six weeks. Just leave the soil as it is and treat and water it as you would otherwise. After six weeks (we will remind you by email) it’s time to:

  • Take scoops of soil from the mixed plot and fill the SAMPLE tube you received.
  • As a control, take soil from your garden that is 50 cm away from your mixed plot, and put this in the CONTROL tube you received. 
  • Send both tubes by post to our lab in the envelope provided – we will cover the postage. 
  • Scan the QR code you received and simply fill the description and geographic location of your experiment site.

Next, what we will do is: 

  • 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 you will receive from us at the end is: 

  • The nutrient levels and pH of your garden soil  
  • The microbial composition! 
  • An overview of our collective results (this may take a little while, because it is quite complicated!)

 

Detailed video instructions