A low-tech test with big potential
As part of the Hort2thefuture project, the European Training Academy (EUTA), led by Steve Quarrie, is working with growers in Serbia and North Macedonia to test a simple but powerful method for measuring soil health. Known as the teabag test, it uses the rate of teabag decomposition as an indicator of microbial activity in the soil.
The idea is straightforward. A teabag is weighed, buried in the soil, and left for a few months. It is then dug up, cleaned, dried, and weighed again. The loss in weight reflects the breakdown of organic material by soil microbes. This practical and affordable method has sparked widespread interest among growers keen to better understand the health of their soils.
Fine-tuning the method
While the concept is simple, there are some technical considerations. Early versions of the test used non-biodegradable teabags, meaning the bag itself remained intact and the weight loss was solely from the tea inside. However, many teabags are now made from biodegradable materials, such as modified starch or plant-based plastics. This complicates things, as the bag itself may also degrade underground.
To address this, Steve Quarrie is running a trial in his own garden to test the breakdown of different teabag brands. Four brands of green tea in pyramidal bags have been buried at a depth of around 12 centimetres. Some will be unearthed after one month, and others after two months, to examine how well the bags withstand life in the soil.
More than just a bag of tea
Selecting the right teabag has proven more complex than expected. There are differences in the materials used, the size and type of tea leaves, the presence or absence of a tag, and even the colour of the “green” tea, which can range from pale green to almost black.
Teabags with tags are easier to locate once buried, and they offer a simple way to label each replicate. There is also interest in whether whole leaves break down at a different rate than crushed fragments. These details could affect how reliable and consistent the test results are.
Next steps
By autumn 2025, the team expects to publish a recommendation on which teabag brands and types work best for this kind of soil testing. In the meantime, growers involved in the project are gaining hands-on experience with the method and contributing to a better understanding of how to apply it in real-world conditions.