Boosting soil citizen-science using Tea Bag Index method towards soil security in Australia

Citizen science is becoming a significant contribution to large scale soil surveys. TeaComposition is a citizen science project introducing the Tea Bag Index (TBI) method to students in Australia to support research on soil decomposition using tea bags (green and rooibos). Soil microbial driven decomposition is an essential soil function that releases soil organic matter (SOM) and nutrients, i.e., soil ecosystem services. The TBI experiments enable citizens to understand this process (increasing soil connectivity) and this information is valuable for assessing urban soil conditions. With 430 TBI in-field incubations between 2017 and 2020, this project engaged more than 3200 students who tested the TBI method on more than 50 school grounds and collected soil samples for analyses of soil properties. Approximately 50% of the tea bags were recovered and mean TBI parameters were: decomposition rate (k) = 0.02 gd−1 and stabilisation factor (S) = 0.32. Soil texture, SOC and SI had the most significant relationships with TBI. Clay and Slaking Index (SI) had negative impacts on k (rs = -0.37, -0.22, p ≤ 0.05, respectively) and SOC had a negative effect for S (rs=-0.27; p ≤ 0.05). These results suggest a combination of high clay and SOC may be related to reduced potential for C sequestration. Regarding citizen science, this study suggests further research using a local tea brand and shorter burials. This suggestion aims to increase Australian citizen participation.