Apparently there’s no shortage these days of clever experiments to help illustrate important points about the health and functioning of soils.
Last November we shared a story about South Dakota State University Extension using ‘tighty whities’ — men’s white cotton briefs, which contain high amounts of carbon — buried in a field to measure the level of soil microbiology.
At the 21st annual No-till on the Plains Winter Conference this week, Shenandoah, Iowa no-tiller Chris Teachout shared another interesting test: this one involving tea bags buried in the soil to measure decomposition rates.
This involves burying pyramid-shaped Lipton Green and Rooibos tea bags 3-4 inches in the ground and letting them ‘steep’ in the soil over 40 days (official website says 3 months). After that you pull the bags out, oven dry them and weigh them on a gram scale to measure the amount of mass remaining.
“The Rooibos has a higher carbon-to-nitrogen ratio like cornstalks and heavy cereal rye, while the green tea is like alfalfa or clover and degrades really rapidly,” says Teachout, who no-tills 1,850 acres of crops and has been rebuilding his soils through seeding cover crops.
While you let this experiment steep in your mind, you should know this is really part of a bigger, worldwide effort dubbed “The Tea Bag Index” and more information and protocols are available on their site.
The method was developed and tested by a team of researchers from the University of Utrecht, Umeå University, The Netherlands Institute of Ecology and the Austrian Agency for Health and Food Safety Ltd.
The project started in 2010 and will last at least until 2020 as participants from around the world are sending in their bags and samples.
Researchers say one method to analyze decomposition rates in a field is measuring litter mass loss using litterbags, but making the bags and weighing, sealing or sowing them proved to be too time consuming. And to get an overview of decomposition rates and carbon sequestration, researchers would have to do various measurements in time.
After experimenting with various types of tea, researchers settled on rooibos and green tea because of their differing chemical makeup. Green teas contain a lot of water soluble carbon and rooibos tea contains more acid insoluble carbon, they say.
Organizers of the project hope the results will yield a parameter for soil decomposition rate in the global soil map.
Just one piece of advice from Teachout: Don’t leave the harvested bags sit around in the kitchen, or someone may end of with an “earthy” cup of tea they’ll never forget.