http://www.decolab.org/tbi/concept.html). There are several experiments running across the world and Sarah put out a call for people to participate in the UK project.
We each receive three pairs of tea bags (one green tea and one rooibos) and bury each pair in different parts of the garden. After three months we dig them up and send them back to Sarah for analysis with soil samples and a completed questionnaire. More information about the project is at http://teabagindexuk.wordpress.com/.
Suggested places to bury them are the lawn, a spot that has been treated with organic matter and an area that you are particularly interested in investigating, for example a bare patch or an area that is often waterlogged. We are allowed to choose other spots but the important thing is to fill in the details on the questionnaire of the location and whether fertilisers, pesticides or herbicides have been or are used.
The lawn was not an option for me. We do have a small patch of grass but the tea bags have to be buried about 3 inches deep and at 1.5 inches under our lawn you hit builders rubble! So, I decided to put the first pair in the middle of my herb patch. I don't add any compost or fertiliser to this area other than some leaves from the comfrey plant that is growing there.
The second pair went into an area close to the compost heap that is regularly fed garden compost and is used for growing brassicas and squash. I buried the third pair in a small patch of ground in front of the house. It is a bit of a problem area in that it gets full sun during the day and dries out very quickly. I've not had much luck growing anything in it apart from a few wild flowers, bulbs, rosemary, onions and masses of rudbeckia.
So now we just sit back and wait for three months.