Beneath our feet, in the velvet underground of the soil, there’s music. Its various rhythms are punctuated by sudden clicks and scrunches with quiet lulls in between. Most of that noise is likely the sounds made by moving and eating, of life in the soil going about its daily business. The richness of life in the soil is vast - scientists suggest that soil is in fact our planet’s most biodiverse habitat. Soil is especially rich in microbes and mini beasts (bacteria, fungi and viruses, and invertebrates) and all this is connected together in complex food webs which also connect with life above ground too. Not all of these organisms make sounds or make sounds that we can pick up with microphones but by listening-in to what we can hear, we may be able to learn a lot about all this activity and use the soil soundscape to helps us assess how healthy our soils are.

Healthy soils with lots of different organisms function better than depleted soils. The richness and diverseness of organisms enhance overall soil structure and the way the particles in the soil clump together or aggregate, with plenty of spaces for air and water in between. All this boosts the ecosystem services that healthy soils deliver for sustaining life above ground, productive farming, carbon storage, and air and water quality, so finding new ways to assess and monitor soil health are beginning to attract more attention. It’s always good to find a method that minimises disturbance, is relatively cheap and easy, and can be copied by someone else in the future.

As part of my ecology masters degree at UEA I’m running a project at Martlesham Wilds testing out this new science of listening to the soil or soil ecoacoustics. It’s an exciting time for my research because at the moment the Martlesham site is a wonderful mosaic. The different land use histories on farm have created a series of distinct managed habitats, all very conveniently located next to each other. Besides the former organically-farmed fields there are grazing meadows, mature trees and wildlife friendly hedges, woodland and copse and the many tracks used by the heavy farm machinery to access the fields through the cropping year. This is important because we need to know if the various habitats sound different from each other and if they do sound different, how we might begin to interpret this variation.

As well as finding out how the soil soundscape of the different habitats varies, by making recordings at different times of the day and through the seasons we can make sure that what we have recorded isn’t an artefact because of time of day or season. We can also see how the sounds of the soil change with the weather.

So if this is why it’s a good idea to start listening to the soil how do we do it? Soil ecoacoustics are low tech. A metal probe is sunk into the earth to a known depth - I’m using two different depths of probes - and then a very sensitive contact microphone is attached to the probe and the microphone attached to a recorder. Some of my probes will stay in the soil for the duration of the project and some will be put in just for individual recordings. Contact microphones work on vibrations so the munching movement of worms as they pass through the soil, or the soil-shifting of ants are picked up by the probe and that energy is converted into sounds. It’s a bonus that Martlesham is quiet because I have to use a sound proof hood over the probes and mics to cut out as much external sound as I can. So far so simple, but there is a bit of wizardry in some special software that turns the raw recordings I feed into the computer into a sort of score or metric that I can use for my statistical analyses. And because this is a new technique I will be getting my hands dirty sifting a few soil samples to compare what can be found in a spade’s worth of soil with what the recordings are telling us.

But for now, as I start my recording sessions, if you see me on site with my green basket and red bucket you will know that we are hoping to add a new dimension to how we understand the Martlesham reserve, because we want it to be every bit as Wild in the soil as we hope it will become in the world above.