Soil fungi and teabags respond to loud sounds

The soils are alive with the sounds of music. Want your soil health to improve? Try making it noisier, say Australian scientists.

The researchers have found that playing soundscapes can make friendly soil fungi grow faster. The discovery could help restore microbial health to the worlds soils, 75% of which are substantially degraded.

Sounds played at volumes of 70-90 decibels, and a pitch of 8KHz, encouraged things to decompose more quickly than ambient background noise at 30 decibels.

“This was informed by previous research that suggested 8 kilohertz at around 80 decibels increases the activity of E. coli bacteria,” says Dr Jake Robinson, a microbial ecologist at Flinders University and lead author on a pre-print (not peer-reviewed) paper.

The researchers first tested the soundness of their theory by playing Youtube soundscapes to teabags.

“The humble teabag is often used in ecological studies to get information about soil decomposition,” Robinson tells Cosmos.

“We basically played sound to these tea bags in the soil to see if it had an effect on the decomposition rate or the fungal biomass. Teabags that received the sound treatment significantly increased in biomass compared to the control group.”

Person in bookshop holds up book
Jake Robinson with his 2023 book.

Specifically, the researchers used green tea and rooibos tea, which Robinson says are used because they have very different consistencies.

“Green tea bags are more leafy, and the rooibos is more woody. [We wanted] to see if that had different effects on the decomposition rate, because you’d expect woody stuff to decompose slightly slower.”

After seeing the sound-treated teabags decompose faster, the researchers turned to a common soil fungus – Trichoderma harzianum – to see if sound had the same effect.

“This fungal species is known to be beneficial for plants. We cultured it in petri dishes, and then did the same thing: we applied sound to the petri dishes, and we found that it significantly increased growth rate.”

The researchers aren’t sure why sounds help the fungi to grow, although they have a few ideas.

“It might be that microbes, including fungi, can convert the soundwave energy into an electrical charge, which stimulates their activity,” says co-author Christian Cando-Dumancela, a research assistant at Flinders University.

Robinson says that the study is a progression of ecoacoustics: studying ecology via listening to soundscapes.

“We’ve developed special microphones that you can put in the soil and listen to the sounds of the little animals in the soil. And that gives you an indication of soil health,” he says.

“But this is actually applying sound.”

The researchers are keen to investigate their soundscape technique further, to see if it can work at a larger scale. Other research recently published by the team has highlighted the threat to microbial communities in degrading soil, and their importance in keeping soil healthy.

“Can we use sound in a positive way? And also, can we kind of prevent the negative sounds that might be damaging our ecosystems?” says Robinson, adding that global noise pollution may also be having a negative effect.

This isn’t a brand-new idea – sound has been proposed to control botrytis fungi in grapes, points out Robinson – but there is still much research to be done before they can establish what will help and hinder the soil.

“We don’t know too much about it yet. The next step is trying to understand the mechanisms, and where we can select for different sounds to promote different communities in the soil,” says Robinson.

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