Buried Underwear Shows that Humus Promotes Soil Life and Pro-tects against Drought

The aim of the ‘Proof by Underpants’ project was to obtain exten-sive information on the soil quality of gardens and farms, for the first time with the help of the general population. Initial results show that humus plays a key role in the soil, helping it cope better with climate-induced drought.

In April 2021, under the guidance of Agroscope and the University of Zurich, one thousand volunteers from all over Switzerland buried cotton underpants in gardens, meadows, croplands and fields in order to measure the quality of Swiss soils. The data from 880 sites across the whole of Switzerland were included in the analyses, making this the biggest, most extensive project of its type to date (see project description below). Initial findings are now available.

The more humus, the faster the decomposition rate

In the study, researchers investigated how fast the underpants rotted down in the various soils. Humus content was revealed as one of the main factors for speed of decomposition, and hence for soil health. According to Franz Bender, head of the project at Agroscope and the University of Zurich, “The more organic material the soil contains, the more nutrients available to the millions of soil organisms, and the faster the decomposition of the underwear.”

Important for the water balance

Private gardens have the highest humus content. “This is primarily due to the increased use of compost. Composting releases valuable nutrients that also serve as food for soil organisms” says Bender. On average, the humus content on farmland is 23 per cent lower than in gardens. Accordingly, the underpants decomposed more slowly there. The study also demonstrated how important humus content is for the soil water balance. “The more humus a soil contained, the more water it was able to store” added Bender.

Humus as an engine in the soil

“If we want to arm the agricultural sector against increasing drought, keep yields high and produce more sustainably, soil humus content is as good a place as any to start” affirms Marcel van der Heijden, Director of the study at Agroscope and the University of Zurich. “Humus acts as an engine for the entire food web in the soil, ensuring that the soil ecosystem functions optimally and thus also stores more water” adds van der Heijden. Already-known measures for increasing the humus content in soils are e.g. a permanent groundcover, reduced tillage, and the application of compost or mulch. The humus-balance calculator, a free online tool available to all, can help farmers build up their humus stocks.

Information on soil organisms

Researchers discovered over 18,900 types of bacteria and 6500 different fungi – a huge variety of soil organisms demonstrating that millions of lifeforms populate every cubic centimetre of soil. Among these are springtails, pseudoscorpions, woodlice, nematodes, fungi and bacteria. These organisms exercise an important function: they recycle organic matter such as leaf litter, grass cuttings, dung and cadavers, transforming it all into nutrients for plants, and thus producing ‘free fertilisers’ for our gardens and the agricultural sector. More information on soil organisms can be found in the book accompanying the project, Der Dschungel im Boden (‘The Jungle in the Soil’).

Information on the ‘Proof by Underpants’ project

In April 2021 researchers from Agroscope and the University of Zurich launched the Citizen Science project ‘Proof by Underpants’. Using a standardised process, one thousand lay researchers buried underpants and teabags in their gardens, meadows and crop fields. In addition, they collected soil samples and recorded management data. “Without the collaboration of citizen scientists we would never have gathered so much data. This is the biggest project of its type in Switzerland to date”, confided Franz Bender. In the laboratory, the degree of decomposition of the underwear was measured precisely by means of digital scans and the supplied soil samples were analysed. Homepage – Proof by Underwear - Citizen Science App (beweisstueck-unterhose.ch)

Public and media event

The Festival of Soil Life took place at Agroscope’s Zurich-Reckenholz site on 28 Sept. 2022. Researchers from Agroscope and the University of Zurich presented the initial results of the project. A walkable soil profile provided a unique window onto the world beneath our feet. Visitors could observe the heroes of the underground – the soil organisms – by means of a microscope with a screen, or dig up underwear buried in the field. In addition, decomposed underwear from the project were displayed on the ‘wall of evidence’.



Last modification 27.09.2022

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