Digging into the world of worms
Updated: Mar 4, 2022
Most people ignore earthworms or dismiss them as slimy, insignificant little creatures yet Charles Darwin, no less, wrote “There are few animals which have played so important a part in the history of the world than the earthworm".
Earthworms provide productivity, flood mitigation and carbon storage so healthy soils don’t just grow food, they also recycle nutrients, filter drinking water and store large amounts of carbon in the form of tiny fragments of plants, micro-organisms and animals.
Darwin learnt a huge amount about earthworms in 40 years of experiments and believed that ‘judging by their eagerness for certain kinds of food, they must enjoy the pleasures of eating’. Earthworms eat as much as their full weight every day in decaying organic matter and what comes out the other end is pure goodness.
Darwin estimated that all soil has passed through an earthworm at some time!
Earthworm manure (casts) is natural fertiliser containing mircoorganisms, inorganic minerals and enzymes, plus organic matter. There are up to ten common earthworm species in agricultural soils and are divided into three groups: litter-dwelling earthworms (epigeic); topsoil earthworms (endogeic) and deep-burrowing earthworms (anecic). None of the earthworm groups like acidic peat soils are unable to thrive in heavy, waterlogged soil or in soil compacted by dense numbers of livestock or heavy machinery. Numbers and species are also depleted in soils that are robustly and regularly dug, stirred and overturned so regular deep ploughing can be detrimental.
For such an important group of animals, earthworms have been under-researched by British farmers for decades until 2018 when everything changed...
British earthworm survey
In 2018, the #60minworms study was launched in order to standardise methodology and support farmers to monitor their own field (or fields) and to generate results to help identify potentially over-worked soils.
The lead scientist, Dr Jackie Stroud, a National Environment Research Council (NERC) and Soil Security Fellow at Rothamstead Research confirmed that ‘earthworms are sensitive and responsive to soil management which makes them an ideal soil health indicator’.
The results released in 2019 showed that the average field had nine earthworms in every spadeful of soil whilst top fields could have almost thirty. 42% of fields had poor earthworm biodiversity meaning either very few or none of the surface and deep burrowing worms were seen. Surface dwelling worms provide lots of food for song thrushes whilst the absence of deep burrowing worms on 16% of fields is concerning. They are ‘drainage worms’ with vertical burrows that aid water infiltrating and ultimately help combat water-logging. With slow reproduction rates, their recovery, even with changed management practices, could take a decade or more. The full paper can be found here.
Armed with such invaluable information, The LANCE Trust is keen to monitor the earthworms in Lark Meadow over time in order to see what, if any, changes occur with the establishment of a perennial, species-rich meadow.
Lark Meadow earthworm survey
On 4th October 2021, clutching spades and information sheets, four members of LANCET arrived at Lark Meadow eager to find out more about earthworms.
A stiff breeze blew across the meadow and the ground was damp. Recently tilled, the soil was loose so it was easy to dig the five pits in the W-shape recommended by the previous study. We spread the worms on our mat and began our first tentative analysis of the species found.
Thanks to the information sheet, it was easy to divide the worms into categories but harder to distinguish between the age-groups. It all depends on the saddle and although some were obviously juveniles and some adults, there were some that barely had a saddle. Calling them ‘teenagers’, we decided to put them in the adult category.
One of our pits had just a solitary adult topsoil earthworm. The others were more promising, yielding an average of just under 4 adult top-soil worms and 2.5 juveniles (species unknown) per pit. This means that, currently, as far as earthworms are concerned, Lark Meadow is just below the national average with a lack of the deep-burrowing and surface worms. Let’s see what happens next. Our next survey will be in Spring 2022, please contact us if you want to take part.
You can use the AHDB earthworm survey information sheet to help you survey your own field, garden or community-space. Find out more about earthworms at www.earthwormsoc.org.uk or on their Facebook page.