It’s an Early Bird that Catches the Worm

The lowly Earthworm is probably not something that most people spend much time wondering about.
For most people it’s a creature that inhabits the dark damp Earth and only emerges when a hungry blackbird drags it from its slimy burrow to feed its young. Gardeners will come across them, but as digging is now (thankfully) less fashionable, even gardeners may be unaware of the wriggly worms under their feet.
It is easy to hugely underestimate just how important this creature is to the whole survival of mankind. Charles Darwin was the first scientist to really study the Earthworm. In his book, with the truly unsexy title “The Formation of the Vegetable Mold Through the Actions of Earthworms” interestingly, Darwin refers to soil as “vegetable mold” and this is partly what soil is made up of – a mixture of sand, silt, clay, general stony debris and vegetable wastes.
It is the latter to which the worm plays such an important role, enabling waste organic materials to be rapidly transformed into humus and potential plant foods. The Earthworm does not labour alone in its task as it has the support of several billions (as yet nobody has been able to estimate the actual numbers) of tiny micro-organisms.
Many attempts have been made to calculate the actual amount of material per hectare that Earthworms are able to process, but by all accounts, the numbers in a healthy soil are quite eye watering. Sadly, many agricultural soils are very low in Earthworm populations; some are almost entirely devoid of this important creature. Aggressive tillage, heavy chemical usage and lack of suitable organic material for Earthworms to feed on have led to a rapid decline, resulting in severe soil structural problems, bad drainage and soil inability to support any form of cropping without resorting to heavy chemical inputs. Many flood incidents are actually as a result of bad soil management and lack of Earthworms.
For several years we have been conducting trials on the farm looking at the use of our own grown ramial chipped wood. This comes from our willow coppice planted on a useless boggy corner of one of our fields. The trial is being run by The Organic Research Centre, with whom we have had over three decades of involvement with a wide range of on-farm trials. The trial is on a plot of one hectare (10,000 square metres), which is one of our rotational vegetable cropping areas, that we have been growing on for over 32 years. The trial consists of comparing the application of ramial chipped wood (RCW) to composted material. The trial is scientifically set out to take into account a range of different areas of the plot; the researchers are monitoring a range of factors such as organic matter content, pH, nutrient contents, mycorrhizal activity and Earthworm populations. The data collected will be analysed to enable a picture of the soil health to be portrayed. Earthworm populations have long been known as a valuable indictor of soil health.
Calculating the numbers of Earthworms present is a challenging task and involves a considerable degree of fairly heavy digging. The wonderful worm women from Organic Research Centre visit the site several times annually to conduct trial digs and worm counting. This involves digging numerous 200mm square hole at various locations across the site and sifting through the soil to separate and count the worms. Our soil is exceptionally stony and by no means easily dug, so this is hard work. The worms are sorted into their different types as well as whether they are juveniles or seniors. The former is a valid indication that the population is increasing rapidly, and this is considered to be the ideal population.
The most recent count has revealed some staggering results. An average number of over 1,000 Earthworms were present for every square metre of topsoil across the field. This does not allow for those worms that are living below the 200mm of topsoil, so the figure is likely to be even higher. Over the one-hectare plot this calculates out at around 10 million earthworms. It’s not easy trying to imagine what this looks like.
So, I have done some homework to try and ascertain what sort of pile this would be: 1,000 earthworms would, given their average size, weigh approximately a rather convenient 1 kg. Over the 10,000 square metres of the field this would equate to around 10 tons. These figures are by no means accurate and could well be a gross underestimate, but it serves to illustrate the potential that worms can have. The amount of soil that these busy invertebrates move around is also difficult to estimate but some research has indicated that a population of this magnitude could well be moving the entire topsoil within 10-20 years. Annually this would be around 150-300 tonnes.
So, the humble earthworm has a pivotal role to play in soil management. On the farm we are managing our soils to give them as much possible help as we can to thrive and prosper. Our food production is dependent on their presence.

2 replies
  1. Annie Leymarie
    Annie Leymarie says:

    Lovely to read that among your own ‘livestock’ there are seniors as well as juveniles. One often-heard justification of ‘proper’ livestock farming is that nature is very cruel, there are predators always eating the non-carnivores, who never make it to a mature age, so that’ humane’ killing in farming is actually a better option for the animals. I’m glad that at least some worms get a chance to live a ripe old age (by worms’ standards)!

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  2. Lettie
    Lettie says:

    I rent a 7.5 pole very stoney alottment. I have access to free wood chippings. It’s only my second year. I have already noticed more worms and more friable soil in the areas I mulched last year. The local blackbirds have been feeding their young with some of the worms..

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