For eight days in November I returned for more earthworm survey work with the Natural History Museum Soil Biodiversity Group, this time in Somerset and Berkshire. A small team of volunteers this time, just myself and long-time SBG volunteer Irfaan, travelled first to the Somerset site to continue work started the previous week. We had been informed the Somerset site was the most beautiful yet but when we arrived on Monday the fog was so thick we had to take David’s word for it! Thankfully, by Tuesday the sun had returned to reveal a superb landscape, the countryside you imagine from hundreds of years ago, with little patchwork fields fringed with ancient hedgerows.
Four fields are sampled per farm, covering a spectrum of management intensity, such as how often the field is grazed, how much fertiliser (animal or artificial) is added and whether it has been ploughed or used for crops in the past. The field we worked first was the lowest intensity field at the Somerset site, not surprisingly as it was some distance from the nearest track, was steep and had springs running through it. This field had never been ploughed, giving an odd feeling of being possibly the first people to disturb the soil. It also had the biggest Yellow Meadow Ant (Lasius flavus) mounds I have ever seen!
For a change from sheep and cows the fields at the Somerset site were grazed by Shire Horses which noised around us and the kit expecting food and generally being a distraction, having to be chased away at intervals. As handsome as the Shires were, I was more excited and distracted by the lovely Noon Flies (Mesembrina meridiana).
Within each field a bare minimum of 18, preferably 20, samples are made. Half of these are located at random using a combination of a randomly chosen direction and distance. The direction is decided using a super scientific method of David spinning around.
It is double blind so that some else who is not watching calls out when to stop, although this sometimes has to be done a couple of times if the random direction is in an unsuitable place, such as too close to the edge of the field or trees which may have different micro-environment to the rest of the field. The distance from the previous pit to the next is then determined by a random number table. The rest of the samples are coverage pits which are spread out over the field.
Once the location is marked with a flag it’s time to start over again taking measurements, digging a pit, taking samples and hunting for worms!
On Thursday we left Somerset for Berkshire, unfortunately still with a field left to finish. The site in Berkshire was the Organic Research Centre Elm Farm.
Excitingly the very first pit had a bumper crop of the UK’s largest earthworm – Lumbricus terrestris emerge when the mustard solution was added, some were bigger than by baby snakes at home! Could this be because of higher organic inputs in this field than Somerset? The statistics will tell us in time (hopefully!).