Today I conducted a worm survey on my allotment. I chose three locations. Firstly on ground which had been covered with weed suppressant fabric and was not used to grow a crop in the last growing season.
Second was an uncovered patch that had gone a bit wild after the legumes and squashes had been harvested
The third sampling site was patch where onions and beetroot had been grown and was not heavy with weeds.
At each location I dugout a cube ( spade's width and depth) of soil onto a white plastic sheet. Then I sifted through by hand using a spatula (a toy sandpit spade actually) and counted the worms that were big enough to be visible. The first observation as that there were precious few earthworms at any of the three sites. Sources talk about 5 to 25 worms per square foot, but I only counted a total of 8 (not counting a centipede, millepede, wireworm and a snail.
The fabric covered area was the worst, yielding just one very pink knotted worm (see top photo). The other two sites were close although the less weedy site just edged it at 4 genuine earthworm.
Overall I am worried at how few worms I turned up. The original aim of this survey was to attempt to assess the effect of weed suppressant fabric on soil health, as indicated by the number of earthworms. Just one worm is a fairly clear result. This is not a result I welcome as I have found the fabric to be a boon, saving me lots of hours of weeding while producing good yields (of sweetcorn strawberries and brassicas for instance). I may repeat my survey in wetter weather. (The normal Edinburgh torrent has abated for the last week.) But it looks to me that I should stop using the fabric, except in desperation.
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