Individual study: Deep-burrowing earthworms are consistently more abundant on untilled fields: experiments on five UK farms
Edwards C.A. & Lofty J.R. (1982) The effect of direct drilling and minimal cultivation on earthworm populations. Journal of Applied Ecology, 19, 723-734
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A replicated trial on three farms in the UK (Edwards & Lofty 1982) over five years found that one or both species of deep-burrowing earthworm Lumbricus terrestris and Allolobophora longa were significantly more abundant in untilled than in deep-ploughed plots at all three sites in all five years. After five years, untilled plots had 16.8, 8.6 and 1.2 L. terrestris/m2 on average at Woburn, Rothamsted and Boxworth experimental farms respectively, compared to 7.8, 0.3 and 0.1 L. terrestris/m2 on deep ploughed plots. Shallow working earthworm species showed few differences between untilled and ploughed treatments. In two studies with one year of monitoring, earthworms were also more abundant in untilled plots than ploughed plots. There were 250 earthworms/m2 in plots untilled for four years compared to around 50 earthworms/m2 in annually ploughed plots, and around 100 in plots ploughed for two of the four years at North Creake, Norfolk. At Lee Farm, Sussex there were between 5 and 70 L. terrestris/m2 in untilled fields, compared to between 1 and 12.5 L. terrestris/m2 in ploughed fields. There were between three and seven replicates of each treatment at each farm. The Woburn experiment on winter wheat ran from 1965 to 1971, plots were 6.4 x 18.0 m. The Rothamsted experiment on winter wheat started in 1972 with sampling from 1975 to 1979, plots were 33 x 13.5 m. The Boxworth experiment also on winter wheat started in 1971 with sampling from 1974 to 1978, plots were 36 x 13.5 m. This study is partly the same study as (Edwards 1975).