Individual study: Reduced tillage systems for use on organic farms do not benefit earthworms; an experiment at the University of Kassel experimental farm, Frankenhausen, Germany
Metzke M., Potthoff M., Quintern M., Hess J. & Joergensen R.G. (2007) Effect of reduced tillage systems on earthworm communities in a 6-year organic rotation. European Journal of Soil Biology, 43, 209-215
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A replicated controlled trial at the University of Kassel experimental farm, Frankenhausen, Germany, (Metzke et al. 2007) found that neither of two methods of reducing tillage suitable for use on organic farms enhanced numbers of earthworms (Lumbricidae) in the soil. Ploughing is important for weed control in organic farming, so both systems involved some soil inversion. A ridge culture system, using a shallow plough that formed ridges and loosened the soil with a spike to 35 cm depth, and a shallow inversion plough to 10 cm depth, were compared with conventional ploughing to 30 cm depth. There was no difference in the abundance or total biomass of earthworms between the conventional ploughing and shallow ploughing. On average between 5 and 30 earthworms/m2, and between 2 and 40 g earthworm/m2 were found in the different crops for these treatments. Under the ridge culture system there were significantly fewer earthworms (3-20 earthworms/m2 on average), and lower biomass of earthworms (0-27 g/m2 on average). The experiment began in 2003, with twelve replicates of each treatment. Plots were managed organically. Earthworms were monitored by hand sorting and extraction, in October 2005.