Impact of low-input farming systems on earthworm populations in cereal crops - a paired farm approach in NW-Switzerland.

Summary

Effects of two different low-input farming systems on earthworms were compared. The study was performed in a 3-year field survey using a paired-farm approach in six different locations in northwestern Switzerland. Earthworms were extracted from soil sampled from 24 winter cereal crops and two herbaceous strips applying a combined method of extracting with a 0.33% mustard solution and a consecutive handsorting.
Differences of earthworm communities were found between and within the farming systems. In 14 of 24 cases, earthworms from organic fields were significantly richer in abundance and biomass than in the low-input integrated crop management farmed plots (ICM=no insecticides, fungicides and growth regulators); whereas the biomass resp. the abundance of ICM fields were significantly higher in four resp. five cases. The number of earthworm species and juveniles were mostly significantly lower in ICM fields. Anecic species such as Lumbricus terrestris (Linnaeus), Nicodrilus longus (Ude) and Nicodrilus nocturnus (Evans) as well as endogeic species such as Nicodrilus caliginosus (Savigny), Allolobophora rosea (Savigny) were, in two of three years, significantly more numerous in the organic fields than in the low-input ICM fields.
Using a cluster analysis dissimilarities of earthworm communities were detected between the two farming systems. Multivariate analysis showed that the farming method, the cereal density and the soil potassium content were significant factors altering the earthworm fauna. The late use of the plough in autumn was found to have a major negative effect on earthworm abundance, irrespective of farming system. Farming practices that may considerably influence earthworms between these farming systems are discussed.
(submitted to Soil Applied Ecology)