Effects on earthworm populations of reducing pesticide use in arable crop rotations

The SCARAB project is a field-scale, six-year investigation of the effects of pesticide use on invertebrates and soil microflora in arable crop systems common in the U.K. Two pesticide regimes are being compared: current farm practice (CFP) which represents typical levels of use in the study localities, and reduced input approach (RIA) in which inputs have been reduced by 50% and no insecticides used. The treatments began at three farms in 1990, and effects on earthworm populations have been monitored twice yearly since Spring 1993. Particular attention was paid to age and species composition. Results up to Spring 1994 showed that although some differences existed between earthworm populations in RIA and CFP plots they lacked consistency over time and between the pairs of plots, and were of negligible magnitude compared with overall differences between the farms. It was concluded that the two pesticide regimes caused no ecologically significant differences in earthworm populations at this stage of the project. The substantial differences in earthworm populations between farms were largely consistent with the expected effects of differences in climate, soil types, crop types, cultivations and pesticide use, although the relative importance of these factors can not yet be assessed.