The arthropod fauna of organic versus conventional cereal fields in Denmark

In 1987 and 1988, respectively, the arthropod fauna was studied in 21 and 17 matched pairs of organic and conventional cereal fields at various distances from the field boundary using a D-vac suction sampler and a sweep-net. In 1987, aphids were scarce and insecticides rarely used in conventional fields, while the opposite was true in 1988. In 1988, when aphids were dominant, total arthropod density was highest in conventional fields. Excluding aphids and Collembola, total density, species diversity, total biomass and number of bird food items were consistently and often significantly higher in organic than conventional cereal fields. This was also the case with a number of single arthropod orders, families and species. Density, species diversity and biomass of arthropods decreased from field margin towards midfield, but more so in conventional fields. Consequently, the difference between organic and conventional cereal fields is larger when measured in the midfield than in the field margin.