Effects of conventional and organic farming practices on the community structure of soil macroarthropod predators

The impact of conventional and organic farming practices on the community structure of selected soil-dwelling macroarthropods in cornfields was examined as part of a Conversion Project experiment in Pennsylvania. Pitfall trap samples were collected during the months of June and August from plots in three farming systems: organic treatment with animal manure (AMT), organic treatment with legumes (LT) and conventional treatment (CT).; Representatives of the Order Coleoptera comprised the majority of macroarthropods collected. Carabid and nitidulid beetles were most abundant and diverse in the organic plots in June and August. Staphylinid beetles were less affected by the lower organic matter inputs and the use of herbicides, common in conventional systems, than the carabids and nitidulids.; Web-building and cursorial spiders made up the next largest group of macroarthropods collected, with greatest abundances and diversities in AMT in June and in CT in August. Phalangids (harvestmen) were also collected in greatest abundance and diversity in the organic plots in both June and August. Millipedes, centipedes and woodlice, although less significant numerically, were most abundant in the organic plots in June and August. (Abstract shortened by UMI.)...