Soil arthropod community structure in an organic cover cropping system

The changes in soil arthropod community structure were estimated in an organic cover cropping system in 2008. Two varieties of mustard, Brassica juncea ‘Florida Broadleaf’ and Brassica hirta ‘Tilney’ were grown as an early spring cover crop then were mowed and tilled into the soil prior to planting of the cucurbit crop. Upon maceration of the plant tissue, glucosinolates in the tissues break down into toxic compounds which are used as a fumigant. It was the aim of this study to evaluate the non-target effects of these compounds on the soil arthropod community. Epigeal arthropod activity was estimated using pitfall traps and euedaphic arthropods were extracted from soil cores using a high-gradient microarthropod extractor at sampling dates concomitant with field operations. The fauna from each sample was sorted into taxonomic categories and identified to the most specific taxonomic level. The statistical analyses include measures of total abundance, species richness, Shannon’s diversity index and Pielou’s evenness index. The community level responses will be measured against the different sampling dates throughout the season using a principal response curve.