Ground Beetle Abundance in Organic and Conventional Corn Fields

The abundance of ground beetles (Coleoptera: Carabidae) was compared on 4 pairs of conventional and organic farms. All farms compared had identical locations, soil types, and cropping histories, but differed in that one farm in each pair was conventionally managed; the other, organically (no use of commercial fertilizers or pesticides). During the summer sampling period, organic farms had significantly greater numbers of carabids captured in pitfall traps in 3 of 4 pairs. Differences in abundance during this time ranged from 20 percent to almost 7-times greater on organic farms. Organic farms also had about twice the number of species found on conventional farms, but had approximately the same level of diversity as measured by the Shannon-Wiener index.