Invertebrates can negatively or positively affect agricultural crop development and yield. Soil properties can mediate outcomes most invertebrates have on agricultural crops. Agricultural practices like over fertilization, high density planting and routine pesticide applications disrupt soil health, leading to degraded soils. Cover crop application has shown to increase invertebrate diversity and reduce soil degradation in agricultural systems. Soil amendments, like dredged sediments, are gaining increasing attention since they may further reduce soil degradation by improving low-quality soils. However, it is unknown how dredged sediments in combination with a cover crop influence invertebrate community structure. Goal of this research is to investigate differences in invertebrate community composition between neighboring, 2.3-acre plots of 100% dredged sediments. Each plot was planted with corn but one was left fallow over the winter and cover crop Lolium perenne grew on the other. To identify how cover crop use alters invertebrate communities in dredged sediments, ten pitfall traps were placed in each plot. Pitfall traps were monitored for 15 weeks and organisms from each trap were collected. Invertebrates that could not be caught by trap were collected by hand and identified in the lab. Shannon diversity index and relative abundance were performed on these invertebrate counts.
Results/Conclusions
Collections from the cover crop plot had a Shannon diversity index of 2.556 and consisted of 25 invertebrate genera, while the plot left fallow had a slightly higher diversity index of 2.698 with 28 invertebrate genera. The four most abundant families present in both plots were the Carabidae (ground beetles), Chrysomelidae (leaf beetles), Coccinellidae (lady beetles), and Lycosidae (wolf spiders). Of these four families, Carabidae (P = 0.23), Chrysomelidae (P = 0.979), and Coccinellidae (P = 0.417) exhibited no significant difference in abundance between the cover crop and fallow plots. Lycosidae (P < 0.01) were significantly more abundant in the cover crop plot. The slight difference in diversity between the two plots, skewing in favor of the fallow plot, could be due to the unexpected abundance of weedy plants that grew from the seed bank within the dredged sediments, resulting in high plant diversity. Results from this study contribute to a broader understanding for how dredged sediments can impact agriculture as a soil amendment when used in combination with a cover crop.