Impact of integrated sheep grazing for cover crop termination on weed and ground beetle (Coleoptera:Carabidae) communities

Cover crops are a suite of non-marketable plant species grown to improve soil quality. They may have additional benefits including reduced weed pressure and enhanced habitat for beneficial arthropods, but they do not provide direct revenue. Integrating sheep grazing for cover crop termination could make the use of cover crops more economically feasible. However, if grazing shifts biological communities to assemblages of less desired species, producers are unlikely to use this method of cover crop termination. We compared weed and carabid beetle (Coleoptera:Carabidae) communities between cover crops terminated by sheep grazing and those terminated by mowing. Our study consisted of two trials of a two-phase experiment. In the first phase (cover crop phase), we seeded a four-species cover crop to enhance nutrient cycling and prevent erosion. The cover crop consisted of buckwheat (Fagopyrum esculentum), sweetclover (Melilotus officinalis), beets (Beta vulgaris), and peas (Pisum sativum). The cover crop grew to anthesis, and was terminated by either sheep grazing or mowing. In the second phase (cash crop phase), we sowed three cash crops through the previously grazed or mowed plots to assess legacy impacts of cover crop termination strategies on weed community structure. Both years, weed species richness and biomass were greater prior to than after cover crop termination, but overall weed diversity, species richness, and biomass did not differ between grazed and mowed plots. We found no difference in weed diversity, species richness, biomass, or density in the cash-crop phase between previously grazed and mowed plots. Despite temporal differences in species richness and activity-density, carabid diversity, species richness, and activity-density did not differ between grazed and mowed plots. Overall, our results suggest that grazing and mowing act as similar ecological filters of both weed and carabid beetle communities.