Maximizing summer cover crop conservation benefits for improved vegetable production

Many vegetable crop rotations leave little time or space to integrate flowering habitat for beneficial arthropods and pollinators. Lack of floral resources can contribute to population decline, which in turn can lead to insufficient pollination services and increased pest incidence. In Minnesota, flowering cover crops may present a valuable opportunity to provide key multifunctional ecosystem benefits to vegetable production. We investigated the effect of two flowering warm season cover crop systems on beneficial insect populations. Systems included 1) early cover crop planting followed by a broccoli (Brassica oleracea) cash crop, and 2) early spring lettuce (Lactuca sativa) followed by a late summer cover crop planting in three Minnesota regions. Cover crop species included 1) buckwheat, 2) sorghum sudangrass and cowpea, 3) phacelia, 4) oats and field peas, 5) crimson clover, and 6) sunflower. To determine abundance and phenology of attractive floral cover crops, we measured beneficial arthropod abundance, richness, evenness, and overall arthropod community diversity via observational and destructive (insect vacuum) sampling, and flower counts. In the first year, planting time affected flower phenology with greater flower production observed in the early versus the late planting, with the exception of Sunflower, which requires more time to flower. Major genus groups of bees including, Apis, Bombus, Halictus, and Lasioglossum, where mostly attracted to phacelia in the early cover crop system. Buckwheat and sunflower also attracted some of these groups in the late system. Results demonstrate the capacity of cover crops to expand the seasonal availability of floral resources in agroecosystems.