Establishing on-farm pollinator habitat can mitigate native pollinator and pollination ecosystem service declines, and federal programs are available to provide technical and financial assistance to farmers interested in habitat installation. Although sufficient seedbed preparation to limit weed competition is thought to be the most important step toward achieving good pollinator habitat establishment, preparation recommendations vary and studies have not investigated seedbed preparation techniques in the context of the U.S. Department of Agriculture (USDA) Farm Bill programs for pollinator conservation. To address this, we assessed the effects of two seedbed preparation methods, conventional inversion tillage and no-till with herbicide, on wildflower establishment and weed competition during the first year after planting. Experiments were conducted in Blacksburg, VA, and were replicated in 2015 and 2016. In addition, we tracked seedbed preparation methods and pollinator habitat establishment on seven farms located on the Eastern Shore of Virginia and Maryland in 2016. The wildflower mix consisted of nine species of forbs and two species of grasses: the forbs were black-eyed Susan (Rudbeckia hirta L.), partridge pea [Chamaecrista fasciculata (Michx.) Greene], plains coreopsis (Coreopsis tinctoria Nutt.), lanceleaf coreopsis (Coreopsis lanceolata L.), purple coneflower [Echinacea purpurea (L.) Moench], narrowleaf mountain mint (Pycnanthemum tenuifolium Schrad.), wild bergamot (Monarda fistulosa L.), Maximilian sunflower (Helianthus maximiliani Schrad.), and showy tickseed [Bidens aristosa (Michx.) Britton] or Indian blanket (Gaillardia pulchella Foug.); the grasses were splitbeard bluestem (Andropogon ternarius Michx.) and little bluestem [Schizachyrium scoparium (Michx.) Nash]. In the experiments, wildflower establishment was greater after no-till with herbicide than after tillage preparation (2015: P = 0.09; 2016: P = 0.002). Predominating weed species varied by study, with more common lambsquarters (Chenopodium album L.) and hairy galinsoga [Galinsoga ciliata (Raf.) S.F. Blake] growth after tillage treatments, and more hairy vetch (Vicia villosa Roth) growth after no-till preparation. On-farm pollinator habitat establishment on the Eastern Shore was highly variable, but more wildflower forbs established after tillage-plus-herbicide than tillage-only seedbed preparations (P = 0.01). Across sites, we found a large degree of site-specific variation in wildflower establishment and predominant weed species.
Gina M. Angelella and Megan E. O’Rourke
Gina M. Angelella, Laura Stange, Holly L. Scoggins and Megan E. O’Rourke
On-farm pollinator refuge habitats can supplement floral and nesting resources to support wild and managed pollinator communities. Although the popularity of installing these habitats has grown, and federal programs provide technical and financial advice to participating landowners, recommendations regarding habitat establishment and species composition vary. We examined the effects of seedbed preparation, seed mix composition, and herbicide applications on pollinator refuge establishment and pollinator visitation in a controlled experiment across 2 years. Seedbeds were prepared either by a no-till method with glyphosate herbicide or by repeated conventional inversion tillage. Seed mixes contained either nine annual, biennial, and perennial forbs (mix AP); seven annual, biennial, and perennial forbs that are tolerant to imazapic herbicide (mix IT); or nine perennial forbs (mix P). Mixes AP and P were grown with and without application of the graminicide herbicide sethoxydim and mix IT was grown with application of the herbicide imazapic. Seedbed preparation methodology had a strong impact on pollinator refuge establishment. A no-till approach generated greater wildflower and lower weed cover relative to tillage, leading to a greater number of blooms. In particular, there were more Indian blanket, purple coneflower, slender mountain mint, and wild bergamot blooms following a no-till seedbed preparation, indicating that certain species are more vulnerable to the effects of tillage than others. The AP and IT treatments displayed more wildflower and less weed percent cover than the P treatments during the first year, but in the second year wildflower and weed cover were similar across all mixes grown with and without herbicide. Overall pollinator abundance, which was dominated by native bees, correlated positively with wildflower bloom counts, suggesting that habitat establishment methods that increase wildflower blooms can positively affect the pollinator conservation value of the habitats. This research indicates that establishing on-farm wildflower habitats can be most successful with no-till seedbed preparation, a mixture of annual, biennial, and perennial forb species, and that herbicides applied after planting wildflowers may not be worth the costs of application.