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Growing a cover crop living mulch between plastic-mulched beds may reduce soil erosion while providing other agroecosystem services. However, information regarding the relative differences among living mulch species to maximize services and minimize competition for nutrients and water in adjacent plastic-mulched beds is limited. A 2-year experiment in Michigan evaluated nine living mulch species for biomass production, in-season weed suppression, and potential for cash crop competition. Species included three warm season grasses {Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot], teff [Eragrostis tef (Zuccagni) Trotter, and sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan]}; three cool season grasses [barley (Hordeum vulgare L.), rye (Secale cereale L.), and wheat (Triticum aestivum L.)]; and three clover species grown in combination with rye {Dutch white clover (Trifolium repens L.), New Zealand white clover (T. repens L.) and yellow blossom sweet clover [Melilotus officinalis (L.) Lam.]}. Although all living mulch treatments significantly reduced in-season weed biomass relative to the weedy control in 2018, weeds were generally a dominant component of total biomass in all living mulch treatments other than teff. Weed biomass was negatively correlated with living mulch biomass, and teff exhibited both the greatest biomass and weed suppression in both years. However, despite spatial and physical separation, all living mulches demonstrated the potential to compete with a cash crop by reducing soil inorganic nitrogen and moisture levels in adjacent plastic mulch–covered beds. Growers interested in integrating living mulches into plasticulture systems must consider desired benefits such as enhanced weed suppression, soil quality, and harvesting conditions alongside potential risks to cash crop yields.

Zonal management of cereal–legume cover crop mixtures may help address weed and nitrogen management challenges common in organic reduced tillage systems. During a field study conducted over 3 years in Michigan, we evaluated the effects of cover crop management, tillage, and supplemental mulch on organically produced acorn squash (Cucurbita pepo). During the fall season before squash production, rye (Secale cereale L.) and vetch (Vicia villosa Roth) cover crop mixtures were sown in two distinct spatial arrangements: a “mixed planting,” in which seeds were sown in the same rows, and a “zonal planting,” in which vetch was planted only in the in-row zone and rye was planted only in the between-row zone of the subsequent squash crop. During the following spring season, cover crops were mowed, and four tillage and cover crop management combinations were established: full-width tillage with the mixed planting of rye–vetch (full-till mixed); strip-till with the same mixed planting (strip-till mixed); strip-till with the rye–vetch zonal planting (strip-till zonal); and strip-till with the zonal planting and additional rye mulch added between crop rows immediately after crop establishment (strip-till zonal plus rye). The strip-till mixed treatment resulted in yields equivalent to those of the full-till mixed treatment despite lower available nitrogen and greater early weed competition in some cases. Within strip-till treatments, zonal planting of rye–vetch provided no benefits relative to full-width planting (treatment 2 vs 3) and resulted in lower total cover crop biomass, a higher density of escaped weeds, and lower squash yields during 1 of 3 years. Supplemental rye mulch improved weed suppression and yields in strip-till zonal treatments and resulted in yields equivalent to those of the full-till mixed treatment in all years, but it provided no benefits relative to strip-till mixed. Our results demonstrate that strip-till organic squash production can produce yields equivalent to full-till production in Northern climates, but that zonal planting and supplemental mulch have limited benefits for addressing ongoing weed and nitrogen management challenges. Growers must weigh costs associated with these challenges against potential benefits for soil and pest regulating ecosystem services before adopting these agricultural conservation practices.