The effects of cover crop and termination method on common lambsquarters ( Chenopodium album ) seedbank dynamics in a potato rotation in Atlantic Canada

Abstract

Common lambsquarters ( Chenopodium album L.) is one of the most troublesome weeds in Atlantic Canadian potato ( Solanum tuberosum L.) production systems. A high proportion of C. album in this region has been identified as resistant to commonly used herbicides and has become increasingly difficult to control with existing management practices. Atlantic potato producers have adopted cover crops into their rotations for soil conservation and nutrient cycling benefits, as well as suppression of crop pests, including weeds. Four cover crops and termination methods were evaluated for their ability to suppress C. album populations in a potato rotation at Harrington, PE, and Fredericton, NB, from 2018 to 2020. Brown mustard [ Brassica juncea (L.) Czern.], buckwheat ( Fagopyrum esculentum Moench), timothy ( Phleum pratense L.), and a mixture of hairy vetch ( Vicia villosa Roth), annual ryegrass [ Lolium perenne L. ssp. multiflorum (Lam.) Husnot], and crimson clover ( Trifolium incarnatum L.), were spring sowed and terminated by mowing, roller-crimping, disking, or glyphosate in fall. Effects of cover crops and termination methods were consistently greater at Fredericton than at Harrington and were attributed to lower initial C. album seedbank density. Buckwheat and brown mustard cover crops established rapidly and reduced C. album densities in the subsequent potato crop by greater than 46%. Termination via disking and glyphosate improved marketable yields, yet the soil incorporation through disking buckwheat maximized the weed suppressive effects and reduced the germinable fraction of the C. album seedbank by 64% when compared with glyphosate. Our results highlight the importance of the starting seedbank density on the success of weed management tactics, where higher initial weed seedbank density can hinder the success of cover crop establishment in potato rotations. Further, these results verify the importance of proper cover crop selection for managing the seedbank in potato rotations and reduce the impact of herbicide-resistant weeds on production systems.