Wild mustard (Sinapis arvensis) response to field pea (Pisum sativum) cultivar and seeding rate

Field studies were conducted at Morden, Manitoba from 1992 to 1995 and Wadena, Saskatchewan in 1995 to investigate the effect of cultivar selection and seeding rate on field pea competitiveness with wild mustard. Cultivars that had both long Vines and rapid canopy development (leaf area index) were more competitive with wild mustard than those with short vines and slow canopy development. Cultivars differed markedly in their ability to suppress weed growth. Wild mustard density was affected in 2 of 4 yr by cultivar selection, while weed biomass was affected in 3 of 4 yr. Field pea yield losses under weedy conditions differed among cultivars and those cultivars that more effectively reduced wild mustard density or biomass had the lowest yield losses. Yield losses from wild mustard competition did not differ among cultivars when weed pressure was high and weeds emerged 1 wk before the crop. Seeding rate of Titan, a cultivar with long vine length, affected wild mustard biomass more than Trump, a cultivar with a short vine length.