Wild mustard interference in traditional and semi-leafless field peas

Field studies were conducted in 1987, 1988 and 1989 to determine the competitive effect of wild mustard (Sinapis arvensis L.) on two field pea (Pisum sativum L.) cultivars; Century, a traditional cultivar, and Tipu, a semi-leafless cultivar, each planted at recommended (172 kg ha −1 ) and half the recommended seeding rate (86 kg ha −1 ). For both cultivars, 20 wild mustard plants m −2 reduced seed yields from 2 to 35% at the recommended seeding rate and from 4 to 35% at the low seeding rate. Tipu was more competitive with wild mustard when planted at the recommended seeding rate than when planted at half the recommended rates. Seeding rate had only a moderate effect on wild mustard competition in Century in years with normal precipitation. For both cultivars the effect of wild mustard interference on yield was influenced by the amount of precipitation received, with the greatest yield losses occurring in seasons with normal to high rainfall.