Relationship between relative time of emergence of Tartary buckwheat (Fagopyrum tataricum) and yield loss of barley

A nonlinear regression model was used to describe the relationship between Tartary buckwheat [Fagopyrum tataricum (L.) Gaertn.] density and relative time of emergence, and yield of barley (Hordeum vulgare L.). Yield loss increased the earlier the weed emerged relative to the crop. The model is being used in computerized decision support systems for weed management in western Canada. Key words: Fagopyrum tataricum, Hordeum vulgare, nonlinear regression model, relative time of emergence, decision support system