Development of equations for estimating yield losses caused by multi-species weed communities dominated by green foxtail [Setaria viridis (L.) Beauv.

Abstract

Multiple regression equations were developed to describe the relationship between percentage hard red spring wheat (Triticum aestivum L.) loss and the density and shoot dry weight of multi-species weed communities dominated by green foxtail [Setaria viridis (L.) Beauv.]. Data were collected over a 10-yr period from fields sown by farmers near Regina, Saskatchewan. Weed densities averaged 470 plants m−2, with green foxtail constituting 85% of the total number of plants and 57% by dry weight. Other important species included in the equations were stinkweed (Thlaspi arvense L.), common lamb’s-quarters (Chenopodium album L.), wild buckwheat (Polygonum convolvulus L.), and wild mustard (Sinapis arvensis L.). Including crop density as a variable made a significant improvement in the efficiency of the equations. Precipitation and growing degree-days (base 5 °C) were related to the residuals from the analysis relating wheat loss to weed abundance. These environmental variables were significantly related to crop loss, but only for the residuals of the equation where weed densities were used as independent variables. Hyperbolic and sigmoidal equations were less efficient at describing the data than were multiple linear regression equations. Key words: Green foxtail, spring wheat, competition, multi-species, multiple regression, crop loss