Trait-based weed control decisions compared to economic thresholds for site-specific weed management

Four decision concepts were tested for ex-ante chemical weed control decisions to be integrated into site-specific weed management (SSWM). Two concepts assess the economic profitability of a weed control treatment: one considers the abundance of weed taxonomic groups, and the other takes into account individual weed species. The third and fourth concepts utilize weed functional traits to quantify a species’ ability to provide ecosystem services (service potential) and its competitive ability (disservice potential), thereby informing management decisions. Based on grid-based manual weed assessments in five winter cereal fields in Germany, species-specific weed distribution maps were created using an interpolation approach. For each square meter of the fields, a weed control recommendation was generated using each of the four decision concepts, followed by the creation of weed control maps. Control recommendations by the two economic decision concepts showed the highest similarity across all fields, recommending weed control for 23 %–100 % (weed groups) and 6 %–100 % (species-specific) of the total field area. The concepts based on functional weed traits recommended weed control for 2 %–50 % of the area. Both economic decision concepts recommended a weed control treatment in areas recommended to be left untreated when functional traits are considered. The analysis revealed strengths and weaknesses in all concepts and recommends combining functional weed traits and economic profitability. • Combining economic thresholds with SSWM did not consistently reduce herbicide use. • Species-level economic thresholds showed no substantial improvement to taxonomic group levels. • Including weed functional traits in the concept reduced herbicide use. • Economic threshold recommended weed control in areas with high ecosystem services.