Evaluating seed impact mill efficacy during commercial soybean and wheat harvest

Context Harvest weed seed control (HWSC) targets weed seeds as they pass through the harvester. Seed impact mills are aftermarket modifications that are mounted onto the back of the harvester and are one way to implement HWSC. These mills process the chaff fraction as it exits the harvester and kills the weed seeds therein. Aims Two experiments were conducted to evaluate the integrated Harrington Seed Destructor (iHSD) in soybean and the Redekop Seed Control Unit (SCU) in soybean and wheat. The purpose was to determine weed seed kill by the mill (weed seed kill) and seed loss in the straw (weed seed fate) during commercial harvest. Methods During harvest, a known amount of weed seeds was fed into the harvester front or directly into the mill and captured in the chaff or straw of harvester outputs. Six weed species were tested in soybean with the iHSD, and three species each were tested in soybean and wheat with the SCU. Key results The mills delivered >98% seed kill on all tested species during soybean harvest. In wheat, seed kill was >91% for Italian ryegrass and >99% for the other two species tested. During soybean and wheat harvest, <7% of seeds escaped HWSC in the straw fraction. Conclusions These data indicate that both mills generate high seed kill during grain crop harvest and very few seeds escape HWSC in the straw fraction. Implications Seed impact mills could be used during harvest to reduce the return of problematic species to the soil seedbank.