Fate of Weed Seeds after Impact Mill Processing in Midwestern and Mid-Atlantic United States

Abstract Harvest weed seed control (HWSC) technology such as impact mills that destroy weed seeds in seed-bearing chaff material during grain crop harvest, has been highly effective in Australian cropping systems. However, the impact mill has never been tested in soybeans and weeds common to soybean production systems in the Midwest and Mid-Atlantic US. We conducted stationary testing of Harrington Seed Destructor (HSD) impact mill and winter burial studies during 2015-2016 and 2017-2018 to determine (i) the efficacy of the impact mill to target weed seeds of seven common weeds in Midwestern and five in Mid-Atlantic US, and (ii) the fate of impact mill processed weed seeds after winter burial. The impact mill was highly effective in destroying seeds of all the species tested, with 93.5-99.8% weed seed destruction in 2015 and 85.6-100% in 2017. The weak relationships (positive or negative) between seed size and seed destruction by impact mill, and high percentage of weed seed destruction by impact mill across all seed sizes indicate that the biological or practical effect of seed size is limited. The impact mill-processed weed seeds that retained at least 50% of their original size, labeled as potentially viable seed (PVS), were buried for 90 d over winter to determine the fate of weed seeds after winter burial. At 90 d after burial (DAB), the impact mill processed PVS were significantly less viable than unprocessed control seeds, indicating that impact mill processing physically damaged the PVS and promoted seed mortality over winter. A very small fraction (< 0.4%) of the total weed seed processed by the impact mill remained viable after winter burial. The results presented here demonstrate that the impact mill is highly effective in increasing seed mortality and could potentially be used as a HWSC tactic for weed management in this region.