Evaluating two impact mills seed kill efficacy and horsepower draw for use in U.S. wheat production

Abstract Seed impact mills like the Redekop Seed Control Unit (SCU) and the integrated Harrington Seed Destructor (iHSD) have the potential to fit within the U.S. wheat ( Triticum aestivum L.) production system, but they may be affected by changes in crop yield and harvest residue moisture, which can have an impact on chaff flow rate and chaff moisture, respectively. This research aimed to determine the seed kill of problematic weed species and how varying chaff flow rates and chaff moisture affect seed kill and horsepower draw of the SCU and the iHSD. Four different chaff flow rates were tested at 0.75, 1.5, 2.25, and 3.0 kg s −1 , which span 0.5× to 2× of a combine’s standard throughput. Additionally, four chaff moisture contents were tested at 10.7%, 16.4%, 22.1%, and 27.8%, which span and exceed typical harvest conditions. Results indicated that >91% of all weed seeds of the tested species were killed by either mill. Seed kill decreased by 7.9% and 0.08% for every 1-kg increase in chaff flow rate for Italian ryegrass [ Lolium perenne L. ssp . multiflorum (Lam.) Husnot] and hairy vetch ( Vicia villosa Roth), respectively, for the iHSD. Seed kill also decreased by 3.4% for every 1-kg increase in chaff flow rate for weedy L. perenne ssp . multiflorum for the SCU. Increasing chaff moisture resulted in seed kill decreasing by 0.43% and 0.015% for every 1% increase in chaff moisture for weedy L. perenne ssp . multiflorum and volunteer canola ( Brassica napus L.), respectively, with the SCU. Both chaff flow rate and chaff moisture had a significant effect on horsepower draw for both mills compared with an empty mill. Despite the increase in horsepower draw and the decrease in seed kill, these data indicate the potential for seed impact mills to operate in less than ideal conditions while still providing seed kill rates >74%.