Updated April 27, 2021:
This project involves the evaluation of non-chemical control methods for integration into an overall weed management
program. Emphasis is on waterhemp, and a subset of the work was conducted on Missouri soybean fields. In 2020, the team concluded a 3-year evaluation of fall-seeded cereal rye, which was sown at 30, 50, 70, 90, or 110 lbs/acre, to suppress early season waterhemp emergence. Soybean was planted into the non-terminated cereal rye. Findings
include:
• Cereal rye planted at 50 lbs/acre resulted in comparable levels of early season waterhemp suppression to the higher seeding rates.
• Cereal rye seeded at 30 lbs/acre resulted in less consistent suppression.
• Soybean stand and yield were similar regardless of the cereal rye seeding rate.
Additional ongoing objectives of this project focus on minimizing the amount of viable waterhemp seed that returns to the soil. The Seed Terminator™ was tested in four mid-Missouri soybean fields in 2019 and three in 2020. The machine is a multi-stage hammer mill that is integrated into a commercial combine. The mills rotate at 2,500 rotations per minute to grind weed seed. Questions being addressed include:
• What percentage of waterhemp seed passes into the Seed Terminator™?
• How effective is the machine at rendering seed nonviable?
• How does the implement affect fuel usage and engine load of the combine?
Preliminary results indicate that during soybean harvest approximately one third of waterhemp seed returned to the soil due to header loss. Of waterhemp seed that successfully passed through to the thresher, 72% made it into the Seed Terminator™. Approximately 92% of waterhemp seed that entered the Seed Terminator™ was damaged. On average, combine fuel consumption was 4.1 gal/hour greater and engine load was 17.6% higher when the Seed Terminator™ was engaged. Data analysis of the 2020 samples continues.
Finally, a side-by-side comparison is being conducted to evaluate the effects of different non-chemical control options on a dense stand of multi-resistant waterhemp in soybean. At soybean harvest in 2019, the Seed Terminator™ and narrow windrow burning were implemented, and cereal rye was planted in a subset of those treated plots. Waterhemp density counts were conducted in the spring of 2020. Plots with cereal rye and the Seed Terminator™ treatment had the least waterhemp emerge in the spring. This objective is being repeated with the addition of weed electrocution as another non-chemical treatment. Waterhemp density counts will be conducted in the spring of 2021.