We propose to work with the growers who make up the Iowa Soybean Association long-term cover crop network to coordinate seedling emergence surveys prior to cover crop termination, at planting, prior to postemergence herbicide application and late season prior to harvest. We will work closely with the growers to determine optimal time to collect data and avoid disturbing normal production practices. Soil cores will also be collected in each field to conduct lab and greenhouse analysis of weed seed present by species to give an idea what is present. All data will be analyzed and summarized to be used in winter meetings and multiple years of data collection are expected to contribute to publication.

Determine the impact of cover crops on weed species population in the seed bank.
Determine if cover crops impact weed species diversity.

Outcomes of the research will provide data to support cover crop recommendations and adoption, extension presentations, fact sheets, and peer reviewed publications.

Updated September 9, 2025:
In order to gain a greater understanding of the impact of cover crops on long-term soil seedbank weed species composition and populations, we propose using the Iowa Soybean Association network of cover crop fields to do emergence surveys in the field throughout the season and additional soil core analysis. These two analysis methods will help determine if long-term cover crops significantly reduce weed species diversity, and if the number of weed seeds per species is impacted. We hypothesize that species diversity may be greater in fields which have long-term cover in use, but that weed seed number will be reduced.
To date, we have contacted all growers participating in the cover crop study with Iowa Soybean Association who are willing to allow us to collect data throughout the season. We are currently collecting initial counts and soil cores for the seedbank analysis, and will continue to collect weed counts in the cover and no cover strips throughout the season. Once all data are collected and seed is separated from soil, we will analyze results and begin creating deliverables.

This research will help determine the impact of cover crops on long-term seedbank dynamics and will provide insight on the additional benefits which cover crops may provide.