Field testing of the Redekop seed control unit in soybean and wheat production systems in Virginia

Seed impact mills are machines that are mounted directly to the back of a combine and are one way to implement harvest weed seed control (HWSC). Seed impact mills kill weed seeds during harvest, preventing seeds from being added to the soil seedbank. Previous research has indicated that seed impact mills have high seed kill rates (>90 %) for problematic weeds in soybean and wheat. While these mills are effective, there are many ways that seeds could bypass the seed impact mill, such as shattering and seed loss at the header during harvest, which could reduce the effectiveness of these mills. In the field, tracking weed density in the following seasons after harvest could indicate overall effectiveness of using a seed impact mill. The purpose of this experiment was to track emergence of common ragweed (Ambrosia artemisiifolia) and Italian ryegrass (Lolium perenne ssp. multiflorum) in soybean and wheat fields, respectively, after harvesting with a seed impact mill. Seven soybean fields and four wheat fields in commercial production were tracked for A. artemisiifolia and L. perenne ssp. multiflorum density, respectively. For testing, each field was divided into two sections: with and without the use of the seed impact mill. Weed emergence was recorded in the following seasons. Density reductions for A. artemisiifolia after one year of HWSC were 26 % and 77 % at the postemergence herbicide and harvest timings, respectively. There was also a 99 % reduction after two harvests with HWSC, but a single HWSC harvest followed by a conventional harvest resulted in a 330 % increase. The density reduction of L. perenne ssp. multiflorum after one harvest was 48 %. These data indicate that seed impact mills can be an effective tool for reducing inputs into soil seedbank and weed densities in following seasons in systems under commercial production.