The Effects of Cereal Rye (Secale cereale) Seeding Rate and Termination Timing on Weed Control and Soybean Yield

Alyssa Essman
Graduate (PhD)
Mark Loux
Horticulture and Crop Science

There has been increased interest in cover crops in recent years due in part to their ability to suppress weeds. Growers have been experimenting with different cover crop termination timings in an attempt to maximize weed suppression. The most common cover crop used in Ohio is cereal rye (Secale cereale L.). A field study was conducted twice from fall of 2018 through the fall of 2020 at the OARDC Western Agricultural Research Station in South Charleston, Ohio to evaluate different rye termination systems. The objectives of this research were to determine the effects of: (1) rye seeding rate; (2) termination timing; and (3) herbicide system on weed density and soybean yield. Rye seeding rates were 0, 50, and 101 kg ha-1. Termination timings were 7 days before soybean planting, 7 days after soybean planting, and 21 days after soybean planting. Spring residual herbicides were flumioxazin + chlorimuron ethyl and none. Measurements included rye biomass, weed density, soybean density and soybean yield. The density of giant foxtail (Setaria faberi Herrm.) was reduced at both rye seeding rates compared with no cover in year one. The presence of rye did not affect density of giant ragweed (Ambrosia trifida L.) in either year, compared with no cover. Terminating rye 21 days after soybean planting was associated with the lowest weed density but was not always significantly different than rye terminated 7 days after soybean planting. Giant foxtail density was lower in treatments with a residual herbicide both years. Level of residual herbicide did not have an effect on the density of giant ragweed. Terminating rye after planting resulted in increased soybean yield in year one, but yield was reduced at the 21 day after plant termination timing in year two. These results suggest that adjustments to termination timing may have more of an effect on weed suppression from a rye cover crop than adjustments to rye seeding rate. Rye can be terminated 7 days after soybean planting to aid in the suppression of weeds without reducing soybean yield. Spring-applied residual herbicides are still needed to provide adequate weed control into the growing season.