Influence of Cereal Rye Management on Weed Control in Soybean

Quintin R. Johnson,Mark J. VanGessel,Barbara A. Scott,Kurt M. Vollmer

doi:10.3389/fagro.2020.600568

Quintin R. Johnson, Mark J. VanGessel + Show 2 more

Open Access

https://doi.org/10.3389/fagro.2020.600568

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Abstract

Cereal rye as a cover crop is often used to improve soil health and as part of integrated weed management programs. Despite this, cereal rye biomass is often not managed for optimal weed suppression. This study evaluated the effects of managing cereal rye as part of an integrated weed management strategy in soybean. Factors consisted of levels of cereal rye management (no cereal rye, no nitrogen, or 20 kg/ha of nitrogen); cereal rye termination timing (20 or 10 d before soybean planting); and residual herbicide treatment applied at cereal rye termination (with or without). Winter annual weed control with cereal rye was generally greater compared to no cereal rye. Winter annual weed control was consistently better when cereal rye was terminated at 20 d before soybean planting compared to 10 d; while summer annual weed control was improved if termination was delayed. Effect of cereal rye management on summer annual weed control varied by weed species. In the absence of residual herbicides, Palmer amaranth control responded to the different levels of cereal rye management. However, morningglory spp. only responded to rye with supplemental N applications. Large crabgrass control was similar for treatments containing cereal rye, regardless of nitrogen input. Our results demonstrate the importance of cover crop management when incorporating cereal rye into an integrated weed management program for soybean.

Highlights

Cover crops provide a number of ecological services, or benefits
Altering cereal rye management resulted in different levels of biomass, with cereal rye responding to nitrogen applications
Our results show that while residual herbicide treatments were very effective for summer annual weed control, cereal rye with spring N was a consistently successful weed management tactic

Summary

Introduction

Cover crops provide a number of ecological services, or benefits. These benefits include reducing erosion, preventing nutrient loss, providing pollinator habitat, fixing atmospheric nitrogen, and increasing soil microbial densities. Most cover crops are planted under cost-share programs that specify deadlines for fall planting dates, but allow termination in early spring. Non-selective herbicide applications to terminate cover crops often provide excellent control of emerged weed seedlings. Early spring termination often occurs before there is sufficient cover crop biomass to provide weed suppression of later-emerging weeds. Cover crops allowed to advance to the late-vegetative or early-reproductive stages produce significantly more biomass. The cover crop tissue contains a higher C:N ratio that resists decomposition and allows the dead biomass to persist longer (Wagger et al, 1998; Pittman et al, 2020)

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