Effect of winter cereal rye cultivar selection and herbicide choice on seedling disease, pathogen populations, nitrogen dynamics and growth and yield of corn

Aug 2023


Winter cereal rye (CR) is the most popular species of cover crop grown in Iowa. In some years and fields, reduced corn yields have been reported following CR. To date, the mechanism of the yield reduction in corn following CR is unknown; therefore, devising management strategies to overcome this problem is difficult. Proposed reasons include, seedling disease, allelopathy, and nitrogen (N) immobilization. The goal of this research is to improve understanding of the factors affecting corn yields after a CR cover crop. We hypothesize characteristics of a CR cultivar (biomass and/or allelochemical production) affect the biological values of CCs as a conservation practice. We also hypothesize applications of glyphosate used to terminate CR promote buildup of corn seedling pathogens and the “green bridge” between CR and corn.


  1. Compare the effect of CR cultivar on seedling disease, Pythium and Fusarium, soil N dynamics, concentrations of benzoxazinoids (BX) in soil, and corn growth and yield-
  2. Compare the effect of herbicide used to terminate CR on CR regrowth, corn seedling disease, Pythium and Fusarium, and corn yield.
  3. Present research to stakeholders.


An experimental plot field trial will be established over two years at the ISU Agriculture Engineering and Agronomy Farm on a field with a history of seedling disease of corn. The field trial will have a history of corn-soybean rotation. A split plot design with six replications will be used. Main plot treatments will be CR cultivar, and a no cover crop control. Subplots will have glyphosate or paraquat applied 0-5 days before planting. Each herbicide program will also be applied to the no-cover crop check plot at CR termination. From each plot the following data will be collected: CR biomass, BX concentrations, soil net immobilization, corn growth parameters, seedling disease severity and soilborne pathogen populations.

Project Updates

Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.

December 2023

Cereal rye varieties were purchased and drilled at 1 million seeds per acre on 5 October 2023. Establishment of the cereal rye in each plot was detected with Canapeo on 3 November 2023. A grad student was recruited for the project. He will start 1 January 2024.