Effect of winter cereal rye cultivar selection and herbicide choice on seedling disease, pathogen populations, nitrogen dynamics and growth and yield of corn
Issue
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.
Objective
- 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-
- Compare the effect of herbicide used to terminate CR on CR regrowth, corn seedling disease, Pythium and Fusarium, and corn yield.
- Present research to stakeholders.
Approach
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.
July 2025
Activities during this reporting period included:
- Shoots of cereal rye of each variety were sampled to measure biomass produced. Cereal Rye shoots will be analyzed to determine C/N.
- Soil samples from the corn row were taken • 5 DAP for BX (allelochemicals) analysis and quantification by LC/MS.
- Soil samples from the corn row, bulk soil, and seedling roots of corn were taken (from Serafino, Elbon, and control plots) at 1 DBP, 7 DAP, and growth stage V3 (18 DAP) to analyze Pythium spp. populations through q-PCR.
- Soil samples were taken to measure N availability at 1 DBP and growth stage V3.
- Corn seedlings from each plot were sampled at stage V2-V3 to assess seedling disease (root rot), and measure height and dry weight, and will also be analyzed to determine C/N.
- Stand counts to measure corn germination were done at growth stage V2-V3.
- CR regrowth was evaluated 29 days after CR termination with glyphosate and paraquat herbicides. 100% of herbicide efficacy was observed on glyphosate plots and 98.75% in paraquat plots.
- NDVI of corn was measured at growth stage V7 using a handheld sensor (Trimble Green Seeker) to assess canopy development and vigor of corn across treatments.
Related activities and accomplishments
3 presentations
Posters to be presented at: 2025 Plant Health Conference, Honolulu, HI "Evaluating the Effect of Cereal Rye Variety and Herbicide Choice on Seedling Disease and Yield of Corn" and 2025 CANVAS Conference, Salt Lake City, UT "Studying the Allelopathic Effect of Winter Cereal Rye Variety on Seedling Disease and Yield of Corn"
PhD student on the team submitted a proposal to 2025 NC-SARE Graduate Student Grant Program
July 2024
Shoots of cereal rye of each variety were sampled to measure biomass produced. Cereal rye shoots will be analyzed to determine C/N. Regrowth of cereal rye after glyphosate and paraquat was evaluated. Soil samples were taken from the corn row 6 DAP for BX (allelochemicals) analysis and quantification. Soil samples were taken from the corn row, bulk soil and corn seedlings were collected (from Serafino, Elbon, and control plots) 1 DBP, 7 DAP, 14 DAP (stage VE) and at stage V3 to analyze Pythium populations in bulk soil, rhizosphere soil and seedling roots through q-PCR. Soil samples were taken to measure N availability 1 DBP and at stage V3. Corn seedlings from each plot were sampled at stage V3 to assess seedling disease (root rot), and measure height and dry weight and will also be analyzed to determine C/N.
Related Accomplishments and Activities
One poster presentation: at 2024 North Central Division American Phytopathological Society meeting in Manhattan, KS, June 10-12.Gonzalez, E. and Robertson, A.E. 2024. Effect of cereal rye cover crop varieties on corn seedling disease.
An abstract was submitted to the 2024 Tri-Society meeting in San Antonio TX in November.
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.