Can adjustments to nitrogen rates reduce corn yield drag and disease implications following a cereal rye cover crop?
Issue
Cover cropping is a practice that expands the time a living plant is present between harvest and planting of annual crops. Cereal rye is the most prevalent cover crop grown in Iowa because of its winter hardiness as well as its contribution to soil health and water quality. Greater cereal rye biomass increases the benefits received, however there are tradeoffs associated with greater cereal rye biomass – most importantly for growers is the potential for corn yield drag. The two most detrimental reasons for a reduction in corn yield following cereal rye are soil N dynamics and seedling disease. To encourage the inclusion of cereal rye as a cover crop on the Iowa landscape for scavenging and recycling N, disease suppression and soil health, there is a need to understand the role of both N and disease as contributors to corn yield drag.
Objective
The goal of this proposal is to improve our understanding of the importance of seedling disease and N dynamics as influenced by cereal rye on corn growth and development.
Approach
An intense field trial will be established at an ISU Research Farm in central Iowa and a less intense field trial will be located at the Southeast Research Farm. Both trials will use six N rates under both cereal rye and no cereal rye cover crops. The intense trial will evaluate the N and disease interactions at three landscape positions. The knowledge gained from this research will (i) improve our understanding of cereal rye biomass effect on N dynamics and seedling disease, (ii) decipher the ability to reduce corn yield drag by adjusting N application rates, and (iii) provide farmers with best management practices to ensure a successful corn production following cereal rye cover crop.
Project Updates
Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.
November 2024
FINAL REPORT
The key question for this project was to explore the impact of CR biomass accumulation on the corn yield drag. To do that, researchers planned to evaluate the effect of N at planting on: (i) corn seedling disease (ii) soil N dynamics, and (iii) corn growth, development and yield.
During the two years of the project, we collected soil samples seven times per year during the corn season in Ames to evaluate net nitrogen mineralization at 0, 180 and 300 lb N/acre. The data from 2022 shows a net zero of mineralization for 0 lb. N/acre in the backslope and toeslope positions, also for all hillslope positions at 180 lb. N/acre, and at 300 lb. N/acre at the winter fallow treatments.
We saw a positive net N mineralization for the plots with cereal rye in the summit at 0 lb. N/acre and in the backslope at 300 lb. N/acre. And a negative net N mineralization for the plots with cereal rye at the summit and toeslope at 300 lb. N/acre. In addition, the data from 2023 shows a net zero of mineralization from all winter fallow plots at 0 lb. N/acre, 180 lb N/acre and backslope at 300 lb. N/acre. We also saw a net zero N mineralization for the plots with cereal rye at the summit at 180 lb. N/acre. We saw positive net N mineralization only in the cereal rye plots at all hillslope positions at 0 lb. N/acre. And negative net N mineralization at 180 lb. N/acre in cereal rye plots at the backslope and toeslope position, and at 300 lb. N/acre in the winter fallow plots at the summit, and both treatment plots at the toeslope position.
Corn grain yield measurements were collected from both locations. Both locations show a statistical effect in yield for hillslope position (Ames only), N rate and cereal rye presence treatments.
Additionally, the percentage of Pythium damage for both locations was determined. The samples were collected at V7 at 0, 60, 120 and 300 lb. N/acre for both cereal rye presence treatments. In Crawfordville, we saw a statistical effect of the treatments in disease severity and no evidence of a statistical effect for disease severity for 2023. In Ames, it is possible to see for both years a statistical effect of the treatments.
This field trial was funded for a 3rd year (INRC Award Number 2023-05) where the 3rd field season will be combined with the 1st and 2nd field season to provide a fuller picture in a year with less drought severity and more cover crop biomass accumulation.
Related accomplishments and activities
Information about this project was shared (or was the focus) for three field days, 11 presentations and one workshop.
One graduate student and 8 undergraduates were employed as assistants on this project.
January 2024
In the summer of 2023, between V6 and corn maturity, three in-situ mineralization tubes were placed and collected in two-week intervals at the Ames location, the last one being before corn harvest. At both locations, Ames and Crawfordsville, plant height was taken at VT. Final plant density and number of ears were collected before harvest. The Crawfordsville location showed differences between nitrogen application rates. Ames location showed primary difference among landscape positions, but has difference between nitrogen rate and presence of cereal rye as well.
Related accomplishments and activities
2 Field days, 1 Presentation, 1 Workshop
June 2023
In the spring of 2023, cover crop biomass was collected from early April until termination (May 4th for Crawfordsville and May 20th for Ames). Two biomass samples were taken in Crawfordsville and eight in Ames. Corn was planted in both locations on the day after termination, and the nitrogen treatments were applied on the same day as planting. Four sequential in-situ mineralization tubes were placed and collected in two-week intervals prior to and following corn planting. Three additional in-situ soil sampling periods will occur between V6 and corn maturity. Plant density, plant height and disease seedling samples were collected from both field locations. The Crawfordsville location is showing nitrogen application rate differences. The Ames location shows differences between plots with and without cereal rye in the growth stage. In addition to that, the plots in Ames are starting to show differences in landscape position.
Other Activities:
2 Field days, 4 Presentations.
Project submitted related to INRC project:: Beyond Cereal Rye: Expanding Iowa’s Cover Crop Options - $15,000 request.
December 2022
In the summer of 2022, three in-situ soil sampling periods were conducted between V6 and corn maturity at the Ames location. Corn height was collected at VT/R1. Drone flights occurred every 3 to 4 weeks to assess plant health. At corn maturity stand and ear counts were determined prior to harvest. The trial at Crawfordsville was harvested on 3 October and the 2023 cover crop seeding occurred on 4 October. In Ames the corn harvest was on 3 November and the new cover crop seeding occurred on 7 October at the Sorenson farm. On 1 November and 8 November, cover crop biomass was collected from Crawfordsville and Ames respectively. Detailed soil sampling was completed on 12 November in collaboration with Dr. Bradley Miller.
Other Activities:
4 Presentations.
Project submitted related to INRC project:
USDA-SARE: precision cover cropping (targeted use of cover crops to address sub-field resource concerns)
June 2022
In the spring of 2022, cover crop biomass was collected in mid-April and at the time of termination at both Ames and Crawfordsville. Three sequential in-situ soil mineralization tubes were placed and collected in two-week intervals prior to and following corn planting. Three additional in-situ soil sampling period will occur between V6 and corn maturity. Plant density, plant height and disease seedling samples were collected from both field locations. The Ames location is showing nitrogen application rate differences very nicely.
Other activities included one field day.
January 2022
In the fall of 2021, two research locations were established with the drill seeding of a cereal rye cover crop following soybean harvest. The Ames location is at the Kelley farm and has three landscape positions (summit, slope, toeslope). Soil samples were taken to determine nutrient analysis for fertility applications as well as to characterize the soils. The second location is at the Southeast Research and Demonstration farm (Crawfordsville, IA), which only contains one landscape position.
Other activities included one presentation.