Assessing the effectiveness of spatial and temporal separation of a cereal rye cover crop from corn on nutrient reduction and corn yield.
Issue
Adding a cereal rye cover crop (CR) to corn-soybean rotations is a proven strategy to consistently reduce nutrient loads entering surface waters via subsurface drainage. Despite these co-benefits, farmers are hesitant to adopt CR cover crops in their productions systems because of higher management costs and higher risk of corn yield declines. The goal of this research is to identify management practices for CR that maintain nutrient reduction goals, maximize co-benefits and eliminate barriers to adoption.
Corn seedling disease is an important factor in yield reduction because CR acts a “green bridge” for soil borne pathogens that infect corn seedlings in spring. The research team has demonstrated the duration between CR termination and corn planting reduced seedling disease and mitigated yield decline. In some years, however, cold temperatures and frequent precipitation events during spring prevent farmers from terminating CR early enough to avoid seedling disease. It has also been demonstrated that separating CR from the corn rows in space by varying CR row orientations mitigated the negative effects of CR on corn growth, seedling disease and yield. However, separating the CR from corn both temporally (i.e., early termination) and spatially (i.e., planting orientation) has the potential to limit co-benefits provided by CR by reducing biomass production and soil surface coverage.
In this study, researchers aim to combine two CR management practices, i.e. planting CR in the corn interrow and terminating it the time of corn planting, to answer: (i) could spatially separating the CR from the corn crop alleviate the need to terminate the CR prior to planting the corn, and could combining the two practices allow for more CR growth and provide improved ecosystem services? Assessing these management scenarios could provide farmers with more flexibility when implementing CR as part of their rotations.
Objective
The results from this study will improve understanding of how spatial and temporal management of CR affect corn growth, development and yield, seedling disease, nutrient recycling, soil erosion and water infiltration. The following objectives will guide comparison of the effect of cereal rye (CR) planting proximity to corn rows and CR termination dates on:
- CR biomass growth and N accumulation;
- Nitrate and dissolved organic carbon losses via leaching;
- Corn seedling disease, growth, development and yield; and
- Soil surface cover, infiltration rates, runoff rates, erosion and soil carbon and nitrogen dynamics.
Approach
Researchers will conduct a field trial at the Iowa State University (ISU) Boyd Farm in 2022-2023 and 2023-2024. The field study will utilize a randomized complete block design with five treatments with four replications of each:
(i) Corn planted 15” from CR, terminated 7 to 10 days before planting (DBP);
(ii) Corn planted 15” from CR, terminated 0 to 3 days after planting (DAP);
(iii) Corn planted 7.5” from CR, terminated 7 to 10 DBP,
(iv) Corn planted 7.5” from CR, terminated 0 to 3 DAP;
(v) No CR (control)
Once emerged, the corn row will be located either 7.5 inches (treatments i and ii) or 15 inches (treatments iii and iv) on either side from the terminated winter rye. CR will be drilled immediately after soybean harvest in early to mid-September to ensure good cover crop establishment. Most data collection will occur in summer 2023 and 2024.
Project Updates
Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.
December 2023
A preliminary analysis of rye biomass accumulation, seedling disease, infiltration and soil loss was done. Results so far include:
- Rye biomass accumulation followed expected trends given the interaction of planting rates and growing degree days.
- Later termination in the 19-cm spacing plots led to twice as much biomass as the early termination date.
- We observed less seedling disease of corn which was separated from CR by 19 cm and 30 cm, compared to seedling disease on corn that was not spatially separated from CR (0 cm) (P<0.05). Moreover, seedling disease was more severe when the CR was 19 cm from the corn compared to early terminated CR at 19 cm. However, at 38 cm, there was no difference in seedling disease at either termination timing, and seedling disease severity was not different from the no CR check.
- The relationship between CR biomass production and provision of agroecosystem services was inconsistent. Infiltration rates were not different across treatments. All CR treatments significantly reduced soil loss compared to a no CR control.
At R6, the number of total plants, ears and barren plants were recorded from two 17ft, 5in long rows. The middle rows of each plot were harvested. Soil samples were collected from each plot after harvest and are being analyzed for total C, total N, inorganic N, microbial biomass C and N, and 24-hour CO2 respiration
Other Activities
Water quality proposals related to INRC-funded work submitted for funding: Further Development of Best Management Practices For The Winter Rye Cover Crop-Corn Production System Co-PIs:Peter O’Brien, Stefan Gailans AFRI-CARE (Critical Agriculture Research and Extension) 5/24-4/27 $296,924
July 2023
Researchers on the project:
- Initiated plot-scale field experiment Installed resin lysimeters to monitor soil nitrate leaching.
- Completed first year of cereal rye green cover and biomass sampling.
- Completed first year of rainfall simulations and field soil hydraulic properties data collection.
- Completed seedling disease data collection and did a preliminary analysis. As expected, radicle root rot severity was greatest in the drilled rye with no skip row terminated 0-3 days after planting (DAP) and least in the no cover crop control. In the 15" rye terminated 7-10 days before planting and 0-3 DAP, root rot severity was not different to the no rye control.
Proposals submitted
Benefits of winter cereal rye cultivar selection and herbicide choice in mitigating corn yield drag. INRC 2023 - Total cumulative amount: $82,780
Trial plots showing spatial and temporal separation of cereal rye cover crop
December 2022
A winter cereal rye cover crop was planted at the ISU Boyd farm in September 2022 in preparation for field trials.
Other activities included six presentations and reports for Extension publications.