Expansion of agricultural production has irrevocably altered the earth’s landscape, impacting climate patterns, wildlife populations, soil health, water quality, and rural communities (USGS, 2007). Global meat and egg consumption are increasing: the USDA reports a 58% increase in global meat consumption over the past 20 years while egg production in the United States increased by 17% between 2008 and 2017. This demand is linked to a growing global population as well as changing human preferences and improved income levels. Coupled with meat and egg production is the production of manure, which can be managed as either a waste product or as a valuable resource to enhance crop production and build soil health. Here we propose an integrated study of novel management practices including manure management, tillage, and cover crops in corn-soybean cropping systems for long-term study of crop yield, soil health, and environmental resilience

The goal of this project is to assess the benefits of manure application and cover crops on soybean crop health and yield, water quality, and soil health. A new field site has been designed for extensive comparison of manure application timing, cover cropping strategies, and strip till management, with immediate and ongoing goals of evaluating crop health, yield, and environmental benefits. Our new field site will lead to multi-year study of environmental datasets. We will integrate our findings into educational materials and outreach activities led by Dr. Daniel Anderson and the Iowa Manure Management Action Group.

1) Active dissemination of information from this project through existing Extension programs and other scientific outlets. We will present information from these studies at ISU Research and Demonstration Farms Field Days, state and regional Extension meetings, and Iowa Learning Farms events as appropriate. Results from the first two years of research at the site (2021-2022) will be presented at the Soil and Water Conservation Society International Annual Conference (Denver, CO) and at the 2022 International Drainage Symposium (Des Moines, IA).
2) Development of educational and outreach materials to be used by Iowa Manure Management Action Group
3) Semi-annual and annual reports will be submitted to ISA.

Update:
This project is an extension of a long-term study evaluating the impacts of field management combining poultry manure, cover crops, and reduced tillage. In 2021, the Land mAnagement for improved Yield, Environmental Resilience, and Sustainability (LAiYERS) research site was established and the treatments were initiated with our first soybean crop planted after the subsurface drainage tiles and sampling wells were installed. The Iowa Egg Council funded initial plot establishment, site development, and continued research. Funding for the soybean crop analysis, water quality, and soil characteristics was provided by Iowa Soybean Association. The system considers manure application timing, cover crops, strip till, and nutrient application timing. This unique study will provide important information to farmers on how to best manage these systems for a range of environmental benefits, including soil health and resiliency to climate change. Ongoing evaluation of water quality and soil health is essential to measure and identify impacts of combined management practices.

Each of the nine system treatments are replicated in triplicate. The spring UAN treatments, with and without cover crops, serve as the experimental control. Supplemental nutrients, such as phosphorus, will be applied as field conditions indicate. An additional UAN treatment includes a split UAN application with spring side dress to address concerns with yield loss due to potential low nitrogen availability following cover crops. The manure application treatments allow for a side by side comparison of early winter and spring manure application with and without cover crops. We also include a balanced manure treatment with manure applied every 5 years (early winter application after soybeans in years 1 and 3). The plot and sampling well installation was completed in June 2021. Plumbing in the sampling wells and flow monitoring instrumentation has continued through 2022 as we prepare for electrical installation to the sampling wells. We anticipate electrical installation to be completed in November of 2022.

Manure or UAN fertilizer application timing impacted concentration results, with expected increases in concentrations after spring manure and UAN applications. In general, plots that were treated with manure in early winter 2021 (EW manure and balanced EW manure) had much higher early spring concentrations compared to the other treatments.
Fall soil analysis showed accumulation of phosphorus in the surface soil (0-6”) at plots that were treated with manure in early winter 2021 or spring 2022. All plots have M3-P levels indicating high or very high phosphorus. Total available nitrogen was relatively low in the fall for all treatments.

Progress Toward Project Metrics
KPI #1: Data on yield, soil and water quality. Measured annually by collection of environmental datasets.
Fall soil samples were collected on 11/3/22-11/4/22 and delivered to AgSource Laboratory in Ellsworth, IA for analysis. Select soil analysis results are presented in this report. Subsurface tile drainage water samples will be collected throughout the 2023 drainage season, with the first samples estimated to be collected in mid-April. Soybeans will be planted by May 15th, and soybean plant analysis will be conducted periodically throughout the growing season.
KPI #2: Improved understanding of manure integrated cropping systems and their impact on soybean yield and soil and water quality.
This metric will be achieved through continued progress on KPI #1. We are beginning the third year of research and data collection at the LAiYERS plots. The preliminary results indicate differences in water quality, specifically nitrate concentrations, in response to treatment. The lowest nitrate concentrations were measured Although the plots were planted to soybeans in 2021, these plots had yet to receive the first fertilizer-cover crop combination treatments. The 2023 soybean crops will be the first year to reflect treatment impacts.

View uploaded report

Update:
This is the third year of research at the LAiYERS (Land mAnagement for improved Yield, Environmental Resilience, and Sustainability) plots, evaluating the impact of poultry manure and cover crop impacts on water quality, soil health, and crop yield. The plots were established in 2021, with subsurface tiles and drainage sampling wells installed in spring, and soybeans planted (date) after installation was complete. The first treatments were initiated in the fall of 2021 with cover crops planted to the designated plots (Systems 1, 3, 4, 6, 8) and the early winter and balanced poultry manure treatments applied (Systems 4, 5, 8, 9). The spring fertilizer and poultry manure treatments were applied in 2022 for the corn year of the rotation.

Progress since our initial funding includes planting, harvest, and cover crop termination dates from 2021 through soybean harvest 2023. Additional field work in 2023 will include the early winter manure application for the 2024 corn year, scheduled to be applied on November 15th. The attached pdf provides a detailed timeline of activities.

Early analysis shows differences between treatments.
Differences in drainage water NOx-N concentrations were observed by treatment in 2023. The lowest measured concentrations were with the spring poultry manure treated plots, followed by the early winter and balanced manure plots. The highest concentrations were measured at the UAN plots, although these differences may not be statistically significant. All plots last received fertilizer treatment for the 2022 corn year (early winter 2021 or spring 2022). Data will be statistically analyzed and detailed in the final report.

Soybeans were harvested on October 9th. Preliminary analysis suggests a negative impact on crop yields with cover crops. The 2023 cover crop was terminated late (June 19) as part of an experimental design to evaluate the impact of cereal rye on weed suppression. While there was a measurable decrease in weed coverage with cover crops, a better balance in termination timing to achieve optimal yields is necessary.

Progress Toward Project Metrics
KPI #1: Data on yield, soil and water quality. Measured annually by collection of environmental datasets.
Environmental sample collection was completed throughout the 2023 season. Soybean plant samples, including leaf greenness and root nodules, were collected at various growth stages (V2, V5, R1) and cover crop samples were collected for biomass and tissue analysis at termination. Soil samples were collected with the soybean roots to a depth of 5-7” for nutrient analysis. Subsurface tile drainage water samples will be collected throughout the 2023 drainage season. The soybeans were planted on (date) and harvested on (date).
KPI #2: Improved understanding of manure integrated cropping systems and their impact on soybean yield and soil and water quality.
We have completed the third year of research and data collection at the LAiYERS plots. We continue to analyze the data to evaluate the treatment impacts on water quality, soil nutrient changes, and crop growth. The drainage data includes a year with fertilizer application (corn year; 2022) and no fertilizer application (soybean year; 2023), with distinct differences by treatment for each. Preliminary results suggest late termination of cover crops negatively impacted soybean yields.
This summer we were able to expand our outreach with the project to include a visiting elementary school teacher who was participating in the Research Experience for Teachers (RET) program at Iowa State University. With assistance, she evaluated and presented a poster highlighting the early results comparing the impact of cover crops on weed canopy, soybean plant greenness, and soybean root nodules. This data will be further evaluated to identify any system treatment effects on these characteristics.
Additional sample processing and data analysis will be completed over the next few months and included in the final report.

View uploaded report

View uploaded report 2

The long-term outcome of this study would be to inform manure management and cover cropping management to optimize crop yield and environmental benefits and will directly benefit soybean farmers by providing strategies that reduce risk through yield stability and potentially yield increase. As soon as we have sufficient data from the site, we will be able to provide practical management recommendations to farmers and tie these best practices to economic outcomes as we have in past efforts. Further, these efforts will lead to fewer environmental impacts through less impaired waters, protected public health, and more sustainable agricultural systems. This information will be important for producers who are making management decisions and for state agencies that have responsibility for water quality. Producers will have valuable information to help guide management options while policy makers will have new information on manure management as part of watershed management plans.