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Title: Can Adjustments to Nitrogen Rates Reduce Corn Yield Drag and Disease Implications Following a Cereal Rye Cover Crop?

Location: Ames and Crawfordsville, Iowa

Time Period: 2021 - Present

Research Team: Mark Licht, Marshall McDaniel, Alison Robertson, Fernando Marco, and Jyotsna Acharya

Project Description: 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 include: 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. 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. 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. 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.

Publications:

Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Mark Licht (lichtma@iastate.edu) prior to planning any site visits.

Title: Dam! Impacts of Beaver Dams on Surface and Groundwater Quality

Location: 

Time Period: 2020 - Present

Research Team: Billy Beck, Thomas Isenhart, Keith Schilling, Peter Moore, Richard Schultz, and Tyler Groh

Project Description: Beaver (Castor canadensis) activity (i.e., damming of streamflow) holds significant potential to impact in-stream nutrient processing, through reduction of streamflow velocity and increase of water residence time within pools, trapping of sediment and organic material, raising of riparian groundwater tables and restoration of channel-floodplain connectivity. Thus, dams may represent a “no-cost in-stream conservation practice” that provides compound benefits beyond water quality and quantity, such as enhanced wildlife habitat and increased riparian vegetation diversity. Few studies have focused exclusively on beaver dam impacts to in-stream nutrient processing and watershed-scale nutrient loading, especially in the agricultural Midwest, where watersheds frequently exhibit elevated nutrient loads, flashy hydrology and stream channel incision.

The overall goals of this project are to identify and quantify key nutrient-removal processes associated with beaver dams and estimate the potential impact of dams on watershed-scale nutrient loading within the agricultural Midwest. To achieve project goals, we will pursue three main objectives: 1) quantify hydrologic impacts of beaver dams at the stream reach-scale in select Iowa watersheds; 2) quantify in-stream and shallow groundwater nutrient processing impacts of beaver dams at the stream reach-scale in select Iowa watersheds; and 3) expand stream reach-scale results to estimate watershed-scale hydrologic and nutrient loading impacts of beaver dams.

Publications:

Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Billy Beck (wjbeck@iastate.edu) prior to planning any site visits.

Title: Field Trials to Evaluate N Export from Perennial Groundcover Corn Systems

Location: Northeast Iowa Research and Demonstration Farm, Iowa State University

Time Period: 2020 - Present

Research Team: D. Raj Raman, Kenneth J. Moore, and Daniel A. Andersen

Project Description: Corn and soybean dominate the Midwestern landscape. Both are annuals, only present on the landscape for a fraction of the year. In their absence, they cannot intercept and protect soil from rainfall, nor can they slow runoff and promote infiltration. Members of the research team pioneered a perennial groundcover (PGC) system for corn, wherein a summer-dormant perennial groundcover, such as fescue, provides year-round soil cover. Managed correctly, the corn thrives because the cover is dormant in the summer. The PGC approach requires fewer late and early-season field activities, which are barriers to wider adoption of annual cover crops. Modeling predicts that PGC-corn can reduce runoff, enhance soil organic matter and reduce nitrogen leaching. However, further field research is needed to validate modeling to better understand the impact of a PGC-corn system on nitrogen loss. This project will provide experimental data that can be used to validate models and to estimate the potential impacts on nitrogen-export of widespread PGC-adoption. 

Publications:

Funders: Iowa Nutrient Research Center, complimentary funding from the Iowa Pork Producers Association started 9/1/21.

Disclaimer: This is an active research site; please contact D. Raj Raman (rajraman@iastate.edu) or Daniel S. Andersen (dsa@iastate.edu) prior to planning any site visits.

Title: The effectiveness of carbon credit programs at reducing nutrient losses: An assessment of public and private conservation programs and their interactions

Location: Iowa

Time Period: 2021 – July 2023

Research Team: Hongli Feng, Sarah Carlson, Susanne Hickey, Elizabeth Reaves, Lisa Schulte-Moore, and Wendong Zhang

Project Description (300 words max.): There have been intense interests in carbon sequestration and greenhouse gas (GHG) emission reduction in the agricultural sectors recently. Meanwhile, there have been decades of efforts and investment to reduce nutrient loss from agriculture. From a policy standpoint, carbon and nutrient reduction are inseparable for to two reasons: (a) most conservation practices that reduce nutrient loss also sequester carbon; and (b) both government and private incentives can be used to support the same set of conservation practices. By investigating these links, our team of cross-disciplinary researchers and non-governmental organization (NGOs) partners will evaluate how carbon credit programs will affect nutrient loss reduction with a focus on farmers’ decision-making regarding program participation.

Publications:

Funders: Iowa Nutrient Research Center

Title: Influence of bank stabilization on floodplain sediment and phosphorus storage

Location: Nishnabotna River, IA

Time Period: 2021 - Present

Research Team: Peter Moore and Tom Isenhart

Project Description: Eroding river banks are frequently stabilized with rock, concrete, or wood when infrastructure or property is threatened. There is also growing interest in using bank stabilization as a way to reduce nutrient loading from bank erosion. However, little is known about the impacts of bank stabilization on the sediment deposition process on opposing point bars and adjacent floodplain, whose dynamics are closely coupled with bank erosion. If arresting bank erosion also reduces sediment and P deposition and storage elsewhere, the nutrient reduction benefits of streambank stabilization may be less than expected. We are comparing the sediment and P concentrations of eroded and deposited sediment in five stabilized and five un-stabilized river bends in the Nishnabotna River watershed to determine whether bank stabilization has any systematic impact on reach-scale sediment and P storage. We are using aerial imagery and LiDAR elevation data to estimate the total volumes of sediment eroded and deposited from each stabilized and un-stabilized bend. We’re also mapping and sampling different sediment types on each point bar and adjacent floodplain to characterize both the sediment eroded and deposited and its P concentration. We’ll compare the results to determine whether sediment and P storage on point bars and adjacent floodplains is reduced in bends with bank stabilization structures.

Publications:

Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Peter Moore (pmoore@iastate.edu) prior to planning any site visits.

Title: Advanced Modeling of Soil Erosion, Sediment Delivery and Nutrient Export from Iowa Watersheds

Location: Walnut Creek Watershed, Jasper County, Iowa

Time Period: 2020 - Present

Research Team: Matthew Streeter, Rick Cruse, Brian Gelder, Chunmei Wang, and Kevin Cole

Project Description: Soil sediment and sediment bound phosphorus export from agriculturally dominated watersheds is a global crisis that has far-reaching, potentially severe environmental and economic impacts. Multiple sources are known to contribute to surficial exports from these watersheds including in-field sheet and rill erosion, ephemeral gully erosion and streambank erosion. However, accurately quantifying suspended sediment and P export from watersheds is difficult.

The Water Erosion Prediction Project (WEPP) may be utilized to help quantify sediment yields from agricultural fields. Sensitivity analysis and validation indicated that WEPP has high runoff and sediment yield accuracy for small watersheds. Still, scaling up WEPP Watershed to a HUC-12 scale may be difficult. The Daily Erosion Project (DEP) may be used to scale up WEPP, but these new outputs must be ground-truthed with field-collected data.

This project will help to identify and quantify the effects of ephemeral gullies on sediment and P loss. Ultimately, this project will work towards delineating sources of sediment and P export, i.e., hill slopes or ephemeral gullies, from Iowa watersheds, using Walnut Creek watershed in Jasper County, Iowa, as a test for soil erosion, sediment, and nutrient export modeling.

Publications:

Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Matthew Streeter (matthew-streeter@uiowa.edu) prior to planning any site visits.

Title: Continued assessment of corncobs as an alternative carbon source to enhance bioreactor performance for improved water quality

Location: Boone, Iowa

Time Period: 2021 - 2023

Research Team: Michelle Soupir, Ji Yeow Law, Thomas Isenhart, Natasha Hoover, Gary Feyereisen, Morgan Davis

Project Description: Woodchip bioreactors are a cost-efficient practice to remove nitrates (N) from tile drainage, but the limited regional woodchip supply poses challenges for broad-scale bioreactor implementation efforts. Additionally, poor N removals were observed in woodchip bioreactors when the temperature was low, and N export was high in the spring. These challenges motivated researchers to seek alternative bioreactor carbon substrates that are low-cost, locally available, and can provide improved N removals. Among the carbon substrates evaluated in lab studies, corncobs have shown promising N removals rates and costs. This project aims to investigate the long-term performance of corncob-amended woodchip bioreactors under field conditions. The project objectives are to evaluate and compare i) hydraulic efficiencies, ii) N removal rates, and iii) N removal costs in nine replicated pilot-scale bioreactors (PBRs) using three different woodchip-corncob mixture ratios at three hydraulic retention times (HRTs). Three PBRs were filled with woodchips only (WC100); three PBRs were filled with 75% (by vol.) woodchips and 25% corncobs (CC25); and three PBRs were filled with 25% woodchips and 75% corncobs (CC75). The PBRs from each carbon treatment were operated at 2-, 8-, and 16-hr HRTs, respectively. Our early results showed that hydraulic efficiency was highest in WC100 (0.92±0.14), followed by CC25 (0.86±0.16) and CC75 (0.58±0.17). CC75 exhibited the highest N removal rates (11.6-21.1 g N m-3 d-1), then followed by CC25 (5.7-9.7 g N m-3 d-1) and WC100 (2.0-8.0 g N m-3 d-1). When compared to WC100, the N removal costs of CC75 and CC25 were up to 8.3 and 2.1 times lower, respectively. Overall, the early data suggested that corncob-amended woodchip bioreactors had better nitrate removal rates and cost-efficiencies but lower hydraulic efficiencies. Nonetheless, continued assessment of these PBRs is essential to understand the long-term performance that could be affected by different carbon substrate degradation rates.

Publications:

Schaefer, A., K. Werning, N.L. Hoover, U. Tschirner, T.B. Moorman, G. Feyereisen, A.C. Howe, M.L. Soupir. 2021. Impact of flow on woodchip properties and subsidence in denitrifying bioreactors. Agrosystems, Geosciences & Environment DOI: http://dx.doi.org/10.1002/agg2.20149

Martin, E.A., M.P. Davis, T.B. Moorman, T.M. Isenhart, M.L. Soupir. 2019.  Impact of hydraulic residence time on nitrate removal in pilot-scale woodchip bioreactors. Journal of Environmental Management. 237:424-432. DOI: 10.1016/j.jenvman.2019.01.025

Davis, M.P., E.A. Martin, T.B. Moorman, T.M. Isenhart, M.L. Soupir. 2019. Nitrous oxide and methane production from denitrifying woodchip bioreactor at three hydraulic residence times. Journal of Environmental Management. 242: 290-297. DOI: 10.1016/j.jenvman.2019.04.055

Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Michelle Soupir (msoupir@iastate.edu) prior to planning any site visits.

Title:  Integrating Social and Biophysical Indicators of Nutrient Reduction Progress in Iowa Watershed Projects

Location:  Boone River Watershed, Central Turkey River Watershed, Miller Creek Watershed, West Branch of the Floyd River Watershed, Cedar Creek Watershed, Walnut Creek Watershed, North Raccoon Watershed, and Ioway Creek Watershed

Time Period:  2019 -2021

Research Team:  Laurie Nowatzke, Lori Abendroth, J. Arbuckle, Jamie Benning, Zhengyuan Zhu, Giorgi Chighladze, Stephanie Bowden, Jiaming Qiu, and Suraj Upadhaya

Project Description:  In response to the Iowa Nutrient Reduction Strategy—a statewide framework to reduce Iowa’s nitrogen and phosphorus losses by 45 percent—numerous state and federal agencies, universities, and private organizations conduct work across the state to promote agricultural soil and water conservation. There are several efforts in place to measure Iowa’s overall progress towards these goals. However, their geographic scale of analysis is statewide and they do not capture outcomes at finer spatial resolutions.

To overcome the challenges associated with geographic scale, this study explores the factors that impact nutrient reduction in watershed project areas which are a few hydrologic unit code-12 watersheds in size (i.e. generally, 20,000 to 150,000 acres). Because there has been limited empirical research on the factors that influence the progress or effectiveness of watershed projects that aim to reduce nutrient loss, this study aims to address the research question: On a watershed project scale, what are the primary indicators for predicting nutrient reduction effectiveness? These indicators may fall into a variety of operational categories, including but not limited to availability of funding and financial incentives, participation by diverse stakeholder groups, extent of outreach work among farmers and the wider community, and the extent of agricultural conservation practice use.

In a highly innovative approach, this project integrates disparate data from social and ecological sources. In agriculture, social and biophysical scientists alike have long called for integration of biophysical factors into research on farmer behavior and the potential impacts of that behavior. The proposed research integrates biophysical data (e.g. land use, water monitoring data) and social data (e.g. outreach efforts, farmer surveys) in novel social-ecological analyses, in order to contribute to a better understanding of the social and biophysical factors that influence land use and modeled nutrient reduction outcomes at the watershed level.

Publications: 

Funders:  Iowa Nutrient Research Center

Title: Quantifying soil nitrogen dynamics in manured fields

Location: Multiple Locations within the state

Time Period: 2021 - 2022

Research Team: Sotirios Archontoulis, Marshall McDaniel, Peter Kyveryga and Scott Nelson

Project Description: The goal of this project is to enhance our understanding on soil N dynamics in manured fields via field experimentation and simulation modeling. Our objectives are:
1. Quantify soil N temporal dynamics in 30 manured fields spread across Iowa over two years (via field sampling) and subsequent years (via APSIM modeling).
2. Determine soil N immobilization/mineralization patterns and crop N availability from different manure sources and application timings.

Publications:

Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Sotirios Archontoulis (sarchont@iastate.edu) prior to planning any site visits.

Title:  Comparison of Biofuel Cropping Systems (COBS)

Location:  Boone

Time Period:  2008-present

Research Team:  Michael Thompson, Matt Helmers, Matt Liebman, and Robert Horton

Project Description:  The experiment is large-scale (24 plots, each 27 m x 61 m, four replications of each system) and compares biomass production, fossil fuel replacement value, and environmental impacts for continuous corn grown for grain and stover removal with (CCW) and without (CC) a rye cover crop; multi-species perennial crops grown for aboveground biomass with (PF) and without (P) fertilizer; and a conventional corn-soybean grain system, used as a comparison baseline.

Twelve aluminum culverts were buried vertically at the ends of the center drainage lines from pairs of individual plots. Drainage lines from the plots are directed to sumps in the culvert, and drainage is pumped through plastic plumbing fitted with a plated sprayer nozzle and a water meter. Back pressure created by the meter forces a constant fraction (~0.25%) of all drainage to be diverted to a 10-L sampling bottle. The in-line flow meter is read when water samples are taken, and the system is also set up for continuous logging of the flow meters through switch-closure logging. This configuration provides the infrastructure for continuously monitored flow-volume measurements and flow-integrated sampling of subsurface drainage from each plot.

Drainage water samples have been collected weekly from the outlets of each plot during flow periods. Concentrations and loads of nitrate (NO₃-N) and phosphate (PO₄-P) were determined. Drainage water samples collected from the PF and P cropping systems had the lowest flow weighted mean concentration and load of NO₃-N, which means the prairie cropping systems substantially limited the leaching of NO₃-N even when the prairie received nitrogen fertilizers. Additionally, the continuous corn system with cover crops had lower nitrate-N concentration and load than the continuous corn system with no cover crop. Overall, the mass loss of PO₄-P is quite low -- less than 0.14 kg/ha for all treatments.

Publications:  Daigh, A.L.M., U. Ghosh, J. DeJong-Hughes, and R. Horton. 2018. Spatial response of near-surface soil water contents to newly imposed soil management. Agric. Environ. Lett. 3:180032. doi:10.2134/ael2018.06.0032.

Daigh, Aaron L. M., Xiaobo Zhou, Matthew J. Helmers, Carl H. Pederson, Robert Horton, Meghann Jarchow and Matt Liebman. 2015. Subsurface drainage nitrate and total reactive phosphorus losses in bioenergy-based prairies and corn systems. Journal of Environmental Quality 44:1638-1646.

Funders:  Leopold Center for Sustainable Agriculture, Iowa Nutrient Research Center, Agronomy Department, ISU, College of Agriculture and Life Sciences, ISU

Disclaimer:  This is an active research site, please contact the research team prior to planning any site visits.