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corn and soybean drainage research plots
Nutrient Management

Title:  Gilmore City DWRF

Location:  Gilmore City

Time Period:  1989-present

Research Team:  Matt Helmers, Carl Pederson, Emily Waring, and Chelsea Clifford

Project Description:  Research focused on the effects of nitrogen (N) management on crop production and tile drainage water quality has been conducted in north-central Iowa near Gilmore City since 1989. The research site ag drainage well (ADW) includes 72 individually drained plots that are 50 feet wide and 125 feet long. Tile lines were installed at a depth of 3.5 feet spaced 25 feet apart. The center tile line from each plot is pump monitored continuously for drainage volume with a flow meter and a flow-proportional sample is passively collected for nitrate-nitrogen (nitrate-N) and dissolved phosphorus (P) analysis. Drainage flow is recorded and water samples are collected for analysis weekly. Soil types at ADW include Nicollet, Webster and Canisteo, all of which are clay loams. The 30-year average annual rainfall for ADW is 33.5 inches.  At ADW, multiple management practices have been examined for their impact on N and P loss and crop yield.

Crops: Corn-soybean, continuous corn, perennial forage.

Management Practices: Cover crops, tillage, land use, N-fertilizer source/rate/timing.

Treatments were changed in the fall of 2015 and current is studying the impacts of: Cereal rye winter cover crop vs. no rye (with and without tillage), conventional tillage (fall chisel plow with spring cultivation) vs. no-till (with and without rye), timing of N-application and use of nitrification inhibitor.

Publications:  Qi, Z., M.J. Helmers, R.D. Christianson, and C.H. Pederson. 2011. Nitrate-nitrogen losses through subsurface drainage under various agricultural land covers. Journal of Environmental Quality 40: 1578-1585.

Lawlor, P. A., M.J. Helmers, J. L. Baker, S. W. Melvin, and D. W. Lemke. 2008. Nitrogen application rate effects on nitrate-nitrogen concentrations and losses in subsurface drainage. Trans. ASABE 51(1): 83-94.

Funders:  Primary funder since 1989 has been the Iowa Department of Agriculture and Land Stewardship, in part, through funds authorized by the Iowa Groundwater Protection Act. Research from 2011-2015 was part of a regional collaborative project supported by USDA-National Institute of Food and Agriculture, award number 2011-68002-30190, “Cropping Systems Coordinated Agricultural Project: Climate Change, Mitigation, and Adaptation in Corn-based Cropping Systems,” project website: Have also had support from Koch Agronomic Services from 2016-2019.

Disclaimer:  This is an active research site, please contact Matt Helmers ( prior to planning any site visits. 

Drainage well
Nutrient Management

Location:  Northeast Research and Demonstration Farm

Time Period: 1988-present

Research Team: Matt Helmers, Antonio Mallarino, Dan Andersen, Brian Dougherty, John Sawyer, Michelle Soupir, and Ramesh Kanwar

Project Description:  The Northeast Research and Demonstration Farm (NERF) has 36 1-acre research plots equipped with a drainage water monitoring system installed in 1988. Plots have 1-4 percent slope with Kenyon, Floyd, and Readlyn soils. Tile lines are installed at a depth of four feet spaced 95 feet apart. Management practices are evaluated for their impact on nitrate-N and dissolved phosphorus (P) loss and crop yield. To quantify the impact of these practices, researchers are monitoring subsurface drainage volume and collecting flow-proportional water samples for nitrate-N and dissolved P analysis. The 30-year average annual rainfall for NERF is 29.7 inches. The average tile drainage flow from 2001-2015 is 4.5 inches.

At NERF, multiple management practices have been examined for their impact on N and P loss and crop yield. 

Crops: Continuous corn, corn-soybean rotations, extended corn-oats-alfalfa rotation (1993-1998)

Management Practices: Rye cover crop, tillage/no-till, swine manure/urea ammonium nitrate (UAN), varied N application rates and timing, stover removal, nitrification inhibitor. 

Since 2016, treatments aim to study the impacts of N-management and in-field practices, including:

  1. Early fall vs. late fall vs. spring application of swine manure
  2. Conventional tillage vs. no-till
  3. Cereal rye cover crop vs. no cover crop
  4. Nitrification inhibitor
  5. One ton/acre gypsum application


Funders:  Support was provided in part by USDA-Agriculture Research Service, USDA-Cooperative State Research, Education and Extension Service, Leopold Center for Sustainable Agriculture, National Pork Producers Association, Iowa Agriculture and Home Economics Experiment Station, and Iowa State University College of Agriculture and Life Sciences. Support is provided in part by the Iowa Pork Producers Association and Calcium Products, Inc.

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

Prairie strip

Title:  Water quality performance of prairie strips

Location:  Four Locations throughout Iowa

Time Period: 2014-present

Research Team:  Matt Helmers, Chris Witte, Lisa Schulte Moore, and Matt Liebman

Project Description:  The STRIPS project (Science based Trials of Rowcrops Integrated with Prairie Strips) conducted at Neal Smith National Wildlife Refuge (NWR) near Prairie City, Iowa ( has documented water quality benefits as well as increased biodiversity across several taxa, achieved by integrating tallgrass prairie vegetation (prairie strips) into row-cropped watersheds. The experimental watersheds at Neal Smith NWR incorporating as little as 10% field acreage in prairie strips within no-till corn/soybean row crops reduced losses of sediment by 95%, nitrogen in runoff by 84%, phosphorus in runoff by 89%, and water runoff by 60% compared to watersheds without prairie strips. Over the past few years the ISU team has been working to install prairie strips throughout Iowa. The ISU team received funding from IDALS, USDA-FSA, USDA-NIFA, and the Iowa State University College of Agriculture and Life Sciences to establish monitoring infrastructure at six of these prairie strips sites. The six sites with monitoring infrastructure are the paired comparison sites. 

Our preliminary surface runoff results  indicate that surface runoff volume is usually less in the drainages with prairie strips, but not by much. One notable exception is the McNay site and there are at least two contributing factors to why measured runoff is greater in the treatment as opposed to the control field. Firstly, we have had some difficulty getting all of the runoff to flow through the flume for measurement on the control field, as some runoff is failing to enter the grassed waterway where the flume is installed. We hope to fix this problem before monitoring begins in 2020. Secondly, there is a side slope seep in the treatment field that we believe contributes to greater runoff volume as well as reduces infiltration of rain into the soil. In general, the drainage areas with prairie strips are losing less nitrogen, phosphorus, and sediment. However the results are not as dramatic as the work at Neal Smith likely due to the paired field comparison sites all having grassed water ways. 


Funders:  Iowa Department of Agriculture and Land Stewardship, Iowa Nutrient Research Center, USDA Farm Services Agency, Foundation for Food and Agriculture Research, US. Forest Service Northern Research State, and USDA-NIFA

Disclaimer:  These are an active research sites, please contact the research team prior to planning any site visits. 

Iowa landscape

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 Squaw 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.


Funders:  Iowa Nutrient Research Center

Stream monitoring

Title: Iowa Water Quality Information System

Location: University of Iowa, Iowa City, Iowa

Time Period: 2012-present

Research Team: Christopher S. Jones, Ibrahim Demir, Jerry Mount, Larry Weber, and Gabriele Villarini

Project Description: The Iowa Water Quality Information System (IWQIS) is a network of water quality measurement devices deployed in streams distributed across the state of Iowa. The IWQIS design is based on the vision and technical expertise of the generalized water cyberinfrastructure developed at the Iowa Flood Center. IWQIS provides an integrated and scalable workflow environment to support end-to-end cyberinfrastructure for sharing scientific research and observations, as well as scientific visualization, communication of observations and modeling results that assist watershed management and research.

A wide variety of data are available for immediate public use through IWQIS ( The measured water quality parameter of most interest is nitrate (NOx-N) concentration, although pH, turbidity, specific conductance, dissolved oxygen and temperature are also measured at numerous sites. Discharge measurements are available at 35 sites, and at these locations NOx-N load and yield data are also available.

Data is also harvested from sites operated by USGS. All the USGS sites include discharge measurements along with additional water quality parameters at some sites. IWQIS sites generally fall into one of four categories: statewide load estimation, water quality initiative (WQI) demonstration projects, research projects, and USGS sites.

Equipment owned by the Agricultural Research Service (ARS-USDA) and Coe College also is part of the IWQIS network. All archived data is made available upon request.


1) Jones, C.S., Davis, C.A., Drake, C.W., Schilling, K.E., Debionne, S.H., Gilles, D.W., Demir, I. and Weber, L.J., 2018. Iowa statewide stream nitrate load calculated using in situ sensor network. JAWRA Journal of the American Water Resources Association, 54(2), pp.471-486.

2) Jones, C.S., Drake, C.W., Hruby, C.E., Schilling, K.E. and Wolter, C.F., 2019. Livestock manure driving stream nitrate. Ambio, 48(10), pp.1143-1153.

3) Jones, C.S., Kim, S.W., Wilton, T.F., Schilling, K.E. and Davis, C.A., 2018. Nitrate uptake in an agricultural stream estimated from high-frequency, in-situ sensors. Environmental monitoring and assessment, 190(4), p.226.

Funders: Iowa Nutrient Research Center, Housing and Urban Development (Iowa Watershed Approach), National Science Foundation, Carver Trust, and Polk County Water Trails

Disclaimer:  This is an active research site, please contact Chris Jones ( prior to planning any site visits.

Allelochemical test on corn germination.
Nutrient Management

Title: Improved understanding the role of winter cereal rye allelochemicals in winter rye-corn production system.

Location: Laboratory research at Iowa State University.

Time Period:  2018 - 2021

Research Team:  Alison Robertson and Jyotsna Acharya

Corn yield reduction following a cereal rye cover crop has been attributed to, amongst other factors, allelochemicals released from decomposing cereal rye residue. Allelopathy is a complex biological process including interaction between two plants in which one plants release chemical compounds that influence the development and the growth of the other plants, prepares plants to increase its survivality through defence mechanism. Allelochemicals also affect plant-microbiome interactions. We are conducting studies in the lab to understand if if allelopathy may play a role in seedling disease. In our first study we  evaluated the effect of 6-Methoxy-2-benzoxazolinone (MBOA) on corn seedling growth, mycelial growth of seven pathogenic species of Pythium and root rot of corn seedlings caused by Pythium species. Greater root rot severity in corn was observed on corn seedlings grown in the presence of Pythium lutarium, P. oopapillum, P. torulosum and P. spinosum on media amended with MBOA. These data suggest that corn seedling disease caused by Pythium species could be more severe when corn is planted following a cover crop of winter cereal rye due to the presence of allelochemicals that are released from the cover crop. We are now repeating this experiment using root extracts from rye.

Publications: Acharya, J., Kaspar, T. and Robertson, A.E. XXXX. Effect of 6-Methoxy-2-benzoxazolinone (MBOA) on Pythium species and corn seedling growth and disease. Plant Disease (in press)

Funders:   Iowa Nutrient Research Center.

Map of Walnut Creek Watershed Iowa

Title: Building cross-scale predictability of land-to-aquatic nitrogen loads in agriculture-dominated watersheds

Location: Walnut Creek Watershed, IA

Time Period: 2021 - Present

Research Team: Chaoqun Lu, William Crumpton, Tom Isenhart, and David Green

Project Description: Modeling assessment is becoming increasingly important to developing quantitative insights into the processes governing nutrient exports from land to water bodies, and to making predictions about future conditions. However, the efficacy and attribution capacity (i.e., “get right answer for right reasons”) of the existing water quality models is uncertain owing to limited model testing against long-term observations of nutrient concentration, flow, and loading within a hydrologic hierarchy system. To address this problem, we propose to develop a data-model integration framework to identify and quantify the issues leading to model incapability in accurately estimating N delivery across scales. In this project, we will test and improve a process-based hydro-ecological model to simulate in-stream N transport and decay processes, and benchmark the model’s performance using long-term water quality monitoring data at the delivery scale, along ditches and stream channels downstream of the outlets of subsurface drainage networks, and at the scale of a United State Geological Survey Hydrologic Unit Code 12 (HUC 12) watershed (~5000 ha). This work will be conducted in the HUC 12 Walnut Creek watershed located approximately 5 miles south of Ames, Iowa. The Walnut Creek watershed has been subject to extensive monitoring of nutrient loads and flows over decades at various scales, at multiple locations along the mainstem of Walnut Creek and some of its tributaries. In this project, we will employ a portion of the historical flow and nutrient concentration time-series monitoring data to improve and calibrate the model, and validate it with the remainder. Then, the improved model will be applied in the entire watershed to quantify the relative contributions of in-field and edge-of-field management practices, and in-stream processes on nitrate-N reductions observed at the watershed outlet under current climate conditions. Finally, we will identify “hot-spot” areas within the watershed that are prone to losing excessive quantities of N through hydrological flushing.


Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Chaoqun Lu ( prior to planning any site visits.

Pothole wetland in a field

Title: Reducing Phosphorus Export through Farmed Pothole Surface Inlets with P Filters and Blind Inlets

Location: Iowa State Been and Bennett Farms

Time Period: 2020 - Present

Research Team: Amy Kaleita, Michelle Soupir, and Chad Penn

Project Description: Much of Iowa contains landscape features known as prairie potholes – landscape depressions with little natural surface drainage and soils that limit infiltration. Many of these features that occur in farmed areas have artificial subsurface drainage installed, with a surface inlet to drain away standing water. Past observations into the water quality of the standing water in these features indicate that phosphorus levels in this ponded water can be high, making the drainage system a source of phosphorus export from the field. This project will study approaches for intercepting and treating phosphorus before it moves out of the field through the drainage network.


Funders: Iowa Nutrient Research Center

Disclaimer: This is an active research site, please contact Amy Kaleita ( prior to planning any site visits.

Cereal rye cover crop
Nutrient Management

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.


Funders: Iowa Nutrient Research Center

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

beaver dam

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


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.


Funders: Iowa Nutrient Research Center

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