Project : USDA ARS

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Research Project: Practices and Technologies for Sustainable Production in Midwestern Tile Drained Agroecosystems

2025 Annual Report

Objectives
Objective 1: Elucidate field and instream governing processes that control water quality and ecological response. Goal 1.1: Develop water table, soil moisture, and evapotranspiration measurement capacity within a subset of EOF network sites to better understand the water balance in tile drained landscapes. Hypothesis 1.2: The majority of observed edge-of-field P losses are attributable to old soil P rather than recently applied P fertilizers. Hypothesis 1.3: Preferential flow to subsurface tile drains are dominated by contributions from a relatively narrow band of the soil surface extending less than 1 m on either side of the drain. Objective 2: Quantify the response of ecosystem services (e.g., water quality, habitat, and biodiversity) to conservation practice implementation. Hypothesis 2.1: Implementation of conservation/aspirational practices (ASP) will significantly reduce edge-of-field surface and subsurface nutrient loss compared to business as usual (BAU) practices. Hypothesis 2.2: Including two or more conservation practices (stacking) will provide greater nutrient loss reductions compared to single practice implementation. Hypothesis 2.3: Improvements in soil health indicators will be associated with reduced edge-of-field nutrient losses. Hypothesis 2.4: Installation of instream inserts within an agricultural headwater stream will create riffle pool sequences that will increase instream habitat diversity and improve fish community integrity at the microhabitat spatial scale. Hypothesis 2.5: Installation of instream inserts in conjunction with channel rerouting and wetland creation will increase instream habitat diversity, improve fish community integrity, increase dissolved oxygen concentrations, and reduce downstream transport of nutrients. Hypothesis 2.6: Channelized agricultural headwater streams with greater instream habitat diversity will exhibit less nutrient concentrations and less within-season variability in nutrient concentrations and greater fish biodiversity and abundance. Objective 3: Contribute to LTAR network science, data synthesis, and model development through data collection and development/assessment of predictive tools. Hypothesis 3.1: Aspirational management systems (ASP) will improve soil health indicators compared to business-as-usual (BAU), but the degree of improvement will depend on site-specific factors. Goal 3.2: Identify the best environmental predictors of fish community structure in agricultural headwater streams in the Eastern Corn Belt LTAR node. Goal 3.3: Collect and synthesize data for Ohio high priority, agricultural tile drained watersheds.

Approach
Improved drainage, including subsurface tile and channelized streams, is required for sustainable agricultural crop production on an estimated 200 million ha of cropland worldwide. Another 425 million ha could benefit from improved drainage. The Midwest U.S. produces roughly 65% of the Nation’s annual corn and soybean production, largely as a result of artificial drainage. However, improved drainage has been linked to downstream water quality issues that include harmful algal blooms (e.g., Lake Erie and Gulf of Mexico) and hypoxia (e.g., Gulf of Mexico). Future climate predictions for the Midwest U.S. indicate more intense fall and spring storms and increasing temperatures that will heighten the importance of efficient drainage systems that maintain or improve ecosystem function and are in balance with new and/or enhanced production management practices, referred to as conservation/aspirational practices. Voluntary, incentive, and regulatory efforts have been applied to address agricultural nutrient loss and ecosystem function; yet, the problems persist. A combination of plot, field, and stream-scale research will be used to: isolate and understand the governing processes that control hydrological, water quality, and ecological responses; assess existing and novel management and conservation practices for their ability to reduce nutrient loss, enhance stream habitat and increase aquatic biodiversity; and synthesize the findings into improved simulation algorithms/scenarios for existing models and/or the development of new predictive tools. Successful completion of the proposed research will provide producers; certified crop advisors; extension specialists; researchers; drainage industry; conservationists; local, state, and federal action agencies; Western Lake Erie Basin (WLEB) and other watershed stakeholders; and decision/policy makers a better understanding of the governing controls and processes of nutrient dynamics in tile drained landscapes; quantitative assessments to develop and inform design, selection, and implementation of conservation practices; and enhance or improve the development and testing of prediction technologies.

Progress Report
In support of Objective 1: Goal 1.1. Corn and soybean production in the humid, poorly drained upper Midwest U.S. requires water management for sustainable production. Understanding the water balance and partitioning between pools is critical for understanding and improving crop production, reducing offsite nutrient transport, and enhancing prediction technologies. Soil moisture, soil temperature, and water table stage sensors have been installed in select fields to facilitate water balance assessment and data collection is ongoing. Additionally, eddy covariance instruments which facilitate evaporation and transpiration measurements have been installed in one paired set of fields. A cooperative agreement was established with university partners to facilitate data collection and processing from the eddy covariance systems. ARS and university partners are using the data to better predict seasonal water availability and crop stress. Hypothesis 1.2. Phosphorus losses from agriculture are a major cause of surface water quality degradation such as harmful algal blooms, but it remains unclear how much phosphorus is lost from recently applied fertilizers (new P) compared to old phosphorus stored in soils (old P). Research continues on developing a novel statistical model (generalized additive model) for assessing new and old phosphorus losses that would enable improved assessments of the importance of phosphorus fertilizer applications on edge-of-field phosphorus losses. Work was done in collaboration with an ARS scientist in Stoneville, Mississippi. Hypothesis 1.3. Water movement through soils is often dominated by flow through large pores (e.g. earthworm burrows) and soil cracks, particularly in high clay soils. This preferential flow can transport relatively high concentrations of nutrients as well as pesticides directly into subsurface tile drains, thereby negatively impacting water quality. A field experiment utilizing a bromide tracer to assess preferential flow paths was completed in spring of 2025. Analysis of bromide concentrations in water samples collected during the experiment is ongoing. In support of Objective 2: Hypothesis 2.1. Progress continues on assessing the soil and water quality impacts of crop production and conservation practices. Surface and subsurface water quantity and quality data collection as well as site specific producer management data from approximately 24 fields (12 pair) and 20 plots is progressing. Specific practices being examined include fertilizer timing, fertilizer placement, the use of forages and cover crops in the rotation, growing three crops in two years compared to one crop annually, and drainage system design. Baseline data is being collected on eight plots for a future assessment of fertilizer source. The results are important for informing producers about optimal practices to keep nutrients in the field where they are applied as well as the tradeoffs associated between nitrogen and phosphorus. Hypothesis 2.2. Drainage ditch design, specifically the two-stage ditch design, has been offered and supported as a method to address nutrient transport in sensitive watersheds. Assessment of the two-stage ditch design to address nutrient transport has been completed and shared with stakeholders. The findings indicate that the two-stage design reduces sediment transport and nutrients attached to the sediments, providing producers and conservationists a method to reduce offsite nutrient transport. Hypothesis 2.3. Collection of soil quality and soil hydrology data continued across the edge-of-field water quality sites. A closely related collaboration with university researchers continued, focused on assessing soil health and water quality outcomes from long-term soil health fields. Measurements of both soil health and water quality at these locations continued. Hypothesis 2.4. Fishes and instream habitat (hydrologic and benthological variables) were sampled in the fall 2024 and spring of 2025. This data will serve as baseline data to evaluate the effects of a novel conservation practice. Hypothesis 2.5. Weekly grab samples of water for measurements of ammonia, nitrate, nitrite, total nitrogen, dissolved reactive phosphorus, total phosphorus, and dissolved organic carbon concentrations were collected from September to October 2024 and then ongoing since April 1, 2025. Hydrologic variables, benthological variables, and fishes were collected in the fall of 2024 and spring of 2025 and dissolved oxygen data loggers were deployed in spring 2025. These data will help evaluate the effects of a novel conservation practice. Hypothesis 2.6. Retrieved and initiated summaries and analysis of national database on physical, chemical, and biological characteristics of agricultural streams and rivers in the United States. This newly retrieved data will complement field data already collected as part of this project evaluating the effect of novel conservation practices. In support of Objective 3: Hypothesis 3.1. The Long-Term Agroecosystem Research Network (LTAR) is a national research effort led by USDA-ARS focused on finding solutions that maintain or increase agricultural productivity, environmental quality, and rural prosperity. The network encompasses 19 research locations including both croplands and rangelands. The Soil Drainage Research Unit leads the Eastern Corn Belt location, in collaboration with university researchers and ARS personnel from the National Soil Erosion Research Laboratory. Soil health across the cropland locations is being analyzed to assess how management influences soil health in different regions; datasets from LTAR cropland common experiment sites continued to be assembled and nine of eleven datasets were collected by spring 2025. In a parallel effort focused solely on Ohio research sites, a statistical analysis of the effects of aspirational management practices on soil health indicators was completed. Goal 3.2 Modeling of the relationships of multi-species fish response variables with hydrologic variables, water temperature, precipitation, and air temperature, has been completed. This research will provide information that will help farmers and stakeholders determine which conservation practices are most effective. Goal 3.3. Continued contributing to LTAR algal limitation project with the monthly collection of water samples from two Upper Big Walnut Creek, Ohio sites in support of this cross-location project beginning this June. Additionally, continuing to collect water samples for measurements of ammonia, nitrate, nitrite, total nitrogen, dissolved reactive phosphorus, total phosphorus, dissolved organic carbon concentrations, and hydrologic variables. This research will help farmers and stakeholders determine target nutrient levels to reduce eutrophication within agricultural streams and rivers. Plot and field scale crop production, management, and water quality data for the Eastern Corn Belt, LTAR common experiment continues to be collected. An overview manuscript and dataset were published within the special collection on LTAR common experiments. Data has also been collected and shared that supports cross location projects being led from the drainage working group within the LTAR network. Three years of seasonal data to support the dominant flow pathways project has been collected and shared with the project lead. The dominant flow pathways project seeks to understand and partition flow through preferential (fast flow) and soil matrix (slow flow) pathways. The improved understanding will inform development of simulation tools as well as management practices to reduce nutrient transport in each pathway, thus keeping the nutrients on the ground where they are placed. Likewise, hydrology and water quality data has been collected and shared with the modeling/simulation team to improve those components. Improved simulation routines provide confidence to policy makers and action agencies using the models.

Accomplishments
1. Management practices to minimize phosphorus loss in the Western Lake Erie Basin watershed. Nitrogen and phosphorus are one of the largest annual expenditures that Midwest corn and soybean producers face. Additionally, a binational agreement between the U.S. and Canada established a 40% reduction goal for phosphorus loading to address nutrient pollution concerns in the Western Lake Erie Basin. In an effort to minimize the amount of agricultural phosphorus lost, ARS researchers in collaboration with university partners determined that fields exceeding recommended soil phosphorus levels disproportionately contributed to losses; that is, elevated fields account for approximately 20% of the annual phosphorus runoff into lakes and streams. However, the findings further noted that there is excess phosphorus in all fields, regardless of soil test phosphorus concentrations. Implementing crop production management practices that require less phosphorus or help to retain phosphorus where it is applied will reduce annual input costs, potentially increase profitability, and improve the health of the Western Lake Erie Basin. These findings will be beneficial to producers and extension specialists that seek practices that require less nutrients while sustaining agricultural production.

2. Establishment of long-term agroecosystem research sites in the Eastern Corn Belt supports assessment of sustainable crop production. The Long-Term Agroecosystem Research (LTAR) network was established to inform national scale agricultural questions related to productivity, profitability, and environmental concerns. The Eastern Corn Belt node is representative of row crop agricultural production systems in the poorly drained humid regions of the U.S. Midwest spanning the Ohio River Valley and the Great Lakes Region of Ohio and Indiana. The Eastern Corn Belt is responsible for 10 to 15% of the annual national corn and soybean production. Water management continues to be a primary focus for balancing crop production needs and environmental goals in the Eastern Corn Belt. Specifically, the Eastern Corn Belt node is investigating the practice of growing three crops in two years compared to one crop annually. Demonstrating crop and water management practices that facilitate a system of producing three crops in two years compared to a single annual crop potentially enhances soil health, improves nutrient efficiency, and provides an additional revenue stream for the farmer.

3. Lower intensity weed control improved yield but increase weed populations during the organic transition period. Organic agriculture requires a three-year transition from conventional production prior to full organic production, but information is limited regarding the best management practices for producing grain crops during the transition period. In collaboration with university researchers, an ARS scientist assessed the effects of weed control method and fertility source on grain yields, weed populations, and soil health during the organic transition period. Less frequent tillage for weed control increased grain yield by 7% over a three-year crop rotation of corn-soybean-small grain. Less frequent tillage also tended to increase weed populations, a trend that should be closely monitored after the organic transition period is completed. Utilizing an organic fertilizer with a higher carbon content did not impact weed populations or grain yields, and neither tillage frequency nor fertility source influenced soil health within three years. This study demonstrates the potential benefits of lower tillage intensity and shows that multiple fertility sources can provide similar outcomes. These insights can be used by producers undertaking organic production to improve agronomic outcomes during the organic transition period.

4. Quantified loss of large instream wood as result of stream channelization and documented that adding small instream wood does not affect fishes and water flow. The straightening and enlarging of stream channels for agriculture removes instream wood (logs, branches, etc.) that serves as cover for fishes in agricultural headwater streams. It is also a common practice to add instream wood after stream channelization. Quantitative information on the reductions of instream wood in agricultural headwater streams as a result of channelization and the impacts of adding small instream wood are lacking. An ARS scientist in Columbus, Ohio, and a university student assessed: 1) the assortment and amount of large instream wood in channelized and unchannelized agricultural headwater streams and 2) the influence of adding small instream wood on fishes, water depth, and water flow in pools within channelized agricultural headwater streams in central Ohio. The results quantified that stream channelization reduces the assortment and amounts of large instream wood in channelized streams to less than half of that observed in unchannelized streams. The results also indicated that adding small instream wood to pools within channelized agricultural headwater streams did not influence multi-species fish response variables, water depth, and water flow. These results provide information that will help farmers and agricultural stakeholders improve their recreational fishing opportunities by developing stream management plans that minimize instream wood removal and when needed adding instream wood as fish cover to their streams.

5. Documented long-term trends in herbicide concentrations in a large agricultural watershed. There is a lack of information on long-term trends in herbicide concentrations in agricultural streams and rivers, especially those that serve as drinking water sources for Midwestern cities. ARS scientists from West Lafayette, Indiana, and Columbus, Ohio, measured atrazine, metolachlor, and simazine concentrations for ten years in the large agricultural stream that is the drinking water source for Fort Wayne, Indiana. Atrazine and metolachlor concentrations did not exhibit annual or temporal trends. Simazine concentrations decreased to very low concentrations likely due to declining usage. These results provide valuable information for farmers and agricultural stakeholders that will help them develop watershed management plans to protect Midwestern drinking water sources.

U.S. DEPARTMENT OF AGRICULTURE

Soil Drainage Research: Columbus, OH