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Research Project: Conservation Practice Impacts on Water Quality at Field and Watershed Scales

Location: National Soil Erosion Research Laboratory

2022 Annual Report

Objectives
Objective 1. Advance the knowledge and improve mathematical representation of processes affecting sediment, nutrient, and pesticide losses in surface and subsurface waters. Subobjective 1.1. Quantify surface and subsurface hydrologic processes affecting transport and transient storage of sediments and chemicals. Subobjective 1.2. Evaluate and improve scientific understanding of nutrient dynamics from the rhizosphere, upland areas, riparian zones, and drainage waterways. Objective 2. Develop methods to reduce pollutant losses from agricultural fields and watersheds, thus protecting off-site water quality. Subobjective 2.1. Develop removal strategies for dissolved phosphorus in drainage water. Subobjective 2.2. Test the impact of established and new conservation practices at the field and watershed scale. Subobjective 2.3. Determine optimal BMPs for control of runoff, sediment, and chemical losses from agricultural fields and watersheds, under existing and future climates. Objective 3. Improve erosion and water quality modeling systems for better assessment and management of agricultural and forested lands. Subobjective 3.1. Develop WEPP model code, including testing and scientific improvement. Subobjective 3.2. Improve ARS soil erosion and water quality model software architectures, interfaces, and databases for end-user model delivery. Objective 4. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the Midwest region, use the Eastern Corn Belt LTAR site to improve the observational capabilities and data accessibility of the LTAR network and support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Midwest region. Research and data collection are planned and implemented based on the LTAR site application and in accordance with the responsibilities outlined in the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects. Subobjective 4.1. Quantify the relationship between soil quality and water quality under different cropping and management scenarios at the CEAP and Eastern Corn Belt LTAR sites. Subobjective 4.2. Develop techniques that enhance field-to-watershed scale parameterization for improved hydrologic model predictions at the CEAP and Eastern Corn Belt LTAR sites. Subobjective 4.3. Provide data management and services for CEAP and LTAR research sites.

Approach
Lab experiments will be used to study topographic driven surface hydraulic processes and soil hydraulic gradient driven subsurface flow effects on sediment and chemical loading and transient storage. Landscape attributes will be used to confirm the lab findings on conditions for sediment and chemical transport processes and processes such as deposition and hyporheic exchange. Field rainfall simulation experiments will be conducted using pan lysimeters to collect leachate to assess the effect of fertilizer placement on phosphorus leaching to subsurface tile drains. Stable water isotopes will be measured at the outlet of a headwater watershed during storm events to identify potential flow pathways and infer potential nutrient sources. We will use lab prototypes to assess the efficiency of steel slag in three potential field-scale phosphorus removal structure configurations, i.e., blind inlet, cartridge, and in-ditch slag dam for testing, and information obtained will be used to design field-scale installations for testing in the St. Joseph River Watershed (SJRW). We will subject steel slag materials to anaerobic conditions, and determine the effects on P solubility, and also explore the feasibility of regenerating materials for P removal structures. Field- and watershed-scale studies will be conducted to assess the impact of conservation practices on water quality, and field-scale studies will be used to assess the impact of drainage design and drainage water management on water quality. The Water Erosion Prediction Project (WEPP), Agricultural Policy Extender (APEX), and Soil and Water Assessment Tool (SWAT) models will be applied to monitored fields and small catchments in the SJRW in northeastern Indiana. Data from General Circulation Models (GCM) will be downscaled to develop modified climate inputs which will allow examination of the impacts of projected future climate on flow and pollutant losses. WEPP development efforts will occur in: Atmospheric CO2 impacts on plant growth; Model response to subsurface tile drainage; Water quality components to simulate nutrient and pesticide pollutant losses. Model development and testing efforts will include maintenance of the WEPP model scientific code, development of user interfaces, model databases, and user support. The WEPP module in the NRCS Cloud Services Innovation Platform (CSIP) software architecture will be made available as an option in the NRCS Integrated Erosion Tool (IET). Additionally, a separate WEPP web-based interface is being developed that allows WEPP to be run using standard NRCS databases. Data will be collected from the new Eastern Corn Belt LTAR sites once they are identified. Real-time weather information, field-measured profile soil moisture data and remotely sensed surface soil moisture content from agricultural fields will be used to improve prediction of surface runoff and tile flow and better understand runoff generation mechanisms. Topographic attributes, soil profile characteristics, and land management will be used to quantify potential for runoff and tile flow (i.e., profile drainage).

Progress Report
This is the final report for this project which terminated in March 2022. See the report for the replacement project, 5020-12130-004-000D, “Assessment of Sediment and Chemical Transport Processes for Developing and Improving Agricultural Conservation Practices” for additional information. Over the entire length of this project, substantial progress and achievements have been made related to all four of the objectives. Related to Objective 1, new knowledge and improved mathematical representation of hydrologic, physical, and chemical processes affecting sediment, nutrient, and pesticide losses in surface and subsurface waters, nutrient loss primarily occurs during large storm events, with the majority of nutrient export occurring via the subsurface tile drainage network, if present. Both in-field and in-stream processes affect nutrient concentrations and loads, with findings highlighting the need to implement conservation practices that consider in-field nutrient and water management as well as in-stream processes. Phosphorus losses to tile drains immediately after fertilizer application were largely a function of fertilizer placement and the effect of tillage on preferential flow pathways through the soil. Results showed the utility of using isotopic tracers for improving interpretation of water quality data and the challenge of mitigating phosphorus loss in tile-drained landscapes. A new and novel slow-release N fertilizer was tested in various flow-through soil incubation experiments for the purpose of quantifying N-release kinetics and comparing different variations of the same type of fertilizer. High frequency measurements of discharge (10 min), nutrient concentration (daily; 3 hours during events), electrical conductivity, and stable water isotopes were collected for a fourth year on the Matson Ditch within the Upper Cedar Creek watershed in northeastern Indiana. These datasets are being used to understand the dominant components of stream discharge (e.g., new water versus old water) and to quantify how and when nutrients such as nitrogen and phosphorus are transported from upland fields to the stream. Datasets will continue to be analyzed throughout the next year, with findings used to inform water and nutrient management strategies in the replacement project. Related to Objective 2, develop methods to reduce pollutant losses from agricultural fields and watersheds, thus protecting off-site water quality, unit scientists have explored phosphorus removal materials and provided design information and software for construction of P-removal structures. We designed and then helped Levy Corporation construct a large underground tile drain P filter using 60 tons of slag, on a large swine farm near Holland, Michigan. Increased adoption of this practice, and training of people for providing the service, will decrease dissolved phosphorus loading to surface water bodies and improve water quality. We improved a blind inlet by construction with steel slag, a material that has a high affinity for dissolved P. Use of steel slag over the traditional limestone-gravel resulted in appreciable filtration of dissolved P, particulate P, nitrogen, glyphosate, and dicamba, over a three-year period. The project developed a feasible and economical procedure for regenerating phosphorus filter media, and the cost of P removal can be reduced to less than half compared to the cost of purchasing new filter media, which makes the conservation practice more affordable when conservationists are implementing P removal structures. Our P-Trap software allows for the lay conservationist to design a site-specific structure using any P filter media that they have available, and for achieving their desired goals. After input of site characteristics like expected water flow rates, filter media choice, and desired P removal goal and system lifetime, the P-Trap software provides exact design specifications for the user. Monitoring of the phosphorus (P) removal structure constructed one year earlier near Waterloo, Indiana, (steel shavings-gravel mixture) was continued with satisfactory results. The structure has handled flow rates > 100 gpm, thereby treating 100% of tile flow. Outflow water was additionally analyzed for biological toxicity analysis to ensure the safety of effluent; results clearly showed zero toxicity. The P removal structure constructed last September in Delaware County, Ohio (using activated aluminum) in cooperation with ARS-Columbus research scientists, was additionally tested beyond regular monitoring in an experiment. Briefly, tile inflow was spiked over a 2-week period into the inflow tile drain while outflow drainage samples were collected and analyzed for calculating P removal. New P sorption materials were evaluated via flow-through method. This included various “designer” biochar samples, activated alumina, and Magnesium (Mg)-carbonates. In addition, these, and other P sorption materials (PSMs) were tested via batch P removal experiments to compare to flow-through results. We have provided appreciable guidance and consultation to various state agencies, private industry, and non- profits with regard to dissemination, choice of PSMs, and design of new P removal structures throughout the U.S. At least one company has adopted our developed method of regenerating iron (Fe)-based PSMs in their P filters. Results of a multi-state study on gypsum + cover impact on soil properties were published, and indicated that as a soil amendment, flue gas desulphurization gypsum (a byproduct of coal-fired power plants) does not add trace metals of environmental concern to soils. The assessment of subsurface tile drainage system design and drainage water management is ongoing. A fourth year of high frequency discharge and nutrient concentration was collected from paired field sites to evaluate the impact of drainage water management practices. Preliminary data analysis suggest that field subsurface drainage layout impacts both surface runoff and tile discharge leaving the field. However, additional data collection is likely needed to evaluate the effectiveness of the practice due to several gaps in the dataset due to instrument error and power issues at the field site, with the data to be collected in the upcoming year in the replacement project. Related to Objective 3, to improve erosion and water quality modeling systems for better assessment and management of agricultural and forested lands, a web-based interface for NRCS soil erosion predictions with the WEPP model has been developed along with comprehensive databases for climate, cropping, management operations, and soils for hillslope profile simulations. A prototype NRCS watershed/field web interface is also in development, and work will continue on that in the new replacement project. Numerous development efforts in the WEPP science model have been completed, including updates to tile drainage, atmospheric carbon dioxide level effects on plant growth, and temporally-changing channel parameter updating in watershed simulations. The WEPP-WQ (WEPP-Water Quality) model for multiple overland flow elements (OFEs) has been completed and validated, as well as a watershed version allowing simulation of chemical loss and transport in channels and impoundments. Additional work to obtain and utilize more datasets for watershed validation will continue in the replacement project. An updated erosivity map for the United States for use with USLE (Universal Soil Loss Equation) technologies including RUSLE2 (Revised Universal Soil Loss Equation version 2) was developed and published. Updated weather station data from 1970 to 2013, along with improved gap-filling and spatial interpolation were used to create the new map, which show substantial changes in erosivity in most of the U.S. Related to Objective 4, changing rainfall patterns due to climate change is increasing nutrient losses from croplands. We evaluated rainfall patterns and their influence on water quantity and quality across the Maumee River Basin, the largest contributor of nutrient loads to Lake Erie, from 1975-2017. Heavy (daily rainfall between 1-3 inches) and very heavy (daily rainfall >3 inches) increased by 45% over the 40-year study period, with increases primarily occurring during the spring and summer. Rainfall patterns were strongly tied to nutrient loadings at both the field and watershed scales. Edge-of-field monitoring showed that 80% of annual nutrient loadings occurred during storm events during only a small fraction of the year (one week to two months). This indicates that innovative water and nutrient management practices (i.e. controlled drainage, cover crops, etc.) in the Maumee River Basin will be needed for agricultural production to sustainably adapt to climate change. A multi-location (n=22) project was initiated and completed assessing phosphorus budgets across the United States and Canada including many sites within the Conservation Effects Assessment Project (CEAP) and Long-Term Agroecosystem Research (LTAR) network. To date, an open-access dataset including phosphorus inputs, outputs, and budgets for 61 cropping systems has been published via the USDA Ag. Data Commons along with a peer-reviewed publication describing the dataset in the Journal of Environmental Quality. Additional work is ongoing examining the uncertainty in phosphorus fluxes and budgets to help identify areas where networks such as CEAP and LTAR can work to reduce uncertainty in phosphorus budgets through coordinated measurements and to better understand relationships between management practices and phosphorus losses.

Accomplishments
1. Developed the P-FLUX dataset critical to develop management practices to mitigate environmental impacts of agriculture. Phosphorus is a critical nutrient needed for crop growth, but once transported from agricultural fields can result in water quality impairment downstream. Led by ARS researchers in West Lafayette, Indiana, the P-FLUX dataset represents a collaboration between 47 scientists with data spanning 22 U.S. states and two Canadian provinces. The P-FLUX dataset was developed to summarize and compare phosphorus inputs, outputs, and budgets across diverse cropping systems in the U.S. and Canada. Data on phosphorus management practices and losses from 61 cropping systems including row crop, rangeland, forage, and bioenergy systems are contained within the dataset, which is publicly available for download through the USDA Ag Data Commons (https://data.nal.usda.gov/dataset/ltar-phosphorus-budget-summary-0). Datasets such as P-FLUX are critical for improving phosphorus use efficiency and developing management practices to mitigate environmental impacts of agricultural systems.

2. Developed steel slag phosphorus (P) filters which removed 77% P over a one-year period. Excess transport of dissolved P from soils to sensitive surface waters such as the Western Lake Erie Basin and Lake Macatawa has partly caused a negative ecological impact through the gradual increase of lake eutrophication. Phosphorus removal structures are landscape-scale filters that remove dissolved P before reaching surface waters through filtration by various media. Steel slag is a readily available and inexpensive industrial by-product that has been proven effective for removing P from surface water. ARS researchers in West Lafayette, Indiana, designed and constructed three P removal structures on a swine farm located in Holland, Michigan for treating tile drainage water that flows into Lake Macatawa. These units removed up to nearly 77% P over a one-year period. Evaluation of toxic metals polycyclic aromatic hydrocarbon compounds, and cyanide were all below drinking water standards, thus greatly improving the quality of water flowing into the Lake. Use of P-removal filters can greatly reduce off-site dissolved P losses, thus reducing potential levels of harmful algal blooms and lake eutrophication.

3. Identified techniques for evaluating phosphorus (P) filtration media in real life scenarios to ensure proper design to maximize P removal before it affects water quality. Phosphorus filter media are the heart of P removal structures employed for reducing the impact of agriculture on water quality. Differences in techniques for testing filter media regarding P removal can provide a range of results, which affects design of P removal structures and prediction of their performance. ARS researchers in West Lafayette, Indiana, conducted experiments for comparing traditional laboratory techniques to a system that employed a flowing solution which was more representative of a filter. The study showed that P removal measured with traditional techniques that utilize a long contact time and unrealistically high P concentrations in static batch systems are vastly different from a flowing solution technique. The differences highlight how traditional tests highly overestimate P removal in real field P removal structures. This information will allow conservation planners and engineers to properly design P removal structures for achieving specific water quality improvement goals.

U.S. DEPARTMENT OF AGRICULTURE

National Soil Erosion Research Laboratory: West Lafayette, IN