Location: Agroecosystems Management Research2017 Annual Report
Objective 1: Assess conservation practices and develop conservation planning tools that can improve agricultural water quality in the Midwest. Sub-objectives: 1) Develop and evaluate practices for reducing surface water contaminants in artificially drained landscapes; 2) Evaluate practices to reduce runoff and sediment losses from urban sites; and 3) Develop and evaluate tools to optimize placement of conservation practices within Midwest watersheds for improved environmental benefits. Objective 2: Determine the effects of climate, land use, and conservation practices on hydrology and water quality in agricultural watersheds. Sub-objectives: 1) Quantify hydrologic and water quality dynamics and their responses to changes in land use, conservation, and climatic conditions in Iowa watersheds; 2) Determine effects of landscape hydrology on soils and water quality in naturally and artificially drained landscapes; and 3) Map stream channel and bank movement in context with riparian land use and geomorphic setting to identify opportunities for restoring riparian ecosystems. Objective 3: Determine the fate and transport of pathogens and trace emergent compounds in agricultural soils and streams. Sub-objectives: 1) Determine transport pathways and environmental residence times of zoonotic pathogens associated with animal agriculture and the effects of management practices on those processes; 2) Determine transport pathways and environmental residence times of veterinary pharmaceuticals and the effects of management practices on those processes; 3) Determine if exposure to trace antibiotic residues in soil or stream sediment affects the persistence of antibiotic resistant bacteria and resistance genes; and 4) As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in Upper Mississippi River Basin region, use the UMRB LTAR to improve the observational capabilities and data accessibility of the LTAR network, to support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Upper Mississippi River Basin, as per the LTAR site responsibilities and other information outlined in the 2012 USDA Long- LTAR Network Request for Information (RFI) to which the location successfully responded, and 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.
This project will conduct research to investigate the effects of agricultural management practices at field and watershed scales, the dynamics of watershed hydrology, and fundamental processes relevant to contaminant behavior in watersheds. Under the first objective, field studies will evaluate practices that can reduce loss of nitrate-nitrogen from cropped fields. These practices include resaturated buffers and bioreactors, practices that intercept tile drainage, and two practices that can reduce N loss to tiles, namely side-dressing of anhydrous ammonia and fall-planted cover crops. Bioreactor denitrification capacities will be assessed with microbiological assessments, and modeling studies will be conducted to extend experimental results on conservation practices to other areas of the Midwest. Research will be conducted to develop and evaluate watershed analyses to place conservation practices for improved water quality outcomes and determine how those strategies can be regionalized across the Midwest. Conservation needs also exist in urban environments and an experiment to determine how compost amendments can reduce urban runoff will be carried out. The second objective will be conducted in three Iowa watersheds, where stream monitoring will provide databases for watershed modeling studies, and for testing hypotheses about impacts of changes in climate and land use on water quality and hydrology. This research will be supported by efforts to identify field-scale patterns of hydrology and water quality, and better understand how new mapping techniques using Light Detection and Ranging (LiDAR) data can assist in understanding field hydrology, river corridor management, and targeting of conservation practices. The third objective will employ a mix of laboratory and field studies to evaluate environmental transport and residence times of pathogens and veterinary pharmaceuticals in soils and streams, and determine if exposure to trace antibiotic residues in soil or stream sediment affect the persistence of antibiotic resistant bacteria and antibiotic resistance genes. A breadth of watershed monitoring, controlled experiments in field and laboratory, and modeling techniques will be employed in the research. Publications, tools for conservation planning, and databases available to other scientists will be produced. Results are intended to enable agriculture to better manage water resources for multiple needs, particularly in the Upper Mississippi River basin.
This is the final report for project 5030-13000-010-00D (terminated April 2017). Ongoing studies on conservation practice assessment, the Agricultural Conservation Planning Framework (ACPF) (Objective 1), and watershed assessment and water quality (Objective 2) are being continued under a new project 5030-13000-011-00D. The new project includes activities that are part of Long Term Agroecosystem Research (LTAR). Objective 1.1. Much of this project’s effort focused on development and evaluation of conservation practices in tile drainage systems. Saturated buffers, bioreactors, cover crops, and timing of N fertilizer applications were evaluated, and progress in modeling the performance of cover crops and bioreactors was achieved. Saturated buffers were shown cost effective in removing nitrate from tile drainage water before it enters surface waters. This conservation practice has been adopted by the Natural Resources Conservation Service (NRCS) through Conservation Practice 604, is now cost shared by USDA, and can be installed on existing riparian buffers. Denitrification dynamics were documented for a pilot scale bioreactor. There was substantial progress in describing denitrification rates as related to nitrate concentration, temperature, type of carbon substrate, and hydraulic residence times, providing information to ensure greater predictability in performance among bioreactor installations. As residence time in three bioreactors increased, nitrate removal efficiency increased from 8% to 55%. At nitrate concentrations of 30-50 ppm, woodchip microbial communities became saturated with respect to nitrate. Nitrate concentrations in field drains are often >25 ppm. Measurement of a gene responsible for a denitrification enzyme showed that low nitrate removal at low temperature reflects reduced activity rather than reduced denitrifier abundance. A simulation model successfully captured bioreactor nitrate removal. Results were used to study scalability of bioreactors, suggesting this practice could reduce nitrate loads at the watershed scale. Denitrification in a woodchip wall bioreactor was as effective in 2016 as when installed 17 years ago. This long-term data on a bioreactor’s useful lifetime is key to estimate its cost effectiveness. We have documented that anhydrous ammonia can be used as a side-dress nitrogen source. We also showed that applying anhydrous ammonia before corn planting or as side-dress optimized crop yield and reduced nitrate losses to drainage better than fall-applying nitrogen. We continued to show that fall-planted rye cover crops can reduce nitrate in subsurface drainage tiles. This has led to cover crops becoming integral to the Iowa Nutrient Reduction Strategy for reducing nitrate in surface waters, and adoption across the Midwest has grown. Simulation modeling also had a role in this research. The Root Zone Water Quality Model was modified to simulate nitrous oxide emission and the effects of winter rye cover crops on N loss to subsurface drainage. Winter rye cover crops could potentially reduce nitrate-N loss from Midwest tile drains to the Mississippi River by about 20%. Through modeling experience gained from agricultural systems model research, a collaboration between ARS researchers and university collaborators led to model parameterization guidelines that are being included in a national standard for simulation modeling. Objective 1.2. Conservation practices are also applied in urban environments and there is need to understand how turf-grass species and soil amendments can improve soil health and protect urban streams. Use of compost, native grass species, and phosphorus-sorbing amendments were evaluated in studies conducted in collaboration with urban conservationists. Landscapers and greenhouses have new information to improve turf growth and rooting, which can reduce runoff from recently developed sites. Objective 1.3. A new approach to optimize (or target) placement of conservation practices was provided. In collaboration with NRCS, the Agricultural Conservation Planning Framework (ACPF) was developed, progressing this research past our five-year goals. Spatial databases covering >6000 HUC12 watersheds and 1.6 million agricultural fields were built, which can be used with the ACPF toolbox within geographic information systems software to identify conservation practice placement opportunities in fields, at field edges, and in riparian zones. Nearly 200 individuals from local, state, and federal agencies, agricultural commodity and environmental organizations, and private consultants were trained to use the ACPF toolbox in training sessions. Data were downloaded for >1700 watersheds. The ACPF is being used in implementation of the Iowa Nutrient Reduction Strategy and watershed projects in six other states. Objective 2.1. Stream flow and water quality records were maintained for two Iowa watersheds throughout the five-year project. These data were used in modeling studies by ARS and university researchers. Three collaborative cross-watershed comparisons were conducted to better understand sediment and nutrient losses in context, with results highlighting the importance of seasonality of nutrient losses, and of post settlement erosional history impacts on current sediment loads. Long-term records of precipitation and crop yield climate were evaluated, revealing shifts toward more springtime precipitation and larger rainfall events. These trends increase the climatic risks to crop establishment and production, and increase the importance of conservation practices for reducing soil erosion. Objective 2.2. Work under this sub-objective comprised several studies that examined landscape and timing controls on soil properties, soil and phosphorus movement, and crop-water use. A long-term (11 year) field edge monitoring project showed that most runoff losses occurred from storms with less than 2.4 inches of rainfall. Careful timing of manure application to avoid applying before runoff-producing rainfall can help control runoff losses of phosphorus. Farmed glacial depressions occur across much of the upper Midwest. Soils at edges of these depressions can accumulate carbonates (lime), which may impact nutrient availability and movement. Information on how lime is distributed around glacial depressions was produced that could help understand spatial patterns in yield monitor data and be applied in precision agriculture. Research was also conducted that showed patterns of soil susceptibility compaction were related to moisture redistribution, and that a twisted shank chisel plow could reduce soil displacement, helping maintain productivity of upland soils. Objective 2.3. Stream movement and stream-bank sediment losses along South Fork Iowa River (SFIR) tributaries after major flooding in 2008 were determined. Three tributary streams were widened by 1.7 to 3.5 feet on average, meaning about 21 acres of land became part of these channels. For every yard of stream length 1.1 tons of riparian soil were lost. Below the confluence of two tributary streams, the SFIR was widened by 14.5 ft, representing 8.1 tons of sediment lost per yard of stream length. The 2008 floods substantially altered these channels, but less bank erosion occurred where riparian buffers were present, suggesting buffers may help maintain stream corridors even under extreme flooding. Objective 3.1. The transport and persistence of manure-borne pathogens, antibiotics and antibiotic resistance genes were investigated. Salmonella is a bacterial pathogen subject to transport off-site after manure application. Transport of Salmonella into subsurface drains beneath fields that received poultry manure prior to corn planting was tracked. Salmonella was detected in poultry manure and drainage water along with fecal indicator bacteria E. coli and Enterococcus. Salmonella was more persistent than E. coli or Enterococcus in soil and drainage water. Antibiotic-resistant Enterococcus was found in soil after swine manure application, but was rarely detected in drainage water. Marker genes for pathogenic E coli, Campylobacter, Staphylococcus were detected in SFIR stream water; concentrations were elevated in samples taken after manure application. Swine hepatitis E virus was also detected. The SFIR watershed has a high density of swine and manure is applied to land with tile drainage. Objective 3.2. This research examined movement of antibiotics in soils receiving swine manure from swine that received antibiotic-supplemented feed. Greater concentrations of tylosin were found in the surface than subsurface soil, but tylosin was found in drainage water. Using in-situ samplers we measured low concentrations of tylosin in stream water and stream sediments. Concentrations of tylosin in water are not typically associated with development of new resistance genes, but may provide pressure to retain such genes. Objective 3.3. Swine manure application to fields with subsurface drainage increased concentrations of tylosin-resistance genes in soils, which persisted for several months. In years of above average rainfall, greater quantities of resistance genes were transported in drainage water from soils receiving manure than soils without manure. There was no relationship between persistence of resistance genes and concentration of tylosin in soil. These field-scale results were comparable to research findings from the SFIR, where tylosin-resistance genes were present in 89% of the water samples. Greater abundance of resistance genes coincided with periods following manure application. The research shows bacteria in swine manure carry antibiotic resistance genes that persist in soil and are transported off-site, with potential to transfer those genes to pathogens of humans and animals.
1. Saturated buffers for nitrate removal from tile drainage. Streamside buffers are a proven practice for removing nitrate from both overland flow and shallow groundwater before it can enter surface waters. However, in landscapes with tile drainage, most of the subsurface flow leaving farmers’ fields is passed through the buffers in tiles leaving little opportunity for nitrate removal. ARS scientists in Ames, Iowa, and university cooperators showed that re-routing a fraction of field tile drainage through the riparian buffer as subsurface flow can remove hundreds of pounds of nitrate each year, keeping it out of surface waters. Saturated buffers have been adopted by USDA-Natural Resources Conservation Service (NRCS) as Conservation Management Practice #604 and are now eligible for Environmental Quality Incentives Program (EQIP) funding across the Midwest. Research shows that the practice potentially could be installed along thousands of miles of rivers in Iowa alone with the potential of removing millions of pounds of nitrate from our Nation’s surface waters.
2. Expanded utility of agricultural conservation planning software and database. The Agricultural Conservation Planning Framework (ACPF) has been developed by scientists in Ames, Iowa, to provide on-line data and software that assists USDA-Natural Resources Conservation Service (NRCS) and conservation partners in watershed planning efforts. The ACPF database was expanded to include more than 7,000 Midwest watersheds; data for about 1,600 watersheds was accessed by ACPF users. Nearly 200 individuals representing federal, state, and county agencies, universities, environmental and agricultural-commodity advocacies, and private engineering consultants have received training on use of the software in seven two-day training sessions. Among several improvements this year, a tool that identifies locations where riparian buffers can receive and treat artificial drainage water via subsurface discharge was developed. Statewide results were developed for Iowa and suggested about 14,000 miles of stream bank length may be suited to this inexpensive and passive treatment option for nitrate removal and water quality improvement. This information is of interest to agricultural, conservation, and watershed improvement advocates who recognize the importance of water to agriculture and society and the potential of new technologies in water management and planning. (#333982)
3. Enhancing an agricultural systems model to simulate subsurface drainage. Subsurface drainage under corn and soybean production in the U.S. Midwest contributes to nitrogen (N) export to the Mississippi River and hypoxia in the Gulf of Mexico. With projected increases in crop production and fertilizer N use, it is important to manage cropping systems to maximize yield while minimizing N export. Scientists from ARS laboratories in Ames, Iowa, and Fort Collins, Colorado, and cooperators in Müncheberg, Germany, modified an agricultural system model called HERMES to simulate drain flow. The modified HERMES model was then tested using four years of field data from central Iowa fields in corn-soybean with winter rye as a cover crop (CC) and without winter rye (NCC). The modified model accurately simulated N loss to subsurface drainage under both CC and NCC, and the simulations agree with field data that winter rye cover crop substantially reduced N loss to drainage. The use of this modified model will help improve agricultural management and reduce N transport to streams and rivers. (#326356)
4. Compost improves urban soil. Urban construction results in compacted soil that reduces water movement into soil, which increases runoff of water and nutrients. ARS researchers in Ames, Iowa, with co-workers showed that application of lawn-waste compost and prairie grasses on urban soil reduced soil compaction and loss of nutrients and sediment in runoff. Compost with or without prairie grasses is recommended to improve urban soil. (#324935)
5. Compost addition to existing lawns helps retain water and nutrients. Application of compost containing cattle manure and other organic wastes to a commercial urban lawn did not increase nutrient loss in runoff. There is concern that the surface application would result in higher nutrient loss in runoff. An ARS researcher in Ames, Iowa, showed that surface additions of compost with aeration decreased the compaction at the soil surface and visually improved the surface soil structure. There were no increases in nutrient loss in runoff for lawns with surface-applied compost. Surface additions of compost with modest application rates and aeration treatment can be recommended for existing urban lawns. (#337127)
6. Impact of extreme floods on stream banks quantified. Stream bank erosion is known to increase during extreme flood events but is difficult to quantify. An ARS scientist in Ames, Iowa, assessed bank erosion along the South Fork Iowa River (SFIR) tributaries caused by major flooding in 2008 by mapping channel movement using high-resolution imagery and elevation data. The 2008 floods widened three tributary streams by 1.7 to 3.5 feet on average, meaning about 21 acres of land became part of these channels, and 1.1 tons of riparian soil were lost for every yard of stream length. Along 6.1 miles below the confluence of two tributary streams, the SFIR was widened by 14.5 ft, representing 8.1 tons of sediment lost per yard of stream length. The 2008 floods substantially altered these channels, but less bank erosion occurred where riparian buffers were present. Evidence that buffers may help maintain stream corridors even under extreme flooding is of interest to the conservation community and those interested in reducing impacts of extreme events on streams and aquatic ecosystems.
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