Location: Agroecosystems Management Research2021 Annual Report
Objective 1: Design, place, and assess conservation practices for improved water quality and environmental benefits. Sub-objectives: 1.1: Develop and evaluate practices for reducing surface water contaminants in artificially drained landscapes; 1.2: Evaluate perennial systems to reduce runoff, sediment, and phosphorus (P) losses; and 1.3: Increase the efficacy of the Agricultural Conservation Planning Framework (ACPF) toolbox as an approach to conservation planning for improved water quality within Midwest watersheds. Objective 2: As part of the Long-Term Agroecosystem Research (LTAR) network, and in concert with similar long-term, land-based research infrastructure in the Upper Mississippi River Basin Region, use the Upper Mississippi River Basin Experimental Watersheds 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 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 Greenhouse gas Reduction through Agricultural Carbon Enhancement network (GRACEnet) and/or Livestock GRACEnet projects. Objective 3: Quantify the effects of landscape attributes and management practices on the fate, transformation, and transport of antibiotics, antibiotic-resistant bacteria and other emerging contaminants in surface runoff, drainage water, and streams in agricultural watersheds.
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 saturated buffers, bioreactors, fall planted cover crops, and protected surface inlets to subsurface drainage. Bioreactor denitrification capacities will be assessed with microbiological assessments, and modeling studies will be conducted to investigate management practices that may reduce N loss to subsurface drainage in the context of historical climate data. Research will be conducted to improve agricultural conservation planning across the Midwest. Conservation needs also exist in perennial agricultural systems and investigations into the water use, runoff, erosion, and P losses will be carried out. Under the second objective, field and watershed studies will be conducted as part of the Long-Term Agroecosystem Research (LTAR) network that will support research to sustain or enhance agricultural production and environmental quality in the Upper Mississippi River Basin region. The third objective will employ a mix of laboratory, field, and modeling studies to evaluate environmental transport of pathogens and veterinary pharmaceuticals under different landscape attributes and management practices. 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.
Objective 1.1. Experiments evaluating cover crops (rye or camelina) on Nitrogen (N) loss in tile drains from corn-soybean cropping systems was completed for 2020 and is in progress for 2021. The relay cropping of camelina appears to offer approximately 0.5 Mg of oilseed harvest on average, but tile drainage analysis continues to suggest the practice is less effective than rye for decreasing N loss in tile drains. This research is part of the Cropland Common Experiment for the Long-Term Agroecosystem Research (LTAR). Efforts to complete development of a database for the current and historical data for this site were continued. Data has been provided to stakeholders assessing impacts of climate change on N loss and crop yield in corn-soybean rotations with winter cover crops, suggesting that implementing winter rye cover crop in a corn-soybean rotation effectively addresses the goal of future drainage N load reduction under climate change in a northern Mississippi River Basin agricultural system without affecting cash crop production. As part of the effort to evaluate effects of winter rye cover crop in corn/soybean systems on N loss to drainage, data describing an experiment with rye fertilized at several N rates and planted using several methods to determine N content and biomass of the rye has been provided to stakeholders. This information will help determine if fertilized and harvested rye could provide a revenue incentive for producers to plant winter rye cover crops while still reducing N loss to drainage as suggested by previous research. Objective 1.2. Data collection and analysis continues for the rainfall simulator comparison of long-term rotations with conventional short rotations. Data showing that organic mixed grass and legume forage used more soil water in the spring and fall than conventional corn and soybean has been provided to stakeholders in addition to data examining cover crop growth and evapotranspiration in an organic system. Objective 1.3. Efforts to extend the Agricultural Conservation Planning Framework (ACPF) have been progressed through an inter-agency agreement with NRCS (Natural Resources Conservation Service). The ACPF uses geographic information systems (GIS) software to analyze high resolution data on soils, land use and terrain, to identify locations suited to a variety of conservation practices at watershed scale. Results are presented as a menu of conservation practice placements that can help engage landowners to participate in watershed improvement efforts. While use of the ACPF has largely been in the Midwest, an inter-agency agreement has funded efforts to develop ACPF results for watersheds in eleven states, four of those outside the Midwest; the results were provided to NRCS for review by state and field staff. The capacity of NRCS staff to engage in the project was limited due to the COVID pandemic, but feedback from enough watersheds was obtained to identify several ways to improve the ACPF GIS toolbox, which have been written up as a discussion document to help inform future development of the ACPF. In addition, routines that help to propose and test conservation planning scenarios in terms of financial costs and estimated nutrient-loss reductions (i.e., water quality improvements) are being developed in collaboration with Iowa State University. The agreement with NRCS has also funded ACPF training efforts, led by the University of Wisconsin, and an assessment of NRCS readiness to incorporate ACPF (as a new GIS-based technology) into their planning processes, particularly as a part of NRCS watershed planning programs. Objective 2. Water flow and quality data, and meteorological data were obtained from the experimental watersheds, and laboratory measurements were completed for the 2020 sampling season. The sampling and analysis for the 2021 year are currently being conducted. Data from these watersheds were contributed to the Sustaining the Earth's Watersheds, Agricultural Research Data System (STEWARDS) database supporting the CEAP (Conservation Effects Assessment Project) and the LTAR network. Objective 3. Data was provided to the scientific community that focused on antibiotics, antibiotic-resistant bacteria and other emerging contaminants, including: 1) degradation of tetracycline, sulfamethazine, and tylosin in soil collected from prairie strips and row crops in central Iowa, and 2) seasonal variations in export of antibiotic resistance genes and bacteria in runoff from an agricultural watershed in Iowa.
1. Winter rye cover crop (CC) reduces nitrogen (N) loss to drainage under climate change. Hypoxia or dead zones in coastal oceans have been expanding since the 1960s and are forecast to increase with climate change if reduction strategies are not implemented. Implementing a winter rye CC into agricultural systems is one of the more promising strategies to reduce N loads to subsurface drainage without reducing cash crop production, but its effectiveness in the Mississippi River Basin (MRB) under expected climate change is uncertain. ARS scientists in Ames, Iowa, and El Reno, Oklahoma, used the field-tested Root Zone Water Quality Model (RZWQM) to produce simulation results that suggest implementing winter rye CC in a typical Upper Midwest cropping rotation effectively addresses current goals of future N load reduction to drainage under projected climate change in a northern MRB agricultural system without affecting cash crop production. This research will help decision makers and agricultural scientists more clearly understand nitrate transport reductions to subsurface drainage from conservation practices such as winter rye CC in corn-soybean rotations under future climate conditions, which will help in the design of effective management systems to reduce hypoxia in the Gulf of Mexico and reduce N export to the MRB.
2. Riparian settings compared among landscape regions. Riparian buffers can improve water quality, but regional evaluations of riparian buffering opportunities are rare. ARS scientists in Ames, Iowa, along with cooperators, utilized the Agricultural Conservation Planning Framework (ACPF) to evaluate riparian settings for 32 watersheds representing three landscape regions of Iowa. The results showed where buffers of different designs could be placed across each watershed’s stream network to filter runoff, treat nitrate in shallow groundwater, and/or protect streambanks. Riparian zones found below small runoff-contributing areas, where narrow (20-33 ft wide) buffers are sufficient to filter runoff and protect streambank, were common and occupied more than 50% of streambank lengths in northern and southeast Iowa landscapes. However, in east-central Iowa, headwater streams showed broad, low-lying riparian zones, where wide buffers (>75 ft) could help reduce nitrate transport in shallow groundwater, while providing a land base for perennial biomass crops. The ACPF riparian analysis helped identify regional differences in riparian management opportunities; this approach could help action agencies (NRCS and state conservation agencies) develop regional strategies to prioritize conservation efforts.
3. Slope position on the landscape affects soil water movement to and from drainage lines. ARS scientists in Ames, Iowa, showed that the subsurface redistribution of water kept the water table depth shallow at the downslope positions on the landscape and deeper at the upper landscape. The shallow water table depth allowed prolonged tile outflow at the lower positions as water moved from upslope to downslope. The prolonged tile outflow at a downslope tile showed that water flow was lateral as well as vertical, which allowed water to connect between plots. Barriers (6' deep) between tiles (4' deep) did not completely prevent the subsurface lateral water flow, but the barriers slowed the lateral water flow. Upslope positions often had water table depths below the barriers when the water table at downslope positions remained above the tile. This information is important for scientists who study tile outflow in field plots to show that experimental tile plots can be difficult to completely isolated from each other.
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Neher, T.P., Lanying, M., Moorman, T.B., Howe, A.C., Soupir, M.L. 2020. Seasonal variations in export of antibiotic resistance genes and bacteria in runoff from an agricultural watershed in Iowa. Science of the Total Environment. 738. Article 140224. https://doi.org/10.1016/j.scitotenv.2020.140224.
Logsdon, S.D., Cambardella, C. 2021. Soil water flow due to surface topography in research drainage plots. Agrosystems, Geosciences & Environment. 3(1). Article e20128. https://doi.org/10.1002/agg2.20128.
Malone, R.W., Garbrecht, J.D., Busteed, P.R., Hatfield, J.L., Todey, D.P., Gerlitz, J., Fang, Q., Sima, M., Radke, A.G., Ma, L., Qi, Z., Wu, H., Jaynes, D.B., Kaspar, T.C. 2020. Drainage N loads under climate change with winter rye cover crop in a northern Mississippi River Basin corn-soybean rotation. Sustainability. 12(18). Article 7630. https://doi.org/10.3390/su12187630.
Schaefer, A., Werning, K., Hoover, N., Tschirner, U., Feyereisen, G.W., Moorman, T.B., Howe, A.C., Soupir, M.L. 2021. Impact of flow on woodchip properties and subsidence in denitrifying bioreactors. Agrosystems, Geosciences & Environment. 4(1). Article e20149. https://doi.org/10.1002/agg2.20149.
Nunes, M.R., Karlen, D.L., Veum, K.S., Moorman, T.B. 2020. A SMAF assessment of U.S. tillage and crop management strategies. Environmental and Sustainability Indicators. 8. Article 100072. https://doi.org/10.1016/j.indic.2020.100072.
Bhar, A., Feddersen, B., Malone, R.W., Kumar, R. 2021. Agriculture model comparison framework and MyGeoHub hosting: Case of soil nitrogen. Inventions. 6(2). Article 25. https://doi.org/10.3390/inventions6020025.
Tomer, M.D., Porter, S.A., James, D.E., Van Horn, J.D., Niemi, J. 2021. Comparing riparian buffer design classification data among watersheds representing Iowa landscapes. Agrosystems, Geosciences & Environment. 4(2). Article e20159. https://doi.org/10.1002/agg2.20159.