Location: Agroecosystems Management Research
2022 Annual Report
Objectives
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.
Approach
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.
Progress Report
This is the final report for project 5030-13000-011-000D (terminated in April 2022), which has been replaced by new Project 5030-13000-012-000D. For additional information, see the new project report.
Some of the overall impacts of the project were featured in the NP211 Annual Report summaries over the last five years. For years 2017-2019, the National Laboratory for Agriculture and Environment had five accomplishments highlighted as significant and high impact research
(https://www.ars.usda.gov/natural-resources-and-sustainable-agricultural-systems/water-availability-and-watershed-management/docs/annual-reports/). Titles and summary statements of these high impact accomplishments are: 1) Expanded utility of agricultural conservation planning software and database Agricultural Conservation Planning Framework, (ACPF); 2) Cover crops (CCs) reduce nitrogen (N) export to streams and rivers (HERMES model improvement); 3) Improving nitrate removal using saturated buffers with tile drainage; 4) Antibiotic resistance genes and antibiotics can be transported off agricultural fields in subsurface drainage water; and 5) Improving water quality with field-edge nitrate removal (Saturated riparian buffers, (SRBs), are a promising new development).
Objective 1: Nitrate loss from artificial subsurface drainage (tiles) underlying agricultural fields is a major source of reactive N (e.g., nitrate) in surface waters. Examples of conservation practices aimed at reducing nitrate load in farm field drainage include SRBs, woodchip bioreactors, and CC systems.
Results showed SRBs can remove 40-90% of nitrate leaving a farmer’s field via drains before it enters a stream or river. It was shown that nitrate removal within saturated buffers is primarily due to denitrification process (conversion of nitrate to non-reactive N gas) and that this conversion does not increase the production of nitrous oxide – a powerful greenhouse gas. Overall, total emissions of nitrous oxide from SRBs were less than those from fertilized fields, but no different from traditional riparian buffers. Thus, the establishment of SRBs has shown the potential to remove nitrates from the surface waters without additional emissions of nitrous oxide into the atmosphere. This research resulted in the development of a new USDA-National Resources Conservation Service (NRCS) conservation practice standard (#604) and installation of dozens of new SRBs across Midwest farms.
Woodchip bioreactors as a tool to remove nitrate from tile drainage are becoming a more important conservation practice as evidenced by the updated USDA-NRCS conservation practice standard in 2020 (#605). However, because of short hydraulic retention time, the nitrate removal potential of bioreactors is somewhat low. ARS scientists tested if electrical stimulation would improve the performance of woodchip bioreactors. This work showed while electrical stimulation could remove an additional 37-72% of annual nitrate loads with woodchip bioreactors, this additional removal was more costly than nitrate removal without electrical stimulation.
Field results continued to show fall planted rye CCs significantly reduce N loss to subsurface drainage. Related modeling studies with rye CCs resulted in: 1) harvesting fertilized winter rye CC in corn-soybean (C-S) rotations is a promising strategy to provide additional producer revenue and reduce N loss to drainage compared to business-as-usual practices; 2) implementing winter rye CCs in a typical Midwest C-S rotation effectively reduces N load to drainage under projected climate change without affecting cash crop production; and 3) in collaboration with German scientists (Christian Kersebaum and others at the Leibniz-Centre for Agricultural Landscape Research, June 1 - July 31, 2015) funded by an Organization for Economic Cooperation and Development Research Fellowship, the HERMES model was modified to simulate drainage and effects of rye CCs and was field tested with data from central Iowa.
Overall, new information obtained shows that saturated buffers, bioreactors, and winter rye CCs are effective practices to reduce N loss to drainage.
Perennial and organic systems in agriculture may act as conservation practices, but data on ground cover and water budgets and associated tools to obtain this data are needed. Key outcomes and findings include: plants can use more soil water than previously realized; organic rotations have more ground cover, use more water, and have less runoff at key times of the year than conventional systems; an effective procedure to determine evapotranspiration (how much water the various plants and cropping systems use at different times of the year) was developed; and an effective procedure to determine leaf area index (growth of various plants over the season) was developed, which is important in estimating ground cover and crop water use during growth. Overall, new information to improve our understanding of perennial and organic systems was obtained and new techniques were developed to gain insight into the water budgets and growth characteristics of these systems.
The ACPF was developed to provide watershed databases and software tools that can be used to present realistic options for placement of conservation practices that can improve water quality outcomes. The ACPF has contributed to at least 18 journal articles since 2017. Key results and outcomes of these studies include: 1) Riparian lengths suited to the saturated buffer practices in selected tile drained Iowa watersheds occupied 30-70% of streambanks in most watersheds studied and could treat tile drainage from 15-40% of the watershed areas; 2) ACPF helped identify regional differences in riparian management opportunities to remediate water quality; and 3) ACPF helped determine opportunities to place water detention practices for several Minnesota watersheds. The ACPF has been used in watershed planning by conservation districts, state agencies, environmental consulting firms, the U.S. Army Corps of Engineers, and several agricultural and environmental organizations. The overall impact of the ACPF is that an effective tool was developed that helps action agencies and conservation scientists to better understand and implement conservation practices.
Objective 2: Stream flow and water quality records were maintained for Iowa watersheds throughout the five-year project. Data from these watersheds were contributed to the Sustaining the Earth's Watersheds, Agricultural Research Data System (STEWARDS) supporting the Conservation Effects Assessment Project (CEAP) and the Long-Term Agroecosystem Research (LTAR) networks. These data were used in studies by ARS and university researchers.
The LTAR Common Experiment was established to inform improvement and adoption of sustainable intensification systems by comparing multiple outcomes in “aspirational” systems with ‘business as usual’ systems that represent typical management practices in the region. As part of the LTAR Common Experiment, the Upper Mississippi River Basin site in Ames, Iowa, established a replicated field experiment comparing an aspirational corn-camelina-soybean relay cropping system with a conventional C-S system for performance in terms of harvestable yield, N loss in drainage and nitrous oxide emissions from soil. Results showed that the relay system had lower corn and soybean yield and higher nitrous oxide emissions than the conventional system, indicating the need for careful evaluation and optimization of sustainable intensification systems to ensure environmental and production goals are met. An article reporting these findings was submitted to a journal.
Objective 3: Antibiotic resistance in animal agriculture potentially impacts human health, but little is known on their transport from tile drained fields to downstream environments. Studies conducted in an Iowa watershed with more than 800,000 swine show 1) higher levels of antibiotic resistance genes (ARGs) in tile drainage and surface water in spring and fall following swine manure application; and 2) the presence of veterinary antibiotics in these waters. Based on ARS research it was established that ARGs and antibiotics are transported off farmed fields treated with swine manure and are present in subsurface drained riverine environments.
Accomplishments
1. Winter rye and clover may have more utility as cover crops in the upper Midwest compared to turnips and hairy vetch. Over time, cover crops (CCs) may improve the soil quality, and hence the crop production. ARS researchers in Ames, Iowa, completed a study showing that some of the CC mixes contained plants that could survive the winter such as winter rye and red clover; however, turnips and hairy vetch often did not survive well in the upper Midwest winters and may not be suitable for this region. The CCs had no effect on the main crop yields during this three-year study. This information is important for scientists and crop advisors on the best use of CCs in the upper Midwest.
2. Organic agricultural systems may use more soil water than conventional systems. Long-term crop rotations in organic agricultural systems provide Nitrogen (N) additions through legumes and residual organic materials to improve soil properties and may use more water in the spring and fall resulting from the plant biodiversity compared to conventional corn-soybean (C-S) systems. ARS scientists in Ames, Iowa, completed a study showing that organic forage took up more water in the spring and fall than conventional C-S rotation. A four-year rotation (corn, soybean, oat with first-year alfalfa, second year alfalfa) was intermediate in water use. These results suggest having crops on the land for a longer portion of the season helped dry the soil during wet periods, which may reduce runoff and leaching which is information vitally important for organic farmers and their advisors.
3. Cover crops and no-till show mixed results on nitrogen losses. Croplands with corn and soybean in the central United States are highly productive, but they pose a risk to the environment when N is lost as nitrate in subsurface drainage or as nitrous oxide emissions. To meet increasing demand for environmentally sustainable farming, management practices must aim to reduce these impacts without sacrificing yield. ARS scientists in Ames, Iowa, assessed nitrate losses, nitrous oxide emissions, and crop production in systems using two conservation practices: planting CCs and using no-till management. No-till management did not affect either nitrate losses or nitrous oxide emissions. CCs reduced nitrate losses but not nitrous oxide emissions. Nitrous oxide emissions appear linked with fertilizer N applications and weather patterns rather than CCs or tillage. Overall, the mechanisms regulating nitrate loss and nitrous oxide emissions did not appear linked and neither practice consistently reduced both nitrate losses and nitrous oxide emissions, suggesting it may be necessary to combine multiple conservation practices to reduce N loss in corn and soybean systems. This study will help decision makers and agricultural scientists more clearly understand N dynamics in C-S rotations with CCs, which will help in the design of more effective management systems to reduce N export from agricultural fields and increase environmentally sustainable practices.
Review Publications
Logsdon, S.D., Cambardella, C.A., O'Brien, P.L. 2021. Multispecies cover crops in organic agricultural systems in the upper U.S. Midwest. Agrosystems, Geosciences & Environment. 4(4). Article e20221. https://doi.org/10.1002/agg2.20221.
De Jong Van Lier, Q., Logsdon, S.D., Pinheiro, E.A., Gubiani, P.I. 2022. Plant Available Water. In: Hallett, P., editor. Encyclopedia of Soils in the Environment. 2nd edition. New York, NY: Elsevier. https://doi.org/10.1016/B978-0-12-822974-3.00043-4.
O'Brien, P.L., Emmett, B.D., Malone, R.W., Nunes, M.R., Kovar, J.L., Kaspar, T.C., Moorman, T.B., Jaynes, D.B., Parkin, T.B. 2022. Nitrate losses and nitrous oxide emissions under contrasting tillage and cover crop management. Journal of Environmental Quality. 51:683-695. https://doi.org/10.1002/jeq2.20361.
Logsdon, S.D., Cambardella, C.C., Delate, K. 2021. Organic agriculture effect on water use, tile flow, and crop yield. Agrosystems, Geosciences & Environment. 4(3). Article e20200. https://doi.org/10.1002/agg2.20200.
