Location: Agroecosystems Management Research2020 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 2019 and is in progress for 2020. The relay cropping of camelina appears to offer approximately 0.75 Mg of oilseed harvest, but is less effective than rye for decreasing N loss in tile drains. Data on soil health parameters have been collected and are awaiting analysis. 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. Significant progress was made to assess impacts of climate change on N loss and crop yield in corn-soybean rotations with winter cover crops. We obtained modeling data for Ames, Iowa, that suggests 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, we continued collecting data for an experiment with rye fertilized at several N rates and planted using several methods to determine N content and biomass of the rye. 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 previous research suggests. Objective 1.2. We continued evaluation of leaf area index and crop water use in research plots that compared conventional corn and soybean, and four-year organic rotation (corn, soybean, oat with first year alfalfa, second year alfalfa) and organic mixed forage. Another comparison was made for cover crops after oat or into corn or soybean all in an organic system. A manuscript is in preparation on 3.5 years of leaf area index and crop water use data in the first trial. The organic mixed forage used more water in spring and fall than the organic four-year rotation, which used more than the conventional two-year rotation. Another manuscript is in preparation on water flow patterns in the same study. As water table levels dropped below the tiles, slow drainage (vertical and lateral) continued. A small amount of lateral flow occurred between plots despite plastic barriers 1.83 m deep. This small lateral flow mainly influenced water balance, not nutrient flow. The blocking pattern in the field experiment accounted for the water balance variation apparent in the research plots. The photographic procedure was useful in the cover crop trial for distinguishing ground cover of different cover crops in mixtures. Sub-objective 1.3. There was significant progress in extending the Agricultural Conservation Planning Framework (ACPF). The ACPF provides watershed databases and software to identify locations where conservation practices can be placed to attenuate runoff and treat tile drainage water. An Interagency Agreement (IAA) with the Natural Resources Conservation Service (NRCS) is providing support for evaluation of ACPF results in watersheds in eleven states (WI, NE, MO, KS, IA, IL, IN, OK, AR, MS, and MD). Trials in OK, AR, MS, and MD will include ARS Conservation Effects Assessment Project (CEAP) watersheds. The project is facilitated through a sub-agreement with Iowa State University, through which funding is being shared with the University of Wisconsin - Madison, the University of Minnesota, and Purdue University. Training courses are being developed, and social research is being conducted that is aimed to assess readiness of NRCS to adopt new conservation planning technologies like the ACPF. An ACPF utility is being developed to enable nutrient reduction and economic effects of watershed scale conservation planning scenarios to be estimated and compared. A Special Section of the Journal of Soil and Water Conservation was published, providing a suite of seven new articles on the ACPF. One of these papers evaluated water storage opportunities in three adjacent watersheds. Water storage opportunities can be estimated at watershed scale, providing a reference storage capacity for each watershed that can be used to evaluate interim goals for implementation of new practices. Objective 2. Water flow and quality data, and meteorological data were obtained from the experimental watersheds, and laboratory measurements were completed for the 2019 sampling season. The sampling and analysis for the 2020 year are currently being conducted. In addition, a study documenting historical changes in the adoption of specific conservation practices in the South Fork of the Iowa River was published. Data from these watersheds were contributed to the Sustaining the Earth's Watersheds, Agricultural Research Data System (STEWARDS) database supporting the CEAP and the LTAR network. Data from the South Fork of the Iowa River and the LTAR common experiment were included in a publication comparing water budgets across 18 LTAR sites. Objective 3. Studies documenting the persistence of antibiotics, antibiotic-resistant bacteria and antibiotic resistance genes in corn-soybean cropping systems were completed and a draft publication has been prepared. The study examined how different swine manure application times (with different temperature and moisture conditions) affected persistence of these constituents. Application timing had either no effect or inconsistent effects on antibiotic resistant bacteria or antibiotic resistance genes. Resistance was increased after manure application and declined to baseline levels within four months. Sulfamethazine and tylosin were not persistent, but tetracyclines were persistent and were detected at elevated concentrations at all times in soils receiving manure every other year.
1. Plant growth (crops and weeds) may vary for organic versus conventional management. Evaluating crop rotations is important to understanding and optimizing agricultural systems. ARS researchers in Ames, Iowa, took overhead pictures throughout the year from organic forage, organic four-year rotation, and conventional corn-soybean rotation. They developed a procedure to determine leaf area index (growth of various plants over the season) on organic research plots. The technique developed works well for assessing plant growth of each plant type in a mix over the season. Separating weeds from crops enabled us to verify that in the wet year of 2018, weeds in organic soybean reduced soybean yield. This research is of interest to agronomists involved with plant competition and crop growth modeling research.
2. Organic long-term rotations use water for longer times of the year than do conventional management systems. Techniques are needed to assess site-specific plant water use. ARS researchers in Ames, Iowa, describe a procedure to determine evapotranspiration (how much water the various plants and cropping systems use at different times of the year) on organic versus conventional research plots. The techniques developed work well for assessing water use for each plant type in a mix over the season. The longer-term rotations do indeed use more water in the spring and fall than conventional corn and soybean cropping systems. Spring is a crucial time of the year when there may be excessive runoff losses of sediment and phosphorus and leaching loss of nitrate. Drying the soil through plant use of water could reduce runoff and drainage at this critical time of the year. This research used imagery that may be captured by small remotely-operated aerial vehicles and would be of interest to agronomists who are developing new technologies to determine evapotranspiration.
3. Plants utilize draining water and water in the subsoil. Understanding how much soil water is available for crop use is important for crop management. ARS researchers in Ames, Iowa, showed that plants start taking up water before the soil is drained to "field capacity" (i.e. even while the water is still draining). Plants can extend their root zone as surface soil dries out revealing they can use more soil water than previously realized. This information is important for crop water managers and their advisors.
4. Watershed analyses to assess flood mitigation planning goals and implementation strategies. Watershed planning goals may be aimed to reduce flooding using water detention practices that can also provide water quality benefits and/or create wetlands for wildlife habitat. To achieve interim (i.e., 10-year) planning goals, can new practices be placed at random in a watershed, or must larger sites with the greatest potential to intercept and store runoff be primarily targeted? Utilizing the Agricultural Conservation Planning Framework (ACPF), ARS scientists in Ames, Iowa, collaborated with the Minnesota Water Resources Research Center staff in Mankato, Minnesota, and assembled spatial data summarizing opportunities to place water detention practices for three Minnesota watersheds. Thirty randomly placed practices could achieve at least one 10-year planning goal in each watershed, showing recruitment strategies do not always need to target larger, priority sites to ensure success. In comparison to targeting of large water storage sites that are often challenging to implement, where open enrollment strategies can succeed in the interim, they may also demonstrate new practices to enhance social acceptance and enable ongoing conservation progress toward longer term goals. These results suggest an avenue for collaborative research among social and conservation scientists, and are of interest to conservation planners, planning agencies, watershed modelers, and policy analysts.
5. Estimating tile drained areas in Iowa watersheds that could be treated for nitrate removal using saturated riparian buffers. The saturated riparian buffer is a conservation practice that diverts agricultural tile drainage into riparian (streamside) soils, which can effectively remove nitrate from drainage water at little cost. Conservation planners want to understand the potential role for this practice to address nitrate losses from agricultural watersheds with tile drained cropland. Scientists with ARS in Ames, Iowa, applied the Agricultural Conservation Planning Framework (ACPF) in 32 Iowa watersheds to determine the extents of riparian zones suited for saturated buffers and the extents of tile drained lands found above those same riparian zones. Riparian lengths suited to the saturated buffer practice occupied 30-70% of streambanks in most watersheds and could treat tile drainage from 15-40% of the watershed areas. Therefore, saturated buffers have an important potential role for water quality improvement in many tile drained watersheds in Iowa, but to a lesser extent where large land areas drain to points of stream initiation where riparian practice options are limited. These results will be of interest to conservation planners seeking to identify viable options to reduce nitrate loads from Midwestern agricultural watersheds.
6. Conservation practice placement options developed from high resolution data may inform regional conservation planning strategies. Precision conservation planning tools use high-resolution data to identify conservation practice placement options for watershed improvement plans. Comparisons using results from these planning tools across multiple watersheds could help to identify regional conservation strategies, which might help conservation action agencies target conservation programs more effectively. For 32 Iowa watersheds, ARS scientists in Ames, Iowa, determined the Agricultural Conservation Planning Framework (ACPF) practice placements for controlled drainage, contour buffer strips, water and sediment control basins, and grassed waterway practices, then compared densities of practice placements (amount per unit area) among landscape regions. For grassed waterways, results showed how placements for grassed waterways in a watershed can be optimized at any selected density. For the other three practices, densities of suitable sites differed among regions; these differences were nuanced but suggest that development of regional conservation strategies may be feasible. This information progresses one of the earliest (1930s) USDA visions for use of regional landscape classifications and is of greatest interest to those involved with conservation of agricultural landscapes from planning, policy, and research perspectives.
7. Precision conservation planning maps help engage farmers in watershed improvement projects. The Agricultural Conservation Planning Framework (ACPF) provides a menu driven approach and maps depicting conservation practice options that are meant to assist planners to engage farmers in watershed-scale conservation planning. But can this strategy for producer engagement be successful? Rural sociologists at Purdue University, collaborating with ARS scientists in Ames, Iowa, interviewed 15 farmers across four Midwest watersheds, to ask about their perceptions of precision conservation after they received ACPF conservation planning options for fields they farm. Farmers were receptive towards ACPF-generated conservation options on their fields; the menu-driven approach provided farmers a sense of autonomy in planning, validated farmer’s natural resource concerns, and facilitated "watershed thinking" by farmers about where water flows from the edges of their fields. While the ACPF approach encouraged new conservation efforts, farmers also suggested ways to best communicate planning options presented in maps and emphasized that one-on-one engagement between planners and farmers is critical in motivating conservation. This research is of interest to state and federal agencies and environmental organizations who are involved with watershed improvement efforts, in which successful farmer engagement is key to success.
8. Conservation practices in South Fork Watershed. Conservation practices (CP) for erosion prevention include contour buffers, terraces, grassed waterways, water and sediment control basins (WASCOBs), and ponds. Quantifying the amount and placement of CP in watersheds is one step in assessment of their potential effectiveness at the watershed scale. ARS scientists in Ames, Iowa, used geographic information system (GIS) mapping techniques and aerial photography to document installation and removal of these CP from the 1930s to 2016. The study was performed in the South Fork of the Iowa River in central Iowa as part of the Conservation Effects Assessment Program (CEAP). Installation of CP increased in each decade from the 1930s to 2002 and then increased only slightly from 2,169 CP in 2002 to 2,282 in 2016. Grassed waterways were the most numerous and treated the largest area within the watershed The mean duration of 1,696 grassed waterways installed before 2007 was 31.6 ± 18.6 years, and the duration of WASCOBs averaged 24 years, suggesting that farmers are making long-term commitments to these CP. Land areas treated with CP tended to be greater in the sub-watersheds where estimated erosion was greater. Land areas treated by existing grassed waterways (21,609 ha) tended to match areas identified for that CP by the Agricultural Conservation Planning Framework (ACPF) tool. However, the ACPF identified additional areas where grassed waterways could be installed, primarily in the western part of the watershed. These techniques, which integrate CP amounts and placement in relation to potential placement of CP, provide a different perspective on conservation planning that may interest soil conservationists.
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