Location: Agroecosystems Management Research2015 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.
Objective 1.1. Significant progress has been made in several efforts to identify water quality benefits of conservation practices. First, we have continued monitoring the impacts of fall-planted cover crops on water quality and crop yield. Rye cover crops continue to reduce nitrate losses by ~50% while oat cover crops reduce nitrate losses by ~25%. Fall tillage appears to increase nitrate losses, even with fall-planted cover crops. Efforts to improve the rye cover crop model within the ARS model Root Zone Water Quality Model (RZWQM) using long-term field data were continued. Second, two existing bioreactors continue to show marked reduction in nitrate losses to tile drainage. The in-field bioreactor is now in its 15th year and still reducing nitrate as efficiently as when first installed. The second bioreactor has given us insight into the operation and potential of these systems for nitrate reduction over a range of flow rates and input nitrate concentrations. Third, we have installed two new saturated buffers and continue to monitor the performance of these and two existing saturated buffers. This practice appears to be working well at these sights and has received much attention from Natural Resource Conservation Service (NRCS) and Midwest states for inclusion into their non-point water quality programs. Finally, work to develop a greenhouse gas component of the RZWQM model for tile drainage conditions in Iowa was initiated. Objective 1.2. Field research was initiated to evaluate the effects of compost additions on soil properties in urban/suburban settings. Measurements indicated decreases in soil density and increased water contents occurred in areas treated with compost. However, infiltration capacities were not affected, suggesting that compost addition may not reduce urban runoff risks from high intensity rainfall events. Objective 1.3. A set of mapping tools that can be used within the geographic software environment to identify locations suited to different types of conservation practices has been developed into a toolset that is being released for public use. Stakeholders in Iowa, Minnesota, Indiana, and Illinois participating in watershed water quality improvement projects have helped to evaluate the utility of the Agricultural Conservation Planning Framework (ACPF) toolbox in a variety of landscape settings. Training sessions have been held in Iowa and Minnesota, which have provided feedback to help improve the utility and ease of use of the ACPF toolbox. The toolbox identifies options for installation of a variety of conservation practices to assist with local planning, and provides a research platform to explore how landform regions (such as NRCS's Major Land Resource Areas of MLRAs) are distinct in terms of the types and extents of practice placement opportunities, information that could be used in conservation program development by federal and state agencies. Objective 2.1. Under Objective 2, monitoring of stream discharge and nutrient/sediment losses from three watersheds (South Fork Iowa River, Walnut Creek (N), and Walnut Creek (S)) was continued through the year. This ongoing effort is providing some of the longest term continuous records on water quality of agricultural watersheds that are available in the Midwest. Objective 2.2. Field research was also conducted to evaluate changes in nutrient concentrations in shallow groundwater in tile drained landscapes. Tile drains carry this shallow groundwater to the streams we are monitoring, and this research will help us understand what controls some of the water quality changes we observe in streams. Temporal trends showed declines in nitrate concentrations in about half our monitoring wells during the growing season. Objective 2.3. Sediment losses observed in streams often originate from bank movement. We have developed maps to help us quantify volumes of bank sediments that have moved downstream during major flood events that have occurred in the South Fork Iowa River watershed. Objective 3. Research on the contributions of subsurface tile drainage to the transport of pathogenic bacteria (Salmonella) was completed at a site near Ames, Iowa. This research showed that Salmonella were transported in tile drainage water after poultry manure application. In related work, genes specific to Salmonella were detected in waters of the South Fork of the Iowa River, but at levels too low to quantify. This is evidence of some Salmonella transport as this watershed is dominated by subsurface drainage. A four-year study of the transport of antibiotic-resistance genes in subsurface drainage was completed in north-east Iowa. In years with average or greater precipitation, some antibiotic resistance genes were transported with greater frequency and in greater numbers after swine manure application.
1. Software to assist with conservation planning in agricultural watersheds. Conservation planning could more consistently lead to better water quality if landowners could identify a set of viable choices for intercepting and treating water flows with conservation practices. ARS scientists in Ames, Iowa, have developed the Agricultural Conservation Planning Framework (ACPF) toolset which uses soil, land use, and topographic data to identify multiple locations suitable for a variety of conservation practices across a watershed. The toolset can suggest where runoff and subsurface tile flows can be intercepted by different practices and produce maps showing how riparian buffer vegetation and widths can be varied to match streamside settings. Results provide an inventory of opportunities to improve water quality across a watershed, which can enable local landowners and farmers to identify preferred practices and locations, and to better participate in watershed planning. Because detailed input data necessary are becoming broadly available, this new technology for watershed planning could help agriculture more effectively address national-scale water quality concerns by leveraging local opportunities and preferences. The ACPF is being evaluated in four states, including several projects with long-term monitoring, to document eventual water quality benefits at the watershed scale. (Log #309186 and #309184)
2. Potential of bioreactors to reduce nitrate losses from watersheds. Wood chip bioreactors are a promising new conservation practice that allows bacteria that grow naturally on the wood chips to convert nitrate in drainage water to atmospheric nitrogen gas. ARS scientists in Ames, Iowa, and West Lafayette, Indiana, estimated the quantity of wood chip needed for nitrate removal in bioreactors to achieve certain targets from drainage water in three watersheds. They found the design of bioreactors contains an inherent trade-off between cost and size, which governs effectiveness. Bioreactors sized to provide an average 12 hours of treatment time could achieve a 20-30% reduction in the total annual nitrate loss from these watersheds, but 0.3% of the watershed areas would need to be converted to bioreactors. This study provides conservationists and water quality experts information on the quantity and number of denitrification bioreactors required to achieve certain nitrate removal targets at the watershed scale. Effective nitrate removal technology is required in order to reduce nitrate in drinking water sources and to reduce hypoxia in the Gulf of Mexico. (Log #296249)
3. Crop water use from upslope and depressions. Crops may take up water at different rates for different parts of the field, which makes farm management more difficult. ARS scientists in Ames, Iowa, showed that the rate of water uptake was greater for the upland area of the fields than for the lowland areas during silking and pollination of corn. Crop development was delayed in the upland areas, but final plant growth and grain yield were similar. For the upland areas, the soil was dried to wilting point for the depths of 1.6 to 3 feet. Lowland soils remained wet even as the corn continued to take up water, due to replenishment from the water table. A shallow water table provides additional water to crops but these areas have heightened risk of flooding/inundation. This information is of interest to scientists, crop consultants, and farmers who want to utilize spatial data on yield and soil properties to improve the potential benefits of precision crop management. (Log #275790)
4. Variations in land use and climate. Greater understanding of climate impacts on historical crop yields are needed to convey future climate risks to producers. ARS researchers in Ames, Iowa, analyzed detailed crop production records for each county in the Midwest from 1950 to the present to assess yield gaps (i.e., differences between potential and actual yields) for corn, soybean, and wheat as related to variations in climate over this period. Results showed an increase in "lost" areas (defined as area planted but not harvested) during the past five years due to more extreme weather patterns during the spring growth period. Climate patterns across the Midwest show an increase in spring precipitation, with a decrease in summer precipitation coupled, and an overall increase in annual precipitation. The shifts in spring precipitation cause greater risk in crop establishment and decrease the number of workable field days for crop establishment. Differences between spring and summer precipitation across the Midwest in the last five years were the greatest observed since 1895. There have been no major shifts in cropping patterns during the past 10 years; however, these changes in seasonal precipitation have had a negative impact on productivity. This information will be helpful in communicating the ongoing risks of climate change to farm producers, which will help them identify and adopt strategies to address those risks.
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Jaynes, D.B., Isenhart, T.M. 2014. Reconnecting tile drainage to riparian buffer hydrology for enhanced nitrate removal. Journal of Environmental Quality. 43:631-638.
Logsdon, S.D. 2015. Event- and site-specific soil wetting and seasonal change in amount of soil water. Soil Science Society of America Journal. 79:730-741.
Smith, T.E., Kolka, R.K., Zhou, X., Helmers, M.J., Cruse, R.M., Tomer, M.D. 2014. Effects of native perennial vegetation buffer strips on dissolved organic carbon in surface runoff from an agricultural landscape. Biogeochemistry. 120:121-132.
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Tomer, M.D., Porter, S.A., Boomer, K.M., James, D.E., Helmers, M.J., Isenhart, T.M., McLellan, E. 2015. Agricultural conservation planning framework: 1. Developing multi-practice watershed planning scenarios and assessing nutrient reduction potential. Journal of Environmental Quality. 44:754-767.
Tomer, M.D., Boomer, K.M., Porter, S.A., Gelder, B.K., James, D.E., McLellan, E. 2015. Agricultural conservation planning framework: 2. Classification of riparian buffer design-types with application to assess and map stream corridors. Journal of Environmental Quality. 44:768-779.
Xu, J., Logsdon, S.D., Ma, X., Horton, R., Han, W., Zhao, Y. 2014. Measurement of soil water content with dielectric dispersion frequency. Soil Science Society of America Journal. 78(5):1500-1506. DOI: 10.2136/sssaj2014.01.0044.
Logsdon, S.D. 2015. Relation of depressional flooding to soil water and upslope accumulated area. Transactions of the ASABE. 58(2):343-352.
Rondinelli, W., Hornbuckle, B., Patton, J., Cosh, M.H., Walker, V., Carr, B., Logsdon, S.D. 2015. Different rates of soil dyring after rainfall are observed by the SMOS satellite and the South Fork In Situ Soil Moisture Network. Journal of Hydrometeorology. 16(2):889-903. doi:10.1175/JHM-D-14-0137.1.
Logsdon, S.D., Singer, J., Prueger, J.H., Hatfield, J.L. 2014. Comparison of corn transpiration, eddy covariance, and soil water loss. Soil Science Society of America Journal. 78:1214-1223. DOI: 10.2136/sssaj2014.01.0044.
Jaynes, D.B. 2015. Corn yield and nitrate loss in subsurface drainage affected by timing of anhydrous ammonia application. Soil Science Society of America Journal. 79:1131-1141.