Location: Agroecosystems Management Research
2017 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 report is for the new project which began April 2017 and continues research from 5030-13000-010-00D.
Objective 1. Ten saturated buffers have been installed in Iowa and are now being continuously monitored for flow, water table position, and nitrate removal. A pilot scale denitrifying bioreactor is being investigated for the sixth year. Nitrate removal is being monitored by measuring nitrate loads entering and leaving the bioreactor. Nitrous oxide emissions are monitored both dissolved in the tile water and emitted as gas from the bioreactor. A new treatment plan with fertilizer applied at different times has been implemented for the corn-soybean rotations with and without a fall planted rye cover crop. The new treatment plan includes pre-plant fertilizer application and post-plant side-dress according to late spring soil nitrate testing. Crop biomass and yields, along with nitrate, phosphorus, and potassium losses in tile drainage are being measured. The Root Zone Water Quality Model (RZWQM) was used in ongoing work to simulate growth and N uptake of rye cover crops and to develop a greenhouse gas component of RZWQM representing tile drainage conditions in Iowa. For the most part the model accurately simulated N loss to drainage and N2O emissions over the period of study 2002-2010 and the simulations agree with field data that winter rye cover crop substantially reduces N loss to drainage. A draft manuscript has been completed and is currently in review by co-authors. Preliminary work on the long-term rotations in fields of co-operators was conducted that included evaluation of plant cover, rainfall simulation, and soil structure measurements. The long-term rotations are alfalfa included in corn and soybean rotations. Work on the perennial systems includes developing methods to determine evapotranspiration and evaluating the relationship between landscape features and tile drainage. Work on the Agricultural Conservation Planning Framework (ACPF) toolbox has included developing conservation practice placement maps for the South Fork Watershed, which have been placed online. The online results are being shared with local landowners and others interested in the ACPF. Work on the surface inlets protected with filter socks has included identifying inlets for study, investigating different filter material, installing filter socks filled with the most promising material, installing automated samplers, and processing water samples.
Objective 2. Three experimental watersheds are instrumented and collecting water quantity data, meteorological conditions, and are sampled for water quality: Walnut Creek in Story County, Walnut Creek in Jasper County, and the South Fork of the Iowa River (SFIR). Sites were identified and soil baseline measurements were made for the Long-Term Agricultural Research (LTAR) Common Experiment at the Kelly Farm near Ames, Iowa, the Coles Farm in the South Fork of the Iowa River, and the Brooks field near Ames, Iowa. Experimental treatments for the LTAR Common Experiment initiated at Kelly Farm include variations on corn-soybean rotations, with one alternative treatment including a winter rye cover crop and N fertilizer rate determined by late spring soil nitrate testing (LSNT), and another treatment having a winter camelina with LSNT N management. The Kelly farm site has plots that have individual tile drains which allow direct measurement of drainage and nitrate losses. At the Coles Farm, baseline soil sampling was completed and an eddy flux tower is operational to measure CO2 and water fluxes. Installation of a phenocam is in progress. This site's cropping system is a corn-soybean rotation with strip tillage and winter rye cover crops. The Brooks field represents the conventional corn-soybean system with tillage and late fall N application. Research to develop a water budget for the SFIR was initiated. The initial budget was based on the Kelly Farm site where drainage and evapotranspiration account for 20% and 75% of annual precipitation, respectively. At the SFIR evapotranspiration will be estimated from existing data from multiple flux towers and drainage will be estimated as non-storm event flow. A draft data management plan was created for the Upper Mississippi River Basin (UMRB) and ARS personnel were redirected to help execute this plan.
Objective 3. A study examining the leaching of antibiotic resistance genes in soil columns was continued. Distinct microbial communities were found using non-metric multidimensional scaling (NMDS) analysis of 16S-rDNA sequences extracted from soils with and without manure treatments for over 25 years. Analysis of the data is on-going.
Accomplishments
1. Alternative fill material for reactive barriers. Water entering surface inlets connected to subsurface tile drains in agricultural fields can have high concentrations of herbicides; particularly, if surface runoff occurs shortly after herbicide application. The effectiveness of using alternative fill materials (biochar, limestone, steel slag, tire chips) as components in reactive barriers (blind inlets, filter socks) as a replacement or buffers for surface inlets was investigated by collaborating ARS scientists from Ames, Iowa, Oxford, Mississippi, and West Lafayette, Indiana. Of the materials investigated, biochar was substantially more effective in reducing concentrations of the herbicide atrazine. As result, the biochar used in this experiment has been used to fill filter socks placed around surface inlets and in ditches in field experiments currently being conducted in Ames, Iowa, and Oxford, Mississippi. Implementing this technology will improve surface water quality in agricultural watersheds that include surface inlets connected to subsurface drains.
