2011 Annual Report
1)a plot-scale rainfall simulation study with three VBS designs and a control treatment (no plants) to assess the ability of VBS to reduce the transport of three herbicides and three VAs in surface runoff; and.
2)a growth chamber study, in which the effect of seven forage species on soil degradation of the herbicide, atrazine, was investigated. All VBS significantly reduced the transport of herbicides (atrazine, metolachlor, glyphosate) and VAs (sulfamethazine, tylosin, enrofloxacin) in surface runoff, with native grass VBS most effective for reducing herbicide transport and tall fescue VBS most effective at reducing VA transport. Equations developed to relate buffer width and load reduction provide needed design criteria for implementation. All forages tested showed significant increases in atrazine degradation compared to soil without plants, with eastern gammagrass, smooth bromegrass, and switchgrass showing the greatest ability to enhance soil degradation of atrazine. Overall, these studies demonstrated that VBS are effective at reducing contamination of water resources by herbicides and VAs via a two-step process in which:.
1)the contaminants are initially deposited within the VBS by sediment trapping and/or improved infiltration; and.
2)accelerated degradation of the contaminants occurs following deposition in the VBS soil. 3. ARS researchers in Columbia, Missouri: Identification of the strengths and weaknesses of the pathogen module in Soil and Water Assessment Tool (SWAT). In 2001, a pathogen module was inserted in the SWAT, a computer simulation program that simulates the movement of water and pollutants in agricultural watersheds. A review of the results obtained by different modelers was needed to assess the strengths and weaknesses of the model. Five case studies were reviewed, including one in which an ARS researcher collaborated with scientists from the French Institute for the Exploration of the Sea (IFREMER) to use the SWAT model to simulate pathogen transport in a coastal watershed and estimate the impacts of contamination on shellfish production by linking SWAT to a hydrodynamic model of the coastal waters. This application in itself expands the range of application of SWAT. The review highlighted and compared these applications in terms of sampling protocols, input parameter values, and how well the model simulated concentrations. In all case studies reviewed, direct bacteria inputs into streams had a major impact on the model results, in part because of the sampling protocol that over-characterizes base flow conditions. Results indicate the need for better stream sampling procedures that allow bacterial analysis of storm water samples and for additional field studies to revise and fine-tune the equations that simulate the transport of bacteria in surface runoff. These results are useful for scientists who are planning research in this field and for model users who look for information on the model’s capabilities and limitations. 4. ARS researchers at Ames, Iowa: Watershed studies that were part of USDA-ARS’s Conservation Effects Assessment Project (CEAP) reviewed. CEAP watershed research at 14 ARS locations included watershed modeling, field studies to assess practices, and evaluation of practice placement in watersheds. Identifying water quality impacts from conservation practices in large agricultural watersheds is challenging: field studies show conservation practices improve water quality, but water quality problems have persisted in larger watersheds. This apparent dissociation between practice-focused assessment and watershed monitoring occurred because:.
1)Conservation practices were not targeted according to critical sources and pathways of contaminants;.
2)Sediment in streams often originated more from channel and bank erosion than from erosion of soil in fields;.
3)Timing lags, historical legacies, and shifting climate combined to mask effects of practice implementation; and.
4)Water quality management strategies that address single contaminants do not consider inherent trade-offs among multiple contaminants. These lessons can be leveraged to improve strategies for implementing conservation programs and to set water quality goals with realistic timelines. 5. ARS researchers at Ames, Iowa: Trace contaminants in woodchip bioreactors evaluated. Woodchip bioreactors are promising new technology to remove nitrate from the Mississippi River Basin and reduce hypoxia in the Gulf of Mexico. The woodchips support populations of bacteria which convert nitrate to nitrogen gas, a process called denitrification. ARS scientists and Iowa State University scientists examined the potential of these bioreactors to remove agricultural chemicals from field drainage water. Two antibiotics and a herbicide were rapidly removed from water in a laboratory-scale woodchip bioreactor. The mechanism of removal appears to be binding to the woodchips. Two antibiotics, enrofloxacin and sulfamethazine, temporarily suppressed denitrification activity and reduced populations of denitrifying bacteria. The herbicide atrazine did not affect denitrification. Woodchip bioreactors, which are effective in nitrate removal, will also remove pesticides and veterinary antibiotics from drainage water. This information will be of use to farmers and state and federal action agencies in setting priorities for the expenditure of conservation monies to improve surface waters affected by excess nitrate. 6. ARS researchers at Ames, Iowa, and Oxford, Mississippi: Examining the role of wetlands in watershed water quality management. Nutrient removal wetlands can reduce watershed nitrate loads and provide other ecosystem services, but their placement and contributions to nutrient reduction will need to be determined on a watershed specific basis. ARS scientists in Ames, Iowa, and Oxford, Mississippi, collaborated with researchers at Iowa State University and The Wetlands Initiative obtained detailed topographic data for a 16,000-acre watershed in Illinois through a laser altimetry (LiDAR) survey. Applying conservative selection criteria, they identified 11 sites that could be converted to wetlands with minimal loss of productive cropland. These wetlands could intercept and treat tile drainage from 30 percent of the watershed. A modeling exercise showed that these wetlands could reduce nitrate loads from the watershed by as much as 16 percent. However load reductions among the wetland locations varied considerably, depending on watershed-to-wetland area ratios, and nitrate loads generated above each wetland that depended on differing land uses. These issues will need to be considered by policy makers interested in developing incentive structures that encourage wetlands, including the establishment of nutrient trading schemes. 7. ARS researchers in Ames, Iowa, and Ft. Collins, Colorado: Water table control, nitrogen (N) rate, and weather affect nitrate loss to subsurface drainage. Control of subsurface drainage can reduce nitrate loss to tile flow, but the effects may vary with different N application rates and weather conditions. ARS scientists in Ames, Iowa, and Fort Collins, Colorado, used the Root Zone Water Quality Model (RZWQM2) to investigate long-term effects of controlled drainage. Changing from free to controlled drainage reduced measured annual N loss in tile flow by 22 percent, but the model over-predicted this effect by 10 percent, possibly because surface slope reduced the effect but was not simulated by the model. Long-term RZWQM2 simulations (1996-2008) suggest that N loss might be reduced by 39 percent through controlled drainage and decreased N rates, with minimal decreases in corn yield. This research will help agricultural scientists better understand effects of controlled drainage towards and its potential role in reducing N losses from tile drainage. 8. ARS researchers in Ames, Iowa: Soil Quality Assessment data sets for 14 Cropland Conservation Effects Assessment Progect (CEAP) watersheds and two Natural Resources Conservation Service Special Emphasis watersheds have nearly been completed. There are only a few missing analyses from selected sites and these are anticipated to be finished by the end of 2011. The first CEAP soil quality assessment manuscript, developed for the South Fork watershed in Iowa, has been accepted for publication in the Soil Science Society of America Journal. It showed that when the data were separated by areas of normal or poor corn canopy development, mean indicator values were slightly lower in poor canopy areas. Using multiple soil parameters, the Soil Management Assessment Framework (SMAF) confirmed that areas with poor canopy development had lower overall soil quality ratings, but no single indicator scored the lowest in all 50 fields. When the data were separated by landscape position (hilltop, sideslope, toeslope or depression) or by previous crop (corn or soybean), soil organic carbon was the only significantly different property between well- and poorly-developed canopy areas. A majority of fields had multiple indicators that, when scored using the SMAF, had ratings that were at least ten percent lower in the poorly-developed canopy areas than in well-developed areas. This field-by-field assessment showed that even across these highly-productive croplands, soil quality variation is directly related to crop canopy development. Soil quality assessment thus provides an approach for identifying soil-based causes for differences in crop productivity. 9. ARS researchers in El Reno, Oklahoma: Rapid geomorphic assessment successfully integrated into SWAT to evaluate conservation practices. Lack of data for hydrologic models, such as the Soil Water Assessment Tool (SWAT), for model parameterization and evaluation remains a weakness to modeling globally. Scientists utilized low-cost geomorphic data, obtained through rapid geomorphic assessment (RGA), to parameterize SWAT stream channel variables. The study was conducted in southwestern Oklahoma within the Cobb Creek sub-watershed. Model simulations of reservoir sedimentation were compared to long-term average annual reservoir sedimentation rates obtained from a bathymetric survey measured from an acoustic profiling system (APS). In the modeling study, application of riparian buffers along unstable stream reaches identified by the RGA reduced suspended sediment concentration at the sub-watershed outlet by 67 percent, which is within the same order of magnitude as the findings of previous field studies. Study results indicate promise for using the RGA and APS methods to obtain data to improve water quality simulations in ungauged watersheds. 10. ARS researchers in Tifton, Georgia: Assessment of the impact of agriculture on the Jobos Bay National Estuary: The Jobos Bay National Estuarine Research Reserve (JBNERR) is a semi-enclosed ecosystem along the southeast coast of Puerto Rico. Agriculture, including vegetable, row crop, tree fruit, pasture, and poultry, is an important land use within the watershed. To better understand the potential impact of agriculture on JBNERR, the watershed was designated as the first USDA tropical Conservation Effects Assessment Progect. ARS researchers at Tifton, Georgia, identified an agricultural field near the land/estuary interface for detailed study. Groundwater and water quality studies in the area indicate that the primary mode of transport to the estuary is through surface runoff generated during intense rainfall events. Groundwater transport is expected to be low due to low rates of movement in the surface aquifer. These findings should be valuable to management agencies selecting conservation practices that will reduce surface runoff and agricultural chemical loading to the bay during these intense rainfall events. 11. ARS researchers in Tifton, Georgia, and Temple, Texas: Simulation of riparian buffers impact on water quantity and quality in the Coastal Plain: Riparian buffers are an extremely important component of Coastal Plain Watersheds, dramatically impacting the quality of surface and subsurface flow reaching Coastal Plain streams. Until recently, large scale watershed simulation models have not adequately addressed these riparian buffers in their simulation methods. ARS researchers at Tifton, Georgia, in cooperation with ARS researchers in Temple, Texas, and researchers at Tarleton State University in Waco, Texas, incorporated these functions into the Soil Water Assessment Tool and Agricultural Policy Environmental Extender (APEX) models. Preliminary tests were conducted to examine the accuracy of the new simulation methods. These new simulation tools appear to offer significant improvements in the way riparian buffers are simulated in these models. 12. ARS researchers in Tifton, Georgia: Transition to a glyphosate-resistant world: While glyphosate is relatively non toxic to humans and environment impacts are small, intense use of this product has been accompanied by the evolution of glyphosate-resistant populations of several economically damaging weeds. Some of the most promising replacement herbicides for cotton growers in the Southeastern USA are products that contain the active ingredient fomesafen. While effective, concerns persist about the potential for fomesafen to be carried into rivers and streams with stormwater runoff from treated fields. We conducted studies to evaluate two mitigation strategies, incorporation with irrigation after herbicide application and use of conservation-tillage. Both practices were found to reduce fomesafen runoff potential by more than 2-fold. Results indicate that these practices should be implemented wherever possible to reduce fomesafen runoff risk. 13. ARS researchers in Tifton, Georgia: Windows of risk at the interface between weather and soil management: Runoff and sediment losses measured from one of region’s most productive soils, the Tifton loamy sand, provided information on how conservation tillage can reduce losses and help producers manage natural resources and agrichemical losses from peanut cropping systems. We quantified losses at 3 times during the growing season: at-planting, early postemergence (4 weeks), and after digging and harvest. Runoff ranged from 9-22 percent of applied rainfall and sediment yields were from 100 to 1400 kg ha-1. The conventional till plots averaged 60 percent more runoff and 3.3-fold more sediment loss than strip till plots. The most runoff was observed from conventional till plots in the Fall and the least from strip till plots in the Summer. The most sediment loss was from conventional till plots in the Spring and the least from strip till plots in the Summer. These results are important for conservation program planning in that they demonstrate the added value conservation tillage can provide during the peak water demand period of the summer (increased infiltration) and during the period of highest erosion risk (spring planting). 14. ARS researchers in Oxford, Mississippi: Fraction of sediment derived from channel sources determined for watersheds. Determining the dominant sources of sediment in agricultural watersheds is important for designing practices that will reduce sediment loads to streams. Measurements using naturally occurring radionuclides to track sediment on CEAP have revealed that most of the sediment in the studied watersheds was derived from channel sources. This indicates that if erosion control practices reduce sediment concentration without reducing runoff volumes from fields, sediment loading in the channels may not be significantly reduced. Information on the sources of sediment is essential for watershed managers to design effective sediment control measures on agricultural watersheds. 15. ARS researchers in Oxford, Mississippi: Sediment contributions from streambanks are a significant source of sediment in several Conservation Effects Assessment Progect (CEAP) watersheds. Conservation efforts to reduce sediment loadings to receiving streams and other water bodies may only be successful if mitigation measures target the major sources of sediment. Channel sources are largely ignored. Results of research show that Conservation Effects Assessment Progect watersheds such as Fort Cobb and Little Washita, Oklahoma, Goodwin Creek, Mississippi, South Fork Iowa River, Iowa, and Town Branch, New York, produce substantially more sediment than those from stable channels in their respective regions. In some cases, these streams produce orders of magnitude more sediment than their stable counterparts. Reconnaissance of these channels showed that they are dominated by streambank erosion while in comparison, the Little River, Georgia, a stream in dynamic equilibrium without accelerated rates of bank erosion, displayed transport rates similar to calculated background rates. Knowledge of the dominant sources of sediment is necessary for the designing and implementation of measures to stabilize the channels in watersheds and reduce the impacts to aquatic communities and surface-water supplies. 16. ARS researchers in Temple, Texas: New algorithms were developed for a river basin scale model called Soil Water Assessment Tool (SWAT) to simulate on-site septic systems, stream sediment routing, urban management practices, improved phosphorus fate and transport, and stream health. The new algorithms are currently being tested at watersheds across the United States. As part of the Conservation Effects Assessment Progect (CEAP) National Cropland Assessment, SWAT was validated at more than 70 United States Geological Survey stream gages across the country to assure realistic simulation of stream flow, sediment, nutrient and pesticide (atrazine) loads. Final SWAT validation and scenario analysis was completed on the Upper Mississippi river basin, the Chesapeake Bay watershed, the Ohio-Tennessee river basin, and the Great Lakes watersheds. The reports are under review and draft versions are available at the CEAP website. Validation and scenario analysis has been completed for the Missouri, Arkansas-Red, and Lower Mississippi river basins and reports are being developed. The scenario runs are being used to identify places where conservation practices such as conservation tillage, terraces, and Conservation Reserve Program (CRP) will be most efficient and provide the greatest benefits. This will help guide USDA conservation policy and Farm Bill debate. The model is also being used in more than 30 states by US Environmental Protection Agency and is impacting the selection of land management alternatives to resolve water quality concerns. 17. ARS researchers in Columbus, Ohio: Identified need to pair the use of grass filter strips with other conservation practices to improve water quality in channelized agricultural headwater streams. Grass filter strips are a widely used conservation practice in the midwestern United States, but the ecological effects of this practice on agricultural streams has not been evaluated. ARS Scientists from Columbus, Ohio conducted preliminary assessment of the effect of grass filter strips on the physical habitat, water chemistry, and stream communities within channelized agricultural headwater streams. Installation of grass filter strips did not influence vegetative structure, vegetative type, channel form, instream habitat, water chemistry, or the stream biota. Our results suggest that grass filter strips may only widen the riparian zones adjacent to channelized agricultural headwater streams and may only provide limited ecological benefits, unless used in combination with other conservation practices. These results will be useful for state, federal, and private agencies involved managing agricultural watersheds to assist them in meeting their conservation and restoration goals. 18. ARS researchers at Beltsville, Maryland: Wetland hydrology is an important parameter controlling wetland ecosystem services such as nutrient fate in agricultural landscapes but wide-scale forested wetland hydrology has been difficult to study with conventional remote sensing methods. A comparison between LIght Detection And Ranging (LIDAR) intensity data collected during peak hydrologic expression of wetlands demonstrated the strong potential of these data for mapping wetland inundation (>96 percent accurate). Additionally LIDAR provides very intensive topographic information which was found useful for predicting wetland location in the landscape. The ability to more accurately map and monitor wetland function in agricultural landscapes should greatly improve watershed and regional assessments of the impact of these ecosystems on water quality as well as impact of agriculture on health sensitive water bodies such as the Chesapeake Bay. 19. ARS researchers in Betlsville, Maryland: Ditch drainage of agricultural fields can expedite movement of nutrients into surface waters and increase export of agricultural nutrients from croplands. Assessment, by Conservation Effects Assessment Progect scientists, of effectiveness of ditch drainage management to regulate agricultural nutrient movement by ditches in the Choptank has led to the inclusion of control drainage management in the Maryland Department of Agriculture water quality cost share program. 20. ARS researchers in Beltsville, Maryland: Cover crops program has recently grown extensively, from less than $1M in 2004 to nearly $18M as incentive cost shared program in 2010. There is however a need for a well tested and validated management tool/model for quantitative assessment of this BPM program at watershed as well as State levels. Through Conservation Effects Assessment Progect program at the Choptank watershed, ARS scientists are involved in testing and validation of ARS watershed model SWAT at several subbasins above the tidal lines within the Choptank watershed. This has included one of the largest subbasins, the German Branch (GB), and work is underway to validate SWAT model for the whole Tuckahoe Branch covering nearly 700 square miles. Since quality of precipitation data is critical for appropriate application of Soil Water Assessment Tool (SWAT) model and the fact that there was no dense rain gauge network available within the GB subbasin, we examined the implications of using surface rain gauge and next-generation radar (NEXRAD) precipitation datasets on the performance of the SWAT model. Overall, correcting NEXRAD with rain gauge data showed promise and produced better hydrologic model calibration with respect to stream flow at the outlet of the watershed. The optimal water balance obtained using this approach is an essential precursor to acquiring realistic water balance as well as estimates of sediment and nutrient loads in further Tuckahoe Branch model assessment. It is anticipated that a well-tested SWAT model at the Tuckahoe Branch will be a valuable management tool that can be used for evaluation of cover crop and other best management practice's within the Choptank watershed. 21. ARS researchers at Fort Collins, Colorado: Computer simulations extend experimental field data on fertilizer effects for tile-drained fields. Agroecosystem models have not been widely used to capture the variability of nitrogen concentration in tile drainage at a wide range of nitrogen application rates. Scientists at Fort Collins, Colorado, and Ames, Iowa, evaluated the performance of the RZWQM2 in simulating the response of nitrogen concentration in tile drainage to different nitrogen application rates. A 16-year field study conducted in Iowa from 1989 to 2004 was used to evaluate the model, based on previous calibration with data from 2005-2009 at this site. The results showed that the RZWQM2 model accurately simulated the response of nitrogen concentration in tile drainage to nitrogen fertilizer rate. This study supports the use of RZWQM2 as a management tool for helping agricultural managers and decision makers address water quality concerns in tile-drained systems. 22. ARS researchers at Fort Collins, Colorado: Release of Object Modeling System (OMS) Version 3.1. ARS scientists and collaborators at Fort Collins, Colorado released the Object Modeling System (OMS) 3.1 framework for environmental model development. OMS 3.1 includes improved methodology for developing and connecting science components in Formula Translating System (FORTRAN). A new Cloud Services Innovation Platform (CSIP) was developed which utilizes OMS3 as the underlying vehicle for model distribution. The Revised Universal Soil Loss Equation 2 (RUSLE2) model was successfully tested as a cloud computer application under CSIP. Modeling projects currently being implemented in OMS3 by ARS, US Army Corps of Engineers, United States Geological Survey (USGS), and university partners will result in cost reductions in terms of model development, deployment, maintenance, and ongoing application. 23. ARS researchers at Fort Collins, Colorado: Simulating plant phenological responses to water deficits improves watershed scale models. Modeling spatial relationships in plant growth and yield across a watershed requires having a phenology model that accurately simulates crop development responses across a landscape with varying water deficits. To address this problem, ARS scientists at Fort Collins, Colorado, independently released PhenologyMMS (Modular Modeling System) Version 1.2 and also integrated core science code into the Unified Plant Growth Model (UPGM). The PhenologyMMS software, which was highlighted in the May/June 2011 issue of Agricultural Research magazine, has received over 500 subsequent downloads, and numerous direct requests for more information and explanation including the popular press. 24. ARS researchers at West Lafayette, Indiana: To better assess the impacts of conservation buffers and grasslands on water quality at large spatial scales, development and integration of novel approaches are crucial to ensure that these land management practices are functioning properly and meeting their original goals. Recent developments in remote sensing technology have greatly enriched the availability of geospatial data that can be used in hydrological modeling to assess the potential hydrological response of conservation practices over larger areas. A methodology was developed using the object-based image analysis approach with Landsat-5 TM imagery of the year 2005 (OBIA-2005) to quantify conservation buffers and grasslands. The OBIA-2005 land cover data was used in the SWAT hydrologic model to assess the impacts of vegetative conservation practices on total phosphorus (TP) loads. The model was calibrated and validated for discharge and TP loads in the St. Joseph River watershed (SJRW) in northeast Indiana. Vegetative buffers of 30.5m and 61m combined with conservation grasslands generated from the OBIA-2005 resulted in a large reduction of TP loads as compared to no practices. The results also showed that including conservation grassland alone reduced TP loads by less than 2 percent. However, the combination of these practices with the width of edge-of-field buffer strips module of the SWAT model achieved the largest TP loads reduction. These findings demonstrate that improved representation of vegetative conservation practices in geospatial land cover data sets are effective in assessing their impacts on water quality through hydrologic modeling. 25. ARS researchers at University Park, Pennsylvania: Mahantango Creek Watershed data uploaded to STEWARDS: A forty year record of precipitation and stream flow data and a twenty four year record of water quality data from the USDA-ARS Mahantango Creek Watershed in Pennsylvania were uploaded to the STEWARDS database. A series of four journal articles describing the physiography and history of the watershed and associated databases were published in Water Resources Research, a peer-reviewed journal. These journal articles and databases enable and facilitate the use of these data by the general public and scientific community. The Mahantango Creek Watershed is one of a network of 14 USDA-ARS long term research watersheds across the United States that allow for comparative studies of watershed processes and global change.