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Research Project: Developing Agronomically and Environmentally Beneficial Management Practices to Increase the Sustainability and Safety of Animal Manure Utilization

Location: Food Animal Environmental Systems Research

2022 Annual Report

Obj 1: Improve utilization of animal manure and manure byproducts, such as biochar and hydrochar, to increase soil health and agricultural productivity, and protect the environment. 1.1 To evaluate the use of biochars and hydrochars for reducing phosphorus release from high P soils. 1.2 Application of biochar over the bedding materials inside the poultry house to reduce ammonia emission and improving the quality of the resulting poultry litter for crop production. 1.3 Evaluate biochar effects on composting cattle manure to mitigate carryover effects of pyridine herbicide. 1.4 Develop a sustainable management practice using poultry litter and cover crop for maximum nutrient use efficiency under a corn production system. Obj 2: Quantify, characterize, and develop strategies to reduce atmospheric emissions, including gases, particulate matter, and other emissions of concern, from animal production facilities and manure application sites. 2.1 Evaluate the fate of atmospheric emissions from agricultural systems. 2.2 Characterize the spatial and temporal profiles of nitrogen in the gas and particle phase from agricultural emissions. 2.3 Model the physical processes that are responsible for the production of atmospheric aerosols from farm waste compounds. 2.4 Reduce malodors characteristic of animal wastes by the use of high sugar containing agricultural by-products. 2.5 Develop novel and cost-effective nano-filtration materials to capture ammonia, GHG, and odors from livestock production facilities. Obj 3: Develop mathematical models and evaluate practices for managing and treating manure to obtain clean bioenergy; reduce gaseous emissions; minimize losses of nutrients, estrogens, hormones, and other compounds of concern; and control the survival and transport of antibiotics, antimicrobial resistant bacteria, and foodborne pathogens. 3.1 Evaluation and optimization of naturally occurring enzymes to improve anaerobic digestion of recalcitrant livestock wastes to reduce emissions and obtain bioenergy for sustainability. 3.2 Use of sound to enhance biogas production and reduce sludge from animal production facilities. 3.3 Investigate effects of supplemental ionophores on animal performance, manure nutrient composition, and soil chemical and biological characteristics of cattle grazing tall fescue or cool-season annuals. 3.4 Quantifying estrogens and their sulfonated conjugates originating from dairy practices. 3.5 Develop, calibrate, and evaluate field-scale fate and transport models for describing P loss from agricultural fields in the Western Lake Erie Basin (WLEB). 3.6 Modeling transport, fate, and risk management of nitrate and common and emerging pathogens in agriculturally-impacted groundwater systems. 3.7 Characterize the epidemiology, serotype distribution and antimicrobial resistance of Salmonella in broiler production system. 3.8 Determine the prevalence and resistance genes of extended spectrum beta-lactamase (ESBLs) producing Escherichia coli in broiler production system.

A significant challenge facing U.S. agriculture is how to safely and sustainably manage the more than one billion tons of animal manure produced annually. Our research is directed at optimizing methods of manure application, storage, and treatment to improve agricultural productivity while protecting the environment and human health. Our research will investigate the use of poultry litter for improving crop yield and soil health. We will evaluate novel methods for using biochar to reduce phosphorus release from soils to protect water quality, to reduce ammonia levels in poultry houses, and to reduce the release of pesticides from composted manure. To protect air quality we will characterize and identify formation processes of ammonia, amine, and aerosol emissions from agricultural facilities; develop treatment technologies for reducing emissions from livestock production facilities; develop cost-effective nano-filtration materials to capture ammonia, greenhouse gases, and odors from livestock production facilities; and evaluate the use of acoustic technology to reduce gas emissions from anaerobic digestors. We will identify enzymes to optimize biogas production from recalcitrant livestock wastes, test whether manure nutrient composition can be modified by feeding ionospheres to cattle, and study the fate of estrogens following anaerobic digestion of dairy cattle waste. Our research will test the accuracy of field-scale models for predicting phosphorus loss from tile-drained agricultural fields. We will investigate the transport of bacteria in karst topography. Finally, our research will help protect human health by defining the epidemiology and antimicrobial susceptibility of major Salmonella serotypes circulating in broiler production systems and the prevalence of extended spectrum beta-lactamase producing E. coli in broiler production. Results will be disseminated to the public through fact sheets, web-accessible models, stakeholder meetings, and publications in scientific journals and will benefit the general public by providing much needed information for developing more effective strategies for sustainably managing animal manure.

Progress Report
Objective 1: We are measuring the sorption rate of phosphorus to biochar-amended soils. We have investigated the use of untreated biochar and biochar treated with iron-oxides. The iron-oxide coated biochar was shown to increase sorption of phosphorus in two sandy soils but had no effect in two silt-loam soils whereas the untreated biochar had no effect on phosphorus sorption for all four soils. Regular research activities continued on two field experiments from the previous Project Plan to complete the studies. Collected data are being analyzed for future presentations and publication. First-year research activities of the new Project Plan have started as follows: The quantity of hardwood biochar needed has been acquired, and prior to application on the bedding material in the poultry house will be completely characterized for its constituents. Also, instrumentation for measuring ammonia gas (NH3) is now available at our location. However, since entering poultry producer facilities have been restricted by the Integrators due to COVID, we are still looking for a local commercial poultry producer to collaborate on using his/her facilities for this study. The issue will be solved soon. A field plot site has been identified and flagged on Crider silt loam soil near Bowling Green, Kentucky, to investigate and quantify nutrient use efficiency by corn growth, yield, and greenhouse gas emissions underutilization of animal manure, cover crops and chemical fertilizers. We are collecting background soil chemical information and the plots will be planted as cover crops this fall. We have completed setting up experimental units (composting tumblers), analysis of biological and chemical composition of cattle manure, conducted preliminary animal grazing experiment with pyridine herbicide sprayed pasture feeding and estimating pyridine concentrations excreted in manure, and completed analysis of starting composting mixture for proper moisture content and carbon to nitrogen ratio. Objective 2: We are establishing protocols for new environmental chamber experiments. These experiments will focus on more realistic mixtures of the air emissions from animal operations rather than simple one or two chemical experiments. In addition, we plan to perform experiments at a larger range of ambient temperatures, especially focused on low temperatures observed during wintertime. We are establishing methods for sampling and distinguishing atmospheric nitrogen from animal production operations. This is part of a complicated multi-location project that is focused on determining ammonia deposition from operations of different animal types and different geographic topologies. Scientists from the different ARS locations have been meeting virtually throughout the year and have decided that it would be better to setup one location first so that multiple locations are not repeatedly making mistakes with the setups. Sampling setup will occur first at the Ames, Iowa, location. Other locations, including Bowling Green, will implement field sites later on using information encountered from the first field site implementation. In the meantime, scientists at the Bowling Green location have been working on developing analysis protocols for the organic nitrogen compounds which only the Bowling Green location has capability to analyze. The optimization of nanoparticles formation from plant extracts was studied to examine its feasibility in air pollution reduction, antimicrobial property and delivery of enzyme treatment. In addition, a pilot-scale engineered system to utilize nanotechnology and biotechnology for agricultural air pollution mitigation is in progress. An experiment designed to test the adaptation of methanogenic consortia to alkaline conditions was continued. In these experiments, anaerobic digesters were seeded with dairy manure and then fed dairy manure with increasing concentrations of inorganic bases to test how alkaline conditions affect biogas quality and production as well as microbial community structure. The experiment is being continued to quantify metal carbonates in anaerobic sludge. Objective 3: We are continuing field study in monitoring and optimization of methane production from an anaerobic digestion system (15 million gallons) of poultry litter mixed with food wastes and evaluation of different lignocellulosic enzymes on biogas production from recalcitrant livestock waste feedstocks. A building to house two pilot scale anaerobic digesters was constructed and rebuilding of the anaerobic digesters and wastewater treatment systems has begun. The wastewater treatment system will be used to produce biogas through sound-assisted breakdown of manure sludge. Effluent from the treatment system will be treated to remove nitrogen and recover phosphorus and then discharged into an aerobic lagoon. Water from the lagoon will be mixed with manure and fed back to the treatment system. Except for manure inputs, the systems will operate largely as a closed loop treatment system with little or no discharge to the environment while recovering valuable phosphorus. Establishment of cool-season annual forage (annual ryegrass) was planted into a prepared seedbed in anticipation of comparison to an established cool-season perennial forage (tall fescue). However, due to climatic conditions outside of the control of the researchers the annual ryegrass did not establish due to repeated snow and ice events that damaged the emerging forage and did not allow for sufficient forage growth to support grazing animals (mature cows with suckling calves). As a result, no data were collected during the spring for the project. Several experimental parameters for determining estrogens, estrone and beta-estriol in pristine samples by liquid chromatography-mass spectrometry (LCMS) with solid-phase extraction (SPE) sample preparation and gas chromatograph-mass spectrometry (GCMS) using sorptive stir bar sample preparation have been optimized. We are currently validating this procedure with study samples. Methods for estimating tile runoff in tile-drained fields in the Western Lake Erie Basin are being investigated. We have identified twelve sites within an existing ARS research network that have over four years of runoff data. We have compiled the data and are in the beginning stages of analyzing the data. In particular, we are testing methods to separate baseflow from event flow and to identify distinct runoff events and pair them with precipitation events in preparation of testing hydrological models. We are analyzing over 700 groundwater samples to identify and measure the type and quantity of bacteria, with a focus on antibiotic resistant bacteria strains, including E. coli and other common resistance types. Nearly all samples have been cultured and/or quantified through polymerase chain reaction (PCR) and high-throughput, molecular real-time PCR analysis of antibiotic resistant genes in water samples. Preliminary field sampling was conducted to determine sources and sampling protocols for high-resolution and more focused data collection during the prep and growing seasons. Fieldwork preparation is underway to collect E. coli, antibiotic resistant bacteria and nitrate data over multiple seasons to determine practical best management practices for testing as planned in future milestones. Additional progress was made on greenhouse gases in groundwater, including analysis of microbial processes that affect their cycling in the groundwater system, which will be important for interpreting antibiotic resistant bacteria data. A literature review is being conducted to develop standard operating procedures for the isolation, identification, serotyping and antimicrobial susceptibility testing of Salmonella from poultry cecal contents. We are working to acquire equipment for automated antimicrobial susceptibility system to meet Sub-objectives 3.7 and 3.8. We are developing protocols for culturing and characterization of extended spectrum beta-lactamase-producing E. coli from the cecal contents of poultry. As part of this effort, a paper was published regarding extended spectrum beta-lactamase producing E. coli isolation protocols using samples from a mink farm collected by collaborators. The automated antimicrobial testing system described above is critically important for the success of Sub-objective 3.8 Plans are underway to engage with the stakeholder to start sample collection.

1. Used One Health approach to study foodborne infections. It is critically important to determine the burden of foodborne pathogens along beef cattle processing and distribution chain and humans in a One Health approach to develop microbial risk assessment and mitigation strategies. ARS researchers in Bowling Green, Kentucky, in collaboration with international researchers at Addis Ababa University (Ethiopia) and Ghent University (Belgium), determined the prevalence of Salmonella and Escherichia coli O157 in cattle, retail beef and diarrheic patients. Fecal and beef samples were cultured; isolates were characterized for genotypic relatedness. Escherichia coli O157 was detected at about the same proportion from cattle (7%) and retail beef (6%), and at twice lower proportion in diarrheic patients (3%). Genetically similar strains of Escherichia coli O157 were obtained from cattle, retail beef and humans suggesting potential cattle to human transmission through beef. Considerable Salmonella contamination of retail beef and shared genetically similar strains between cattle and retail beef were observed. Although the link with humans could not be established, the propensity of Salmonella transfer from cattle to retail beef is a potential public health risk. The results indicated that cross contamination at slaughterhouses is an important source for carcass contamination. The study provided data to improve hygienic practices at the slaughterhouses and retail shops through training and process control to ensure meat safety.

2. Determined best manure treatments to effectively remove antimicrobial resistant bacteria prior to land application. Land application is a commonly used animal manure management strategy. Manure contains essential nutrients for plant growth. However, the presence of bacteria including resistant strains is an impediment for effective manure utilization. Manure treatments were developed for the removal of pathogens. Nevertheless, the effectiveness of these treatments was not evaluated for the removal of the antimicrobial resistant bacteria and their resistance genes. ARS researchers in Bowling Green, Kentucky, along with Western Kentucky University evaluated the impact of three commonly used manure treatments, lagoon, anaerobic digestion and composting, on the removal of bacteria and resistance genes. Covered lagoons, anaerobic digestion at higher temperature, and a properly managed composting significantly removed the resistance genes. These results indicate the need for proper treatment technologies as antibiotic resistance mitigation strategies and economic incentives for their wider utilization.

3. Improved a field-scale phosphorus model to protect water resources through effective management strategies. Phosphorus is an essential plant nutrient that is often applied to agricultural fields to maintain or increase crop yields, yet elevated phosphorus in runoff from agricultural fields can degrade water quality. Computer models are often used to guide management decisions for limiting phosphorus loss to protect water quality. The Annual Phosphorus Loss Estimator (APLE) model, developed by ARS, is a commonly used model for evaluating phosphorus loss risk from agricultural fields. ARS researchers in Bowling Green, Kentucky, and Beltsville, Maryland, made significant improvements to the APLE model by incorporating a method for predicting surface runoff. The updated model also allows users to account for model input uncertainties in predictions of phosphorus loss and changes in soil phosphorus levels, thus providing more realistic model predictions. This work provides an improved tool for researchers and nutrient management specialists to evaluate the effectiveness of different management practices on protecting water resources from excessive phosphorus loadings. The updated model is available to the public for download from ARS website (

4. Optimized nanoparticle composite material formation and evaluated their effectiveness on environmental pollutants that affect human health. Contaminants of emerging concern are those man-made or naturally occurring chemicals which are not commonly monitored in the environment but could adversely affect the environment, human health, and biotic communities by entering into the soil and aquatic ecosystems. To increase profit margin along with productivity, the utilization of hormones and other antibiotics to promote animal growth and reduce mortality has contributed to the emergence of resistant bacteria and endocrine disrupting chemicals in the environment. Thus, it is necessary to find a simple and economical way to counter or reduce the proliferation of these emerging contaminants of concern in the environment. Nanoparticle composite that can degrade and breakdown some of these chemicals hold a great promise in this arena. ARS researchers in Bowling Green, Kentucky and South Korea have found a way to synthesize these metallic nanoparticle composite (MNC) sourcing from electronic wastes and agricultural residues that were renewable and nontoxic to aquatic system. The results show that MNC has a remarkable activity against an endocrine disruptor chemical and non-toxic in aquatic ecosystem tests. Therefore, the present study provides a potential eco- friendly and sustainable way for the synthesis of nanoparticle composite for environmental pollution degradation.

5. Determined best method to provide accurate prediction of runoff from tile-drained fields. Surface runoff from agricultural fields has been shown to be a significant pathway of nutrient loss that can have adverse effects on water quality. This is particularly true for tile-drained fields which encompass over 22 million ha of agricultural fields in the United States. The curve number method is commonly used to predict runoff from agricultural fields; however, the curve number method has not been evaluated for use in tile-drained fields. ARS researchers in Bowling Green, Kentucky, and Columbus, Ohio, evaluated the curve number method at 12 tile-drained research sites in the Western Lake Erie Basin of Ohio. Rainfall and runoff observations at each of these sites were used to calculate curve numbers using six published variations of the method. The curve number methods often performed poorly, and sometimes altogether failed to produce a real solution. An alternative model, the complacent-violent method, produced the most accurate results and should be used in place of the curve number method in tile-drained fields. These results provide an improved approach for predicting surface runoff, and thus nutrient loss, from tile-drained fields. Better predictions of runoff will allow modelers and nutrient management planners to better evaluate how different conservation practices may affect nutrient loading from agricultural fields to Lake Erie when addressing water quality concerns in the Lake.

6. Observed biological pre-treatment of recalcitrant livestock wastes improves biogas production. Livestock production wastes with high woody contents (bedding materials) such as poultry litter can serve as the feedstock for biogas production (mainly methane) that could be used as alternative power source. However, these high woody feedstocks are quite difficult to be readily utilized by microorganisms to produce beneficial biogas, methane. Therefore, a pre-treatment and change in operating parameters of cultivating these microorganisms are necessary to improve biogas production from these woody materials as food source. ARS scientists in Bowling Green, Kentucky, and collaborators from South Korea and Mexico carried out an evaluation of various enzymes, substrate and inoculum ratios, temperatures on methane production from livestock wastes (poultry litter) with high woody (lignin and cellulosic) materials. Aerobic and anaerobic batch reactors containing different mixtures of fungal enzymes, operating temperatures, different inoculum feedstocks were set up to evaluate methane production. The results showed that more methane production was observed from feedstocks with enzymatic pre-treatment, higher operational temperatures, and medium substrate to inoculum ratios. Thus, biological pre-treatment utilizing isolated enzymes along with specific operating conditions could substantially improve biogas production which could potentially reduce operating costs and increase power production.

7. Studied oxidation of sulfur compounds under conditions similar to those near agriculture facilities. Several sulfur compounds emitted from animal operations are precursors to particulate matter formation in the atmosphere. The oxidation of these compounds results in the formation of sulfuric acid or methanesulfonic acid as the dominant products in the atmosphere. ARS researchers in Bowling Green, Kentucky, in collaboration with scientists from Western Kentucky University and UC Riverside, performed laboratory experiments in a Teflon environmental chamber to study oxidation and particulate forming potential of these compounds under conditions of elevated humidity. Results indicate that sulfur emissions from agriculture have different atmospheric chemistry than sulfur emissions over oceans. Ocean sources of sulfur and their reactions make up most of the assumptions widely used in regulatory and other air quality modeling of sulfur. These data, however, show that agricultural emissions of sulfur may react in different ways than expected by existing models. These findings suggest that the models used for atmospheric chemistry may need to be reexamined when used for agricultural emission sources of sulfur to improve the prediction of air quality.

8. Observed cover crops and manure impact on corn and soybean yield in a Silt Loam soil. There is renewed interest in soil conservation practices to promote sustainable agriculture by improving soil health and productivity. Collaborative research efforts between ARS researchers in Bowling Green, Kentucky, and Kentucky State University scientists on the short-term, on-farm benefits of cover crops and manure on crop yield and biomass of soybean and maize were examined during two consecutive growing seasons. Aboveground biomass of the soybean and maize were assessed, and yield was determined from hand-harvested plants. In the first year of the study, there were apparent but not significant beneficial effects of animal manure and cover crops on soybean yield but not on biomass. The biomass and maize grain yield in the second year were significant and increased due to the cover crops and manure application. The second-year results showed that farmers could use the management practice of combining animal manure and cover crop for increasing corn grain yield while improving soil health.

9. Determined human presence increases antibiotic resistance prevalence in groundwater systems. Analysis of current samples indicate antibiotic resistant bacteria (ARB) were found present consistently in mixed land use groundwater samples, with agricultural impacts playing an important role, possibly due to potential changes in geochemistry and nutrient loadings. ARS Researchers at Bowling Green, Kentucky, in collaboration with researchers at Western Kentucky University, Tennessee Tech University, and the United States Environmental Protection Agency utilized a spatio-temporal analysis approach to determine presence and concentration of ARB across multiple sites over 1-2 years of runoff and infiltration. Sites with human presence create a proliferation of ARB, which may be compounded by the introduction of ARB from agricultural amendment inputs and further exacerbated by nutrient loadings. Seasonal trends and storm event triggers appear to drive the proliferation of ARBs in these systems, with ongoing analysis underway to quantify and compare land use and hydrologic data. These results suggest ARBs are present in high concentration in groundwater systems and proliferate there, thus potentially impacting microbiomes and negatively affecting drinking water quality and human health.

10. Provided baseline evidence for mink farming as a potential reservoir for human pathogenic and antimicrobial resistant bacteria. Commercial mink production is a significant source of global fur production, and it is a significant economic sector for the United States. Like food animal production, concentrated mink production can be a reservoir for pathogenic and antimicrobial resistant bacteria that can spread through raw animal manure land applications. However, studies focusing on mink production are globally scarce, and absent in the United States. ARS researchers in Bowling Green, Kentucky, along with researchers at Utah State University determined the presence of pathogenic and antimicrobial resistant bacteria through microbial and molecular analyses of mink feces and feed samples collected from a mink farm. Antimicrobial resistance genes conferring resistance to the commonly used antibiotics to treat human infections were readily detected from the mink farm. Escherichia coli resistant to critically important antibiotics for public health, Enterococcus species commonly implicated in hospital acquired human infections were prevalent. Salmonella, the second most common cause of foodborne infections, including a multidrug resistant North American outbreak strain associated with turkey production and poultry associated strain, were detected from the mink farm. These results provide strong evidence that mink farming is important reservoir for human pathogens and their antimicrobial resistance. Our work provides baseline information for future large-scale studies to identify factors responsible for the emergence and persistence of important human pathogens and their antimicrobial resistance in mink production system.

11. Identified viable energy production and increased income for brewers from brewery spent grains. An increase in the number of breweries has led to an increase in the amount of waste with limited means of disposal. One option for disposal, however, is to use waste grain for anaerobic digestion to produce fuel. Experiments conducted by ARS researchers in Bowling Green, Kentucky, used brewery waste as the feedstock for the production of methane by bacteria. The digestate was recirculated through an aerated hose which served as a membrane allowing for the passage of gas while one treatment had no recirculation and another was kept under a low pressure of nitrogen. Aeration at low pressure and high-pressure air increased gas production compared to no recirculation. Treatment with nitrogen slowed gas production and inhibited waste treatment. This experiment shows that partial purging of dissolved gases in wastewater by the small fluxes of oxygen across a permeable membrane improves digestion of brewery spent grains and wastewater treatment giving brewers a viable option for waste disposal and energy production.

12. Optimized liquid chromatography-mass spectrometry (LCMS) and gas chromatography-mass spectrometry (GCMS) estrone and Beta-estriol signals. In anaerobic digestion, bacterial communities are believed to convert estrone and Beta-estriol into their sulfated conjugates. Sulfated estrone and Beta-estriol conjugates contain a greater degree of saturation than their non-conjugated counterparts. The implications are important from a public health perspective because these more saturated forms, also having estrogenic disrupting activity, persist in the environment longer than their non-conjugated forms. We have optimized and calibrated the LCMS and GCMS, which will be used to determine the amount of estrone and Beta-estriol in our dairy cattle feces, urine, and anaerobic digester samples. Optimized signals result in measuring these estrogens at very low levels, which is necessary to study the fate of their conjugates at environmental trace levels. Our next step is to determine the forms of these estrogens that exist before and after anaerobic digestion and if any decomposition during this process would render these estrogens physiologically inactive. Decomposition of these estrogens through anaerobic digestion would result in less estrogenic disrupting activity in the environment from dairy cattle practices. Because these estrogens eventually make their way into drinking water and food supplies, decomposition would result in less human exposure to estrogenic disrupting compounds.

Review Publications
Gelalcha, B.D., Ensermu, D.B., Agga, G.E., Vancuren, M., Gillespie, B.E., D'Souza, D.H., Okafor, C., Dego, O.K. 2022. Prevalence of antimicrobial resistant and extended-spectrum beta-lactamase-producing Escherichia coli in dairy cattle farms in east Tennessee. Foodborne Pathogens and Disease. 19(6).
Kaiser, R.A., Polk, J., Datta, T., Parekh, R.R., Agga, G.E. 2022. Occurrence of antibiotic resistant bacteria in urban karst groundwater systems. Water. 14(6). Article 960.
Agga, G.E., Couch, M., Parekh, R.R., Mahmoudi, F., Appala, K., Kasumba, J., Loughrin, J.H., Conte, E.D. 2022. Lagoon, anaerobic digestion, and composting of animal manure treatments impact on tetracycline resistance genes. Antibiotics. 11(3). Article 391.
Gelalcha, B.D., Agga, G.E., Kerro Dego, O. 2021. Antimicrobial usage for the management of mastitis in the USA: Impacts on antimicrobial resistance and potential alternative approaches. Intech.
Kerro Dego, O., Almeida, R.A., Ivey, S., Agga, G.E. 2021. Evaluation of Streptococcus uberis surface proteins as vaccine antigens to control S. uberis mastitis in dairy cows. Vaccines. 9(8). Article 868.
Loughrin, J.H., Antle, S.W., Bryant, M.D., Berry, Z.P., Lovanh, N.C. 2020. Evaluation of microaeration and sound to increase biogas production from poultry litter. Environments. 7(8). Article 62.
Bolster, C.H., Vadas, P.A. 2022. Updates to the Annual P Loss Estimator (APLE) model. Journal of Environmental Quality. 1-7.
Wessel, B., Bolster, C.H., King, K.W., Shedekar, V.S. 2022. Rainfall-runoff models compared for tile-drained agricultural fields in the Western Lake Erie Basin, Ohio. Journal of Hydrology. 610. Article 127959.
Pearce, A., Slaton, N., Lyons, S., Bolster, C.H., Bruulsema, T., Grove, J., Jones, J., Mcgrath, J., Miguez, F., Nelson, N., Osmond, D.L., Parvej, M., Pena-Yewtukhiw, E.M., Spargo, J.T. 2022. Defining relative yield for soil test correlation and calibration trials in the fertilizer recommendation support tool. Soil Science Society of America Journal. 1-16.
Van Rooy, P., Purvis-Roberts, K.L., Silva, P.J., Nee, M.J., Cocker III, D.R. 2021. Characterization of secondary products formed through oxidation of reduced sulfur compounds. Atmospheric Environment. 256. Article 118148.
Ro, K.S., Woodbury, B.L., Spiehs, M.J., Szogi, A.A., Silva, P.J., Hwang, O., Cho, S. 2021. Pilot-scale H2S and swine odor removal system using commercially available biochar. Agronomy [MDPI]. 11(8). Article 1611.
Tewolde, H., Buehring, N., Way, T.R., Feng, G.G., He, Z., Sistani, K.R., Jenkins, J.N. 2021. Yield and nutrient removal of cotton-corn-soybean rotation systems fertilized with poultry litter. Agronomy Journal. 113:5483-5498. https://doi.10.1002/agj2.20857.
Berry, Z.P., Loughrin, J.H., Burris, S., Conte, E.D., Lovanh, N.C., Sistani, K.R. 2022. Improving anaerobic digestion of brewery and distillery spent grains through aeration across a silicone membrane. Sustainability. 14(5). Article 2755.
Mohan, H., Vadivel, S., Lee, S., Lim, J., Lovanh, N.C., Park, Y., Shin, T., Seralathan, K., Oh, B. 2022. Improved visible-light-driven photocatalytic removal of Bisphenol A using V2O5/WO3 decorated over Zeolite: Degradation mechanism and toxicity. Environmental Research. 212(A). Article 113136.
Agga, G.E., Silva, P.J., Martin, R.S. 2021. Prevalence, serotypes, and antimicrobial resistance of Salmonella from mink feces and feed in the United States. Foodborne Pathogens and Disease. 19(1):45-55.
Agga, G.E., Silva, P.J., Martin, R.S. 2022. Tetracycline- and macrolide-resistant Enterococcus species isolated from a mink farm in the United States. Microbial Drug Resistance. 28(6):734-743.
Gutema, F.D., Rasschaert, G., Agga, G.E., Jufare, A., Duguma, A.B., Abdi, R.D., Duchateau, L., Crombe, F., Gabriel, S., De Zeutter, L. 2020. Occurrence, molecular characteristics, and antimicrobial resistance of Escherichia coli O157 in cattle, beef and humans in Bishoftu Town, Central Ethiopia. Foodborne Pathogens and Disease. 18(1);1-7.
Gutema, F.D., Abdi, R.D., Agga, G.E., Firew, S., Rasschaert, G., Mattheus, W., Crombe, F., Duchateau, L., Gabriel, S., De Zutter, L. 2021. Assessment of beef carcass contamination with Salmonella and E. coli O 157 in slaughterhouses in Bishoftu, Ethiopia. International Journal of Food Contamination. 8. Article 3.
Van Rooy, P., Drover, R., Cress, T., Michael, C., Purvis-Roberts, K., Silva, P.J., Nee, M., Cocker, D. 2021. Methanesulfonic acid and sulfuric acid aerosol formed through oxidation of reduced sulfur compounds in a humid environment. Atmospheric Environment. 261. Article 118504.
Loughrin, J.H., Antle, S.W., Simmons, J.R., Sistani, K.R., Lovanh, N.C. 2020. In situ sonification of anaerobic digestion: Extended evaluation of performance in a temperate climate. Energies. 13(20). Article 5349.
Bolster, C.H. 2021. Comparing unamended and Fe-coated biochar on removal efficiency of bacteria, microspheres, and dissolved phosphorus in sand filters. Biochar Journal. 3:329-338.
Bolster, C.H., Wessel, B.M., Vadas, P.A., Fiorellino, N.M. 2022. Sensitivity and uncertainty analysis for predicted soil test phosphorus using the Annual Phosphorus Loss Estimator model. Journal of Environmental Quality. 51(2):216-227.
Ma, H., Bolster, C.H., Johnson, W.P., Li, K., Pazmino, E., Camacho, K.M., Anselmo, A.C., Mitragotri, S. 2020. Coupled influences of particle shape, surface property and flow hydrodynamics on rod-shaped colloid transport in porous media. Journal of Colloid and Interface Science. 577:471-480.
Hallar, G.A., Brown, S., Crosman, E., Barsanti, K., Cappa, C., Faloona, I., Fast, J., Holmes, H., Horel, J., Lin, J., Middlebrook, A., Mitchell, L., Murphy, J., Womack, C.C., Aneja, V., Baasandorj, M., Bahreini, R., Banta, R., Bray, C., Brewer, A., Caulton, D., de Gouw, J., De Wekker, S., Farmer, D.K., Gaston, C.J., Hoch, S., Hopkins, F., Karle, N., Kelly, J., Kelly, K., Lareau, N., Lu, K., Mauldin III, R.L., Mallia, D., Martin, R., Mendoza, D., Oldroyd, H., Pichugina, Y., Pratt, K.A., Saide, P., Silva, P.J., Simpson, W., Stephens, B., Stutz, J., Sullivan, A. 2021. Coupled air quality and boundary-layer meteorology in Western U.S. basins during winter: Design and rationale for a comprehensive study. Bulletin of the American Meteorological Society. E2012-E2033.