Doctor of Philosophy, The Ohio State University, 2022, Environmental Science

Accelerated erosion-induced topsoil loss threatens the productivity and sustainability of maize (Zea mays L.) cropping systems across the U.S. Corn Belt by adversely impacting soil health. The rehabilitation of soil health in eroded topsoil has been shown to improve with best management practices coupled with soil amendment application. The current study investigated the impact of simulated erosion and annual amendment application on soil health 20 years after establishment at two central Ohio sites (Waterman Farm: WF; Western Station: WS). Simulated erosion was employed in 1997 to create three incremental topsoil depths (TSD) (20 cm topsoil removed (TSD-0); 0 topsoil removed (TSD-1); 20 cm topsoil added (TSD-2). Annual application of three soil amendments (inorganic, synthetic N fertilizer (I); organic, compost manure amendment (O); no amendment (C)) were investigated for their ability to restore soil health in the surface 40 cm of these cropping systems. Increasing TSD resulted in more favorable physical, chemical, and biological soil health attributes primarily through enhanced soil structure, aggregation, water movement and storage, soil pH range, and SOC and soil N concentrations. The organic amendment proved most efficient in regenerating soil health at lower TSD levels and augmenting soil health in systems with greater TSD levels. Greater TSD usually resulted in greater C and N pools after two decades. However, this was variable at levels where greater TSD was present. Soils amended with the organic treatment always produced greater C and N stocks across both sites. The trends in SOC pools were TSD-1 ≥ TSD-2 > TSD-0 at the WF site and TSD-2 ≥ TSD-0 ≥ TSD-1 at the WS site. The trend in TN pools followed the same pattern as SOC pools at the WF site, but was TSD-2 ≥ TSD-1 ≥ TSD-0 at the WS site. Soils with greater TSD and those amended with the organic amendment were more resilient in the face of simulated rainfall and resulted in the smallest incurred losses of (open full item for complete abstract)

Committee: Rattan Lal (Advisor); Kristin Mercer (Committee Member); Steven Culman (Committee Member); Nicholas Basta (Committee Member) Subjects: Agriculture; Agronomy; Environmental Science; Soil Sciences; Water Resource Management

Master of Science, The Ohio State University, 2021, Environmental Science

Soil health indicators are commonly used by researchers to understand how various soil properties are functioning. However, many new indicators have not been applied on working farm conditions and it is not well understood how these novel indicators may be useful to farmers in their management decision-making. This research took an integrated approach combining social science methods and biophysical soil testing to understand the use and value of soil health indicators to farmers in Ohio. A total of 19 soil health parameters were measured and reported back to farmers to discuss how these data could inform their future management decisions and to understand which indicators are most useful to farmers. Interviews were conducted with 20 row crop farmers to gather their insights on the utility of soil health indicators, as well as their management decisions following the 2019 growing season. Ultimately, the research evaluated how soil health indicators varied across selected fields the farmer deemed best and most challenging. This research also assessed which indicators aligned best with farmer perceptions of the soil health data and if the soil health indicators influenced adoption of new management practices among farmers. Findings from the research indicate that biological soil health indicators such as soil protein, respiration (MinC), and permanganate oxidizable carbon (POXC) were able to distinguish between best and most challenging field, were more sensitive indicators than others, and were most aligned with farmer perceptions of their fields. Additionally, this study found that while farmers found many biological indicators insightful, they did not provide sufficient information to alter any change in management. Overall, this study highlights the importance of interdisciplinary work by integrating social and natural sciences to gain a comprehensive assessment of farmers' perceptions and practices in relation to agricultural (open full item for complete abstract)

Committee: Christine Sprunger (Advisor); Nicholas Kawa (Advisor); Steve Culman (Committee Member) Subjects: Agriculture; Environmental Science; Environmental Studies

Doctor of Philosophy, The Ohio State University, 2014, Environmental Science

Increasing proportions of vacant land parcels in post-industrial cities is a growing concern due to decreasing land value and increasing maintenance externalities. Utilizing this urban vacant land for growing food crops can promote local self-reliance and access to healthy food; specifically in low income disadvantaged neighborhoods. However, impact of heavy metal contaminants on soil quality, is a major concern for urban agriculture. Additionally, health of vacant lot soil also depends on the structural bio-diversity of the below ground soil food web. Hence the specific objectives of this research were (i) to assess the level of soil heavy metal concentrations in two post-industrial cities and determine their potential human health risk (Chapter 2); (ii) to evaluate the relationship between heavy metal concentrations and the structure and function of the soil food web using nematodes as surrogates of soil microbial community (Chapter 3); (iii) to test a novel approach of transplantation of an intact soil core to reconstruct the structural complexity of a disturbed soil food web and restore its level of multi trophic interactions to a pre-disturbance level (Chapter 4) (iv) finally, to re-construct the soil food web in urban vacant lot using intact soil cores from relatively undisturbed forest soil, and assess the survival of the introduced nematode species under organic matter with different C:N ratios (Chapter 4) We determined the extent of soil Pb, Cd, Zn, As and Cr concentrations in 43 vacant lots in two disadvantaged neighborhoods in Hough (Cleveland) and Weinland Park (Columbus), Ohio. Results showed that compared to the Ecological Soil Screening levels (Eco SSL) for human ingestion of soil, only 6% of the lots in Weinland Park and 53% in Hough neighborhood had Pb concentrations above the Eco SSL of 400 mg Pb/kg soil. Also, all the studied sites exceeded the Eco SSL value of 0.4 mg As/kg soil; however, soil As concentration in 94% of the lots in Weinl (open full item for complete abstract)

Committee: Parwinder Grewal Dr. (Advisor); Larry Phelan Dr. (Committee Member); Nick Basta Dr. (Committee Member); Rafiq Islam Dr. (Committee Member) Subjects: Environmental Science

Doctor of Philosophy, The Ohio State University, 2024, Environment and Natural Resources

Soils are a non-renewable resource, which is the foundation of all ecosystems. Mismanagement of soil particularly in agro-ecosystems has degraded soil. To guide management of soils, to remediate soils, and enable optimal agricultural production, soil health indicators are needed. The objective of this dissertation was to determine the potential of biological and other soil properties to predict soybean yields. The central approach was based on soil samples from farmers' fields instead of long-term experimental sites (LTES). Farmers' fields in this study represented diverse management practices that exist in the agricultural sector. Soil Health (SH) measurements that are calibrated and that can consistently detect land management are lacking which was shown in Roper's et al. (2017) 2017 publication that found existing SH tests (CASH, Haney) had limited ability to identify agronomic land management practices at a North Caroline LTES. And that they were poorly correlated with crop yields. This means that the quote by the Soil Health Institute “There is no standardized measurement for Soil Health in the United States” is still true. Extensive research has found certain soil enzyme assays to be quite sensitive for detecting land management effects and exhibit seasonal stability. The currently promoted SH indicator scores have limited or inappropriate biological indicators (e.g. microbial biomass and respiration). The latter measurements vary too much on a seasonal basis due to weather variation or a recent short term soil management event (e.g. high organic inputs, disturbance). Thus, the global objective of this dissertation was to determine the potential of biological soil properties, specifically enzyme activities and microbial community biomarkers to quantify SH. Enzyme activity has the added advantage over most other soil biological measurements, that it can be run on air-dried soil and furthermore is relatively simple. This is attractive to commercial labs who wa (open full item for complete abstract)

Committee: Richard Dick (Advisor); Laura Lindsey (Committee Member); Brian Slater (Committee Member); Rattan Lal (Committee Member) Subjects: Microbiology; Soil Sciences

Doctor of Philosophy, The Ohio State University, 2024, Environmental Science

Historical and current anthropogenic activity combined with land turnovers and rampant vacancies have increased human exposure risk to contaminants. This exposure risk disproportionately affects lower income communities and can have detrimental impacts on human health, particularly children. A management solution is needed to address this widespread contamination of vacant lots. Additionally, federal and state regulators continue to lower residential soil Pb standards which will likely require new risk-based approaches to address urban soil Pb contamination. This dissertation examines three different amendment types (P amendments, Fe oxide containing amendments, and potassium permanganate (KMnO4)) for their ability to address urban Pb soil contamination and reduce human health exposure risk. Remediation strategies that can address both organic and inorganic pollutants are also needed. This is addressed in Chapter 3. This dissertation is written as a series of manuscripts to be submitted to the appropriate journals; this will be reflected by slight differences in formatting. In Chapter 1, readily available P sources (biosolids incinerator ash, poultry litter, biosolids compost, and triple super phosphate) of varying solubility were assessed as soil amendments to reduce Pb bioaccessibility and serve as an inexpensive remediation strategy for urban soil. Contaminated soil from Cleveland, OH was treated with the P soil amendments at a 1:5 Pb:P molar ratio and incubated for 3 months. A slurry analysis was also conducted to assess reduction in bioaccessible Pb independent of time. Pb bioaccessibility was evaluated using US EPA Method 1340 at pH 1.5 and the Physiologically Based Extraction Test (PBET). Treatments were largely found ineffective regardless of IVBA extraction method, incubation duration, slurry analyses, or P source. Method 1340 had one significant treatment (combined poultry litter and BIA) but only resulted in a 8% IVBA Pb reduction. The same treatmen (open full item for complete abstract)

Committee: Nicholas Basta (Advisor); Brian Lower (Committee Member); Steven Lower (Committee Member); Darryl Hood (Committee Member) Subjects: Environmental Science; Soil Sciences

Master of Science (MS), Bowling Green State University, 2023, Biological Sciences

Fraxinus ash trees in North America a threatended by the invasive Agrilus planipennis, emerald ash borer (EAB). EAB infestation has wide ranging economic, cultural and ecological impacts upon the North American environment. This study aims to look at the biological impact that infestation of ash trees can have on the soil microbiome around the tree's roots. A previous study has already examined the possible geochemical effects of the trees sampled, and by looking at the effects on the microbiome through 16S ribosomal sequencing, we hoped to gain some estimation of the effect imposed on microbiota surrounding the tree. With a combination of alpha, beta, and network analysis, we can see some possible changes within the rhizosphere associated to the health of trees. Alpha diversity was inconclusive as there was inconsistent data amongst our sampled set of trees. There is confounding points in the data pertaining to geographic differences in sample locations. However, when stratifying to sample locations, beta and network analyses show shifts in the microbiome are significant, with site 2 and 4 beta diversity showing a progression of microbiome makeup to change as health state changed. Differential networks between health states indicate a change in taxa between healthy and unhealthy tree rhizopheres exist. The network topography as well as the strength of edges between networks showed a difference in taxonomic makeup comparing health states with some phyla of note being Verrucomicrobia, Nitrospirae, and Acidobacteria. Because our sample size within each location was small, we recommend further studies be done to explore those differences.

Committee: Zhaohui Xu Ph.D. (Committee Chair); Jungfeng Shang Ph.D. (Committee Member); Angelica Vazquez Ortega Ph.D. (Committee Member) Subjects: Bioinformatics; Biology; Microbiology

Master of Science, The Ohio State University, 2023, Food, Agricultural and Biological Engineering

Interest in agricultural soil health and quality has encouraged farmers across the world to adopt soil health management practices, such as no-till or reduced tillage and cover crops. In-spite of the growing adoption of soil health practices, few studies have focused on their impact on soil and water quality after long-term adoption. To assess the effects of soil health practices, soil and water samples were collected over two years from three paired sites, each representing three different land use management scenarios: (1) agricultural fields with conventional crop rotation and management, (2) agricultural fields with 15 to 45 years of soil health management adoption, and (3) forest soils near each pair of agricultural fields. A combination of 52 soil health indicators were analysed including: microbial communities, enzyme activities, phospholipid fatty acid (PLFA), soil respiration, bulk density, macronutrients, and micronutrients. Edge-of-field and surface runoff analysis included total nitrogen (TN), total phosphorus (TP), nitrate, and dissolved reactive phosphorous concentrations during dry and wet periods over the course of a year. Results suggest that long-term soil health management had little impact on soil health indicators when compared to conventionally managed farms but did reduce TP, TP, nitrate leaching, and water loss. However, further evaluation of the soil health indicators revealed some promising relationships between soil health and water quality. When compared to the forested systems, both agricultural systems were found to have significantly lower biological quality. These results provide some evidence to support the implementation of soil health practices in agricultural fields and a perspective on long-term agricultural management practices compared to native natural soil health.

Committee: Ryan Winston (Advisor); Vinayak Shedekar (Committee Member); William Osterholz (Committee Member) Subjects: Agriculture; Environmental Engineering; Hydrologic Sciences; Soil Sciences; Water Resource Management

Master of Science, The Ohio State University, 2023, Environment and Natural Resources

Since the beginning of time Earth's carbon cycle has self-regulated, experiencing periods of warming and cooling with changing amounts of carbon in the atmosphere. Today, human activity is rapidly changing the climate through the addition of greenhouse gases to the atmosphere like carbon dioxide (CO2). To prevent disastrous outcomes caused by climate change, it is vital to halt greenhouse gas emissions, however, this is only one part of the solution. To keep global temperatures from increasing more than 2° C, CO2 removal must also be an integral part of the solution. The objectives of this research were to conduct a laboratory experiment and investigate the carbonation of concrete within soil as a viable option to sequester atmospheric carbon, analyze how concrete carbonation changes with fragment size, and understand the environmental impacts of adding concrete to soil. Soil samples from Waterman Agricultural and Natural Resources Center were collected and placed into 30 cm columns with different mixtures of crushed recycled concrete to test concrete in soil as an enhanced weathering material. Four different treatments were tested and were comprised of 1) 100% soil (S samples), 2) 90% soil and 10% concrete by weight of 0.25-0.71 mm diameter fragments (F samples), 3) 90% soil and 10% concrete by weight of 8 mm diameter fragments (L samples), and 4) 100% concrete composed of 8 mm diameter fragments (C samples). Four replications of each treatment were tested for a total of 16 samples. Approximately 40 cm3 of deionized water was added to each sample every day from a drip irrigation system for a total amount of 940-990 mm yr-1 throughout the experiment to simulate the amount of precipitation received by Columbus, OH in one year, with leachate continuously collected underneath the columns. After 16 weeks, the soil and concrete mixtures were removed from the columns and tests were conducted on the soil and leachate samples. The results from this study show that con (open full item for complete abstract)

Committee: Rattan Lal (Advisor); Berry Lyons (Committee Member); M. Scott Demyan (Committee Member); Matt O'Reilly (Committee Member) Subjects: Civil Engineering; Climate Change; Environmental Science; Soil Sciences

Master of Science in Environmental Science, Youngstown State University, 2021, Department of Physics, Astronomy, Geology and Environmental Sciences

Although frequently overlooked or omitted, ecosystem services provide an environment for the survival of life on earth, including humans. Soil is a critical compartment for ecosystem services composed of solids, gasses, water, and micro and macro flora and fauna. Soil functions include water holding capacity, nutrient holding and cycling, support for microbial life, carbon capture, and other many other unseen benefits. Within society a main use of soil is agriculture for growth of food, fiber, and other necessities for civilization. Agricultural practices can consist of different techniques, two common categories are conventional and conservation methods. Conventional tillage utilizes turning of the soil to prepare the seedbed and remove unwanted plants. In conservation methods the use of no tillage or reduce tillage is used, where the soil is minimally disturbed, and the seeds are inserted into small slits or openings. Aggressive tillage can affect soil ecosystem function and limit the quality of soil health by decreasing porosity, reducing microbial processes, and increasing erosion. Seven farm fields in Trumbull County, OH, were sampled to investigate the connection between agricultural method and soil quality characteristics that contribute to overall soil health and productivity. Composite soil samples consisting of 2.5 cm soil cores separated into top 15 cm layer and bottom layer were evaluated for organic matter, bulk density, soil texture, plant available phosphorus, pH, total nitrogen, salinity, and percent porosity using standard methods. The data composed of 32 samples, with 16 samples from the top layer and 16 from the bottom layer. The fields were ranked one to four, with a ranking of one indicating conventional methods to ranking of four with the highest amount of conservation practices applied. Statistical analyses included descriptive statistics, mean comparison, one-way ANOVA, Principal Component Analysis, and backwards linear regressions using S (open full item for complete abstract)

Committee: Felicia Armstrong PhD (Advisor); Colleen McLean PhD (Committee Member); Albert Sumell PhD (Committee Member); Lee Beers MS (Committee Member) Subjects: Agricultural Economics; Agricultural Education; Agriculture; Agronomy; Earth; Economic Theory; Environmental Economics; Environmental Education; Environmental Health; Environmental Philosophy; Environmental Science; Environmental Studies; Soil Sciences; Sustainability

Master of Science, The Ohio State University, 2021, Environment and Natural Resources

The linkages between fine root production and soil food webs are poorly understood. Moreover, assessing how these belowground dynamics influence soil health is deeply needed to enhance sustainable agriculture. This thesis explores how contrasting agricultural practices alter fine root dynamics, soil food web structure and function, and soil health indicators over the course of a growing season. Fine root biomass, fine root carbon (C), fine root nitrogen (N), fine root carbon:nitrogen ratios, and fine root biomass:aboveground biomass ratios were measured and correlated to permanganate oxidizable carbon (POXC), protein, mineralizable carbon (MinC), aryl sulfatase (AS), N-acetyl-B-glucosaminidase (NAG), and B-gluscosidase (GLU) in systems of corn-forage-forage no-till, corn-forage-forage chisel, corn-soy no-till, and corn-soy chisel at Hoytville, Ohio (clay site) and Wooster, Ohio (silt loam site). Additionally, nematode communities were identified and used to calculate feeding group abundances and nematode indices to indicate soil food web structure and function. Results indicate that greater fine root N was significantly and positively correlated with greater labile C and N pools and nutrient cycling. In addition, soil health was enhanced at the end of the growing season, especially in corn systems that were consistently rotated with perennial crops. The measurement of soil food web structure and function, through the use of nematode feeding groups and nematode indices, revealed that systems of greater crop rotational diversity and reduced tillage intensity have the potential to provide enhanced soil food web structure and slow C decomposition through top-down regulation of the soil food web and fungal mediated decomposition. Furthermore, results of the non-metric multidimensional scaling (NMDS) vector analysis indicated strong correlations between nematode community structure in corn-forage-forage no-till systems and soil health indicators of POXC, Protein, NAG, GL (open full item for complete abstract)

Committee: Christine Sprunger (Advisor); Steve Culman (Committee Member); Alison Bennett (Committee Member) Subjects: Agriculture

Master of Science, The Ohio State University, 2020, Plant Pathology

It has been documented that beneficial plant-associated bacteria have contributed to disease suppression, growth promotion, and tolerance to abiotic stresses. Advances in high-throughput sequencing have allowed an increase in research regarding bacterial endophytes, which are microbes that colonize the interior of plants without causing disease. Practices associated with minimizing the use of off-farm resources, such as reduced tillage regimes and crop rotations, can cause shifts in plant-associated bacteria and its surrounding agroecosystem. Integrated crop–livestock systems are an option that can provide environmental benefits by implementing diverse cropping systems, incorporating perennial and legume forages and adding animal manure through grazing livestock. It has been found that crop-livestock systems can increase soil quality and fertility, reduce cost of herbicide use and improve sustainability, especially for farmers in poorer areas of the world. This work explores how crop-livestock systems that integrate chicken rotations can impact tomato plant growth, as well as soil and endophytic bacterial communities. Tomato plants were subjected to greenhouse and field studies where biomass was assessed, and bacterial communities were characterized through culture-dependent and -independent approaches. In greenhouse experiments, the greater percent of chicken grazed soil incorporated in the planting substrate, the greater the stunting of tomato seedlings. In the field study, bacterial communities differed significantly by sample origin and plant development stage, regardless of chicken grazing history. Our findings suggest stronger contribution of agricultural management practices during early plant stages on endophytic microbiome, as opposed to later on in the host lifecycle. Taxonomic composition of dominant groups of recovered endophytic bacterial isolates were consistent with those found by amplicon sequencing. Plots with history of chicken grazing had a sig (open full item for complete abstract)

Committee: Maria Soledad Benitez-Ponce Ph.D. (Advisor); Christine Sprunger Ph.D. (Committee Member); Jonathan Jacobs Ph.D. (Committee Member) Subjects: Agriculture; Biology; Ecology; Microbiology; Plant Pathology; Soil Sciences

Master of Science (MS), Bowling Green State University, 2020, Geology

The impact of Emerald Ash Borer infestation on Fraxinus trees in eastern North America has been extensively studied, yet impacts to the soil health as the infestation progresses are not well understood. This study characterized soil samples from 5 health categories of Ash (Category 1: healthy; Category 5: dead) in 4 wooded upland sites in Northwest Ohio to gain a current assessment of soil health on locations with similar soil characteristics and geographic factors. Results indicated a strong positive relationship between canopy openness and health categorization (towards decline tree health). However, only a moderate negative relationship between humification index (degree of aromaticity) and canopy openness, indicating less aromatic soil organic matter beneath infested Ash trees. This suggests leaf litter from formation of epicormic branching may be replenishing or maintaining solid organic carbon stocks in soil even after the tree reaches category 4. Density of epicormic branching may also affect trends in bioavailable total nitrogen (TN) and dissolved organic carbon stocks (DOC: TN). The DOC: N ratio combined with a pattern of decrease and increase exhibited individually by DOC and TN, suggests leaf litter supply to the soil was directly affected by loss of canopy and epicormic branching. This feedback system was more visible in soil testing by the presence of neutral to slightly alkaline pH, which may be facilitating nitrification, maintaining low DOC: N ratios and increasing sensitivity to leaf litter fluxes. The neutral to slightly alkaline pH was most likely the result of high calcium (Ca) concentrations on all 4 sites. Results suggested that Ca concentrations were unaffected by base cation leaching, indicating external influxes of Ca. This study suggests Ash trees on these sites may be lingering at category 3 to 4 for several years with epicormic branching making significant contributions to soil fertility even at category 4. Results from category 4 and 5 o (open full item for complete abstract)

Committee: Angélica Vázquez-Ortega Dr. (Advisor); Nathan Hensley Dr. (Committee Member); Jeff Snyder Dr. (Committee Member); Zhaohiu Xu Dr. (Committee Member) Subjects: Biogeochemistry; Environmental Science; Forestry; Geochemistry; Geology; Organic Chemistry; Soil Sciences; Sustainability

Master of Science, The Ohio State University, 2020, Plant Pathology

Higher crop rotational diversity can improve crop productivity, soil health and soil microbial diversity. This research hypothesized that three-year (3-yr) rotation of soybean-corn-wheat would have higher soybean productivity, better soil health and more diverse soil bacterial community compared to two-year (2-yr) soybean-corn rotation. A rotation experiment was established in 2013 at two research sites in Ohio. Soybean seedling establishment and biomass, crop yield and soil were collected in 2018 and 2019. Higher seedling stand and biomass, and soybean yield were observed in the 3-yr rotation but the results were not consistent across all site-year combinations. Soil organic matter was higher in the 3-yr rotation at three out of four site-years. Similarly, higher soil carbon, nitrogen and active carbon was detected in the 3-yr rotation at one site-year. The bacterial community at NWARS and WARS also different. However, at each site, the diversity of soil bacteria, sampled at soybean seedling stage, did not differ between the 2-yr and 3-yr rotation. Seven major phyla and nine core bacterial sequence variants were found in samples from all treatments. Nevertheless, compared to the 2-yr rotation, the 3-yr rotation had a unique set of six taxa, absent in the 2-yr rotation samples, and higher abundance of Pseudomonas sequence variants and lower abundance of Ralstonia sequence variants. Most of the 3-yr rotational benefits were detected on site-year combinations where environment and weather conditions were unfavorable to soybean growth, such as poorly drained soil, high precipitation, and fewer growing degree days. Hence, under unfavorable conditions, the 3-yr rotation of soybean-corn-wheat is recommended for soybean and soil benefits.

Committee: Maria Soledad Benitez Ponce (Advisor); Laura Lindsey (Committee Member); Ye Xia (Committee Member) Subjects: Plant Pathology

Master of Science (MS), Bowling Green State University, 2019, Biological Sciences

There is a critical need to reduce nutrient losses from agricultural systems in order to protect freshwater ecosystems from nutrient loading. While the main cause of eutrophication of Lake Erie has been shown to be runoff of phosphorus and nitrogen, freshwater eutrophication management should be based on practices that consider complex habitat feedbacks, climatic changes, and nutrient cycling. I conducted a study that manipulated soil macroinvertebrate abundance and rainfall amount in an agricultural mesocosm system. I evaluated the effectiveness of increasing detritivore abundance as a strategy for nutrient management in an agroecosystem by assessing the phosphorus, nitrogen, and carbon levels within the soil, corn, invertebrates, and soil solution (i.e. the water and soluble nutrients held within soil that can leach out when soil reaches its water holding capacity). Overall, I found that increasing detritivore abundance in our soil significantly increased corn biomass by 2.49 g (p<0.001), reduced weed growth by 18.2% (p<0.001), and decreased soil solution volume by 31.03 mL (p<0.001) and nutrients (p<0.05). Depending on rainfall treatment, detritivore abundance also significantly influenced soil total P (p=0.0019), total N (p<0.001), and total C (p=0.0146). Our study provides further support that soil detritivores play a crucial role in soil nutrient cycling and soil health. This study served as one of the first to show that incorporating soil macroinvertebrate abundance into management strategies for agricultural soil will increase soil health of agroecosystems, preserve freshwater ecosystems, and protect the valuable services they both provide for humans.

Committee: Shannon Pelini PhD. (Advisor); Kevin McCluney PhD. (Committee Member); Angélica Vázquez-Ortega PhD. (Committee Member) Subjects: Biology; Ecology

Master of Science, The Ohio State University, 2019, Environment and Natural Resources

Conservation practices, such as no-till and diversifying crop rotations are known for their capacity to reduce soil erosion and improve soil properties. However, the impact of these management practices on emerging soil health tests and the ability of these tests to reflect active organic matter dynamics and nutrient cycling, and corn productivity has not been explored. This project focused on determining the effects of half a century of continuous tillage treatments (moldboard plow, chisel till, and no-till) and crop rotations (continuous corn, corn-soybean, and corn-forage-forage) on soil health indicators and its relationship with crop productivity. The forages were alfalfa in Wooster and red clover and oats in Northwest. Soil labile carbon (C) and nitrogen (N) temporal dynamics were quantified with permanganate oxidizable C (POXC), mineralizable carbon (Min C), and soil protein at six key stages in corn (Zea mays) development: before planting (around three weeks before planting), V5, V10, R1, R4, R6 in the 2017 and 2018 growing seasons. Corn leaf chlorophyll, aboveground plant biomass, nutrient uptake, and grain yield were also quantified. The soil health indicators (POXC, Min C, soil protein) and crop parameters (leaf chlorophyll, total nitrogen uptake, and total aboveground biomass) were higher in reduced tillage (chisel and no-till) compared to moldboard plow and higher in the most diverse crop rotation (corn-forage-forage) compared to corn-soybean. Corn yields were not significantly different between tillage treatments but were higher in the more diverse rotations (corn-soybean and corn-forage-forage) compared to corn monoculture. Although the treatment effects varied by site and year, rotation had a consistently larger effect on soil health indicators and corn productivity than tillage, highlighting the importance of including crop rotations in corn production. We conclude that Ohio soils under half a century of continuous tillage and rotation treatments ha (open full item for complete abstract)

Committee: Steve Culman PhD (Advisor); M.Scott Demyan PhD (Committee Member); Peter Thomison PhD (Committee Member) Subjects: Agriculture; Agronomy; Soil Sciences

Doctor of Philosophy, The Ohio State University, 2019, Environment and Natural Resources

Soil health is an emerging framework that seeks to integrate the physical, chemical, and biological components of soil. It is defined by the USDA as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”. The breadth of this definition has allowed “soil health” to become a context-specific definition, letting soil health be defined in terms of the desired outcomes. In the context of agronomic nutrient management, the primary desired outcome is a tightening of the nutrient cycle to minimize losses to the environment. Here, I use the framework of soil health to understand how soil health indicators influence and are influenced by on-farm nutrient management practices. Three separate studies were conducted to: 1) understand the factors influencing the efficacy of the most widely used biological soil health metric, mineralizable carbon, 2) determine the effect of 12 years of phosphorus (P) restriction on biological and physical soil health in three Ohio sites, and 3) integrate biological soil health indicators into nitrogen (N) management strategies across the Corn Belt. The first study found that mineralizable C was variable across and within soil test labs. However, even after controlling for variations in methodology, a significant amount of the variability was soil-specific. The second study found very few effects of P restriction on soil biological and physical health. However, P restriction slightly increased organic P stocks and resulted in consistent shifts in the balance between the processed and easily-metabolized portions of the active C pool. In the third and final study, an increase in soil biological health was shown to increase the yields for a given N fertilization rate, as well as having slight predictive abilities in predicting whether a site would be responsive to N fertilization. This study also showed that soil biological health may be slightly increased at moderate N fertilization rates. C (open full item for complete abstract)

Committee: Steve Culman (Advisor); Michael Demyan (Committee Member); Kristin Mercer (Committee Member); Nicholas Basta (Committee Member); Jessica Logan (Committee Member) Subjects: Agronomy; Soil Sciences

Master of Science, The Ohio State University, 2018, Horticulture and Crop Science

In Ohio, many organic farmers use the term `balancing' to express the rationale of using a wide variety of soil amendments to improve soil quality and plant health. Soil balancing or the base cation saturation ratio (BCSR) approach is a method first proposed more than 100 years ago that aims to achieve the `ideal soil'. William Albrecht in the 1970's concluded that if saturation of the major exchangeable cations is 65-85% for Ca, 6-12% for Mg, and 2-5% for K, plant nutrition will be balanced. Research conducted by Zwickle et al. (2011) indicated that many organic farmers believe balanced soils produce higher quality crops and have diminished weed infestations compared to unbalanced soils. For many farmers, soil balancing includes using amendments thought to enhance soil biology and increase the soil's capacity to store and release minerals needed by plants. Combined mineral and these organic/bio-active soil products can be very costly, as much as US $1000-1250/ha in the first year. While farmers believe they are benefiting from these expenditures, there is no objective evidence to confirm their belief. I conducted on-farm studies at six locations in Northeast Ohio, with the overall goal of determining the effect of gypsum, with or without “biological stimulants”, on the soil microbial community, crop quality, weed populations, and soil chemical characteristics. Soil seed bank and soil health/biological properties were measured, including soil respiration, active carbon, protein content, microbial biomass, and complete mineral analysis. Crop foliage for nutrient analysis, and crop quality was determined after harvest. Differences in final soil nutrient levels, base saturation, crop and weed community effects were influenced more by the farm than by the treatments applied. After two years, soil sulfur levels were significantly higher in plots amended with gypsum. Failure to detect treatment response by other mineral amendments suggests the relatively narrow difference (open full item for complete abstract)

Committee: Douglas Doohan (Advisor); Warren DIck (Committee Member); Kleinhenz Matthew (Committee Member); Steve Culman (Committee Member) Subjects: Agriculture; Horticulture; Soil Sciences

Master of Science, The Ohio State University, 2017, Environment and Natural Resources

Kernza is a novel perennial grain bred from lines of intermediate wheatgrass (Thinopyrum intermedium). Though recent developments in breeding have increased seed yields, Kernza still produces less grain than most annual cereals creating an economic barrier to farmer adoption. Managing Kernza as a dual-use crop for grain and forage would add another source of revenue thereby increasing the economic feasibility of Kernza and potentially alleviating the barrier to adoption. However, due to Kernza's novelty, little research has been conducted on this specific perennial grain let alone its performance as a dual-use crop. Therefore, the goal for this thesis was to assess the agronomic performance and soil health outcomes of Kernza when managed as a dual-use crop. The first chapter of this thesis addressed whether managing Kernza as a dual-use crop would affect the crop's ability to positively influence soil health, a key selling point for this perennial grain. Specifically, this chapter determined aboveground biomass, root biomass and three soil health indicators under three defoliation treatments: summer cut, summer and fall cut, and no cut (control). Defoliation was carried out using mechanical harvesting equipment. Plant and soil measurements were taken in one month intervals throughout the first and second growing season at the OARDC in Wooster, Ohio. Aboveground measurements included plant height, forage biomass and grain yield which were determined with dry weights of hand harvested quadrat samples. Roots and soils were sampled down to 20 cm using a 4-cm soil probe and separation of roots was carried out using a hydropneumatics root elutriator. Changes in soil health were evaluated using mineralizable carbon (C-min) and permanganate oxidizable carbon (POXC) as measures of active C and soil protein as a measure of organic N. Repeated measures mixed linear model analysis revealed that all plant and soil measurements were significantly affected by date, but only pl (open full item for complete abstract)

Committee: Steve Culman (Advisor); Mark Sulc (Committee Member); Charles Goebel (Committee Member) Subjects: Agriculture; Environmental Science

Doctor of Philosophy, The Ohio State University, 2017, Plant Pathology

Plant pathologists must engage with diverse stakeholders and adopt multidisciplinary approaches to develop practical solutions to plant health problems. Two distinct projects were undertaken in this dissertation research, both requiring participatory and multidisciplinary approaches to address research objectives. The overarching objective of the first research project was to develop methods to improve soil and plant health on smallholder tomato farms in the Morogoro Region of Tanzania. Tomato is the main vegetable cash crop grown by smallholder farmers in this region and its production is constrained by plant diseases, limited access to improved tomato varieties, and poor soil health. Disease surveys were conducted in five villages to determine the most prevalent tomato diseases during both the wet and dry production seasons. The most commonly occurring foliar diseases in both seasons were early blight, bacterial spot/speck, viral diseases, and Septoria leaf spot. Ethnophytopathological activities were conducted to gather local disease knowledge in order to improve farmer and researcher communication and elucidate how farmers perceive key diseases. Mother and baby trials were conducted as a participatory crop improvement approach to introduce and evaluate tomato varieties in three villages. Mother trials were conducted in seven environments, and variance partitioning revealed significant genetic effects for all traits measured. Results from baby trials indicated that introduced varieties were locally acceptable to farmers, except for traits related to marketability. A participatory approach was used to improve soil health monitoring by participating farmers. Baseline soil characteristics were gathered from fifty tomato fields in the region, local soil knowledge was elicited from farmers and used to develop a soil health card, and farmers were trained on the use of a low cost soil test kit. Outcome Mapping was used to evaluate participation in mother and baby trials (open full item for complete abstract)

Committee: Sally Miller (Advisor); Pierce Paul (Committee Member); David Francis (Committee Member); Steven Culman (Committee Member) Subjects: Plant Pathology

Doctor of Philosophy, Case Western Reserve University, 2016, Civil Engineering

Regulating pesticides in residential surface soil, air, drinking water, and food is a worldwide problem since pesticides exposure can significantly impact human health. Approximate 25% of the world's nations have provided pesticide soil standards, about half have provided pesticide drinking water standards, about 44% have provided pesticide food standards, and only the U.S. has provided pesticide air standards. Most regulatory jurisdictions regulate individual pesticide exposures independently, although the total pesticide exposure risk depends on the cumulative exposure from soil, water, air, and food. Even for a single source such as soil, jurisdiction pesticide guidance values often vary by five, six, and even seven orders of magnitude. The highest of these values are almost certainly too high to protect human health, especially for children, and the exposures are increased even further by food, air, and water. For the most common pesticides, the exposure contributions from different exposure pathways have been quantified by using risk models to convert guidance values into daily maximum implied dose limits. Most jurisdictions have higher pesticide standard values is that they derived their standards independently without consideration of all exposures. Few nations have promulgated standards for all exposures and most nations regulate pesticide standard for only one or two pesticide exposures. For many nations, the sum of the daily maximum implied dose limit from each exposure was compared. Also a ranking system based on standard completeness and numerical values has been developed to quantify how conservative a country's pesticide exposure standards are for each exposure pathway, and for a person's total pesticide exposure. Nations in Europe have better performance in pesticide standard regulations. Also human health risk models and recommended standard values were developed to help regulatory jurisdictions around the world rationalize their guidance values th (open full item for complete abstract)

Committee: Aaron Jennings (Committee Chair); Brynjarsdóttir Jenný (Committee Member); Rhoads Kurt (Committee Member); Xiong Yu (Committee Member) Subjects: Civil Engineering; Environmental Engineering