Doctor of Philosophy (PhD), Wright State University, 2023, Environmental Sciences PhD

Successful crop production relies on soils with balanced physical, chemical and biological properties. Demand for greater crop yields has led to the breakdown of soil properties through detrimental agricultural practices. To combat soil degradation, farmers employ field management practices including cover crop application, crop rotation strategies and organic soil amendment addition. These practices, used independently or in combination, can improve soil stability, increase soil nutrient content and functions of beneficial soil microbiota while increasing crop yield. Despite showing promise as an organic soil amendment, dredged sediments are still not well understood, due in part to the fresh or weathered conditions dredged sediments can be applied. Specifically, there is currently no research combining dredged sediments with cover crops, comparing different dredged sediments conditions in a single study or evaluating dredged sediment condition coupled with cropping strategies. To address these knowledge gaps, my dissertation evaluates changes in soil properties and crop responses when dredged sediments are coupled with these practices. I evaluated changes in dredged sediment property responses and corn production following winter rye cover crop application compared to a fallow season in a field experiment where I found cover crop application increased corn yields compared to a fallow season. These differences were driven by microbial-associated nutrient mineralization. Additionally, I quantified soil property and corn responses to different application ratios of fresh and weathered dredged sediments in a greenhouse experiment and determined applications of dredged sediments calculated based on the nutrient recovery ratio are not sufficient to provide benefits to agricultural soils. However, in 100% applications, weathered dredged sediments were more beneficial to corn growth than agricultural soils, while fresh dredged sediments proved detrimental to corn growth. (open full item for complete abstract)

Committee: Megan Rúa Ph.D. (Committee Chair); Silvia Newell Ph.D. (Committee Member); Louise Stevenson Ph.D. (Committee Member); Katie Hossler Ph.D. (Committee Member); Zheng Xu Ph.D. (Committee Member) Subjects: Environmental Science

Doctor of Philosophy, The Ohio State University, 2004, Soil Science

Soil quality indices are useful tools for assessing agronomic/ biomass productivity and ascertaining temporal changes in soil properties in relation to land use and management. This study was conducted in the Lake Victoria region in Masaka, Uganda to: (a) identify key soil properties that impact soil quality and agronomic productivity; (b) evaluate soil quality-management inter-relationships; (c) evaluate the use of soil reflectance as a soil quality indicator, and (d) determine the cost and returns of different cropping systems. Bulk and core soil samples were collected from the 0-20 and 20 – 50 cm depths, from the farmers' fields, in order to determine soil organic carbon, nitrogen, calcium, phosphorous, magnesium, pH, _13C, _15N, coarse fragments, soil bulk density and soil texture. Saturated hydraulic conductivity (Ks) was determined in the field using a tension infiltrometer and soil depth using an auger. The soil degradation rating was assessed by assigning parametric values to levels of SOC, soil bulk density, Ks, soil texture, soil pH, soil depth and the proportion of coarse fragments in the top soil and these parameters were utilized to develop a single index. Air dry samples were scanned using a spectrometer and the first derivative of the spectral data was calibrated against the measured soil properties. Results indicated that soil quality was affected by SOC, soil depth and Ks. No direct effects of management on soil quality were discerned. Good predictions of several soil properties were obtained using the spectral data. Although a majority of farmers planted bananas as the first choice crop, the highest net returns were obtained from coffee while the highest costs were measured for bananas implying that food self sufficiency was the major determinant of the choice of crop to be grown. It was recommended that grasslands must not be converted to agricultural land use because of their high susceptibility to soil degradation and that farmers be sensitized (open full item for complete abstract)

Committee: Rattan Lal (Advisor) Subjects:

Master of Science, The Ohio State University, 2022, Environment and Natural Resources

Oil and natural gas pipelines are essential to the transport of energy materials, but construction of these pipelines commonly causes major disturbance to ecosystems. Due to variability in pipeline installation practices and environments, drawing consensus about how pipeline installations typically impact agricultural ecosystems has been challenging. Here, we conducted a systematic literature review and quantitative analysis of current pipeline studies to determine the magnitude of soil and vegetative responses to pipeline installation and found detrimental impacts to both soil and vegetation variables, including compaction, aggregate stability, and plant biomass. However, best management practices and remediation timeframes vary between studies. Thus, the objective of this study was to determine impacts of pipeline installation on Ohio soil and crop characteristics after a 4- to 5-year remediation period across three independent pipeline installations: the Rover, Utopia, and Nexus pipelines. We performed a 2-year on-farm study in 2020 and 2021 over 29 sites in 8 Ohio counties, directly comparing right-of-way (ROW) and adjacent, unaffected areas (ADJ) of the same agricultural fields. Soil physical, chemical, and biological properties were evaluated, as well as yield and stand counts for field corn, corn silage, and soybean. Detrimental impacts to soil physical characteristics which occurred during pipeline installation persisted through this study period, while variable impacts to soil chemical properties were observed on an individual iii site basis. Finally, satellite image-derived normalized difference vegetation index (NDVI) was used to analyze if ROW versus ADJ differences in agricultural crop yields can be evaluated in a less time- and labor-intensive process compared with traditional on-farm sampling methods. Various soil and yield metrics show that degradation of agricultural land persists past the 4- to 5-year rem (open full item for complete abstract)

Committee: Steve Culman (Advisor); Scott Demyan (Committee Member); Sami Khanal (Committee Member) Subjects: Agronomy; Energy; Environmental Science; Soil Sciences

MS, University of Cincinnati, 2008, Arts and Sciences : Biological Sciences

Polybrominated diphenyl ethers (PBDES) are emerging contaminants commonly used as fire retardants. Their use in a wide variety of products has made them ubiquitous in the environment. PBDEs similarity to other pollutants suggests they will persist in the environment. Little research has been done on actual mechanisms affecting PBDE presence in the environment. Sorption of PBDEs in aging soil systems was studied. Soil composition was not a determinant of sorption. Sorption to soils was reversed by biotic effects of microorganisms and plants. Biodegradation of PBDEs was also examined using sewage bacteria. Rapid degradation of PBDEs was seen in some organisms. While biotic potential for mobilization and degradation of PBDEs exists, their presence in the environment is still increasing. Sorption to soil appears to be the dominant process controlling the fate in the environment.

Committee: Jodi Shann PhD (Committee Chair); Brian Kinkle PhD (Committee Member); Anne Vonderheide PhD (Committee Member); Stacy Pfaller PhD (Committee Member) Subjects: Biology; Microbiology; Soil Sciences

MS, University of Cincinnati, 2005, Arts and Sciences : Biological Sciences

The effects of trees on microbial degradation of PAHs are largely unknown. An experimental soil was spiked with 3 model PAHs (phenanthrene, anthracene, and pyrene) and planted with six tree species. PAH dissipation and mineralization in planted and unplanted soils was monitored for up to 15 months. Initial, year long studies revealed that planting effects were negligible and that rapid PAH dissipation was due to high microbial activity and bioavailability. Further experimentation showed that microbial communities respond differently to two seasonally variable sources of root-derived carbon (root exudation and root mortality/decay). Also, soil nutrient amendments reduced pyrene mineralization in root zone soils. While the ‘rhizosphere effect' was supported by one-time mineralization studies, long term PAH dissipation did not vary according to proximity to roots. Seasonal variation in rhizosphere dynamics may reduce or negate the effect of trees on long term PAH dissipation in the rhizosphere.

Committee: Jodi Shann (Advisor) Subjects: