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, 2017, Agricultural and Extension Education

Glyphosate-tolerant crops were introduced for farmers in 1996, making weed management easier and more economical. However, some weeds have become resistant to glyphosate and a soybean farmer could lose about $22 per acre in yields because of reduced glyphosate effectiveness in their fields (Fernandez-Carnego & Osteen, 2015). New soybean varieties with tolerance to either 2,4-D or dicamba herbicides became available for farmers to control glyphosate-resistant weeds; however, these herbicides volatilize more easily than glyphosate, creating more drift potential during certain weather conditions. Research on herbicide drift has focused on risk mitigation for applicators to reduce or avoid drifting to non-target crops or areas (Wolf & Frohberg, 2002, Ozkan, et al., 1993), literature on the human element of drift, such as crop damage from herbicide drift, was limited. This study was a sequential exploratory, mixed-method research design (Creswell & Plano-Clark, 2010) that explored farmers' perception of risk, self-efficacy, and response efficacy toward possible crop damage from herbicide drift. To provide descriptive data, focus groups were conducted with a randomized sample of grain and specialty crop farmers in four Ohio counties. This qualitative data was used to create questions for a survey as the quantitative data collection. The surveys were sent to a randomized sample of grain and specialty crop farmers in 20 Ohio counties. Protection motivation theory (PMT) was the framework used to describe farmers' perceptions of risk, self-efficacy, and response efficacy. The study began comparing farmers raising grain or specialty crops; however, mixed crop farmers emerged as a well-identified group who raised both types of crops and had different descriptions of interacting with neighbors. Their diversity of cropping systems affected the perspectives of farmers in this study and warrant further research. The grain crop farmers had the lowest perception of risk, a (open full item for complete abstract)

Committee: Emily Buck (Advisor); Jeff King (Committee Member); Robyn Wilson (Committee Member) Subjects: Agriculture; Communication