Date of Award:

8-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Astrid R. Jacobson

Committee

Astrid R. Jacobson

Committee

Yao-Tung Lin

Committee

David W. Britt

Committee

Jeanette M. Norton

Committee

Joan E. McLean

Committee

Youping Sun

Abstract

Among the challenges posed by a growing global population, diminishing arable land and water resources affected by climate change are critical for enhancing crop yields, ensuring food security, and maintaining water quality and environmental health.

Iron (Fe), an essential micronutrient, is vital to plant growth. The partially oxidized form of vivianite, metavivianite (metaVT), is reported to be a promising alternative Fe fertilizer. Previous studies have shown the effectiveness of bulk metaVT on plants grown on calcareous soil for mitigating Fe efficiency and the extremely low solubility of bulk metaVT (Ksp=10-36) in electrolyte solutions, such as CaCl2. The cause of the discrepancy between the results of bulk metaVT under pure laboratory conditions and field application remains unclear. This study explores the applications of nano-sized metaVT (nano-metaVT) as an Fe amendment for crops, as well as using chitosan (CT) as a pH-responsive coating on the nano-metaVT amendment. This study examines the solubilities of nano-metaVT and nano-CT-metaVT in a dilute electrolyte solution and calcareous soil saturated paste extract (SPE), their impact on wheat growth in silica sand, and wheat and bean growth in a calcareous soil under salinity stress. The results indicate that key factors, such as the functional coating on the nano-fertilizers, the presence of soil microbes, and organic ligands in the soil, affect the solubilities of nano-metaVT and nano-CT-metaVT. Moreover, beneficial soil microbes, Pp Pf-5, mitigate wheat abiotic stress by increasing plant transpiration. Finally, the study confirms that nano-CT-metaVT improves bean root dry mass, and the nano-metaVT treatment resulted in increased chlorophyll content in beans. Nano-metaVT demonstrates retention in the soil and lower concentrations of soluble Fe in leachates than Fe-EDDHA.

Globally, disinfection methods have disadvantages, such as the high cost of raw chemicals, generation of toxic by-products, or low disinfection efficiency. It has been proposed that the disinfection observed using heated oyster-shell-derived disinfectant (HOS) is related to reactive oxygen species (ROSs) generation and protein denaturation. The findings provide evidence that cell permeability is crucial in the HOS disinfection process, and singlet oxygen plays an essential role in the disinfection mechanism. Overall, the HOS disinfectant has a high potential to be applied as a universal disinfectant and mitigate the aquaculture waste pollution problem. Furthermore, the study explores the enhanced disinfection efficiency, focusing on the NT-PMMA. NT-PMMA showed higher intensities of singlet oxygen, hydroxyl radicals, and hydrogen peroxide than NT suspension, implying the greater inactivation efficiency of immobilized NT on PMMA than in NT-suspension. The immobilization approach enhanced the inactivation performances of NT-PMMA, making it superior to NT suspension due to the absence of turbidity interference and the uniform distribution of NT.

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