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Abundance of microbial genes relevant to $N_20$ metabolism in agricultural soils under different nitrogen fertilization regimes
Santander Diaz, Laura Denisse
Santander Diaz, Laura Denisse
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t25044_SantanderDiaz.pdf
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2025-12-01
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Nitrogen fertilization influences soil microbial processes that regulate nutrient availability and greenhouse gas emissions. Functional genes such as ureC, nosZ, and nirS represent critical steps in nitrogen cycling, mediating urea hydrolysis, nitrous oxide reduction, and nitrite reduction, respectively. Understanding how different fertilizer formulations affect these genes is essential for improving nitrogen use efficiency and reducing environmental impacts. Conventional fertilizers like Urea and Anhydrous Ammonia (NH3) release nitrogen rapidly, while Environmentally Smart Nitrogen (ESN) provides controlled release. Interestingly, studies report different microbial responses to these fertilizers, so it still remains ineffectively characterized. This study revealed that fertilizer formulation strongly influences microbial nitrogen-cycling gene abundance, highlighting that optimizing nitrogen delivery is crucial to sustaining microbial ecological balance in agricultural soils. Using quantitative polymerase chain reaction (qPCR), gene abundance was measured across fertilization treatments (no fertilizer, Urea, NH3, ESN), rates, and timepoints. Hypothesis 1 was rejected as ureC abundance remained stable across treatments, suggesting microbial adaptation. Hypothesis 2 was partially supported, with nosZ increasing under moderate NH3 rates but declining at higher concentrations, indicating sensitivity to substrate availability. Hypothesis 3 was partially supported; nirS abundance was high under ESN at higher rates in May and lowest under ESN in June, inconsistent with delayed nitrogen release. Distinct fertilizer-specific and temporal patterns demonstrate niche differentiation among nitrogen-cycling microbes. Controlled-release fertilizers such as ESN promote stability, whereas rapid-release NH3 causes transient shifts. These findings highlight that fertilizer type, application rate, and season strongly affect microbial nitrogen cycling, and that optimizing nitrogen delivery supports sustainable fertilizer use and microbial balance in soils.
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Thesis (M.S.)-- Wichita State University, College of Liberal Arts and Sciences, Dept. of Biological Sciences
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Wichita State University
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© Copyright 2025 by Laura Denisse Santander Diaz
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