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Accueil du site → Doctorat → États-Unis → 2022 → Conservation Management and Nitrogen Fertilizer Timing Effects on Microbial Production of Nitrous Oxide and Nitric Oxide in a Semi-Arid Environment

Texas A&M University (2022)

Conservation Management and Nitrogen Fertilizer Timing Effects on Microbial Production of Nitrous Oxide and Nitric Oxide in a Semi-Arid Environment

McDonald, Mark David

Titre : Conservation Management and Nitrogen Fertilizer Timing Effects on Microbial Production of Nitrous Oxide and Nitric Oxide in a Semi-Arid Environment

Auteur : McDonald, Mark David

Université de soutenance : Texas A&M University

Grade : Doctor of Philosophy (PhD) 2022

Résumé
Due to the potency of nitrous oxide (N₂O) as a contributor to the greenhouse effect, and the relationship between N₂O emissions agricultural soil management, understanding N₂O dynamics within agricultural production is an important research topic. This is especially true in expanding semi-arid areas where best management practices for reducing erosion and increasing soil health may also increase conditions favorable for denitrification, one of the major pathways for N₂O production. The purpose of this series of studies was to elucidate the effects best management practices have on soil chemical and biological characteristics associated with nitrogen (N) gas cycling in low carbon content semi-arid soils. In addition, active microbial population dynamics were evaluated to better characterize the biological changes conservation tillage may induce in semi-arid systems. Initial evaluations determined significant effects of the timing of N fertilizer on net N₂O emissions from the soil surface, where N₂O emissions closely followed N fertilizer application. Net consumption of N₂O was also determined during the initial analysis which was attributed to the abundant N₂O-reducing population(s) present in semi-arid soils. As the implemented systems matured, N fertilizer timing effects on soil chemical and biological parameters and N₂O emissions were determined to vary with the time of year sampled, indicating dynamic seasonal changes related to when N fertilizer is applied. However, the effects determined within sampling periods did not always result in changes in pore-space N₂O and NO concentrations. Metatranscriptomic analysis revealed some differences in gene expression across conservation systems. Abundant nitrifier transcripts associated with nitrogen metabolism were identified, supporting the role of nitrification in production of N gases in semi-arid agricultural soils. From the results of this set of studies, it is clear that the mechanisms behind N₂O emissions and N gas cycling are highly complex in semi-arid systems, although the application of N fertilizer seems to have the greatest control over the timing and rate of N gas cycling and N₂O production. It is yet to be determined the exact circumstances leading to the prevalence of N₂O production and consumption in low C content semi-arid soils, but it is likely a combination of factors including many of those evaluated within these experiments.

Sujets : Greenhouse gases Soil microbiology Pore-space gas concentrations Nitrous oxide Nitric oxide Microbiology Metatranscriptomic

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