Banca de DEFESA: SAFIRA YARA AZEVEDO MEDEIROS DA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : SAFIRA YARA AZEVEDO MEDEIROS DA SILVA
DATE: 30/07/2026
TIME: 13:00
LOCAL: VIDEOCONFERÊNCIA
TITLE:

Soil N₂O emissions from maize fertilized with urea and inoculated with Azospirillum brasilense and Nitrospirillum viridazoti

KEY WORDS:

Nitrous oxide, nitrogen fertilizer, denitrification, plant growth promoting bacteria, Nitrospirillum viridazoti, Azospirillum brasilense.

PAGES: 56
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

Nitrous oxide (N₂O) is considered one of the most potent greenhouse gases (GHGs), with a global warming potential approximately 298 times greater than that of carbon dioxide (CO₂) over a 100-year time horizon. In agricultural systems, its primary source is associated with the intensive use of nitrogen fertilizers, which, once applied to the soil, undergo microbial nitrification and denitrification processes that release N₂O into the atmosphere. Among agricultural crops, maize (Zea mays L.) is characterized by its high nitrogen demand, as this nutrient is essential for plant growth and productivity. However, the low nitrogen use efficiency of conventional fertilization systems results in substantial economic and environmental losses, contributing to increased emissions of reactive nitrogen compounds and highlighting the need for more sustainable nitrogen management strategies. In this context, the use of plant growth-promoting bacteria (PGPB) has emerged as a sustainable biotechnological approach to mitigate the negative impacts associated with synthetic nitrogen fertilizers. These microorganisms enhance nitrogen uptake and utilization by plants through several mechanisms, including biological nitrogen fixation, nutrient solubilization, and the production of phytohormones that stimulate root development. Furthermore, some bacterial strains harbor the nosZ gene, which encodes nitrous oxide reductase, the enzyme responsible for the final step of denitrification by reducing N₂O to dinitrogen (N₂), an environmentally harmless gas. Therefore, the application of these PGPB may contribute not only to plant growth promotion but also to the direct mitigation of greenhouse gas emissions. This thesis aimed to investigate the potential of inoculation with Azospirillum brasilense and Nitrospirillum viridazoti to modify N₂O flux dynamics in maize cultivation. To achieve this, experiments were conducted under controlled greenhouse conditions (pots) and in the field using the A. brasilense strains Ab-V5, Ab-V6, and Wa3, as well as the N. viridazoti strain BR11145. In the field experiments, static chambers and soil collectors were installed to quantify gaseous emissions throughout the maize growing season. Nitrous oxide (N₂O) and ammonia (NH₃) concentrations in the collected samples were determined using tunable diode laser absorption spectroscopy and gas chromatography, ensuring high analytical accuracy. Overall, the findings of this thesis demonstrate that the potential of PGPB to mitigate N₂O emissions depends on both the bacterial strain and soil nitrogen availability. Among the strains evaluated, Nitrospirillum viridazoti BR11145 consistently showed the greatest potential for reducing N₂O emissions, highlighting its promise as a bioinoculant for the development of more sustainable agricultural systems with lower environmental impacts.

COMMITTEE MEMBERS:
Presidente - ***.282.827-** - BRUNO JOSÉ RODRIGUES ALVES - EMBRAPA
Interno - 2213075 - EVERALDO ZONTA
Externo à Instituição - ISRAEL OLIVEIRA RAMALHO
Interno - ***.881.579-** - JERRI ÉDSON ZILLI - EMBRAPA
Externo à Instituição - LUC FELICIANUS MARIE ROUWS