Banca de DEFESA: GUILHERME OLIVEIRA DO CARMO
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : GUILHERME OLIVEIRA DO CARMO
DATE: 26/02/2026
TIME: 08:00
LOCAL: Embrapa Agrobiologia - Sala multimeios
TITLE:
Inoculation of diazotrophic bacteria in the forage legume pigeon pea [Cajanus cajan (L.) Huth], cv. Guatã, to promote growth and reduce N2O emissions from the soil.
KEY WORDS:
Pigeon pea; Nitrogen; Bioinput;Symbiotic bacteria; Coinoculation
PAGES: 59
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Fertilidade do Solo e Adubação
SUMMARY:
To mitigate N2O emissions from Brazilian agriculture, the use of bio-inputs with diazotrophic bacteria emerges as a sustainable alternative in promoting Biological Nitrogen Fixation (BNF). Pigeon pea stands out in this scenario for its efficiency in BNF and biomass production, reducing the dependence on nitrogen fertilizers in forage systems. The objective was to test inoculants formulated with Azospirillum spp., Bradyrhizobium spp., and Nitrospirillum spp. regarding N₂O emissions and plant growth promotion. The methodology included (i) in vitro assays in hermetically sealed flasks with/without KNO₃ and with/without C₂H₂ (functional inhibition of the N₂O→N₂ step), with N₂O quantification by gas chromatography to select the best strains to be used in the greenhouse experiment, and (ii) a greenhouse experiment in a randomized block design, with six treatments: T1 – Nitrogenated, T2 – without inoculation, and inoculated T3 - BR2003, T4 - BR1432/1433, T5 - BR1433/BR1432/Ab-V6, T6 - BR1432/BR1433/BR11145, for quantification of BNF, accumulated N (Nac) and shoot dry matter (MSPA), root dry matter (MSR) and nodule dry matter (MSN), and N₂O emissions by portable static chamber. Throughout the cycle. In the in vitro assay under KNO3 + C2H2 conditions with an incubation period of 12 to 14 hours, strains BR1433, BR2003, and BR11145 showed similar average N2O values below 310 ppb. In the greenhouse experiment, with 2 kg Argisol per pot, it was observed in the first cut (70 DAP) that T1 favored plant growth in both MSPA (26.1%) and MSR (83.87%), compared to the control (T2), 10.4 g plant⁻¹ in MSPA and 2.48 g plant⁻¹ in MSR, respectively. The remaining treatments showed similar behaviors. In the nodules, although T6 showed greater nodulation than the other treatments, in the end all showed a similar contribution of FB of around 60%. In the other cuts, with the exception of BNF which increased to an average value of 80% of all treatments evaluated (without nitrogen fertilization), the behaviors of all other variables were similar. Regarding the accumulated N–N₂O emission from the soil in the study in pots with plants in a greenhouse, it increased progressively (~60–200 DAP), with marked increases after the cuts at 70 and 137 DAP, showing a significant treatment effect. In the final evaluation, the absolute control presented the highest accumulated emission, similar to T4, while T6 (BR1432/BR1433/BR11145) resulted in the lowest emission, and the remaining T3 (BR2003) and T5 (BR1433/BR1432/Ab-V6) presented intermediate values. It is concluded that the bacterium Nitrospirillum viridazoti (BR11145) co-inoculated with Bradyrhizobium sp. (BR1433) and Bradyrhizobium sp. (BR1432) significantly reduced N2O emissions from the soil, due to their ability to reduce N2O to N2, a characteristic of great importance in mitigating the emission of this potent greenhouse gas.
COMMITTEE MEMBERS:
Presidente - ***.898.198-** - SEGUNDO SACRAMENTO URQUIAGA CABALLERO - EMBRAPA
Interno - 2213075 - EVERALDO ZONTA
Externo à Instituição - CAIO DE TEVES INÁCIO