Banca de DEFESA: JULIA FERREIRA XAVIER

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JULIA FERREIRA XAVIER
DATE: 30/09/2025
TIME: 13:30
LOCAL: Sala 24
TITLE:

Soils with Limitations for Agricultural Use: Opportunities and Challenges for Agriculture

KEY WORDS:

Histosol. Saline soil. Sustainability. Soil properties. Plant growth promotion.

PAGES: 115
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

Soils with limitations represent a global challenge for agricultural production and highlight the need for the implementation of sustainable management practices, while also constituting sources of genetic resources with potential applications in biotechnological strategies. In this context, the thesis was structured into three chapters. In Chapter I, the attributes of Histosols under different land uses—conventional cultivation and secondary forest—were evaluated. In areas under conventional cultivation, soil tillage and drainage promoted changes in the chemical and biological properties of soils in the 0–10 cm layer. Reductions in pH, total organic carbon (TOC), carbon stocks, and nutrient contents were observed. The composition of the soil macrofauna differed between the areas, with a 69.5% lower density in cultivated soils compared with forest soils. β-glucosidase activity was reduced by 19.85% in cultivated soils relative to forest areas, while arylsulfatase activity decreased by 40.25%. Bacterial diversity was also reduced under cultivation, with lower values of richness and Shannon and Gini-Simpson indices. Soil chemical attributes, mainly C content and pH, were identified as the main drivers of differences in bacterial community structure. The phylum Chloroflexota showed higher abundance in cultivated soils, whereas Bacteroidota was more abundant in forest soils. In Chapter II, the chemical properties and bacterial diversity of the rhizosphere of halophyte plants were assessed. The rhizosphere of five abundant plants from three saline environments was analyzed: S1: Salicornia fruticosa and S2: Sporobolus virginicus, both from a hypersaline tidal flat; S3: Cyperus ligularis, from a hypersaline lagoon; S4: Salicornia fruticosa and S5: Blutaparon portulacoides, from an abandoned salt pan. The rhizosphere of halophytes harbors complex and distinct microbial communities. Soil chemical attributes were the main factors driving differences among rhizospheric communities. These communities were predominantly composed of the phyla Proteobacteria, Actinobacteria, and Acidobacteria, with key species varying according to the host plant. In Chapter III, the ACC deaminase activity of 105 bacterial isolates from the rhizosphere of halophyte plants, belonging to the classes Gammaproteobacteria, Bacilli, and Alphaproteobacteria, was evaluated through qualitative and quantitative methods. It was found that 8.25% (9/105) of the isolates were able to grow in solid and liquid medium with ACC as the sole nitrogen source, most of them belonging to the genus Bacillus. However, enzymatic activity was not detected in the quantitative evaluation. Overall, the results demonstrate that soils with limitations, despite their constraints for agricultural production, host microbial communities and biological attributes of great ecological relevance. The integration of conservation practices with the biotechnological use of these resources represents a promising pathway for sustainable management and for the valorization of these environments.

COMMITTEE MEMBERS:
Externo à Instituição - CAIO TÁVORA RACHID COELHO DA COSTA - UFRJ
Externo ao Programa - 1246489 - EDUARDO CARVALHO DA SILVA NETO - UFRRJPresidente - 1815763 - IRENE DA SILVA COELHO
Externo à Instituição - LUC FELICIANUS MARIE ROUWS
Externa à Instituição - MARIA ELIZABETH FERNANDES CORREIA