Banca de QUALIFICAÇÃO: JOÃO GUEDES BORRÉ

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOÃO GUEDES BORRÉ
DATE: 18/05/2026
TIME: 08:00
LOCAL: VIDEOCONFERÊNCIA
TITLE:

Monitoring Soil Carbon Sequestration in Tropical Pastures with Positive Nitrogen Balance under Different Edaphoclimatic Conditions

KEY WORDS:

Carbon stock; fertilized pastures; forage legume; soil organic matter; greenhouse gas emissions.

PAGES: 20
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

The extensive territorial area and favorable climate for pasture development support pasture-based livestock production in Brazil. However, currently, large areas in Brazil are in a state of degradation resulting from inadequate soil fertility management, especially regarding nitrogen (N) supply. This scenario contributes to the reduction of soil carbon (C) stocks and, consequently, promotes the emission of gases with high radiative forcing to the atmosphere. In many cases, the main approach adopted by producers consists of using nitrogen fertilizers, which are associated with greenhouse gas (GHG) emissions from both their production and field application. This entire set of factors reinforces the idea that Brazilian livestock production poses a high risk to the environment and, particularly, to global warming. Therefore, implementing strategies to reduce the environmental impact of this activity is of great importance. At present, the use of forage legumes has emerged as the most promising alternative to mitigate this issue. In addition to introducing N into the soil through a natural and sustainable process, biological nitrogen fixation (BNF), their impact on pastures optimizes nutrient cycling, favoring soil C accumulation. In this context, this study aims to compare the potential of pastures intercropped with forage legumes or fertilized with N to accumulate soil C in different Brazilian biomes. Total C and N stocks will be evaluated, as well as the physical fractionation of soil organic matter (SOM), including particulate organic matter (POM), water-extractable light organic matter (WLOM), and mineral-associated organic matter (MAOM). Additionally, in order to trace the origin of C, isotopic analyses will be carried out, enabling the exact quantification of the legume contribution to C stocks in the system. The first study area is located in the region of Lavras, Minas Gerais, characterized by a transition zone between the Cerrado and the Atlantic Forest. In this area, pastures consist of Urochloa brizantha cv. Marandu (Marandu grass) intercropped with Arachis pintoi cv. Mandobi (forage peanut) or fertilized with 150 kg N ha⁻¹ year⁻¹. The second area is located in Itabela, Bahia, within the Atlantic Forest biome, where pastures are composed of Marandu grass and forage peanut (Arachis pintoi cv. Belomonte) or fertilized with 150 kg N ha⁻¹ year⁻¹. Nutrient cycling in intercropped pastures differs substantially from that in fertilized pastures. The application of synthetic fertilizer, especially urea, provides high amounts of N to plants within a short period, increasing the likelihood of losses through the reactions this element undergoes in the soil. In contrast, legumes increase N input into the system through the deposition of plant residues with high concentrations of this nutrient, accelerating the decomposition rate of litter. Thus, N release occurs more slowly and gradually in intercropped pastures, favoring the efficient use of this element by microorganisms and plants and, consequently, promoting greater soil C stocks.

COMMITTEE MEMBERS:
Externo à Instituição - BRUNO GROSSI COSTA HOMEM - UFV
Interno - ***.282.827-** - BRUNO JOSÉ RODRIGUES ALVES - EMBRAPA
Interno - 1060711 - MARCOS GERVASIO PEREIRA
Presidente - ***.898.198-** - SEGUNDO SACRAMENTO URQUIAGA CABALLERO - EMBRAPA