Banca de DEFESA: ISRAEL OLIVEIRA RAMALHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ISRAEL OLIVEIRA RAMALHO
DATE: 31/01/2023
TIME: 08:00
LOCAL: VIDEOCONFERÊNCIA
TITLE:

Soil N₂O emissions under Brachiaria pastures managed with nitrogen fertilization or mixed with forage legumes

KEY WORDS:

Emission factor, meta-analysis, Macrotyloma axillare

PAGES: 110
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

Of the greenhouse gases (GHG) of greatest importance in livestock, nitrous oxide (N₂O) is one of the gases with the greatest potential for global warming compared to carbon dioxide (CO₂). In pastures its emission occurs mainly due to the deposition of excreta with high N content on the soil under anaerobic conditions. There is great uncertainty regarding direct and indirect emission factors (EF_N2O) for bovine excreta in tropical regions. For this reason, the objectives of this study were - Chapter I: to carry out a systematic review to compile EF_N2O values of excreta from animals in Brazil and to analyze the EF_N2O of excreta by the FE_urine:FE_feces ratio; in Chapter II: to evaluate in mixed pastures of Urochloa brizantha cultivar Marandu with Macrotyloma axillare (Mixed) or of Marandu in monoculture without fertilization (Control) or with fertilization of 138 kg N.ha^-1.year^-1 (N- fert), under continuous stocking; Chapter III: measure N₂O emissions, volatilization of ammonia (NH₃) from feces and urine and perform a mass balance of urine N using the ¹⁵N labeling technique. The results of the attempt to estimate mean values of EF_N2O for Brazil were satisfactory and the values were similar to the EF for humid climate proposed by the Intergovernmental Panel on Climate Change (IPCC). The meta-analytical statistical approach proved to be sensitive for finding responses between the EFs of urine and feces in relation to edaphic factors, group and diet of the animals and duration of the experiment. The results of these analyses emphasised the need for disaggregation between feces and urine, in addition were able to assist in the disaggregation of EF in other environmental conditions. In comparison with the fertilized (N-fert) and Control grass pasture, the Mixed obtained a diet with a higher protein content and greater digestibility, with a higher nitrogen (N) intake by the animals, without increasing N excretion or direct emission or indirect N₂O. The animals in the Mixed treatment maintained the same weight gain as in the N-fert and Control treatment. Therefore, the use of M. axillare can be a tool for GHG mitigation in a tropical pasture system. Rainfall showed a strong influence on pasture quality and animal performance. However, there was no difference between pasture types in pasture quality and animal performance. Climate also affected the fate of N after deposition of excreta in the soil. The Rainy period was more susceptible to N loss by leaching. Regardless of the time of year, soil is the major destination of urine N. The EF were much lower than the averages compiled by the IPCC. The partitioning between excretion of N-urine:N-feces was also below established (0,66:0,34). It is recommended, therefore, that further studies should be carried out to disaggregate EF_N2O from bovine excreta and the partitioning of N excreted by pasture quality in tropical climates.

COMMITTEE MEMBERS:
Interno - 1104775 - ADELSON PAULO DE ARAUJO
Externa à Instituição - CLAUDIA DE PAULA REZENDE
Externo à Instituição - DANIEL RUME CASAGRANDE - UNESP
Externo ao Programa - 2136627 - NIVALDO SCHULTZ - nullPresidente - ***.889.777-** - ROBERT MICHAEL BODDEY - OUTRO