Banca de DEFESA: CAMILA ALMEIDA DOS SANTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : CAMILA ALMEIDA DOS SANTOS
DATE: 27/11/2020
TIME: 13:00
LOCAL: Departamento de Solos, IA, UFRRJ (virtual)
TITLE:

Nitrogen Balance and N2O Emissions from Exclusive Pasture of Braquiária Marandú or Mixed with Desmódio.

KEY WORDS:

Mixed pasture. N2O emission factor. Biological Nitrogen Fixation. Livestock

PAGES: 134
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Fertilidade do Solo e Adubação
SUMMARY:

Sustainable pasture management models constantly seek ways of animal production with lessenvironmental impact. The introduction of forage legumes in pasture systems may represent an alternative to the use of nitrogen fertilizers. Seeking to understand the nitrogen balance and N2O emissions from exclusive pasture of Brachiaria brizantha cv Marandu or mixed with Desmodium heterocarpon legumes, four hypotheses were raised: the first is that with the introduction of the legume Desmódio in pastures of Marandú braquiária it is possible to achieve similar or higher productivity in relation to the pasture of B. brizantha cv Marandu in a monoculture fertil ized with 150 kg N ha-1 year-1 and that an adequate management allows the legume to persist in the system; the second hypothesis is that the fraction of N excreted by cattle that is converted into N2O does not change in pastures fertilized with urea and pastures mixed with Desmódi0, as well as mandatory CH4 in dung; the third is that the bases of N2O are greater in pastures with legumes compared to pastures of Marandu, but that the addition of nitrogen fertilizer modifies this condition, making it larger as supplied with N2O from the fertilized system; and the fourth hypothesis is that the entry of N via BNF or nitrogen fertilization meets the demand for N from pastures, and has the potential to compensate for losses of N.The study was carried out on the Animal Husbandry Experimental Station of the Extreme South of Bahia (ESSUL), belonging to the Cocoa Research Organisation (CEPLAC) located in the municipality of Itabela, Bahia. The experimental design used was randomized blocks with 3 treatments, B. brizantha fertilized with 150 kg N ha-1 year-1, B. brizantha mixed with Desmodium heterocarpon and pasture of B. brizantha without adding N. Each plot was composed of 5 paddocks, and the grazing system used was rotated with 7 days of occupation and 28 days of rest. The results obtained allowed to conclude that the mixed pasture of Desmodium heterocarpon with Capim-Marandu promoted production of forage and beef cattle
similar to the pasture of Capim-Marandu + 150 kg N ha-1 year-1 and that the adopted management allowed the persistence of legume in the system, with potential for use in tropical pastures. The system mixed grass/legume resulted in a change in the N excretion pathway, with greater excretion in the dung. The N2O EF and the fraction of NH3 lost through urine is similar in mixed grass/legume and fertilized pasture, and the N2O FE for dung is lower in mixed pasture. The entry of N via nitrogen fertilization or by the legume used in the mixed increases background N2O, being greater by the addition of nitrogen fertilizer in relation to the introduction of the legume. Urea fertilization results in N losses due to ammonia volatilization and N2O emission in magnitudes lower than what can be estimated with the respective default loss factors in the IPCC guide. Both the nitrogen fertilization of 150 kg N ha-1 in the form of urea and the entry of N via FBN through the consortium with D. heterocarpon allow to compensate for N outflows in pasture cattle production systems. On the other hand, the addition of nitrogen fertilizers provides greater emissions of greenhouse gases compared to the mixed strategy with legumes.

BANKING MEMBERS:
Presidente - 681.282.827-00 - BRUNO JOSÉ RODRIGUES ALVES - EMBRAPA
Interna - 1740899 - ERIKA FLAVIA MACHADO PINHEIRO
Externa à Instituição - CLAUDIA DE PAULA REZENDE - UFLA
Externo à Instituição - DANIEL RUME CASAGRANDE - UNESP
Externo à Instituição - ABMAEL DA SILVA CARDOSO - UNESP