Banca de DEFESA: DANIEL DA CUNHA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE: DANIEL DA CUNHA
DATA: 25/02/2022
HORA: 09:00
LOCAL: Defesa realizada de forma remota
TÍTULO:

Agronomic traits and adaptation of the CROPGRO-Perennial Forage model to predict the growth of five Brachiaria genotypes

PALAVRAS-CHAVES:

Agronomic traits. Forage growth simulation. Optimal harvest time.

PÁGINAS: 93
GRANDE ÁREA: Ciências Agrárias
ÁREA: Zootecnia
SUBÁREA: Pastagem e Forragicultura
ESPECIALIDADE: Avaliação, Produção e Conservação de Forragens
RESUMO:

Brachiaria spp. play a key role in animal production for grassland-based systems in tropical and subtropical regions of the world. Therefore, the evaluation of forage productivity and canopy characteristics allows us to understand pasture responses over time and identify high-yield genotypes with different defoliation management needs. Our main objective was to compare and explain differences in forage accumulation and canopy characteristics of five species of Brachiaria spp. (Basilisk, Marandu, Mulato II, Piatã and Xaraés) in southeastern Brazil under three levels of nitrogen fertilization (220 kg of N ha-1 yr-1 in year 1 and 0 and 550 kg of N ha-1 yr-1 in year Year 3). While our secondary objective was to adapt the CROPGRO-Perennial Forage Model (CROPGRO-PFM) to simulate the seasonal growth and production of these same genotypes, as well as to describe the adaptations and improvements made to the model. Both objectives were developed from an experiment of mechanically harvested plots with 15 cm stubble every 28 days and 42 days during the wet and dry season, from October 2013 to November 2014 (Year 1) and from September 2015 to September 2016 (Year 3). Response measurements included annual herbage accumulation, plant-part composition, canopy height, herbage bulk density, leaf area index, light interception, and tiller population density. The first objective showed us that there were differences between the genotypes, indicating great variability. Mulato II, Piatã and Xaraés were the most productive genotypes, producing an annual average of 12.1 Mg DM ha-1. The plots fertilized with N produced 2.3 times more forage than the non-fertilized plots. The main contrast occurred between the Basilisk and Xaraés genotypes; Basilisk showed higher tiller population density (1512 vs. 854 tillers per m2) and low leaf:stem ratio (2.4 vs. 12.8) in relation to Xaraés. While the second objective showed us that the model adaptation required the modification of parameters related to the partition between leaf and stem fractions, and the allocation intensity to shoot versus storage tissues based on photoperiod sensitivity. And after these modifications, the CROPGRO-PFM model performed well, providing realistic seasonal growth responses to seasonal climate variations and nitrogen fertilization. From these results, we can infer that the morphological and structural characteristics of the canopy are valuable ways of understanding the management potential of different Brachiaria genotypes. And after adapting the model, we can apply it as a tool to simulate the growth and partitioning of Brachiaria spp. in different scenarios.

MEMBROS DA BANCA:
Interno - CARLA LUIZA DA SILVA AVILA (Membro)
Externo à Instituição - CLYDE FRAISSE - UF (Membro)
Externo à Instituição - DIEGO NOLETO LUZ PEQUENO - CIMMYT (Membro)
Externo à Instituição - LEANDRO COELHO DE ARAÚJO - UNESP (Suplente)
Externo à Instituição - LEONARDO SIMÕES DE BARROS MORENO - EMBRAPA (Membro)
Presidente - MARCIO ANDRE STEFANELLI LARA (Membro)
Interno - MARINA DE ARRUDA CAMARGO DANES (Suplente)