Banca de DEFESA: NATALIA VIANA DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : NATALIA VIANA DA SILVA
DATE: 17/02/2022
TIME: 08:30
LOCAL: ON-LINE
TITLE:

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KEY WORDS:

Cutting age, Mott, Plant sizes, Gas production

PAGES: 56
BIG AREA: Ciências Agrárias
AREA: Zootecnia
SUMMARY:

Elephant grass [Cenchrus purpureus (Schumach.) Morrone] has a high potential for dry matter production, however it presents early stalk elongation that contributes to a rapid reduction in the nutritive value of the forage. The objective was to evaluate the morphological characteristics and the kinetics of gas production in vitro of Elephant Grass genotypes of different sizes, irrigated and under two harvesting frequencies. The experiment was carried out at the Experimental Farm to UFRPE, located in Garanhuns at 8o 53’ 25’’ South latitude and 36o 29’ 34’’ West longitude, during a period of two years (2020 and 2021). The design used was in randomized blocks in a split-plot scheme and four replications, with the main plot consisting of cutting frequencies of 60 and 90 days and the subplots of four elephant grass genotypes, two of which were tall (IRI- 381 and Elephant B) and two small ones (Taiwan A-146 2.37 and Mott). The morphological characteristics were evaluated before each harvest and samples collected in the months of July and September (rainy season), and November and December (dry season) of the year 2020 and 2021. The samples corresponding to each time of the year were used for in vitro gas production analyses. The Elefante B (13.2 mm) Mott (12.7 mm) and IRI-381 (11.4 mm) genotypes had a larger stem diameter in the rainy season and, in the dry season, only Mott (20.4 mm). In the rainy season, there was a higher number of nodes for the genotypes IRI-381 (7.8) and Elefante B (7.2), and the genotypes IRI-381 presented the highest number of leaves per tiller with 12.9. In the dry season, IRI-381 had the highest number of nodes (5.2), while the Mott genotype had the highest number of leaves per tiller (13.8). The Mott genotype had the highest leaf blade/stem ratio with 1.33, and the rainy season stood out over the dry season, with 1.6. The tall genotypes presented higher heights in the rainy and dry seasons, being 135.1 and 188.9 cm for Elephant B, respectively, and for IRI-381, 126.3 and 187.4 cm, respectively. Mott had the highest number of leaves per tiller at 60 and 90 days of harvest. The variable length between node was influenced by the time of year, being greater in the rainy season (8.67 cm), and for genotypes, being greater in tall genotypes with an average of 10.5 cm. For the time of year and harvest frequency interaction, the genotypes showed higher heights at 90 days of harvest. The leaf angle variable was higher at 90 days during the rainy season with 65.4°. For leaf length, the highest average was observed at 60 days of harvest in the rainy season with approximately 62 cm. And for the stem diameter and leaf width, a higher average was observed at 60 days of harvest in the rainy season, with 12.9 and 1.5 cm, respectively. The number of leaves per tiller was higher at 90 days in the dry season, with approximately 12 leaves. The variable total gas production (Vt) of the whole plant, in relation to cutting age, was higher at 60 days of age (297.35 mL). For leaf blades, it was higher for Mott (304.4 mL) and Taiwan A-146 2.37 (294.31 mL). For the stem fraction, the total gas production (Vt) was affected by the interaction frequency of harvest × season, with higher total gas production being observed in the forage harvested in the dry season of both ages, and at 60 days in both seasons. The frequency of cutting at 60 days is indicated for genotypes of small size in the rainy season, as they present a greater volume of gas produced by non-fibrous carbohydrates and a higher rate of degradation of fibrous carbohydrates, and at 90 days in the dry season, as they still present good fermentation and morphological characteristics.

BANKING MEMBERS:
Externo à Instituição - DIVAN SOARES DA SILVA - UFPB
Externo à Instituição - ANTONIO VANDER PEREIRA - EMBRAPA
Presidente - 385004 - MERCIA VIRGINIA FERREIRA DOS SANTOS