Canopy characteristics and tillering in \'Zuri\' guineagrass pastures in response to grazing frequency and severity

• Ano de defesa: 2020
• Autor(a) principal: Barbosa, Patricia Luizão
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Megathyrsus maximus; Panicum spp.; Acúmulo de forragem; Altura de resíduo; Densidade populacional de perfilhos; Forage; Forragem; Grazing management; Herbage accumulation; Herbage mass; Índice de estabilidade; Interceptação luminosa; Light interception; Manejo do pastejo; Massa de forragem; Meia-vida de perfilhos; Peso de perfilho; Stability index; Stubble height; Tiller density population; Tiller half-life; Tiller mass
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/11/11139/tde-10032020-150901/

Megathyrsus maximus [(Jacq.) B.K. Simon & S. W. L. Jacobs] are grasses characterized by high productivity and nutritional requirements. Zuri guineagrass is productive Megathyrsus maximum, a new grass in the forage market It was selected based on productivity, vigor, carrying capacity, animal performance, resistance to the spittlebugs [Mahanarva fimbriolata (Stål) and M. liturata (Le Peletier de Saint-Fargeau & Serville)] and mainly the \"leaf spot\", a disease caused by the fungus Bipolaris maydis (Nisik and Miyake) and has no scientific studies of the structural characteristics and tillering. The objectives of this research were to describe and explain effects on tillering dynamics and their rates - tiller appearance (TAR), tiller mortality (TMR), tiller survival rate (TSR) and stability index (S) - tiller population density (TPD), tiller mass (TM), apical meristem height (AMH), half-life of tillers, structural and morphological characteristics such as herbage mass and herbage morphological composition, canopy height, leaf area index, light interception, leaf angles of Zuri guineagrass affected by severity and frequency, under rotational stocking. An experiment was carried out in Piracicaba, SP, Brazil, during two summer grazing seasons. The experimental design was a randomized complete block, with a 2 × 2 factorial arrangements, corresponding to two frequencies (LI 95% and 70 cm) and two severities (29 and 57%). The years were analyzed separately. In both growing seasons, there was no treatment effect on TPD and TM (460 and 350 tillers m-2, and 2.05 and 2.56 g tiller-1 in the years 1 and 2, respectively). In the first year the TMR, SI, and AMH were affected by the frequency × severity interaction (P=0.0033, 0.0198 and 0.0397 for the three responses, respectively), the TAR was affected only by severity (P=0.0243). In the second growing season, the AMH and the SI were affected only by the severity (P=0.0004 and 0.0491, respectively). The half-life presented in the first year values between 31 and 75 days, and the second year 41 and 50 days, according to this data and the literature, Zuri could be classified as an exploitative specie. In both growing season the grazing cycle (GC) and grazing interval (GI) were affected by the severities (P<0.0001), the greatest severity (S) had the lesser GC and greater GI. The pre-graze/height (PREht) had the frequency × severity interaction (P<0.0001) in the first year, the height at the LI 95% were ~77 cm. In the second year PREht was affected only by the frequency, and had the height at the LI 95% ~77 cm. The post-graze height was affected by the severity in both years, and had the shorter height at the greater severity. The pre-graze herbage mass (PRHM) was affected by frequency and severity (P<0.05) in the first year, the greater values were recorded for the LI 95% (LI) frequency and the 29% of severity (L). There is no herbage accumulation (HA) effect in the first year, probably due to the lesser adaptation period. In the second year the PRHM was affected only by the severity (P=0.0001), had the greatest value for the L severity, probably because all the mass of the parts (Leaf mass, stem mass and dead material mass) had the greatest values (P<0.005) for the same severity. In the second year the HA was affected by the severity (P=0.0006), the greatest value for the L severity, due to the greater GC. Regardless of the frequency and severity used, the grass showed up that has adjusted to maintain a stable tilleriring. These data suggest that ~77-cm for the pre-graze and ~33-cm for the post graze canopy height is optimal for rotational stocked Zuri guineagrass.