Defoliation heights for palisade grass cv. Marandu in silvopastoral system / [Alturas de desfolhação para capim-marandu em sistema silvipastoril]

The objective was to test the response of Urochloa brizantha cv. Marandu in monoculture and in silvopastoral system (SPS), at two distances from the trees, and define the best defoliation height for SPS. Four intermittent defoliation heights (25, 35, 45 and 55cm) and two distances from tree lines (2.5 and 5.0m) were evaluated in the SPS with a control defoliated with 25cm in full sun. The experiment was performed in a randomized block design with 3 replicates in a 4 × 2 + 1 split plot scheme. The control had higher forage accumulation (46.9kg/ha. day) than the SPS (31.1kg/ha. day). The bulk density was also higher in the control (0.89mg/cm³) than in SPS (0.48mg/cm³). The percentage of leaves (78.06%) and leaf/stem ratio (6.04) did not differ among the treatments. In the SPS, there was an increase of 31.07% in forage accumulation from 25 to 55cm. The forage accumulation and bulk density of Urochloa brizantha cv. Marandu in monoculture is greater than in the SPS regardless of the management goal and the distance from trees. The goal of 55cm in the SPS presented greater forage accumulation.(AU)

O objetivo foi testar a resposta de pastos de Urochloa brizantha cv. Marandu em monocultivo e em sistema silvipastoril (SSP), a diferentes distâncias das árvores, bem como definir qual altura de desfolhação é a mais indicada para manejo em SPS. Foram avaliadas quatro alturas de desfolhação intermitente (25, 35, 45 e 55cm) e duas distâncias das linhas de árvores (2,5 e 5,0m), no SPS, e uma testemunha desfolhada com 25cm, em pleno sol. O delineamento foi em blocos ao acaso, com três repetições, em esquema de parcelas subdivididas 4 × 2 + 1. O controle apresentou maior acúmulo de forragem (46,9kg/ha.dia) que a média do SSP (31,1kg/ha.dia). A densidade volumétrica da forragem do controle (0,89mg/cm³) foi maior que a do SSP (0,48mg/cm³). A porcentagem de folhas (78,06%) e a relação folha/colmo (6,04) não diferiram entre os tratamentos. O aumento das alturas de 25 para 55cm no SSP resultou em aumento de 31,07% no acúmulo de forragem. O acúmulo e a densidade volumétrica da forragem são maiores no monocultivo, independentemente da meta de manejo e da distância das árvores no sistema silvipastoril. A meta de 55cm no silvipastoril apresenta maior acúmulo de forragem.(AU)

Repeatability of agronomic traits in Panicum maximum (Jacq.) hybrids.

When evaluating plants, in particular perennial species, it is common to obtain repeated measures of a given trait from the same individual to evaluate the traits' repeatability in successive harvests. The degree of correlation among these measures defines the coefficient of repeatability, which has been widely utilized in the study of forage traits of interest for breeding. The objective of the present study was to evaluate the repeatability of agronomic traits in Panicum maximum hybrids. Hybrids from three progenies totaling 320 hybrids were evaluated in an incomplete-block design, with consideration of production and morpho-agronomic traits. Of the production traits, total dry matter and leaf dry matter showed the highest repeatability and varied from 0.540 to 0.769, whereas stem dry matter had lower coefficients (0.265-0.632). Among the morpho-agronomic traits, plant height and incidence of Bipolaris maydis had higher coefficients (0.118-0.460). The repeatability values of the agronomic traits were low-to-moderate, and six evaluations were sufficient to provide accuracy in the selection of hybrids regarding total dry matter, leaf dry matter, plant height, and incidence of B. maydis, whereas the other traits require more repeated measures to increase reliability in the prediction of their response.