Objetivou-se com este trabalho avaliar o efeito de doses de nitrogênio (N) e densidades de plantas (D) sobre a dinâmica de perfilhamento do capim-tanzânia (Panicum maximum Jacq.). O delineamento foi em blocos casualizados, com 12 tratamentos e duas repetições em esquema fatorial 4 × 3, com quatro doses de N (0, 80, 160 ou 320 kg ha-1 ano-1) e três densidades de plantas (9, 25 ou 49 plantas m-2). O número de perfilhos foi maior na densidade de 9 plantas m-2 e nas maiores doses de N, principalmente na segunda e terceira gerações. O N influenciou quadraticamente as taxas de aparecimento de perfilhos basilares e totais, que também foram influenciadas pela densidade de plantas e pela interação N × D. A taxa de aparecimento de perfilhos aéreos, no entanto, não foi influenciada pelos fatores avaliados. A taxa de mortalidade de perfilhos totais foi influenciada de forma quadrática pelas doses de N e pelas densidades de plantas. A taxa de mortalidade de perfilhos basilares respondeu quadraticamente à densidade de plantas, enquanto a taxa de mortalidade de perfilhos aéreos aumentou de linearmente com a adubação. Pastos implantados em densidades baixas ou intermediárias adubados com nitrogênio apresentam padrão mais intenso de renovação de perfilhos.

This study evaluated the influence of nitrogen levels (N) and plant density (D) on the tillering dynamics of Tanzania guinea grass (Panicum maximum Jacq.). Treatments were arranged in a completely randomized block design with 12 treatments and two replicates in a factorial scheme (4 × 3) with four levels of N (0, 80, 160 or 320 kg ha-1 N) and three plant densities (9, 25, and 49 plant m-2). Higher number of tillers was observed in the treatment with 9 plants m-2 and under higher levels of N, especially in the second and third generations. Still, the N influenced quadratically the appearance rate of basal and total tillers, which were also affected by plant density and interaction N × D. However, the appearance rate of aerial tiller was not influenced by factors evaluated. The mortality rate of total tiller was influenced quadratically by the nitrogen levels and plant densities. The mortality rate of basal tiller responded quadratically to plant density, whereas the mortality rate of aerial tiller increased linearly with fertilization. Pastures with low or intermediate densities fertilized with nitrogen, presented a more intense pattern of tiller renewal.

The objective of this experiment was to evaluate the nitrogen and plant density influence on the yield, forage dissection and nutritive value of Tanzania grass (Panicum maximum Jacq.). The design was of completely randomized blocks with three replications in a factorial arrangement with four nitrogen levels (0, 80, 160 or 320 kg/ha N) and three plant densities (9, 25 or 49 plants/m²). The plots were cut at 25 cm from soil level when the canopy reached 95% of light interception. The total dry matter forage yield and dry matter forage yield per harvest increased linearly with the nitrogen fertilization. The leaf and stem yield had the same response. The senesced forage yield was quadratically influenced by the nitrogen. The stems ratio in the morphologic composition was high in the high nitrogen levels and in the low plant densities. The leaf:stem ratio showed high values in this trial, but it was increased in plots without nitrogen and high plant density. The pre-grazing height was reduced with the increase in plant density. The nutritive value was favored by the nitrogen fertilization, which increased the crude protein level and reduced neutral detergent fiber and lignin. These factors increased the leaf and stem in vitro digestibility of organic matter. Nitrogen fertilization increases the forage yield of Tanzania grass under rotational grazing. After the establishment, plant density has little influence on the Tanzania grass yield and its forage dissection. The harvest with 95% light interception improves the structure and nutritive value of Tanzania grass pastures.

O experimento foi conduzido com os objetivos de avaliar a altura do dossel com 95% de interceptação luminosa e quantificar a influência da adubação nitrogenada e da densidade de plantas nas características morfogênicas e estruturais de capim-tanzânia. Quatro doses de nitrogênio, N (0, 80, 160 e 320 kg.ha-1), foram combinadas com três densidades de plantas (9, 25 e 49 plantas.m-2), em um arranjo fatorial 4 × 3, em delineamento inteiramente casualizado com três repetições, para avaliação da produção de biomassa, e duas repetições, para avaliação das características morfogênicas e estruturais. O acúmulo de MS total durante o período experimental foi influenciado pela adubação nitrogenada e pela densidade de plantas. No período das águas, as maiores doses de nitrogênio diminuíram o intervalo de colheitas e, consequentemente, aumentaram o número de colheitas. A altura do dossel de capim-tanzânia com 95% de IL foi positivamente influenciada pela densidade de plantas nos períodos das águas e de transição água-seca e seca. A altura do capim-tanzânia com 95% de IL apresentou variações ao longo das avaliações, de modo que os valores foram maiores (próximos a 70 cm) no período das águas, seguido pelos períodos de transição água-seca e seca.

This experiment was carried out to evaluate canopy height of guinea grass with 95% of photosynthetic active radiation interception and quantify the nitrogen fertilization influence and plants' density on the morphogenesis and structural characteristics of Tanzania grass. Four doses of N (0, 80, 160 e 320 kg.ha-1), were arranged with three plant densities (9, 25 and 49 plants.m-2), according to 4 × 3 completely randomized design, with three repetitions. Total dry matter (DM) accumulation throughout the experimental period was influenced by nitrogen fertilization and plants' density. In the rainy period, the higher nitrogen fertilization decreased the harvesting intervals, and consequently, increased the number of harvests. The rate of leaf appearance and the phyllochron were influenced only under nitrogen fertilization in the transition period of rainy and dry weather. Tanzania grass canopy height under 95% of light interception was positively influenced because of the plant densities in rainy period and transition period between rainy/drought and drought. Tanzania grass height under 95% of light interception presented variations along the evaluations and the values were higher (near 70 cm) in the rainy period, followed by transition period rain/drought and drought.

The objective of this work was to evaluate effects of nitrogen fertilization and plant density on morphogenesis of Tanzania guinea grass. It was used a random block design with 12 treatments and two replications in a 4 × 3 factorial arrangement, with four doses of nitrogen (N) (without N application, 80, 160 or 320 kg/ha.year) and three plant densities (9, 25 or 49 plants/m²). Harvest was performed at 25 cm from the ground when the canopy intercepted 95% of the incident light. Rates of leaf appearance and pseudostem elongation were positively and linearly influenced by nitrogen, whereas phillochron and leaf life span were influenced linearly and negatively. Leaf elongation responded positively to two factors, whereas leaf senescence rate and number of live leaves were not influenced by the factors evaluated. Number of total, basal and aerial tillers were greater at the density of 9 plants/m² and at the nitrogen dose of 320 kg/ha.year. Nitrogen increases production of leaves and tillers in Tanzania guinea grass defoliated at 95% of light interception, but high density of plants reduces the number of tiller per bunch.

Objetivou-se avaliar correlações entre características estruturais e valor nutritivo do pasto diferido de U. decumbens cv. Basilisk. O experimento foi realizado em esquema de parcelas subdivididas, segundo o delineamento em blocos casualizados, com duas repetições. Os tratamentos foram combinações dos períodos de diferimento da pastagem (73, 103, 131 e 163 dias) com os períodos de pastejo (1, 29, 57 e 85 dias). A massa de lâmina foliar verde correlacionou-se positivamente com os percentuais de proteína bruta (PB), fibra em detergente neutro potencialmente digestível (FDNpoD) e matéria seca potencialmente digestível (MSpoD), mas negativamente com os teores de fibra em detergente neutro (FDN) e FDN indigestível. As correlações para colmo morto foram inversas àquelas obtidas para lâmina verde. Para o perfilho vegetativo, as correlações foram positivas com PB e MSpoD e negativas com FDN e FDNi. Para o perfilho morto, constataram-se correlações positivas com os percentuais de FDN e FDNi da forragem, bem como associação negativa com os teores de PB, FDNpoD e MSpoD. O índice de tombamento correlacionou-se de forma negativa com o número de perfilhos vegetativos e de forma positiva com o número de perfilhos reprodutivos e mortos. O índice de tombamento também se correlacionou positivamente com os teores de FDN e FDNi e de forma negativa com os percentuais de PB e MSpoD. As características estruturais do pasto diferido estão associadas ao seu valor nutritivo. Ações de manejo que reduzam a massa de colmo morto e o número de perfilhos mortos e perfilhos reprodutivos contribuem para melhorar a estrutura e o valor nutritivo do pasto diferido.

The objective of this study was to evaluate correlations between the structural characteristics and nutritional value of different U. decumbens cv. Basilisk pastures. The experiment was carried out in a split-plot design following a randomized block design with two replications. The treatments were combinations among the different pasture periods (73, 103, 131 and 163 days) and the grazing periods (1, 29, 57 and 85 days). The green leaf blade matter (GLB) correlated positively with the percentages of crude protein (CP), potentially digestible neutral detergent fiber (PDNDF) and potentially digestible dry matter (PDDM), but correlated negatively with neutral detergent fiber (NDF) and indigestible neutral detergent fiber (INDF). Dead stem (DS) correlations were inverse to those obtained for green leaf blade. For vegetative tillering (VT), positive correlations were found with CP and PDDM; negative correlations were found for NDF and INDF of the forage. Dead tiller (DT), correlated positively with NDF and INDF of the forage and negative association with the CP, PDNDF and PDDM rates. The falling index (FI) correlated negatively with the number of VT and correlated positively with the number of reproductive tillers (RT) and dead tillers (DT). The falling index also correlated positively with the NDF and INDF rates and negatively with CP and PDDM. The structural characteristics of the different pasture were associated to their nutritive value. Management actions which result in a reduction in the dead stem matter and the numbers of dead tillers and reproductive tillers contribute to improve the structure and nutritional value of the different pasture.