Characterization of tillers in deferred Piata palisade grass with different initial heights and nitrogen levels

This experiment was conducted to estimate the effects of nitrogen fertilization associated with the initial height of the Piata palisade grass on the number and structural characteristics of individual tillers after the deferment period. An area with Brachiaria brizantha cv. Piata measuring approximately 288 m² was used. Combinations of levels of nitrogen fertilization (0, 75 and 150 kg/ha of nitrogen) and initial heights of the sward (low - 20 cm, medium - 30 cm and high - 40 cm) were evaluated. The experimental design was of completely randomized blocks in subdivided plots with three replications. The number of vegetative tillers, the stem length of the vegetative, reproductive and dead tillers, and the number of dead leaves of the reproductive and the dead tillers linearly increased with the elevation in the nitrogen level. The deferred Piata palisade grass with low initial height showed lower number of dead basal tillers, shorter length of stems and leaf blades in reproductive tillers and lower number of live and dead leaves in vegetative tillers in relation to the one managed with height considered medium and high. Nitrogen fertilization, in association with low initial height, provides the optimization of forage of Piata palisade grass in deferment conditions

Forage mass and structure of piatã grass deferred at different heights and variable periods

The objective of this study was to determine the deferment period and the most adequate initial sward height of Brachiaria brizantha cv. Piatã for deferment in the region of Viçosa, Minas Gerais. For so, the following characteristics were evaluated: masses and bulk density of forage and its morphological components, light interception by the sward, leaf area index, leaf angle, sward and extended tiller height and falling index of the deferred piatã grass. The three deferment periods assessed (65, 85 and 105 days) were randomized to the plots and the three sward heights (20, 30 and 40 cm), randomized in the subplots. The experimental design was of completely randomized blocks, with three replicates, in a subdivided plots arrangement. Masses of forage, green stem and dead tissue were higher in the piatã grass managed with deferment period of 105 days. The mass of green leaf blade was higher in the piatã grass deferred with 20 cm height associated to the deferment period of 85 days, which had, as consequence, greater bulk density of green leaf blade. The interception of light by the sward was greater in the piatã grass kept longer in deferment associated with the higher leaf area index, regardless of its initial height. The heights of the sward and extended tillers were greater in the piatã grass under periods of 85 and 105 days of deferment; however, the falling index was not affected by the factors studied. In the region of Viçosa, Minas Gerais, B. brizantha cv. Piatã fertilized with 75 kg/ha nitrogen and deferred with initial height of 20 cm and for a period of 85 days, from mid April, has adequate productivity and structure for animal production

Análise de crescimento do capim Coastcross-1 sob adubação nitrogenada em duas idades de rebrotação

Avaliaram-se os índices de crescimento do capim Coastcross-1 sob cinco doses de nitrogênio (0, 100, 200, 300 e 400 kg/ha.ano) e duas idades de rebrotação (28 e 42 dias). As doses de nitrogênio foram arranjadas em esquema fatorial 5 × 2, em blocos ao acaso, com três repetições. A adubação nitrogenada foi parcelada em três aplicações, realizadas logo após os cortes. Maiores valores de relação folha/colmo e razão de peso foliar foram obtidos aos 28 dias, em comparação aos 42 dias de rebrotação. Houve redução linear na relação folha/colmo com a adubação nitrogenada (de 1,6 para 1,0 nas doses de 0 e 133 kg/ha.corte de N). Por outro lado, a adubação nitrogenada aumentou linearmente a área foliar específica do capim Coastcross-1 aos 28 dias de rebrotação (de 10,3 a 20,8 m²/kg com o incremento de 0 a 133 kg/ha.corte de N), resultando em elevação da sua razão de área foliar. Na ausência de nitrogênio, a área foliar específica foi maior aos 42 dias (14,3 m²/kg) em relação aos 28 dias de rebrotação (8,6 m²/kg). A idade de rebrotação e a adubação nitrogenada modificam o padrão de acúmulo de forragem e as características do pasto de capim Coastcross-1. Durante a estação de maior crescimento, o pasto de capim Coastcross-1 adubado com maior dose de nitrogênio deve ser manejado com menor idade de rebrotação (28 dias).The Coastcross-1 growth index in relation to five nitrogen doses (0, 100, 200, 300 and 400 kg/ha.year) and two regrowth ages (28 and 42 days) were evaluated. Nitrogen doses were arranged in a 5 × 2 factorial scheme in a randomized complete block design with three repetitions. Nitrogen fertilization was performed in three applications right after the forage harvesting. Higher values for leaf/stem and leaf weight ratio were observed at 28-d regrowth, in comparison with the 42 days of regrowth. Linear reduction of leaf/stem ratio from 1.6 to 1.0 at 0 and 133 kg N/ha.harvest, respectively was observed. The specific leaf area of bermudagrass at 28-d regrowth resulted in increased leaf area ratio (from 10.3 to 20.8 m²/kg with the increase of 0 to 133 kg N/ha. Harvest). At the absence of N treatment, specific leaf rate was higher at 42-d (14.3 m²/kg) in relation to the 28-d of regrowth (8.6 m²/kg). Regrowth age and nitrogen fertilization modify the pattern of forage accumulation and the characteristics of Coastcross-1 pasture. During the summer, the Coastcross-1 grass pasture fertilized with the highest N-dose should be managed at a younger regrowth age (28-d)

Structural characteristics and forage mass of Tifton 85 pastures managed under three post-grazing residual leaf areas

The experiment was carried out on Cynodon spp cv. Tifton 85 pastures grazed by sheep under rotational stocking, with the objective of evaluating the structural characteristics as well as the forage mass of the pastures subjected to three grazing intensities in successive cycles. Treatments were composed of three residual leaf area indices (rLAI; 2.4; 1.6 and 0.8), allocated in completely randomized blocks with seven replications, totaling 21 experimental units. Tiller population density, pasture height, leaf area index, forage morphological composition and pasture forage mass were evaluated. The rLAI modified the tiller population density, which increased linearly with decrease in the rLAI of the pastures. Dry masses of leaf blade, stem and dead material were inferior when the rLAI imposed were lower, which resulted in differentiated forage production among the treatments. Tifton 85 pastures grazed by sheep in rotational stocking under tropical conditions with different rLAI show a modified sward structure over successive grazing cycles, mainly by alteration in the height and LAI of the plants at pre-grazing and by light interception post-grazing, which change the tiller population density. The residual leaf area index of 1.6 is the most suitable for pasture management for being equivalent to the heights of entrance and exit of animals on and from paddocks of 33 and 19 cm, respectively, which avoid great accumulation of dead material and excessive stem elongation, in addition to ensuring tillering in the sward.Universidade Estadual Paulista Júlio de Mesquita Filho Programa de Pós-graduação em ZootecniaUniversidade Estadual Paulista Júlio de Mesquita Filho Departamento de ZootecniaUniversidade Estadual Paulista Júlio de Mesquita Filho Programa de Pós-graduação em ZootecniaUniversidade Estadual Paulista Júlio de Mesquita Filho Departamento de Zootecni