Andreza Luzia Santos

Piata palisadegrass deferred in the fall: effects of initial height and nitrogen in the sward structure

The objective of this study was to evaluate the mass of the forage and of the morphological components, and the sward structure in Piata palisadegrass (Brachiaria brizantha cv. Piata) deferred in function of different initial heights and nitrogen levels. Two levels of nitrogen (75 and 150 kg/ha) and one control without fertilization associated to three initial deferring heights (20, 30, and 40 cm) were evaluated. The design was of completely randomized blocks with three replications in a subdivided plot scheme. A raise in the initial deferment height and in the fertilization elevated the sward and extended tiller heights, the leaf area index, and the light interception by the sward. The piata palisadegrass deferred with an initial height of 40 cm presented a higher forage mass with lower percentage of leaf blades, and higher stem and dead tissue quantity. Additionally, this management strategy resulted in lower bulk density of leaf blade and in higher bulk densities of stems and dead tissue. The utilization of 150 kg/ha of nitrogen raised the production and the bulk density of deferred piata palisadegrass forage and increased production and bulk density of leaves and stems. In the region of Vicosa, Minas Gerais, the piata palisadegrass deferred with an initial height of 30 cm and fertilized with 75 kg/ha of nitrogen in the beginning of the fall presents adequate mass and structure to animal production in the winter.

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. Piata for deferment in the region of Vicosa, 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 piata 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 piata grass managed with deferment period of 105 days. The mass of green leaf blade was higher in the piata 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 piata 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 piata 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 Vicosa, Minas Gerais, B. brizantha cv. Piata 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.

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.

Grazing patterns on signalgrass pasture according to location of cattle feces

This study was conducted to evaluate the defoliation patterns on B. decumbens cv. Basilisk (signalgrass) tiller as a function of influence of feces deposited naturally by cattle. The signalgrass was managed with an average height of 25 cm, under continuous stocking and variable stocking rate. Interval and intensity of defoliation, grazing efficiency and forage loss were evaluated in two sites on pasture - one close and the other distant from feces. The completely randomized block design with three replications was adopted. The defoliation rate of the pasture site close to feces was 40% lower than at that distant from feces. This response pattern was similar to defoliation intensity of leaf blade. The leaf blade of the tiller close to feces also achieved lower de foliation (1.64) than that in the tiller distant from feces (3.97). The relative number of grazed leaf per tiller in the tillers distant from feces was approximately 185% higher than those close to feces. The grazing efficiency was lower in the local close to feces compared with that distant, unlike forage loss. The natural deposition of feces by cattle modifies the grazing and use patterns of B. decumbens under continuous stocking.