Abstract
T
 This study aimed to evaluate the morphogenetic, structural, and productive characteristics of Andropogon gayanus cv. ‘Planaltina’ subjected to different nitrogen fertilization levels and defoliation intensities. The experiment was done in a completely randomized design with a factorial arrangement of six nitrogen doses (0, 100, 200, 300, 400, and 500 kg N ha-1) and two defoliation intensities (15 and 30 cm). The production and structure data were grouped into rainy and dry periods, while morphogenesis data were compared only among different fertilization and defoliation intensities. The total dry forage biomass (TDFB), dry mass of leaves (DML), dry mass of stems (DMS), and dead forage dry mass (DFDM) were then determined. In addition to these variables, the morphogenetic characteristics of the plants and the numbers of tillers alive and dead were evaluated. There was no interaction (P>0.05) between the effects of nitrogen fertilization doses and the intensity of defoliation on TDFB, DML, DMS, and DFDM in both of the evaluated phases (rainy and dry). It was also observed that the rates of leaf elongation, leaf appearance, and leaf blade elongation increased with nitrogen fertilization. On the other hand, the culm elongation rate and phyllochron decreased as the dose applied increased. The defoliation intensity did not influence (P>0.05) the morphogenetic characteristics examined, nor did it affect the senescence rate of nitrogen in leaves and number of live leaves per tiller. The number of dead tillers increased linearly during the rainy period. Based on these results, to improve the efficiency of production of gamba grass it is recommended that it be managed with a defoliation intensity of 30 cm and nitrogen fertilization of 286.52 kg N ha-1 year-1.
Highlights
The successful use of pastures depends on the availability of nutrients or the grass used, and onhaving an understanding of the morpho-physiological mechanisms affecting the grass plants and their interactions with the environment and management
The total dry forage biomass (TDFB) exhibited a quadratic response to nitrogen fertilization (P
TDFB increases with the amount of fertilization applied, it should be analyzed with caution because it does not address the qualitative aspects of pasture
Summary
The successful use of pastures depends on the availability of nutrients or the grass used, and onhaving an understanding of the morpho-physiological mechanisms affecting the grass plants and their interactions with the environment and management. To achieve balance between these purposes, two points of great importance must be considered: the first is the amount of fertilizer to be applied, and the second is the residue that is left after grazing The latter of these factors is important because there is significant flow of carbon to the apical meristems during regrowth, and the former factor acts as an accelerator of this recovery, increasing the growth potential of the grass. This flow of carbon is strongly influenced by the processes of nitrogen absorption, partitioning, and recycling, since the use of carbon in activities associated with meristematic morphogenetic processes has been shown to be highly dependent on there being appropriate
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