Abstract
The objective of this study was to evaluate the effect of different levels of nitrogen supply and plants densities in the productivity of mombasa guineagrass (Panicum maximum) in the period of establishment. The design was of completely randomized blocks, with 12 treatments and three repetitions, with four nitrogen supplies (absence of application, 80, 160 and 320 kg/ha.year) and three plant densities (9, 25 and 49 plants/m²). The plot was cut at 30 cm from the ground when the sward high intercepted 95% of light. The following items were evaluated: sward height at 95% light interception, interval and number of cuts, dry mass production, total dry mass of leaves, stems and dead material and the morphologic composition. Nitrogen increased the dry mass production and the dry mass of stem in winter and summer, and decreased in the fall. The total dry mass of leaf presented decrease of 19% in the summer between the smallest and biggest densities in the 320 kg/ha. The dry mass of dead material had negative effect of the density in the fall. The leaf percentage increased 88% between the smallest and largest nitrogen level at the plant density of 49 plants/m2. Only density influenced the sward height in the condition of 95% of light interception. The number of cuts increased with nitrogen levels in the fall, spring and summer, while the interval of cuts decreased with fertilization in the spring and summer. Nitrogen increases the production of mombasa guineagrass in each cycle.
Highlights
The use of arbitrary variables, such as stocking rate, grazing pressure and rest period duration, which have been commonly used as a parameter of grazing management cannot be considered primary determinants of forage production and animal performance, once their effects are not mediated by canopy characteristics that collectively determine the condition and sward structure (Hodgson, 1985)
The total dry mass production (TDM) was lower in the winter (Table 1), and the limitation or reduction of temperature, water availability and photoperiod probably would have been responsible for lower production of Mombasa grass
Under favorable conditions to the development of plants, the nitrogen fertilization increases dry mass production of P. maximum, because it accelerates growth, increases the size of the leaves, the appearance and development of tillers - factors directly related to production (Davis et al, 2005; Martuscello et al, 2006), increasing the number of harvests
Summary
The use of arbitrary variables, such as stocking rate, grazing pressure and rest period duration, which have been commonly used as a parameter of grazing management cannot be considered primary determinants of forage production and animal performance, once their effects are not mediated by canopy characteristics that collectively determine the condition and sward structure (sward state) (Hodgson, 1985). Since the year 2000, the part of research that aims to control the conditions and the structure of the sward, for input and output of animals on the pasture has intensified, which has demonstrated good results to improve the management of Tanzania and Mombasa grasses (Da Silva, 2004). Light interception, as an object of research to establish management strategy, has shown promising results. In application of these results, a constant relation of sward height and the condition of 95% of light. Nitrogen is a nutrient that influences the morphophysiological characteristics of forages and has no effect on the flow of tissue (Garcez Neto et al, 2002), which can influence the canopy height to intercept 95% of light
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