Abstract
Biomass flow characteristics and forage accumulation were evaluated in Bermudagrass (Tifton 85) pasture managed under intermittent stocking with different management strategies. The management levels utilized were conventional (10 cm residual height and unfertilized), light (20 cm residual height and unfertilized), moderate (20 cm residual height with fertilization of 300 kg N/ha.year) and intensive (10 cm residual height with fertilization of 600 kg N/ha.year). A randomized design was used with repeated measurements over time, in two periods of the year, with four replicates. There was significant effect of management × period of the year on the leaf elongation rate (LER). The management levels under fertilization (0.59 and 0.60 cm/tiller.day for the intensive and moderate management, respectively) and the rainy season (0.49 cm/tiller.day) showed the greatest stem elongation rate. Leaf senescence rate (LSR) before and after and total LSR were modified by the management × period of the year interaction. The intensive management, with 0.38 leaves/tiller.day, as well as the dry period, with 0.27 leaves/tiller.day, showed higher leaf appearance rate. The lowest phyllochron was observed in intensive management and dry periods, as well as an interaction with the management of the same periods of the year. There was management × period of year interaction effect on leaf lifespan; the highest value was found under conventional management and dry period. Both production and forage accumulation rates were higher in the intensive and moderate management levels and dry season, and there was interaction of the intensive management system with the seasons. Managing pastures under moderate and intensive rotational stocking, which occurred mainly in the rainy and dry seasons, respectively, maximizes the flow of tissues and consequently production and accumulation of forage.
Highlights
Morphogenesis in a tropical pasture in vegetative growth can be described by four basic characteristics: stem elongation rate, leaf appearance and elongation rates and leaf lifespan (Chapman & Lemaire, 1993; Candido, 2003)
The management levels (P>0.05), periods of the year (P>0.05), and the interaction between these two factors did not influence the ratio between elongation rate of the first and second leaves formed in regrowth (LER1/LER2)
Even at management levels with higher height, LER1/LER2 behaved in a positive manner, since there is greater residual leaf area index in these pastures, which promotes greater shading of lower leaves in the canopy due to the higher amount of leaves remaining after grazing, compromising the elongation of the first leaf produced in regrowth, due to decrease in photosynthetic potential of this leaf primordium still within the sheaths at the end of the rest period prior to and during grazing (Woledge, 1973; Woledge, 1977)
Summary
Morphogenesis in a tropical pasture in vegetative growth can be described by four basic characteristics: stem elongation rate, leaf appearance and elongation rates and leaf lifespan (Chapman & Lemaire, 1993; Candido, 2003). These characteristics are genetically determined, but influenced by environmental variables such as temperature, water availability and nutrients, which vary widely throughout the year, in addition to grazing management, given by the constant adjustment of the intensity and frequency of defoliation, aiming at better pasture use efficiency (Lemaire & Chapman, 1996). This is because the use of fertilizers, depending on the level, changes the processes intrinsic to the soil-plant-animal system, such as plant development per time unit, which includes the processes of growth and senescence (Santos, 2010)
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