Abstract
The aim of this study was to evaluate during the dry and rainy seasons the morphogenesis traits of two clones of dwarf elephant grass under different management strategies. The study was conducted in a factorial 2 × 2 × 3 design, using two clones, one green and one purple, two residual heights, 25 and 45 cm, and three frequencies of defoliation according to the light interception of 90, 95 and 100%. The design was a randomized block with three replications. The variables were leaf elongation and leaf senescence rate, stem elongation rate and phyllochron. The leaf lifespan and the number of living leaves per tiller were also estimated. The clones presented low stem elongation rates, showing adaptation for grazing use. In the rainy season, the light interception of 100% promoted the highest stem elongation rate and increased the leaf senescence rate. In the dry season, the leaf elongation rate (LER) was higher for the purple clone than for the green one (23 vs 15 mm.tiller-1.day-1). In the rainy season, the LER of the green clone exceeded that of the purple one by 71% (149 vs. 87 mm.tiller-1.day-1). The phyllochron varied among clones only in the rainy season, when the value was 4.6 days.leaf-1 for the green clone and 8.4 days.leaf-1 for the purple one; both of these values are below the mean value observed during the drought (21,6 days.leaf-1). The residual heights did not affect, in an isolated way, any of the variables. The clones are well adapted to grazing, presenting low stem elongation rates. The interval between defoliations should consider the scope of light interception between 90 and 95%. The green clone, with a greater flow of biomass, requires handling with shorter defoliation intervals.
Highlights
Elephant grass (Pennisetum purpureum) is one of the most productive nutritious value tropical grasses (Pereira & Ledo, 2008) its adoption for grazing use is hindered by its early stem elongation, which complicates management (Veiga, 1997)
The phyllochron varied among clones only in the rainy season, when the value was 4.6 days.leaf-1 for the green clone and 8.4 days.leaf-1 for the purple one; both of these values are below the mean value observed during the drought (21,6 days.leaf-1)
The literature suggests that there is a reduction in the leaf elongation rate (LER) as the intensity of defoliation increases (Gomide et al, 2006); Carvalho et al (2005) found no effect of grazing residues of 50 and 100 cm on the morphogenetic traits of Napier elephant grass
Summary
Elephant grass (Pennisetum purpureum) is one of the most productive nutritious value tropical grasses (Pereira & Ledo, 2008) its adoption for grazing use is hindered by its early stem elongation, which complicates management (Veiga, 1997). The study of leaf emergence, leaf elongation and the leaf lifespan (Lemaire & Chapman, 1996) as well as stem elongation in tropical grasses (Sbrissa & da Silva, 2001), may help accelerate the selection of materials in breeding programs (Van Esbroeck et al, 1997) and determine the management of defoliation (Gomide et al, 2006). Gomide & Gomide (2000) founded three live leaves in the Panicum maximum (Jacq.) cultivars Mombaça, Tanzânia, and Centenário with the senescence process beginning 23 days after cutting. For the Vencedor cultivar, the number of living leaves was between five and six, and leaf death was apparent after the 37th day of regrowth
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