Morphogenetic Characteristics of Mulato II Brachiariagrass Under Contrasting Growth Rates and Canopy Height Maintained By Continuous Stocking.

Understanding plant growth is essential to the formulation of sound management in grazed pastures. Forage plant morphogenetic responses help explain plant growth under different conditions and management practices such as frequency and intensity of defoliation. The aim of this study was to evaluate morphogenetic responses  hybrid brachiariagrass (Brachiaria spp) cv. Convert HD 364 (also known as “Mulato II”) to two growth rates (generated by 50 and 250 kg N ha^-1 yr^-1) and three canopy heights (10, 25 and 40 cm) kept constant by continuous stocking. The experimental design was a randomized complete block, with a 3 x 2 factorial arrangement, with three replications. Responses evaluated included leaf appearance rate (LAR), phyllochron (PHY), stem elongation rate (SER) and senescence rate (SR) during the summer (Jan to Apr 2013) in Piracicaba, SP, Brazil. LAR and PHY were affected by growth rate and canopy height. Under low growth rate LAR decreased from 0.144 to 0.083 leaf day^-1 and the PHY increased from 8.95 to 12.3 day leaf^-1. LAR and PHY were similar in 25- and 40-cm canopies (0.095 leaf day^-1; 11.42 day leaf^-1). SER and SR were greater under higher growth rates (0.054 cm day^-1and 0.144 cm day^-1, respectively) and in taller swards (0.074 cm tiller^-1 day^-1 0.184 cm tiller^-1 day^-1, respectively). Growth rate and canopy height can modify sward morphogenetic characteristics and this required that management be adjusted accordingly, so that forage production and utilization are optimized, reducing senescence and stem elongation rates.