Population density and tiller dynamics of Mulato II brachiariagrass in response to canopy height and contrasting growth rates under continuous stocking

Abstract

The livestock industry is one of the major economic activities in Brazilian agriculture. In this context, the use of pastures as the almost-sole feed source makes the activity highly profitable due to low production costs. Brachiaria grasses correspond to 80% of the cultivated pasture areas in Brazil. In most pasture-based production systems, however, grazing management is extensive and often lacks sound grazing management guidelines. In Brazil new forage materials are introduced and rapidly adopted by producers before research information becomes available about their potential, limiting their use or hindering their persistence in grazing systems. The objective of this study is to describe and explain the dynamics of tillering in the hybrid brachiariagrass Convert HD 364 (Mulato II) in response to two growth rates and three sward heights kept by continuous stocking and variable stocking rate. The experiment is being conducted in the Department of Animal Science at ESALQ / USP for two summer growing seasons (2012/2013 and 2013/2014). The experimental design is a randomized complete block with a factorial arrangement including all possible combinations between three steady-state sward heights (10, 25 and 40 cm) and two growth rates generated by nitrogen rates (50 and 250 kg N ha-¹ year-¹), with three replications, totalizing 18 experimental units of 200 m² each. The following variables are being studied: tiller density and demography, average tiller weight, forage mass, grass plant-part composition, leaf area index and location of growing points. These variables are collected every 28 days. The data will be analyzed using the MIXED procedure of SAS and the means will be compared using the "t" test (Pd0.05). It is expected that this study will depict some of the biological bases of the agronomic performance of Mulato II brachiariagrass grazing strategies and subsidize the establishment of appropriate management strategies for it. (AU)