Growth patterns of elephant grass subjected to strategies of rotational stocking management

Abstract

Forage grasses have specific ranges of use and management related to frequency and severity of defoliation that must be respected in order to allow high animal production and productivity sustainably. For that, it is necessary to know how they grow and develop, that being the basic assumption for planning efficient grazing management strategies. In this context, growth analysis is essential, since growth and development are both influenced by biotic and non-biotic factors and such analysis allows that inferences on important physiological processes can be done from simple field agronomic evaluations. The objective with this experiment is to evaluate the patterns of growth and the existence or not of ontogenetic effect (class and age of tillers) on herbage accumulation of elephant grass subjected to strategies of rotational stocking management. Treatments will correspond to combinations between two post- (post-grazing heights of 35 and 45 cm) and two pre-grazing (95% and maximum light interception by sward canopy - LI) conditions, and will be allocated to experimental units (1200 m2 paddocks) according to a 2x2 factorial arrangement and a randomized complete block design, with four replications from October 2011 to April 2012. A pre-experimental period of adaptation of experimental units to grazing treatments is already being carried out since January 2011. The following response variables will be evaluated: sward leaf area index (LAI), crop growth rate (CGR), net assimilatory rate (NAR), relative growth rate (RGR), leaf area ratio (LAR), specific leaf area (SLA) and leaf weight ratio (LWR). At the end of the experimental period, in summer 2012, measurements of leaf appearance and elongation rate, stem elongation rate, final leaf lamina length, stem length, number of expanding, expanded and senescing leaves per tiller will be made on individually marked tillers of different age categories (0 to 2; 2 to 4 and more than 4 months old) from the pool of marked tillers of a concomitant experiment on tiller population density and tiller demography. Data will be analyzed using the PROC Mixed of SAS, means estimated using the LSMEANS command, and comparison made according to Student t test and 5% level of significance. (AU)