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

Author(s)

Veridiana Aparecida Limão

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2010-08-31

Examining board members

Sila Carneiro da Silva; Alessandra Aparecida Giacomini; Carlos Guilherme Silveira Pedreira

• Advisor: Sila Carneiro da Silva

Abstract

Use of forage grasses on pastures without taking into account basic information related to their pattern of growth and development results in lack of knowledge regarding their morphophysiological limits to grazing, which may result in degradation of large areas of cultivated grasslands. Against that background, the objective of this study was to evaluate the growth patterns of mulato grass subjected to strategies of rotational stocking management, aiming at providing important physiological interpretations for planning and structuring grazing management practices. Treatments corresponded to combinations between two grazing severities (post-grazing heights of 15 and 20 cm) and two grazing intervals (time necessary for swards to intercept 95 or 100% of the incident light during regrowth LI), and were allocated to experimental units (1200m2 paddocks) according to a 2x2 factorial arrangement and a randomised complete block design, with four replications, from January 2008 until April 2009. The following response variables were studied: 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). During summer 1, treatment 100/20 resulted in the largest value of CGR, consequence of large remaining LAI associated with the post-grazing height of 20 cm and of the long grazing interval associated with the pre-grazing target of 100% LI. CGR decreased throughout autumun/winter/early spring and late spring. During summer 2, treatment 95/15 showed larger values of CGR than treatments 100/15 and 100/20, consequence of larger values of RGR and residual LAI of swards managed at 95 relative to those managed at 100% LI. NAR and LWR varied only with season of the year. Except during summer 1, swards managed at 95% LI showed larger values of LAR than those managed at 100% LI, a result of morphological adjustments mainly characterised by variations in SLA. Overall, grazing interval was more effective than grazing severity in interfering with most of the response variables studied. Therefore, adequate management of mulato grass under rotational stocking conditions correspond to a pre-grazing height of 30 cm (equivalent to the pre-grazing target of 95% LI) and post-grazing height of 15 to 20 cm. (AU)