Dynamics of forage accumulation in Elephant grass subjected to rotational grazing intensities

Braulio Maia De Lana Sousa,André Fischer Sbrissia,Carlindo Santos Rodrigues,Hélida Christhine De Freitas Monteiro,Sila Carneiro Da Silva,Domicio Do Nascimento Júnior,Márcia Cristina Teixeira Da Silveira,Hélio Henrique Vilela

doi:10.1590/s1516-35982013000900004

Abstract

We assessed the accumulation dynamics of forage and its components in Elephant grass cv. Napier (Pennisetum purpureum Schum.) that were subjected to three post-grazing height treatments (30, 50, and 70 cm) from February through May 2009 (experiment one) and December 2009 through May 2010 (experiment two). In experiment one, the grazing events started when the light interception by the canopy reached 95%. The same was adopted for experiment two, except for the first grazing event, which was based on the height of the apical meristems of basal tillers. The experimental design for both experiments was a randomized complete block with three replications. The pastures that were managed at a post-grazing height of 30 cm exhibited lower rates of leaf and stem growth, total growth and forage accumulation than those that were managed at 50 or 70 cm, indicating that post-grazing height affects Elephant grass. The pastures that were managed at 50 cm exhibited relatively stable accumulation rates and less stem accumulation. Pastures managed at 70 cm of pos-grazing height presented more leaf and stem accumulation. Most apical meristems of Elephant grass should be removed in the first grazing when they reach the post-grazing target height of 50 cm. The elevation in the residual post-grazing height, especially in the summer, raises the regrowth vigor in the Elephant grass cv. Napier pasture. The post-grazing height of 30 cm reduces the growth of the Elephant grass cv. Napier.

Highlights

Forage accumulation in pastures is a function of the balance between the growth and senescence processes (Bircham & Hodgson, 1983) that occur in tillers associated with tillering patterns
The post-grazing height of 30 cm reduces the growth of the Elephant grass cv
With the exception of the aerial tillers in the pastures that were managed at a postgrazing height of 30 cm, the leaf growth rate decreased in the pastures throughout the year, and this result was independent of the tiller category

Summary

Introduction

Forage accumulation in pastures is a function of the balance between the growth and senescence processes (Bircham & Hodgson, 1983) that occur in tillers associated with tillering patterns (e.g., appearance, mortality and survival). The forage accumulation rate reflects the interactions between the genetic attributes of the plant, the environmental effects on its morphophysiological processes and the grazing management (Lemaire & Chapman, 1996). Recent studies with tropical grasses revealed a fairly consistent pattern of forage accumulation in which grass reduces leaf accumulation and enhances stem elongation and leaf senescence rates after the canopy reaches 95% of light interception (Carnevalli et al, 2006; Da Silva et al, 2009). Using severe post-grazing heights can reduce photosynthesis rates in plants and increase apical meristem decapitation, which would increase the time required for the removed leaf area to recover (Brougham, 1956). Using a severe (high) post-grazing height can reduce intraspecific light competition by modifying the light environment in the canopy and promoting increased tissue and tiller renewal, thereby resulting in a younger population of tillers. Some studies have suggested that tiller age influences both morphogenetic and structural characteristics, thereby resulting in a progressive loss of vigor with advancing tiller age (Paiva et al, 2011)

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