Morphogenesis and sward structure of continuously stocked marandu palisadegrass subjected to contrasting morphogenetic rhythms

Author(s)

Lilian Elgalise Techio Pereira

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2009-06-10

Examining board members

Sila Carneiro da Silva; Paulo César de Faccio Carvalho; André Fischer Sbrissia

• Advisor: Sila Carneiro da Silva

Abstract

Productivity of pastoral systems of animal production depends on the use of grazing management strategies that are compatible with the growth rhythm of plants. In that context, knowledge regarding the response of individual plants to management practices used and their consequences to sward structure is necessary. The objective of this experiment was to evaluate the morphogenetic responses and sward structure, as well as their patterns of change throughout the year, of continuously stocked marandu palisadegrass swards maintained at 30 cm and subjected to contrasting morphogenetic rhythms created by nitrogen fertilisation use. Treatments corresponded to three nitrogen application rates (150, 300 e 450 kg/ha de N) plus the control (no fertilisation) and were assigned to experimental units (1200 m2 paddocks) according to a complete randomised block design, with four replications. The following response variables were measured from January 2007 to April 2008: total herbage (HBD), leaf (LBD), stem (SBD) and dead material (DBD) bulk density, vertical distribution of herbage components and sward structure, leaf appearance (LAR) and elongation (LER) rates, stem elongation rate (SER), leaf life span (LLS), final leaf length of fully expanded leaves (FLL), stem length (SL), population density of basal (TPDb) and aerial (TPDa) tillers. Faster morphogenetic rhythms (swards fertilised with 300 and 450 kg/ha of N) resulted in increased HBD, particularly related to leaf and stem components. Such changes were caused by increases in tissue turnover on individual tillers characterised by higher LAR and LER, and in the turnover of tillers in tiller population, which resulted in larger TPDb and TPDa than those recorded under slower morphogenetic rhythms (no fertilised swards and/or fertilised with 150 kg/ha of N). These responses were more pronounced on sward growth relative to senescence fluxes. This indicates the possibility of increasing herbage utilisation efficiency with wise use of management practices that accelerate the morphogenetic rhythm of plants, since responses showed a compensatory behaviour as a means of maintaining tiller structural characteristics and sward structure relatively stable, with differences being mainly a function of seasonal variations in climatic conditions (AU)