Demographic patterns of tillering and herbage accumulation in Cynodon spp. swards under four grazing intensities.

Author(s)

Carlos Augusto Brandão de Carvalho

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2000-03-02

Examining board members

Sila Carneiro da Silva; Moacyr Corsi; Valdo Rodrigues Herling

• Advisor: Sila Carneiro da Silva

Abstract

Herbage dry matter production from pastures is strongly influenced by tiller number and tiller size in plant communities. These factors vary according to climatic and edaphic conditions as well as grass species, highlighting the need for understanding the way they relate to each other in order to increase animal productivity on pastures. The present experiment was carried out at the Animal Production Department, ESALQ/USP, Piracicaba-SP, from 18/08/98 until 08/03/99, aiming at evaluating the demographic patterns of tillering and herbage accumulation in Cynodon spp. swards. Treatments comprised all combinations between three Cynodon spp. cultivars (Tifton-85, Florakirk and Coastcross) and four sward estate conditions (5, 10, 15 and 20 sward surface height - SSH) generated by sheep under continuous stocking and variable stocking rate. The experimental design used was a complete randomised block, with treatments arranged in split-plot and replicated four times. Grass cultivars were assigned to plots and SSH to sub-plots. Pasture responses evaluated were: tiller natality and mortality rates, tiller population densities, herbage accumulation rates and dry matter production. Tifton-85 presented the highest values for tiller population densities, the smallest tiller mortality and the highest tiller survival rates. Herbage accumulation rates as well as dry matter production did not differ among treatments throughout the experimental period. There was a time effect on all variables studied and a dry spell in November/98 caused a decrease in tiller population and herbage accumulation rates. Tiller mortality rates were important determinants of the differences observed in tiller population densities for cultivars and/or SSH. Reproductive growth was a feature for Coastcross and Florakirk during late winter and spring, respectively. Tifton-85 presented a higher tolerance to hard grazing than Coastcross and Florakirk. Hard grazing (5cm) after a period of high mortality rate caused a strong reduction in tiller population densities. (AU)