Full text
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| Author(s): |
Cauê Varesqui Zeferino
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2007-01-23 |
| Examining board members: |
Sila Carneiro da Silva;
Domicio do Nascimento Junior;
André Fischer Sbrissia
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| Advisor: | Sila Carneiro da Silva |
| Abstract | |
Herbage accumulation is a dynamic process mediated by modifications in morphogenetic responses and tiller demography that involves the balance between growth and senescence. Grazing management can alter this balance, affecting the production and the efficiency of utilisation of the produced herbage. The objective of this experiment was to evaluate the patterns of morphogenetic responses and the dynamics of herbage accumulation, characterised by growth and senescence, in marandu grass swards subjected to strategies of rotational grazing management in order to understand and enable the efficient planning and manipulation of the defoliation process, ensuring the adequate use of the this forage plant. The experiment was carried out at Departamento de Zootecnia, USP/ESALQ, from December 2004 to December 2005. Treatments corresponded to combinations between two grazing intensities (post-grazing residues of 10 and 15 cm) and two grazing frequencies (equivalent to the period of time necessary for swards to reach 95 and 100% interception of the incident light during regrowth ? LI), and were allocated to experimental units (1200 m2 paddocks) according to a complete randomised block design and a 2 x 2 factorial arrangement, with 4 replications. The following response variables were analysed: number of live (NLL), senescing (NSL) and expanding (NEL) per tillers; leaf appearance rate (LAR), phyllochron and leaf lifespan (LLS); rates of leaf (LER) and stem (SER) elongation, and rates of sward growth and senescence considering both basal and aerial tillers. In general, considering the entire sward tiller population (basal and aerial), the 95% LI treatments resulted in higher values of NLF as well as NSL, NEL and LLS than the 100% LI treatments. On the other hand, the 100% LI treatments resulted in higher rates of stem elongation than the 95% LI treatments. As for the remaining variables, treatment 95/15 showed a particular pattern of response in relation to the other treatments characterised by higher values of LAR and LER and lower proportion of aerial tillers in sward tiller population. Considering the entire experimental period, both post-grazing residue and sward light interception pre-grazing did not affect the rates of growth and senescence, but the 95% LI treatments showed the highest senescence rates. There was, however, an effect of the LI x season of the year, residue x season of the year and LI x residue x season of the year interactions, which determined an alternate pattern of responses throughout the year for growth, senescence and net herbage accumulation of the sward, with the 95% LI treatments performing better than other treatments during the summer/early autumn and late spring periods. Season of the year had a strong effect on the dynamics of herbage accumulation, with the late winter/early spring corresponding to a critical period for reestablishing conditions for high herbage production during the new pasture growth season. Swards grazed at 95% LI showed lower herbage mass, with low amounts of accumulated dead material and stem, favouring a fast and early return to production early during the new growth season. Marandu grass subjected to rotational grazing management should be grazed when swards reach 95% interception of the incident light during regrowth, around 25 cm pre-grazing height, and animals removed with a post-grazing residue of 15 cm. (AU) | |