Title: Tillering dynamics in kikuyu and tall fescue grass swards cultivated in association

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Abstract: The forage production potential and productive stability of pastures formed by the association of grasses can minimize the impact of seasonality in the distribution of forage mass commonly observed in the southern region of Brazil. The use of management practices should aim at the persistence of species in the system over the time The present proposal has the hypothesis that the spring lowering in pastures formed by the association of kikuyu grass and tall fescue increases the tillering in summer, without changing the dynamics of tillering in winter, regardless of the management goal in pre- grazing used. The pasture was subjected to two canopy management heights in pre-grazing (15 and 20 cm), 40% severity of defoliation of the initial height and two spring strategies: absence or presence of the lowering of the pastures to a residue height of 6 cm. The experimental design was in complete randomized blocks, with three replications in a 2 x 2 factorial arrangement. Factor A was constituted by the height of management (15 and 20 cm) and factor B by the spring management of lowering or not of the pastures. To quantify tiller population density (TPD), leaf area index (LAI), forage mass (FM), participation in forage mass (PFM) and emerged tillers grouped by season (ETS) were used pasture samples collected at 3 points with a unit size of 0.24m². The tillering demographics was obtained by counting the number of tillers that survived and emerged in each month throughout the experimental period in rings with an area of 0.0314m² and later graphs of the pasture tillering were generated. The lowering of pastures in the spring did not stimulate the appearance of kikuyu grass tiller in summer, however, there was a slight reduction in the tall fescue population in winter. The variation in forage mass and leaf area index in the kikuyu grass was associated with the effect of the seasonality, while for tall fescue the variability in the forage mass is due to an interaction between season and management height, being 22% higher in height in pre-grazing 20 cm. Fescue presents a seasonal tillering pattern with an increase in the mortality rate and a decrease in the number of tillers that appeared during the summer and autumn, with subsequent emission of tillers in winter possibly linked to changes in temperature and photoperiod (vernalization), whereas the tiller-grass pattern was related to the availability of growth factors (water, light, temperature and nutrients). The difference between the tillering patterns of the participating species originated transitory population instability after frost event, later surpassed by the tall fescue population increase. The spring lowering decreased the pasture forage mass, regardless of pre-grazing management height (8.5%). Pastures managed at 20 cm and not affected by spring lowering promote the coexistence and persistence of species in the association.

 

Keywords: Association of grasses. Tiller population. Spring management.

 

Author: Valentina Ylluyanka Méndez 

Supervirsor: André Fischer Sbrissia

Dissertation (Masters in Animal Science)

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Title: Forage accumulation and botanical composition in mixed pastures of Festuca arundinacea and Pennisetum clandestinum submitted to different defoliation managements

 

Abstract: Mixed kikuyugrass - tall fescue pastures tend to present tall fescue dominance when managed leniently. It is necessary to find a management tool, which combines the maximum forage production and balanced proportions of these species, decreasing periods of forage shortage. The aim was to determine the forage accumulation and the botanical composition in mixed kikuyugrass - tall fescue pastures submitted to different defoliation management. The experiment was conducted at the Center of Agroveterinary Sciences at the State University of Santa Catarina, Lages, SC - Brazil. A randomized block design with a 2 x 2 factorial arrangement and three replications was used, totaling 12 experimental units. The first factor was the management height, where the pastures were managed under intermittent stocking with two pre-grazing heights (15 and 20 cm) and 40% defoliation (residues of 9 and 12 cm, respectively). The second factor was the presence or absence of a single spring grazing to 6 cmheight (11/19/2020). Data collections occurred over 12 months (11/2017 - 11/2018) evaluating forage mass, botanical composition, leaf area index (LAI) and pasture forage accumulation in pre and post-grazing. Nitrogen fertilization was carried out every two months (60 kg N ha-1 ). Analysis of variance was performed with the aid of the SAS® statistical package using the MIXED procedure. The means were tested by the t test with a 5% significance. There was a difference in the global forage production of pastures, where pastures managed at 20 cm with no spring grazing to 6 cm-height had the highest production (~14 t DM ha-1 ) (P = 0.0522), while the others did not differ from each other (P> 0.05). In the summer, the forage accumulation was greater in the pastures of 20 cm compared to those of 15 cm. In the winter, forage accumulation was higher in no spring grazing to 6 cm-height pastures managed at 20 cm, while 15 cm pastures had similar accumulation, regardless of the spring graze. There were 12 grazing cycles in the 15 cm pastures (spring grazed to 6 cm-height or not), 10 cycles in the 20 cm no spring grazed to 6 cm-height pastures and 8 cycles in the 20 cm spring grazed to 6 cm-height pastures. In the summer, the proportion of kikuyugrass and tall fescue was around 50% for each one in the 15 cm pastures, regardless of the spring grazing to 6 cm-height. Pastures of 20 cm not spring grazed had a higher proportion of tall fescue (~ 66%). In winter, the proportion of tall fescue was higher, reaching ~ 96% of the pasture area. In pre and post grazing, in summer and winter, the amount of weeds was higher in 15 cm pastures, regardless of spring grazing. Pasture LAI did not differ in pre and post grazing during summer, however, in winter, pastures managed at 20 cm had higher LAI. The proportion of dead material, in the summer, was higher in the no spring grazed pastures in the pre-grazing condition. The LAI, leaf and stem of kikuyugrass in pastures of 20 cm no spring grazed showed the lowest values, while the others showed no difference between them. The spring grazing to 6 cm-height performed results in a difference in the annual forage production, with greater production in pastures managed at 20 cm, however, the regrowth period and number of grazing cycles is higher in the pastures managed at 15 cm.

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Keywords: Forage production, grazing, kikuyugrass, species, tall fescue

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Author: Guilherme Romani Mello

Supervisor: André Fischer Sbrissia

Dissertation (Masters in Animal Science)

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Title: Forage yield and chemical composition in tangola grass pastures submitted to intermittent grazing methods

 

Abstract: The tangola grass originates from a natural breed between two Brachiarias (Brachiaria arrecta x Brachiaria mutica), being his first report in Rio de Janeiro. Its characteristics are intermediate to its parents. It is a stoloniferous plant, perennial and with prostrate habitat growth. The objective of this work was to bring additional information about this plant, looking for management strategies that maximize the production of forage and minimize the process of elongation of stems. The treatments consisted of three pregrazing heights, 20, 30 and 40 cm, decreasing by 40% of this height. The design was in randomized blocks, with three blocks and three repetitions. The experiment was carried out at the Experimental Farm of UNIBAVE (Barriga Verde University), in the municipality of Orleans, south of the State of Santa Catarina. The evaluation period was from January 2018 to May 2018 and January 2019 to June 2019 following the development in different growing seasons. It was evaluated: forage mass, forage accumulation rate, stem and leaf accumulation rate, leaf area index, tiller population density and bromatological composition (CP, NDF and ADF) in the different treatments. For forage accumulation rate, stem accumulation rate and leaf accumulation rate, there was no significant difference between treatments. For the percentage of leaf, 25, 22 and 22% for the treatments of 20, 30 and 40 cm, respectively, there was no difference between treatments. For the stem percentage, there was no difference, the values corresponded to 45%, 47% and 49% for the corresponding heights in pre-grazing. Regarding the population density of tillers, basal tillers, aerial tillers and the leaf area index, there was no significant difference between treatments. For the chemical composition, the NDF values for heights of 20, 30 and 40 cm were 55%, 57% and 57% of the DM respectively, the FDA values for the same heights were between 23 and 25%, not having in these two significant differences components. For the CP values there was a significant difference, where the 30 cm treatment showed an average of 24.71% of the DM. Tangola grass pastures have flexibility in grazing management, with forage accumulation not varying between 20 and 40 cm.

 

Keywords: Brachiaria arrecta x Brachiaria mutica. Forage Yield. Canopy Height. Chemical Composition. 

 

Author: Nemora Guliane Mocelin

Supervisor: André Fischer Sbrissia

Dissertation (Masters in Animal Science)