Title: The legacy of nitrogen fertilization and management heights in summer pastures on the dynamics of annual ryegrass

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Abstract: Biodiverse pastures have been an alternative in the sustainable intensification of pastures, since, through the complementarity of species from different functional groups, it is possible to obtain better use of the resources provided by these pastoral ecosystems. In this study, we hypothesize that management heights and N doses applied in the summer in mixed pastures composed predominantly of kikuyu grass (Pennisetum clandestinum) and tifton 85 (Cynodon spp.), and also, white clover (Trifolium repens) legumes, birdsfoot trefoil (Lotus corniculatus L.), forage peanuts (Arachis pintoi) alter the patterns of growth and tillering dynamics of annual ryegrass (Lolium multiflorum L.) cultivated in the subsequent cold season.Thus, the objective of this work was to identify perennial summer pasture management strategies that result in increases in annual ryegrass forage production in the subsequent cool season. The experimental area was approximately 5670 m2 and subdivided into 18 experimental units of 315 m2 . The experimental design used was randomized blocks with a 2x3 factorial arrangement, with three replications per treatment. The experimental treatments used were two pre-grazing heights of the forage canopy (17 and 23 cm) and three doses of nitrogen (50, 150, 250 kg of N ha-1 ). During the cold season, a single management was used, with a pre-grazing height of the forage canopy of 20 cm, associated with fertilization of 50 kg of N ha-1 . The morphogenetic and structural characteristics were determined through the technique of marked tillers, where 20 tillers were marked per experimental unit and evaluated at intervals of four days. The tillering dynamics of the annual ryegrass was determined by means of the monthly count of the emerged and surviving tillers in three rings of 0.01767m² allocated in each experimental unit, and through these, the appearance, mortality and survival rates of tillers and the pasture stability index. The management height and dose did not affect the forage accumulation rates of the annual ryegrass, as well as, they did not influence the population density of tillers, the appearance and survival rates of tillers and the population stability indices.

 

Keywords: Legacy effect, Nitrogen, Biodiverse pastures

 

Author: Danielli dos Santos Comassetto 

Leader: André Fischer Sbrissia

Dissertation (Masters in Animal Science)

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Title: Contribution of aerial and basal tillers on the components of DM accumulation in elephantgrass pastures cultivar BRS-Kurumi (Pennisetum Purpureum, Schum.)

 

Abstract: To optimize forage production, it is necessary to understand the morphological processes and structural characteristics that influence the dynamics of biomass accumulation after successive cuts or grazing. The objective of this work was to verify whether elephant grass pastures managed at contrasting heights (50 or 80 cm) present differences in the contribution of aerial and basal tillers in the forage accumulation process. The experiment was conducted at the Centro de Ciências Agroveterinárias (CAV) of the State University of Santa Catarina (UDESC), SC, between 2021 and 2022. The treatments consisted of two management heights: 50 and 80 cm, with a defoliation severity of 50%, generating residual heights of 25 and 40 cm, respectively. The experimental design was randomized blocks (DBC) with 2 treatments and 3 replications, in experimental units of 145 m². Data were subjected to analysis of variance (ANOVA) and the LSD-Fischer test with a significance level of 5%, using the statistical package InfoStat/P version 2020 for comparison of means. To understand the dynamics of the morphogenesis process that originates the flow of biomass, the technique of tillers marked in 20 tillers per experimental unit was used, 10 tillers allocated in each clump representing the average condition of the canopy. The collections were made with an interval between evaluations of 3 to 7 days. All calculations were based on the caloric sum expressed in Degreedays (GD), considering 16ºC as basal temperature. The variables analyzed included: Number of live leaves (NVF), Percentage of expanding leaves (%FEmExp), Rate of leaf elongation (TAlF), Rate of leaf senescence (TSe), Phyllochron, Longevity, Rate of leaf growth (TCF) and Percentage (%) contribution to accumulation. From the morphogenic point of view, tall pastures and short pastures showed similar values for NVF, %FEmExp, TAlF and TSe. The aerial tillers showed lower phyllochron (38.82 DG.leaf), higher TCF (0.90 g/m² DG.leaf) and lower longevity (211.5 DG.leaf) than the basal tillers, which showed higher phyllochron (51.53 DG.leaf), lower TCF (0.44 g/m² DG.leaf) and greater longevity (304.32 DG.leaf). Aerial tillers also showed smaller size, higher population density (137 tillers.m²) and greater contribution to DM accumulation (67.8%) than basal tillers, which had larger size, lower population density (68 tillers.m²) and lower contribution to DM accumulation (32.2%). Aerial tillers present a greater contribution to dry matter accumulation in pastures of dwarf elephant grass cv. BRS Kurumi basically because they are more, regardless of handling height.

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Keywords: Forage Accumulation, (Pennisetum purpureum Schum.), Tissue Flow, Degreedays, Morphogenesis, Aerial Tiller.

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Author: Karoline Cardoso Vargas

Leader: André Fischer Sbrissia

Dissertation (Masters in Animal Science)

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