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Switchgrass (Panicum virgatum L.) has potential as a biofuels feedstock. Major management questions include cultivar selection, cutting management, and optimizing N fertilization. Four cultivars of switchgrass were evaluated under two cutting regimes at eight locations within KY, NC, TN, VA, and WV in 2000 and 2001. Harvests were made once (in early November) or twice (midsummer and early November). Biomass yields averaged 15 Mg ha-1 and ranged from 10 to 22 Mg ha-1 across locations and years. There was no yield advantage to taking two harvests of the lowland cultivars ("Alamo" and "Kanlow"). If harvested twice, the upland cultivars ("Cave-in-Rock" and "Shelter") provided yields equivalent to the lowland ecotypes. A closer look at Alamo revealed much higher N removal in the midsummer harvests, late-season N translocation out of tillers, and fewer tillers developing under one-cut management. Switchgrass appears to be capable of truly perennial productivity in the upper Southeast USA with 50 kg N ha-1 yr-1 and a single harvest. A second field study was conducted on "Cave-in-Rock" switchgrass at Orange and Blacksburg, VA to examine N dynamics. For the 3-yr study, N fertilizer was applied once in May 2001 at 0, 90, 180, or 270 kg N ha-1. Switchgrass was harvested once (early November) in 2001 and twice (early July and early November) in 2002 and 2003. Tissue, root, and soil samples were collected in May, July, September, and November each year. Nitrogen fertilization had no effect on yield in 2001 and small residual effects in 2002 and 2003. Higher N removal was observed with two-cut management, where a high-yielding July cut had high shoot N concentrations. The amount of N removed as biomass from the 0 N treatments over 3 yr was 227 kg N ha-1; obviously significant amounts of N can be made available by these soils without any fertilizer applied. During the growing season, higher mineral N in soil was observed in July and September, when warmer temperatures increase microbial activity and N mineralization. Nitrogen use efficiency declined with increasing N rates. The low N response could be due to "native" N, to microbiological interactions, and/or to the ability of the plants to create internal N reserves. Proper N management of switchgrass must take into account the dynamics of several N pools. Greenhouse studies were conducted to establish switchgrass' responses to N and P under well-defined, soilless conditions and to examine two N sources. Shoot biomass increased with N fertilization with an observed inflection point at 210 kg N ha-1. In these pot studies, root biomass increased with N only to 115 kg N ha-1. No significant effect of P above 30 kg ha-1 was observed in shoot or root biomass. Biomass yield and tiller number were highly correlated. Biomass production was two times greater with ammonium sulfate than with urea when each was applied at equivalent N rates. Taken together, these findings suggest soils in the upper Southeast USA can supply significant amounts of the N needs of switchgrass, especially when harvested once at the end of the season. / Ph. D.

To decrease dependency of fossil fuels and avoid direct competition with food crops, massive research efforts are investigating next-generation cellulose biofuel crops such as switchgrass (Panicum virgatum). A low-input, sustainable switchgrass production could be achieved by reducing traditional management practices though applying plant growth promoting rhizobacteria (PGPR), of which our understanding is still rather limited. To elucidate physiological mechanisms behind PGPR's beneficial effects, we inoculated switchgrass seedlings with Burkholderia phytofirmans strain PsJN. Two experiments were conducted to determine the initial and long-term responses of switchgrass to PsJN inoculation by tracking growth and leaf physiology. In a third experiments, we tested the effects of PsJN on growth and leaf-level physiology of switchgrass under a moderate pre-drought conditioning and a successive severe drought stress. PsJN inoculation increased biomass and promoted elongation of shoots within 17 days following inoculation. The enhanced root growth in PsJN inoculated plants lagged behind the shoot response, resulting in greater allocation to aboveground growth (p=0.0041). Lower specific root length (p=0.0158) and higher specific leaf weight (p=0.0029) were also observed in PsJN inoculated seedlings, indicating advanced development. Photosynthetic rates (Ps) were higher in PsJN inoculated seedlings after 17 days (54%, p=0.0016), which were related to higher stomatal conductance, greater water use efficiency, and lower non-stomatal limitation of Ps. These rapid changes in leaf physiology are at least partially responsible for switchgrass growth enhancement from PsJN treatment. The early growth enhancement in PsJN inoculated switchgrass linearly decreased with plant age. PsJN inoculation increased Ps of upper canopy leaves by 13.6% but reduced Ps of lower canopy leaves by 8.2%. Accelerated leaf senescence and early flowering were observed in PsJN-inoculated switchgrass, which might contribute to slightly lower aboveground biomass at final harvesting. Drought preconditioning increased Ps of PsJN-inoculated switchgrass during a later severe drought; whereas, control switchgrass only benefited from drought preconditioning when leaf water potential dropped below -1 MPa. This study verified early growth enhancement and accelerated development of switchgrass due to PsJN inoculation. Rapid improvement in leaf physiology is related to enhanced productivity. PsJN inoculation also improve drought tolerance of switchgrass. / Ph. D.

Tall fescue (Festuca arundinacea Schreb.) often becomes dormant in the hot summer months. Switchgrass (Panicum virgatum L.) has potential to supplement the limited carrying capacity of tall fescue in mid-summer. The objective of this study was to determine the seasonal dry matter distribution and quality of tall fescue and switchgrass as influenced by different harvest managements. Switchgrass and tall fescue were studied on a fine-loamy, mixed, mesic Ultic Hapludalf of the Duffield soil series at Blacksburg, VA during 1987 and 1988. Normal harvest management included harvests taken from the first growth in spring until mid to late August. Delayed management included harvests taken from regrowth after a hay crop in mid-May for tall fescue and early June for switchgrass until mid to late August. Three and four harvest intensities were imposed on tall fescue and switchgrass, respectively. Plots were harvested in 1989 to determine the accumulative influence of treatments. Yield, crude protein, neutral detergent fiber, and invitro dry matter digestibility were measured for each harvest of both species. Digestible yield and protein were calculated for each harvest. Clipping either switchgrass or tall fescue at any harvest intensity reduced potential yield compared to forage not clipped. Accumulated forage resulted in high yields but unsatisfactory quality. Delayed harvest management resulted in higher total yield than normal harvest management because of high hay yields. This study indicated that considerable overlap of forage production of tall fescue and switch grass occurred in late spring but abundant high quality switchgrass was available in midsummer when available tall fescue was low. Switchgrass warrants consideration in southwest Virginia as a solution to the problem of limited cool-season forage in midsummer. / Master of Science

Plantas cultivadas em ambientes com média e alta disponibilidade de cádmio apresentam menor produção de folhas e perfilhos devido à maior quantidade de cádmio absorvido, resultando em menor produção de biomassa. O fornecimento de enxofre às plantas pode minimizar os efeitos negativos causados pelo cádmio, uma vez que esse nutriente participa de compostos que atuam no sistema antioxidante, conferindo maior tolerância aos metais pesados. Objetivou-se avaliar as modificações ocorridas: i) nos aspectos morfológicos, morfogênicos e produtivos; ii) no estado nutricional e iii) na resposta do sistema antioxidante do capim-tanzânia (Panicum maximum) cultivado com combinações de doses de enxofre (0,1; 1,0; 1,9; 2,8 e 3,7 mmol L-1) e de cádmio (0,0; 0,5; 1,0; 1,5 e 2,0 mmol L-1) em solução nutritiva. O experimento foi desenvolvido em casa de vegetação, utilizando o esquema fatorial 5² fracionado, em blocos ao acaso, com seis repetições. O primeiro corte do capimtanzânia foi realizado 40 dias após o transplantio das mudas para os vasos e o segundo corte 18 dias após o primeiro. Para a taxa de mortalidade de perfilhos, valor SPAD, concentração de cádmio e a atividade da APX (segundo corte) do capim-tanzânia foi significativa a interação doses de enxofre x doses de cádmio, de forma que o suprimento de enxofre atenuou a taxa de mortalidade, diminuiu a quantidade de cádmio absorvida, aumentou o valor SPAD e a atividade da APX. O teor de água, número de perfilhos, taxa de aparecimento de perfilhos, número de folhas, área foliar, taxa de aparecimento foliar, razão de área foliar, produção de massa seca da parte aérea e das raízes, valor SPAD, concentração de potássio, teor de GSH e a atividade da CAT foram menores com o fornecimento de cádmio na solução nutritiva. De forma contrária, as concentrações de nitrogênio, fósforo, zinco e cádmio, o fator de transporte do cádmio, os teores de GSSG e glutationa, e a atividade da APX aumentaram. O fornecimento de enxofre aumentou a concentração de enxofre na parte aérea do capimtanzânia. Os efeitos causados pelo cádmio são mais acentuados durante a rebrotação, principalmente, em condições de alta disponibilidade do metal pesado. As enzimas CAT e GR apresentaram mais isoformas na parte aérea do que nas raízes do capim-tanzânia, sugerindo que esse tecido é mais eficaz no combate aos danos oxidativos causados pelas altas concentrações de cádmio. O suprimento de enxofre ao capim-tanzânia cultivado em ambientes com alta disponibilidade de cádmio é indicado para aumentar a tolerância da gramínea ao metal pesado. / Plants grown at medium and high cadmium availability has produced low number of leaves and tillers due to the great amount of cadmium absorbed, resulting in lower biomass production. Sulfur supply to plants may mitigate negative effects caused by cadmium, since compounds containing sulfur participate of the antioxidative plant system, resulting in greater tolerance to heavy metals. This study evaluated changes in: i) morphological, morphogenesis and productive aspects, ii) nutritional status, and iii) response of the antioxidative system of Tanzania guineagrass (Panicum maximum) grown under combined sulfur rates (0.1; 1.0, 1.9, 2.8 and 3.7 mmol L-1) and cadmium rates (0.0, 0.5, 1.0, 1.5 and 2.0 mmol L-1) in nutrient solution. The experiment was conducted in greenhouse, by using a fractionated factorial 5², in randomized block design, with six replications. The first harvest of Tanzania guineagrass was performed at 40 days after seedlings transplanting to the pots, and the second at 18 days after the first harvest. Mortality rate of tillers, SPAD value, cadmium concentration and APX activity (second harvest) of Tanzania guineagrass had statistically significant sulfur rates x cadmium rates interaction, since that sulfur supply mitigate the mortality rate, decreased the amount of cadmium absorbed and increased SPAD value and the APX activity. The water content, number of tillers, tiller emergence rate, number of leaf, leaf area, leaf emergence rate, ratio of leaf area, dry mass of shoots and roots, SPAD value, potassium concentration, GSH content and CAT activity decreased with the cadmium supply in the nutrient solution. Contrary to that, nitrogen, phosphorus, zinc and cadmium concentrations were increased as well as the transporting factor of cadmium, GSSG and glutathione contents and APX activity. Sulfur supply increased sulfur concentration in shoots of Tanzania guineagrass and the effects of cadmium were more pronounced during the plant regrowth period, especially under high availability of the heavy metal. Isoforms of CAT and GR showed higher abundance in shoots compared to roots, suggesting higher effectiveness of such tissue in avoiding oxidative damage caused by high concentrations of cadmium. Thus, sulfur supply to the Tanzania guineagrass grown in environment with high cadmium availability is indicated to increase tolerance to this heavy metal.

Made available in DSpace on 2016-01-26T12:51:53Z (GMT). No. of bitstreams: 1 margarethdibo_tese.pdf: 1810718 bytes, checksum: 4df01c13c55a541f2c4aff4668fbacd7 (MD5) Previous issue date: 2004-03-17 / Fundação de Amparo a Pesquisa do Estado de São Paulo / The strategy to contain the vector of Dengue fever in the state of São Paulo is centered around a reduction in breeding places and by chemical controls. To obtain better results in the reduction of the vectorial density it is important to incorporate other measures in the routine approach. Egg traps are considered to be preventative and control measures of Aedes aegypti, however, there are no studies that define the favorite egg-laying locations in residences. The utilization of an infusion of Panicum maximum in traps increases its attractiveness to vector females and increases the number of eggs collected. This study aims to contribute to techniques by using traps to evaluate the number of weeks this infusion remains attractive to females. More importantly, it aims to assess the egg-laying behavior of the Aedes aegypti and Aedes albopictus populations in Mirassol, a town situated in the region of São José do Rio Preto, Brazil. Traps with egg-collecting paddle were installed in 200 houses in 20 blocks giving a total of 10 houses to each block. Half of the blocks were chosen at random for the installation of traps baited with the infusion and in the other half, traps with ordinary water were installed. Two egg-traps were placed inside the house (bedroom and living room) and two outside (one under cover and the other in the open). Weekly visits were made from September to December 2002, to analyze all the traps, collecting the existing sticks and leaving new ones. In the laboratory the viable and nonviable eggs on the sticks were counted. Positive sticks were considered to be those on which eggs were found and these were correlated with the type of trap, infusion or water, the location of the trap within the house and the number of weeks after the start of the trial. A sample of these sticks was placed in water, to hatch the larvae with the aim of identifying the species. The mean numbers of eggs and larvae of the Aedes aegypti and Aedes albopictus were calculated and associated with the location within the house, the type of trap used, infusion or water, and the week number. Analyzing the number of positive sticks, and the mean number of eggs on the traps, it was evidenced that the traps with infusion were more attractive/stimulating for egg-laying for females of the genera Aedes than those with water in the first three weeks of exposition. The uncovered outdoor traps were the most favored location for egg-laying during the entire study period; in second place were the outdoor ones under cover. High values of the Spearman correlation coefficients and p-values less than 0.004 demonstrated a strong correlation between the positivity and the mean number of eggs, indicating that one variable predicts the other. From the analysis of the hatched larvae, Aedes aegypti were identified on 99.6% (CI 95%: 99.04 99.84) of the sticks and Aedes albopictus on 1.8% (CI 95%: 1.19 2.70) of them. In Mirassol the probability of finding eggs of Aedes aegypti on any one stick under these circumstances is greater than 99%. / A estratégia para controle do vetor do dengue no estado de São Paulo está centrada na redução de criadouros e ações de controle químico. Para a obtenção de melhores resultados na redução da densidade vetorial é importante que se incorpore outras medidas de uso rotineiro. Armadilhas de oviposição são consideradas medidas de vigilância e controle de Aedes aegypti, entretanto não existem estudos sobre locais do domicílio preferidos para oviposição. A utilização de infusão de Panicum maximum em armadilhas propicia maior atração às fêmeas do vetor e coleta de maior quantidade de ovos. Através deste estudo, procurou-se subsidiar as técnicas para o uso de armadilhas, avaliar durante quantas semanas a referida infusão manteve sua atração sobre as fêmeas e, principalmente, avaliar o comportamento de oviposição de populações de Aedes aegypti em Mírassol, cidade situada na região de São José do Rio Preto. Instalaram-se armadilhas de oviposição em 200 casas, divididas em 20 quadras, distribuindo-as em 10 casas por quadra. Foram sorteadas 50% das quadras para instalação de armadilhas iscadas com infusão, e nas demais se instalou armadilhas com água. Duas armadilhas foram colocadas no intradomicílio (quarto e sala) e duas no peridomicílio (uma sob cobertura e outra ao relento). Foram feitas visitas semanais entre setembro e dezembro de 2002, para a análise de todas as armadilhas, e substituição das palhetas. Em laboratório, contaram-se ovos viáveis e inviáveis existentes nas palhetas. A presença de ovos na palheta significou a sua positividade, a qual foi verificada quanto à presença ou não de infusão, local de instalação na casa e número de semanas. Uma amostra destas palhetas foi colocada em água, para eclosão de larvas, visando à identificação específica. Os números médios de ovos e de larvas Aedes aegypti e Aedes albopictus foram quantificados segundo o posicionamento no domicílio, presença de armadilha iscada com infusão ou água e o número de semanas. Analisando-se Nota de Resumo as positividades e os números médios de ovos das armadilhas, obteve-se que as armadilhas iscadas com infusão mostraram-se mais atraentes/estimulantes para oviposição pelas fêmeas do gênero Aedes que as com água, nas três primeiras semanas de exposição. O relento foi o local com maior preferência para oviposição durante todo o estudo; em segundo lugar encontrou-se o coberto. Elevados valores dos coeficientes de correlação de Spearman e valores de p inferiores a 0,004 mostraram forte correlação entre positividade e média de ovos, indicando que uma variável prediz a outra. A partir das análises das larvas eclodidas, identificou-se a presença de Aedes aegypti em 99,6% (IC 95%: 99,04 -99,84) das palhetas e de Aedes albopictus em 1,8% (1C95%: 1,19 - 2,70) delas. Em Mirassol, a probabilidade de se encontrar ovos de Aedes aegypti em uma palheta sob estes condições é superior a 99%.

Plantas cultivadas em ambientes com média e alta disponibilidade de cádmio apresentam menor produção de folhas e perfilhos devido à maior quantidade de cádmio absorvido, resultando em menor produção de biomassa. O fornecimento de enxofre às plantas pode minimizar os efeitos negativos causados pelo cádmio, uma vez que esse nutriente participa de compostos que atuam no sistema antioxidante, conferindo maior tolerância aos metais pesados. Objetivou-se avaliar as modificações ocorridas: i) nos aspectos morfológicos, morfogênicos e produtivos; ii) no estado nutricional e iii) na resposta do sistema antioxidante do capim-tanzânia (Panicum maximum) cultivado com combinações de doses de enxofre (0,1; 1,0; 1,9; 2,8 e 3,7 mmol L-1) e de cádmio (0,0; 0,5; 1,0; 1,5 e 2,0 mmol L-1) em solução nutritiva. O experimento foi desenvolvido em casa de vegetação, utilizando o esquema fatorial 5² fracionado, em blocos ao acaso, com seis repetições. O primeiro corte do capimtanzânia foi realizado 40 dias após o transplantio das mudas para os vasos e o segundo corte 18 dias após o primeiro. Para a taxa de mortalidade de perfilhos, valor SPAD, concentração de cádmio e a atividade da APX (segundo corte) do capim-tanzânia foi significativa a interação doses de enxofre x doses de cádmio, de forma que o suprimento de enxofre atenuou a taxa de mortalidade, diminuiu a quantidade de cádmio absorvida, aumentou o valor SPAD e a atividade da APX. O teor de água, número de perfilhos, taxa de aparecimento de perfilhos, número de folhas, área foliar, taxa de aparecimento foliar, razão de área foliar, produção de massa seca da parte aérea e das raízes, valor SPAD, concentração de potássio, teor de GSH e a atividade da CAT foram menores com o fornecimento de cádmio na solução nutritiva. De forma contrária, as concentrações de nitrogênio, fósforo, zinco e cádmio, o fator de transporte do cádmio, os teores de GSSG e glutationa, e a atividade da APX aumentaram. O fornecimento de enxofre aumentou a concentração de enxofre na parte aérea do capimtanzânia. Os efeitos causados pelo cádmio são mais acentuados durante a rebrotação, principalmente, em condições de alta disponibilidade do metal pesado. As enzimas CAT e GR apresentaram mais isoformas na parte aérea do que nas raízes do capim-tanzânia, sugerindo que esse tecido é mais eficaz no combate aos danos oxidativos causados pelas altas concentrações de cádmio. O suprimento de enxofre ao capim-tanzânia cultivado em ambientes com alta disponibilidade de cádmio é indicado para aumentar a tolerância da gramínea ao metal pesado. / Plants grown at medium and high cadmium availability has produced low number of leaves and tillers due to the great amount of cadmium absorbed, resulting in lower biomass production. Sulfur supply to plants may mitigate negative effects caused by cadmium, since compounds containing sulfur participate of the antioxidative plant system, resulting in greater tolerance to heavy metals. This study evaluated changes in: i) morphological, morphogenesis and productive aspects, ii) nutritional status, and iii) response of the antioxidative system of Tanzania guineagrass (Panicum maximum) grown under combined sulfur rates (0.1; 1.0, 1.9, 2.8 and 3.7 mmol L-1) and cadmium rates (0.0, 0.5, 1.0, 1.5 and 2.0 mmol L-1) in nutrient solution. The experiment was conducted in greenhouse, by using a fractionated factorial 5², in randomized block design, with six replications. The first harvest of Tanzania guineagrass was performed at 40 days after seedlings transplanting to the pots, and the second at 18 days after the first harvest. Mortality rate of tillers, SPAD value, cadmium concentration and APX activity (second harvest) of Tanzania guineagrass had statistically significant sulfur rates x cadmium rates interaction, since that sulfur supply mitigate the mortality rate, decreased the amount of cadmium absorbed and increased SPAD value and the APX activity. The water content, number of tillers, tiller emergence rate, number of leaf, leaf area, leaf emergence rate, ratio of leaf area, dry mass of shoots and roots, SPAD value, potassium concentration, GSH content and CAT activity decreased with the cadmium supply in the nutrient solution. Contrary to that, nitrogen, phosphorus, zinc and cadmium concentrations were increased as well as the transporting factor of cadmium, GSSG and glutathione contents and APX activity. Sulfur supply increased sulfur concentration in shoots of Tanzania guineagrass and the effects of cadmium were more pronounced during the plant regrowth period, especially under high availability of the heavy metal. Isoforms of CAT and GR showed higher abundance in shoots compared to roots, suggesting higher effectiveness of such tissue in avoiding oxidative damage caused by high concentrations of cadmium. Thus, sulfur supply to the Tanzania guineagrass grown in environment with high cadmium availability is indicated to increase tolerance to this heavy metal.

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Componentes da biomassa e estrutura do capim-aruana sob duas frequências e duas intensidades de desfolhação. 2015. 56 f . : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Zootecnia, Fortaleza-CE, 2015 / This study evaluated the components of biomass and the canopy structure of aruana grass managed under two frequencies (FD, interception of the photosynthetically active radiation at 85 and 95% incident on the top of the canopy) and two intensities (ID, residual leaf area index of 1.0 and 1.8) of defoliation in a completely randomized design in a 2x2 factorial arrangement with five replications (paddocks). The experiment was conducted at the advanced field of Teaching and Study Center Forage, located in the municipality of Pentecoste, Ceará State. The times of entry and exit of animals were determined using the PAR/LAI Analyzer in Agriculture DECAGON PAR-80 for reading photosynthetically active radiation interception (PARI) and leaf area index (LAI). At the beginning and end of the rest period of each of the five experimental paddocks, the following structural characteristics were evaluated: sward height (cm); height of the first ligule, the oldest below the canopy; grazing horizon and tiller population density. The components of total forage biomass (TFB ha-1 cycle-1) were also quantified at the beginning and end of the rest period, from the collection using two frames of 0.25 m², and sent to the laboratory to separate the components: leaf, stem and dead material. After separation of the TFB components, samples were dried to constant weight in a forced ventilation oven at 55°C to constant weight to estimate the following parameters: total forage biomass (TFB kg ha-1 cycle-1), dead forage biomass (DFB kg ha-1 cycle-1), green forage biomass (GFB kg kg ha-1 cycle-1), green leaf biomass (GLB kg ha-1 cycle-1), green stem biomass (GSB kg ha-1 cycle-1), and green/dead material ratio (GM/DM) and leaf/stem ratio (L/S). The longest rest period was observed in pastures managed with lower rLAI and lower defoliation frequency (95% PARI), with average of 24 days. Biomass components and structural characteristics in the pre-grazing condition were affected (P <0.05) by FD, where the lower defoliation frequency resulted in higher production with considerable contribution of biomass of green stems and dead forage. The pre-grazing height showed a high correlation with the %PARI in the pre-grazing condition (r = 0.9285, P = 0.0001). Pastures managed with lower FD had low L/S, with average of 1.65, while those managed with higher FD, an average of 2.40. With increasing %PARI, we verified higher grazing horizons, with averages of 20.2 and 14.2 cm, for 95 and 85 %PARI, respectively. The components of the residual biomass were affected (P <0.05) by ID, with higher residual forage biomass observed for pastures managed with rLAI of 1.8. Pastures managed with 95x1.8 exhibited higher rGSB ¬and rDFB (P <0.05) compared to the other managements. Pastures managed with 95x1.0 showed an increase in TFB (P <0.05) over successive grazing cycles. Aruana grass supplied to sheep should be managed under 85% PARI frequency and defoliation intensity equal to 1.0 rLAI. / Avaliou-se os componentes da biomassa e a estrutura do dossel em capim-aruana sob duas frequências (FD - níveis de interceptação de 85 e 95% da radiação fotossinteticamente ativa incidente no topo do dossel) e duas intensidades (ID - índices de área foliar residual de 1,0 e 1,8) de desfolhação, em um delineamento inteiramente casualizado, num arranjo fatorial 2x2, com cinco repetições (piquetes). O experimento foi conduzido no campo avançado do Núcleo de Ensino e Estudos em Forragicultura, situado na Fazenda experimental Vale do Curú, localizada no município de Pentecoste-CE. Os momentos de entrada e saída dos animais foram determinados utilizando-se o Analisador PAR/LAI em Agricultura DECAGON PAR-80 para as leituras da interceptação de radiação fotossinteticamente ativa (IRFA) e do índice de área foliar (IAF). Foram avaliadas no início e no final do período de descanso de cada um dos cinco piquetes experimentais, as seguintes características estruturais: altura do pasto; altura da primeira lígula viva, a mais velha abaixo do dossel; horizonte de pastejo e densidade populacional de perfilhos. Os componentes da biomassa de forragem total (BFT) foram quantificados no início e final do período de descanso, a partir da colheita com duas molduras de 0,25 m², sendo encaminhadas ao laboratório para separação dos componentes: folha, colmo e material morto. Após a separação dos componentes da BFT, as amostras foram levadas à estufa de ventilação forçada à 55 °C até peso constante para estimativa das seguintes variáveis: biomassa de forragem total (BFT kg∙ha-1∙ciclo-1), de forragem morta (BFM kg∙ha-1∙ciclo-1 ), de forragem verde (BFV kg∙ha-1∙ciclo-1), de lâmina foliar verde (BLV kg∙ha-1∙ciclo-1), de colmo verde (BCV kg∙ha-1∙ciclo-1), além das relações material vivo/material morto (MV/MM) e folha/colmo (F/C). O maior tempo de descanso foi verificado para os pastos manejados com menor IAFr e menor frequência de desfolhação (95% de IRFA), com média de 24 dias. Os componentes da biomassa e as características estruturais na condição pré-pastejo foram afetados (P<0,05) pelas FDs, onde a menor frequência de desfolhação proporcionou maiores produções, com considerável contribuição de biomassa de colmos verdes e de forragem morta. A altura pré-pastejo apresentou boa correlação com a %IRFA na condição pré-pastejo (r=0,9285; P=0,0001). Pastos manejados com menor FD proporcionaram baixa F/C, com média de 1,65, enquanto pastos manejados com maior FD apresentaram média de 2,40. Com o aumento da %IRFA, foram verificados maiores horizontes de pastejo, com médias de 20,2 e 14,2 cm para as frequências de 95 e 85%IRFA, respectivamente. Os componentes da biomassa residual foram afetados (P<0,05) pelas IDs, com maior biomassa de forragem residual observada para os pastos manejados com IAFr de 1,8. Os pastos manejados com 95x1,8 apresentaram BCVr e BFMr superiores (P<0,05) aos demais manejos. Pastos manejados com 95x1,0 apresentaram incremento (P<0,05) de BFT ao longo de ciclos sucessivos de pastejo. O capim-aruana, para utilização com ovinos, deve ser manejado com frequência de 85% de IRFA e intensidade de desfolhação equivalente a IAFr de 1,0.

Made available in DSpace on 2014-12-17T15:34:43Z (GMT). No. of bitstreams: 1 JoaoVEN_DISSERT.pdf: 2633777 bytes, checksum: a59b41665f97067cdafb895c7d67745c (MD5) Previous issue date: 2012-02-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / He aim of this study was to evaluate the structural characters, herbage accumulation, nutritive value and performance of sheep in different tropical pastures. The treatments were two cultivars and two of the genera Panicum Brachiaria pastures under intermittent stocking and variable stocking rate, in the rainy season. We evaluated the masses and the components of herbage pre grazing in two layers, and after grazing. Chemical analyzes were made of the stems and leaf blades pre grazing in two layers. We used 48 male sheep and whole for the assessment of individual weight gain and area, and anestrous females to adjust the stocking rate. In the cv. Massai showed the highest herbage mass, leaf blades and dead material, and the largest volume density and leaf blade: stem pre grazing. There was no difference among cultivars for the percentage of leaf blade (PLB) in both strata, but the higher the PLB was higher than the bottom. The highest percentage of dead material (PDM) was observed in cvs. Massai and Marandu in the two strata. In cvs. Massai and Piat? were observed lower levels of crude protein in stem and leaf. In stratum 0-25 cm lower nutritional value was observed in the stem in the leaf blades did not grant the nutritional value among the strata. Herbage mass, leaf blade, PLB and proportion of stem in the residue of the Massai pastures were higher than cv. Aruana. There was no difference for efficiencies in harvest leaf and stem between the cultivars. The cv. Massai got the higher accumulation of leaf per cycle per day. Animals kept in grass swards Aruana had the highest average daily gain. The higher stocking rates and earnings per area were observed in grass swards and Marandu Massai. The cultivars are suitable for sheep meat production in the rainy season / O objetivo deste estudo foi avaliar os caracteres estruturais, o ac?mulo de forragem, o valor nutritivo e o desempenho de ovinos em diferentes pastagens tropicais. Os tratamentos constitu?ram em duas cultivares dos g?neros Panicum e duas de Brachiaria, manejadas sob lota??o intermitente e taxa de lota??o vari?vel, na ?poca das ?guas. Foram avaliadas as massas e os componentes da forragem no pr? pastejo em dois estratos, e no p?s pastejo. Foram feitas an?lises bromatol?gicas dos colmos e das l?minas foliares no pr? pastejo em dois estratos. Utilizou-se 48 ovinos machos e inteiros para a avalia??o do ganho de peso individual e por ?rea, al?m de f?meas em anestro para ajuste na taxa de lota??o. Na cv. Massai foram observadas as maiores massa de forragem, de l?minas foliares e de material morto, al?m da maior densidade volum?trica e rela??o l?mina foliar:colmo no pr? pastejo. N?o houve diferen?a entre as cultivares para o percentual de l?minas foliares (PLF) em ambos os estratos, por?m o PLF no superior foi maior que no inferior. O maior percentual de material morto (PMM) foi observado nas cvs. Massai e Marandu nos dois estratos. Nas cvs. Massai e Piat? foram observados os menores teores de prote?na bruta no colmo e na l?mina foliar. No estrato de 0 25 cm foi observado menor valor nutritivo no colmo, nas l?minas foliares o valor nutritivo n?o deferiu entre os estratos. A massa de forragem, de l?mina foliar, PLF e propor??o de colmo no res?duo dos pastos de Massai foram superiores aos da cv. Aruana. N?o houve diferen?a para as efici?ncias na colheita de l?mina foliar e colmo entre as cultivares estudadas. A cv. Massai obteve os maiores ac?mulos de l?mina foliar por ciclo e por dia. Os animais mantidos em pastos de capim Aruana obtiveram os maiores ganhos m?dios di?rios. As maiores taxas de lota??o e ganhos por ?rea foram observadas nos pastos de capim Massai e Marandu. As cultivares testadas s?o adequadas a produ??o de carne ovina na ?poca das ?guas

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Avaliou-se as trocas gasosas, o fluxo de biomassa e as caracterÃsticas estruturais do capim-aruana pastejado sob lotaÃÃo rotativa por ovinos Morada Nova submetidos a quatro nÃveis de suplementaÃÃo concentrada (0,0; 0,6; 1,2 e 1,8% do PC), com perÃodo de ocupaÃÃo de quatro dias e descanso quando da interceptaÃÃo de 90% da radiaÃÃo fotossinteticamente ativa (IRFA), num delineamento inteiramente casualizado, num arranjo em parcelas subdivididas, sendo os nÃveis de suplementaÃÃo as parcelas e os ciclos de pastejo as subparcelas. A condiÃÃo de pÃs-pastejo consistiu em um Ãndice de Ãrea foliar de 1,0. Constatou-se efeito linear crescente para a taxa de alongamento das hastes e taxa de aparecimento foliar em funÃÃo dos nÃveis de suplementaÃÃo. As taxas de produÃÃo e acÃmulo de forragem foram incrementadas pelos nÃveis de suplementaÃÃo. As variÃveis das trocas gasosas das folhas recÃm-expandidas: transpiraÃÃo, condutÃncia estomÃtica, taxa de fotossÃntese foliar, mostraram efeito somente de ciclo de pastejo. NÃo houve nenhum efeito significativo sobre as variÃveis das trocas gasosas das folhas emergentes. Os componentes da biomassa pÃs-pastejo registraram efeito significativo da interaÃÃo nÃveis de suplementaÃÃo e ciclos de pastejo para biomassa de forragem verde residual (BFVr), lÃmina foliar verde residual (BLVr), colmo verde residual (BCVr) e relaÃÃo folha:colmo (F_Cr) residual, estas variÃveis, com exceÃÃo da F_Cr apresentaram efeito quadrÃtico nos ciclos dois e trÃs, confirmando o efeito substitutivo, a partir do nÃvel de suplementaÃÃo de 0,86%, com o mÃnimo estimado de 257,53 Kgâha-Ââano-1, para a BLVr. A relaÃÃo material vivo_ material morto residual apresentou efeito linear crescente em funÃÃo dos nÃveis de suplementaÃÃo. A altura do pasto e a densidade populacional de perfilhos residual foram afetadas somente pelos ciclos de pastejo. A biomassa de forragem verde (BFV) e de lÃmina foliar verde (BLV) apresentaram efeito da interaÃÃo nÃveis de suplementaÃÃo e ciclos de pastejo. A BLV registrou efeito quadrÃtico para os ciclos dois e trÃs, onde os maiores valores foram de 1489,47, no nÃvel de 0,62, do segundo ciclo e de 1554,95 Kgâha-Ââano-1no ciclo trÃs com nÃvel de suplementaÃÃo de 0,14 %. As trocas gasosas nÃo sÃo afetadas pelos nÃveis de suplementaÃÃo. As caracterÃsticas morfogÃnicas do pasto de capim-aruana sÃo afetadas linearmente pelos nÃveis crescentes de suplementaÃÃo. Os componentes estruturais do pasto de capim-aruana sÃo afetados pelos nÃveis crescentes de suplementaÃÃo concentrada, registrando efeito substitutivo do suplemento. / This study evaluated the gas exchange, the biomass flow and the structural characteristics of Panicum maximum cv. Aruana grazed by Morada Nova sheep under rotational stocking and supplied with four concentrate supplementation levels (0.0; 0.6; 1.2 and 1.8% body weight), using four day-grazing periods and rest when the interception of 90% of the photosynthetic active radiation (PAR). The experiment was a completely randomized split-plot design with supplementation levels as plots and grazing cycles as subplots. The post-grazing condition consisted of a leaf area index of 1.0. We observed an increasing linear effect for stem elongation rate and leaf appearance rate according to the supplementation levels. The production and accumulation rates of forage also increased according to the supplementation levels. The different grazing cycles affected the variables of gas exchange of the recently expanded leaves, namely transpiration, stomatal conductance, leaf photosynthesis rate. In turn, no significant effect was detected for the gas exchange variables of emergent leaves. Biomass components during the post-grazing period showed a significant effect of the interaction between supplementation levels and grazing cycles for residual green forage biomass (BFVr), residual green leaf biomass (BLVr), residual green stem biomass (BCVr) and residual leaf:stem ratio (F_Cr). All these variables, with the exception of F_Cr, presented a quadratic effect in the cycles two and three, confirming the substitutive effect from the supplementation level of 0.86%, with the minimum estimated at 257.53 Kgâha-Ââyear-1, for BLVr. The ratio between living and senescent material showed an increasing linear response as a function of the supplementation levels. The pasture height and the residual tiller population density were affected only by grazing cycles. Green forage biomass (BFV) and green leaf biomass (BLV) presented a quadratic effect of the supplementation levels and grazing cycles. BLV showed a quadratic effect for the cycles two and three, where the higher values were 1489.47, at the level of 0.62, in the second cycle, and 1554.95 Kgâha-Ââyear-1 in the third cycle with a supplementation level of 0.14%. Gas exchange was not influenced by the supplementation levels. Morphogenetic traits of the aruana grass pasture are linearly affected by increasing levels of supplementation. The structural components of the aruana grass pasture are influenced by the increasing levels of concentrate supplementation, with a substitutive effect of the supplement.