ABSTRACT
This study aimed to evaluate the morphogenetic, structural, and productive characteristics of Andropogon gayanus cv. 'Planaltina' subjected to different nitrogen fertilization levels and defoliation intensities. The experiment was done in a completely randomized design with a factorial arrangement of six nitrogen doses (0, 100, 200, 300, 400, and 500 kg N ha-1) and two defoliation intensities (15 and 30 cm). The production and structure data were grouped into rainy and dry periods, while morphogenesis data were compared only among different fertilization and defoliation intensities. The total dry forage biomass (TDFB), dry mass of leaves (DML), dry mass of stems (DMS), and dead forage dry mass (DFDM) were then determined. In addition to these variables, the morphogenetic characteristics of the plants and the numbers of tillers alive and dead were evaluated. There was no interaction (P>0.05) between the effects of nitrogen fertilization doses and the intensity of defoliation on TDFB, DML, DMS, and DFDM in both of the evaluated phases (rainy and dry). It was also observed that the rates of leaf elongation, leaf appearance, and leaf blade elongation increased with nitrogen fertilization. On the other hand, the culm elongation rate and phyllochron decreased as the dose applied increased. The defoliation intensity did not influence (P>0.05) the morphogenetic characteristics examined, nor did it affect the senescence rate of nitrogen in leaves and number of live leaves per tiller. The number of dead tillers increased linearly during the rainy period. Based on these results, to improve the efficiency of production of gamba grass it is recommended that it be managed with a defoliation intensity of 30 cm and nitrogen fertilization of 286.52 kg N ha-1 year-1.
Objetivou-se avaliar as características morfogênicas, produtivas e estruturais do Andropogon gayanus cv. Planaltina submetido a níveis de adubação nitrogenada e intensidades de desfolha. O delineamento experimental foi o inteiramente casualizado com arranjo fatorial 6x2, doses de nitrogênio (0, 100, 200, 300, 400 e 500 kg de nitrogênio ha-1) e intensidades de desfolhas (15 e 30 cm). Os dados de produção e estrutura foram agrupados em períodos chuvoso e seco e os de morfogênese analisados somente em função da adubação e intensidade de desfolha. Foi determinada a produção de biomassa de forragem seca total (BFST), massa seca de folhas (MSF), massa seca de colmos (MSC) e massa seca de forragem morta (MSFM). Além dessas variáveis foram avaliadas as características morfogênicas e de perfilhos vivos e mortos. Houve interação (P<0,05) entre as doses e intensidade de desfolhas para a MSFT, MSF, MSC e MSFM em ambas as fases de avaliação. Observou-se que as taxas de alongamento foliar, aparecimento foliar e comprimento da lâmina foliar aumentaram com a adubação nitrogenada. Por outro lado, a taxa de alongamento do colmo e Filocrono diminuíram com a aplicação das doses crescentes. As intensidades de desfolha não influenciaram (P>0,05) nas características morfogênicas, assim como a adubação na taxa de senescência foliar e número de folhas vivas por perfilho. O número de perfilhos mortos aumentou de forma linear durante o período chuvoso. Recomenda-se manejar o capim-andropógon com intensidade de desfolha de 30 cm e adubação nitrogenada de 286,52 kg de N ha-1 ano-1, visando a maior produção.
Subject(s)
Waste Products , Dry Season , Rainy Season , AndropogonABSTRACT
Introducción: La meningoencefalitis eosinofílica producida por Angiostrongylus cantonensis (Chen, 1935), es una zoonosis emergente presente en Cuba. En el país existen escasos estudios de prevalencia de infección en los hospederos definitivos, que puedan determinar sitios de riesgo para el establecimiento de medidas efectivas en la prevención de la enfermedad. Objetivo: Determinar la prevalencia de infección por A. cantonensis en una población natural de R. rattus, su relación con la estructura poblacional y la época del año en una finca que pertenece al Programa de la Agricultura Urbana y Suburbana de Cuba. Material y Métodos: Se realizó un estudio descriptivo en el municipio La Lisa, La Habana. Se hicieron capturas de roedores mensuales durante los períodos lluvioso y poco lluvioso. Se examinaron las arterias pulmonares de los roedores capturados en búsqueda de parásitos adultos. El índice parasitológico de prevalencia fue calculado y comparadas las frecuencias entre los períodos del año y la edad ecológica. Resultados: Se capturaron 63 roedores identificados como Rattus rattus, de ellos 46,03 por ciento estuvo infectado con A. cantonensis, con un incremento de la infección en los individuos adultos (59,46 por ciento) y en el período lluvioso (55,88 por ciento). Conclusiones: Se demuestra por primera vez en Cuba la infección de A. cantonensis en R. rattus. La presencia de individuos adultos, la alta abundancia de roedores y la temporada lluviosa son los factores que incidieron en una mayor infección de A. cantonensis, y que aumentan la probabilidad de transmisión a los hospederos intermediarios y, por ende, el riesgo de transmisión al humano(AU)
Introduction: Eosinophilic meningitis caused by Angiostrongylus cantonensis (Chen, 1935) is an emergent zoonosis present in Cuba. In the country, few studies about the prevalence of infection in definitive hosts, which can determine risk sites for the establishment of effective measures to prevent the disease, have not been carried out so far. Objective: To determine the prevalence of infection with Angiostrongylus cantonensis in a natural population of Rattus rattus, its relationship with the population structure, and the season of the year in an urban farm field belonging to the Programme of Urban and Suburban Agriculture of Cuba. Material and Methods: A descriptive study was conducted in La Lisa Municipality, Havana, Cuba. The rats were collected monthly during the rainy and dry seasons. The pulmonary arteries of the captured rodents were examined for adult worms. The prevalence of parasitological indices was calculated. The frequencies of infection were compared between the seasons of the year and ecological ages. Results: A total of 63 rodents identified as Rattus rattus were captured. Of the total of individuals captured, 46.03 percent were infected with A. cantonensis, with an increase of infection in adult individuals (59.46 percent) and during the rainy season (55.88 percent). Conclusions: The infection of A. cantonensis in its definitive host R. rattus, and its circulation in the study area in the analyzed period was demonstrated for the first time in Cuba. The presence of adult rats, the high quantity of rodents and the rainy season were the factors that contributed to a greater infection of A. cantonensis, which increase the probability of transmission to intermediate hosts, and consequently, the risk of transmission to humans(AU)