Estimativa da evapotranspiração de referência pelo Irrigâmetro nas condições climáticas do sul do Estado do Tocantins

• Autor(a) principal: Giovanelli, Luan Brioschi
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/3620
• topic: Evapotranspiração; Irrigâmetro; Condições climáticas; Dados meteorológicos; Evapotranspiration; Irrigameter; Climate conditions; Meteorological data; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA

In the present issues related to world water scarcity, it becomes indispensable the search for alternatives that optimize the use of this resource for the purpose of irrigation, knowing that this activity takes up about 70% of the total world water extracted from aquifers, rivers and lakes. In this background, the methods for irrigation management are highlighted due to their importance in water preservation and maximization of the agricultural production, besides being essential to increase the performance and sustainability of the irrigation systems. Having mentioned this, the Irrigameter appears as an important alternative for irrigation management, because of its practicality and accuracy to estimate evapotranspiration, process which is used to determine the water requirement of the crops. Researches done with the Irrigameter in different weather conditions and in different seasons allow a better adjustment of the device in order to improve it. Therefore, the aims of this research were: (a) Determine the coefficient of the Irrigameter (KI) for each season, from September 2008 to September 2011, for different water levels inside the evaporator of the Irrigameter, in the south of Tocantins state - Brazil; (b) Establish, for each season, the water level in the evaporator referring to the KI of 1; and (c) Evaluate the effects of the meteorological elements (maximum temperature, minimum temperature, relative humidity, wind speed, and solar radiation) in the evapotranspiration estimated by the Irrigameter (ETI), which operates in different water levels inside the evaporator, for the seasons studied. The study was conducted in the experimental area of the Federal University of Tocantins (UFT), in the University Campus of Gurupi, situated in Gurupi, TO. The experiment was mounted in an entirely randomized delimitation, with seven water levels in the evaporator of the Irrigameter, representing the treatments, with three repetitions. The weather data were collected in an automatic weather station and used for determining the reference evapotranspiration (ET0), using the computer software REF-ET, based on the FAO 56 Penman-Monteith equation. There was a linear increase of the KI with the rising of the water level inside the evaporator in spring and summer. In the fall and in winter, the increase was exponential. The recommended water level in the evaporator, in a way that it estimates an ET0 in the south of Tocantins, for spring is equal to 3,4 cm; for the summer, 4,0 cm; for the fall, 3.8 cm; e for the winter, 2.3 cm. The meteorological elements relative humidity and solar radiation presented a high correlation with the ETl in all the seasons studied. The minimum temperature and wind speed were the meteorological elements with the lowest indirect effect on the ETl, when associated with the other elements.