Desempenho do Irrigâmetro® e de dois minievaporímetros para estimativa da evapotranspiração de referência

• Autor(a) principal: Tagliaferre, Cristiano
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/735
• topic: Irrigâmetro; Minievaporímetro; Evaporação; Evapotranspiração; Irrigação; Lisímetro; Modelo de Penman-Monteith; Irrigâmetro®; Minievaporimeter; Evaporation; Irrigation; Evapotranspiration; Lysimeter; Penman-Monteith method; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA::ENGENHARIA DE AGUA E SOLO

The objective of this study was to evaluate the performance of the Irrigâmetro® and the minievaporimeters UFV-1 and UFV-2 to estimate reference evapotranspiration. Irrigâmetro® is an evapo-pluviometric equipment to be used in irrigation management. Minievaporimeter UFV-1 consists of a PVC cylindrical container, with 250 mm outer diameter and 244 mm inner diameter, 320 mm height and bottom 255 mm distant from the edge. In contrast, the minievaporimeter UFV-2, which also has an evaporator identical to model UFV-1, having, however, another cylindrical PVC container of same height, 5-mm thick, with 450mm outer diameter, which also stores water, forming a fetch border. In each mini-evaporimeter, the maintenance of the constant water level inside the evaporator and the measurement of the amount of water evaporated were carried out using a modified Irrigâmetro® connected to each one of them. The experiments were conducted at the Irrigâmetro® Research and Development Unit of the Agricultural Engineering Department of the Federal University of Viçosa (UFV), Viçosa, MG. The Irrigâmetro® was evaluated with an evaporator of 60-mm diameter and water depth at 35 mm from the edge. To analyze the effect of different water depths on the evaporation rate in the minievaporimeters, the experiment was arranged in a 4 x 2 factorial (four water depths and two types of mini-evaporimeters) complete randomized design, with three replications. The evaporation in the minievaporimeters was obtained at the water depths of 30, 45, 60 and 75 mm from the edge. The evapotranspiration data obtained from the Irrigâmetro® were compared with the reference evapotranspiration (ET0) obtained with the Penman-Monteith method - FAO 56. The evaporation from the minievaporimeters was related with the (ET0) estimated by the Penman-Monteith method - FAO 56 and with the (ET0) determined in the constant water table lysimeter to obtain the coefficients that allowed the estimation of reference evapotranspiration in intervals of one, three, five and seven days. The transformation of evaporation into reference evapotranspiration was carried out by multiplying the mean values of minievaporimeter coefficients (from each water depth and each studied interval) by the evaporation values. The reference evapotranspiration results from the Irrigâmetro® and minievaporimeters were compared with the results from the FAO-24 Modified Penman, FAO-24 Radiation, Class A pan, Hargreaves-Samani (1985) and drainage type lysimeter. The results indicated that: (a) the Irrigâmetro® provided suitable performance compared with the Penman-Monteith method - FAO 56 to estimate ET0 at the intervals of one, three, five and seven days; (b) the Irrigâmetro® can be recommended for water management in irrigated agriculture; (c) the water border reduced evaporation in the minievaporimeter UFV-2 by 1.1 mm d-1, on average, at the different studied water depths compared to the minievaporimeter UFV-1; (d) as the water depth in the evaporator of the two minievaporimeters increased, the evaporation decreased and became closer to the value obtained in the Class A pan; (e) increase in water depths of minievaporimeters UFV-1 and UFV-2 from 30 to 75 mm reduced evaporation from 5.45 to 4.9 mm d-1 and from 4.29 to 3.81 mm d-1, respectively; (f) the minievaporimeters UFV-1 and UFV-2 operating with modified Irrigâmetro® provided suitable performance, compared to the Penman-Monteith method - FAO 56 and constant water table lysimeter, to estimate ET0 in the intervals and the studied water depths; (g) minievaporimeter UFV-1 gave coefficient values equal to 0.51; 0.53; 0.55; and 0.56, while the minievaporimeter UFV-2 gave coefficient values equal to 0.65; 0.68; 0.72; and 0.74, respectively, at the water depths 30, 45, 60 and 75 mm from the edge, in comparison with the Penman-Monteith method - FAO 56; (h) minievaporimeter UFV-1 gave coefficient values equal to 0.47; 0.49; 0.51; and 0.52, while the minievaporimeter UFV-2 gave values equal to 0.59; 0.63; 0.65; and 0.67, respectively, at the water depths 30, 45, 60 and 75 mm from the edge, in comparison with the constant water table lysimeter; and (i) the methods Modified Penman, Hargreaves-Samani and Radiation overestimated the ET0 obtained by the adopted standard methods in all the analyzed intervals, showing behavior opposite to the drainage lysimeter and Class A pan.