Coeficiente de cultura baseado no conceito de graus-dia e avaliação de métodos de estimativa de evapotranspiração da alface hidropônica sob ambiente protegido

• Autor(a) principal: Moura, Carlos Roberto Weide
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5222
• topic: Coeficiente de cultura; Evapotranspiração; Hidroponia; Alface; Crop coefficient; Evapotranspiration; Hydroponics; Lettuce; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::AGROMETEOROLOGIA

The production and consumption of tull lettuce in hydroponics system of a kind NFT (nutrient film technique) increased considerably in last years in Brazil. The automatics system for application of nutrient solution, based on estimation of evapotranspiration ( ETc), has been developed, but one of the big problem is in relation to the cost of implementing the system. The Penman-Monteith method recommended as standard for the estimation of reference evapotranpiration, require measure on solar radiation, temperature, humidity, and air velocity, this make unviable automation of the system for cultivation in small farms. In this context, the present work has the following objectives: a) propose adoption of the coefficient of cultivation (Kc) specific for production of lettuce in hydroponics systems of a kind NFT using the concept of accumulated degree day (GDA), and cultivars Grand Rapids, Regina, and Great Lakes and b) evaluate the precession and exactness of different methods for evapotranspiration estimation after transplanting of lettuce using the implementation of automation system of low cost. To attain the proposed objectives, were conducted two experiments independently, and the combined data s were used to estimate KC and other parameters of the model of evapotranspiration. The other combined data s for validation of estimates realized based on days and hours. The two experiments were conducted in experimental station of Agricultural Meteorology located in the campus of Universidade Federal de Viçosa UFV. The evapotranspiration estimates were realized by the methods of Penman-Mantheit- FAO (PMF), Penman-Monteith modified for conditions aerodynamics of protected environments (PMAP), Priestley Taylor (PT), Solar Radiation (RS), and Solar Radiation Simplified (RSS), and these were after compared with the measured values. To evaluate the performance of the methods, were utilized the following statistical indexes: a) coefficient of correlation r (precision) ,b) agreement index d (exactness ), c) error mean of the estimates ( MBE) and, d) square root of the error mean square of the estimates ( RMSE). The result verified that the sigmoid model for the four parameters was well adjusted with the observed values of Kc for the three cultivars evaluated in the period of transplanting, in proportion of adjusted coefficient of determination of 0,99, 0,98 and 0,98 for the cultivars Grand Rapids, Regina e Great Lakes, respectively. In relation to the estimates of hours value of ETc, observed that the methods PMAP and PMAPS presented better performance statistics when compared with the methods of PMF, PT, RS and RSS. The method of PMF not presented results of statistics in the period of the afternoon, due to the low evaporation pressure of water in the air. For the daily estimates of ETc, the results this work suggested the better performance statistics of the methods PMF,PMAP and RS in relation to the methods PMAPS, PT and RSS, independent of cultivars evaluated. Even though, the method PMF sub estimated systematically the ETc in the initial period of development of Lettuce.