Uso do algoritmo SAFER para evapotranspiração real na cultura da soja
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2018-01-26
Autores
Silva, Yane de Freitas da
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Universidade Estadual Paulista (Unesp)
Resumo
A soja é uma das culturas mais importante na economia mundial, originária de clima temperado, adapta-se bem em uma faixa de 20 a 35 ºC e a necessidade total de água para a cultura é em torno de 800 mm/ciclo, dependendo das condições climáticas, manejo da cultura e duração do ciclo. O conhecimento sobre a temperatura de superfície, o saldo de radiação e a evapotranspiração da cultura em cada fase fenológica é a base para o dimensionamento de sistemas de irrigação e gerenciamento eficiente da água. Desse modo, o objetivo do trabalho foi estimar o albedo de superfície, o NDVI, o saldo de radiação, a temperatura de superfície e a evapotranspiração real da soja, aplicando o algoritmo “Simple Algoritmo Model For Evapotranspiration Retrieving” - SAFER comparado com o método FAO 56, fazendo uso de técnicas de sensoriamento remoto e das variáveis climáticas obtidas em estação agrometeorológica. Constatou-se que o valor médio do albedo de superfície calculado pelo SAFER para todo o ciclo da soja foi de 18%. As áreas com valores de NDVI próximos a 0,8 espera-se maiores produtividades, podendo ser gerados mapas que auxiliarão de forma qualitativa. A temperatura de superfície estimada pelo SAFER apresentou valores bem próximos aos medidos pela estação agrometeorológica. Os maiores valores de saldo de radiação foram encontrados nas fases de pleno desenvolvimento, enquanto que os menores ocorreram em fase próxima a colheita e solo exposto. A ETr média estimada pelo SAFER apresentou redução de 1,91 mm dia-¹ comparada com o método FAO 56.
Soybean is one of the most important crops in the world economy, coming from temperate climate, well adapted in a range of 20 to 35 °C and the total water requirement for the crop is around 800 mm/cycle, depending on the climate conditions, crop management and cycle duration. Knowledge about surface temperature, radiation balance and evapotranspiration of the crop in each phenological phase are the basis for the operation of water efficient irrigation systems. Thus, the objective of this work was to estimate the surface albedo, the NDVI, the balance of radiation, the surface temperature and actual evapotranspiration of soybean applying the algorithm “Simple Algorithm Model For Evapotranspiration Retrieving” - SAFER compared to model FAO 56, using remote sensing techniques and of the climatic variables obtained in agrometeorological station. It was observed the average value of the surface albedo calculated by SAFER for the entire soybean cycle was 18%. Areas with NDVI values close to 0.8 expected higher yields, and maps can be generated that will help in a qualitative way. The surface temperature estimated by SAFER was very close to that measured by the agrometeorological station. Analyzed only by phenological phases, the highest values of radiation balance were found in the phases of full development while the smaller ones, in the near phase the harvest and exposed soil. The mean ETr estimated by SAFER presented a reduction of 1.91 mm day¹ compared to the FAO 56 method.
Soybean is one of the most important crops in the world economy, coming from temperate climate, well adapted in a range of 20 to 35 °C and the total water requirement for the crop is around 800 mm/cycle, depending on the climate conditions, crop management and cycle duration. Knowledge about surface temperature, radiation balance and evapotranspiration of the crop in each phenological phase are the basis for the operation of water efficient irrigation systems. Thus, the objective of this work was to estimate the surface albedo, the NDVI, the balance of radiation, the surface temperature and actual evapotranspiration of soybean applying the algorithm “Simple Algorithm Model For Evapotranspiration Retrieving” - SAFER compared to model FAO 56, using remote sensing techniques and of the climatic variables obtained in agrometeorological station. It was observed the average value of the surface albedo calculated by SAFER for the entire soybean cycle was 18%. Areas with NDVI values close to 0.8 expected higher yields, and maps can be generated that will help in a qualitative way. The surface temperature estimated by SAFER was very close to that measured by the agrometeorological station. Analyzed only by phenological phases, the highest values of radiation balance were found in the phases of full development while the smaller ones, in the near phase the harvest and exposed soil. The mean ETr estimated by SAFER presented a reduction of 1.91 mm day¹ compared to the FAO 56 method.
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balanço de energia, consumo de água, Glycine max, irrigação, modelagem hídrica, sensoriamento remoto, energy balance, water consumption, irrigation, water modeling, remote sensing