Evapotranspiração de canaviais em diferentes fases fenológicas por sensoriamento remoto no Vale do Submédio do São Francisco

Abstract

Sugarcane in Brazil stands out due to its great potential for production of dry mass and energy and, like all crops, it boosts productivity through management and planning. In the Vale do Submédio do São Francisco region, sugarcane production rates are high due to the use of irrigation during the production cycle. Considering the current scenario of scarcity of water resources, better management is increasingly necessary to control the availability of water, increasing the efficiency of irrigation, reducing financial expenses and reducing water waste. It is necessary to improve tools to obtain evapotranspiration, used to estimate the crop's water demand, which allow better planning of the use and conservation of water resources available for agriculture. To this end, several techniques are being employed, such as remote sensing, in addition to the use of mathematical equations to estimate biophysical parameters. This study aimed to estimate the real evapotranspiration according to the Priestley-Taylor method in sugarcane production areas of different phenological phases in the São Francisco Sub-medium Valley region, using orbital remote sensing and meteorological data from 2013 to 2016. We used meteorological data from the National Institute for Space Research (INPE), the National Environmental Data Organization System (SONDA) and the National Institute of Meteorology (INMET). The orbital data were obtained from the Landsat-8 satellite imaging platform in the database of the U.S. Space Agency (NASA). The image processing to obtain the biophysical parameters and the supervised classification occurred in the Quantum Gis 2.18.11 program. MODIS sensor products were used to characterize the behavior of the sugarcane surface throughout its phenological cycle. The biophysical parameters varied according to the density of the vegetation cover and the phenological stage of the sugarcane. The evapotranspiration Priestley-Taylor ranged from 0.00 to 5.84 mm.day-1, the highest values were found in areas with advanced biomass presence, as well as the lowest values were found in areas with low plant presence. This purchased the relationship of proportionality between evapotranspiration and vegetation indices (NDVI, SAVI, IAF and EVI). We conclude that the Priestley-Taylor method (1972) was able to estimate the reference evapotranspiration in sugarcane production areas in different phenological stages in the São Francisco Sub-medium Valley region in a satisfactory way.