Estimativa da necessidade hídrica do algodoeiro irrigado usando imagens de satélite

Abstract

Remote sensing data in the thermal infrared part of the spectrum provides indirect estimates of water stress for vegetated surfaces that is defined as a function of the ratio between actual and potential evapotranspiration rates. Methods to estimate the actual evapotranspiration (ETr) from satellite images with thermal bands are very useful, because they can provide an accurate estimate for large areas. In this context, in 2008 an experiment was carried out in Apodi, RN, in order to estimate the ETr for irrigated cotton. It was used the Bowen ratio obtained with field data to validate data obtained by satellite images through the SEBAL (Surface Energy Balance Algorithm for Land methodology) algorithm. The cotton was seeded in 3.6 ha with 0.9 m between rows. The crop actual evapotranspiration was estimated using three images from Landsat 5, obtained at the 34DAE, 50DAE and 82DAE. The Bowen ratio and reference evapotranspiration (ET0) were determined using meteorological data and also from equipments installed in the experimental area. After the estimation of ET obtained under field conditions and the estimation of ETr by satellite, results were analyzed to evaluate the comparative error. It was observed that the ETr estimated from the algorithm SEBAL shows similar results to those obtained by Bowen ratio and can be used to assess the water requirement of cotton.Pages: 653-65