Estimativa da demanda hídrica da cultura do milho irrigado no Sul do Brasil utilizando imagens orbitais e Kc dual

Abstract

The use of orbital images to provide complementary support to water management in irrigated agricultural systems, with an emphasis on the estimation of crop coefficients, has achieved good results, especially if associated with soil water balance models that estimate irrigation parameters to determine crop evapotranspiration (ETc). This information can support irrigation management and be organized in a geographic information system (GIS), for spatial visualization of the spectral response identified by the normalized difference vegetation index (NDVI), and can identify the efficiency of the agricultural activity in order to portray the local reality. The interaction of the information obtained by the remote sensing with the results found by the soil water balance model allows the understanding of the characteristics of the crop, soil, rainfall and water demand by the crops. In this way, the present study aims to estimate the corn cultivation coefficients, from the NDVI, data obtained by the Sensor OLI image processing (Landsat 8 platform) and data estimated by the SIMDualKc soil water balance model, to determine the ETc demand. The study was conducted in three central pivot irrigated areas in the municipality of Júlio de Castilhos-RS, Brazil, in the agricultural years 2013/14, 2014/15 and 2016/17. The cultivation coefficient (Kc), basal culture coefficient (Kcb) and soil water evaporation coefficient (Ke), estimated by the SIMDualKc model, were evaluated. The Kcb were also estimated from the NDVI, obtained by processing the Sensor OLI images. An approach to estimating Kc NDVI was proposed, integrating the Kcb obtained by the NDVI with the Ke derived by the model SIMDualKc. From the Kc NDVI was estimated with ETc NDVI data for the three evaluated agricultural years, applying the formula ETc = Kc * ETo, where ETo is the evapotranspiration of the reference crop. The proposed methodology allowed to obtain the cultivation coefficients based on the SIMDualKc model and from satellite imagery information to estimate the corn ETc demand in the three years evaluated. The results for the three irrigated areas showed good estimates of the Kcb and ETc ratio achieved by the NDVI, with the Kcb and ETc obtained by the SIMDualKc model.