Variabilidade espacial de atributos físico-hídricos dos solos da Região Norte Fluminense

Abstract

The usage of numerical models to simulate flux of water and solutes has increased in the last decades. However, to be more useful, it is necessary the knowledge of the spatial variability of the attributes soil water retention and hydraulic conductivity. These attributes, frequently, are difficult to be found and/or determined in a given study area, since they require time and more investment. The purpose of this study was to study and to map the spatial variability of saturated hydraulic conductivity (SHC) and available water capacity (AWC) of soils in the north region of Rio de Janeiro State (Brazil). The dataset used belongs to UFRRJ and was generated by the Project of Irrigation and Drainage of the North Fluminense to evaluate areas for producing sugar cane (PROJIR). Data and maps were digitalized and georeferenced, being recorded 314 values of SHC, determined by the double ring infiltrometer method, and 187 values of AWC, from samples taken at 60 cm soil depth. The spatial variability of SHC and AWC were evaluated by geostatistics methods. In order to improving the SHC and AWC estimative, spatial variability of sand, silt and clay contents; as well as, clay flocculation, silt/clay ratio, porosity, bulk density and organic carbon content were also evaluated. The semivariogram analysis, with the adjusted models, showed the spatial dependence of the SHC and AWC variability. The semivariogram analysis showed that the sand content may be used as an auxiliary attribute to improve the spatial interpolation of SHC and AWC, generating maps of isovalues and estimative variance of these attributes. Key words: Geostatistic. Digital Mapping. Soil physics.The usage of numerical models to simulate flux of water and solutes has increased in the last decades. However, to be more useful, it is necessary the knowledge of the spatial variability of the attributes soil water retention and hydraulic conductivity. These attributes, frequently, are difficult to be found and/or determined in a given study area, since they require time and more investment. The purpose of this study was to study and to map the spatial variability of saturated hydraulic conductivity (SHC) and available water capacity (AWC) of soils in the north region of Rio de Janeiro State (Brazil). The dataset used belongs to UFRRJ and was generated by the Project of Irrigation and Drainage of the North Fluminense to evaluate areas for producing sugar cane (PROJIR). Data and maps were digitalized and georeferenced, being recorded 314 values of SHC, determined by the double ring infiltrometer method, and 187 values of AWC, from samples taken at 60 cm soil depth. The spatial variability of SHC and AWC were evaluated by geostatistics methods. In order to improving the SHC and AWC estimative, spatial variability of sand, silt and clay contents; as well as, clay flocculation, silt/clay ratio, porosity, bulk density and organic carbon content were also evaluated. The semivariogram analysis, with the adjusted models, showed the spatial dependence of the SHC and AWC variability. The semivariogram analysis showed that the sand content may be used as an auxiliary attribute to improve the spatial interpolation of SHC and AWC, generating maps of isovalues and estimative variance of these attributes. Key words: Geostatistic. Digital Mapping. Soil physics.The usage of numerical models to simulate flux of water and solutes has increased in the last decades. However, to be more useful, it is necessary the knowledge of the spatial variability of the attributes soil water retention and hydraulic conductivity. These attributes, frequently, are difficult to be found and/or determined in a given study area, since they require time and more investment. The purpose of this study was to study and to map the spatial variability of saturated hydraulic conductivity (SHC) and available water capacity (AWC) of soils in the north region of Rio de Janeiro State (Brazil). The dataset used belongs to UFRRJ and was generated by the Project of Irrigation and Drainage of the North Fluminense to evaluate areas for producing sugar cane (PROJIR). Data and maps were digitalized and georeferenced, being recorded 314 values of SHC, determined by the double ring infiltrometer method, and 187 values of AWC, from samples taken at 60 cm soil depth. The spatial variability of SHC and AWC were evaluated by geostatistics methods. In order to improving the SHC and AWC estimative, spatial variability of sand, silt and clay contents; as well as, clay flocculation, silt/clay ratio, porosity, bulk density and organic carbon content were also evaluated. The semivariogram analysis, with the adjusted models, showed the spatial dependence of the SHC and AWC variability. The semivariogram analysis showed that the sand content may be used as an auxiliary attribute to improve the spatial interpolation of SHC and AWC, generating maps of isovalues and estimative variance of these attributes.