VARIABILIDADE ESPACIAL DE ATRIBUTOS QUÍMICOS DO SOLO EM DIFERENTES OBTENÇÕES DE COORDENADAS GNSS

Abstract

Resulting from the formation and development of its intrinsic characteristics, soil is an extremely heterogeneous system due to its composition, which includes different types of organic materials, minerals, and chemical properties. This study aimed to evaluate the spatial variability and dependence of soil fertility chemical attributes (calcium, magnesium, phosphorus, potassium, aluminum, and potential acidity) and to compare three positioning methods for determining geographic coordinates: GNSS coupled with Leica GS-900, GNSS Garmin Etrex 30, and the Trimble Outdoors Navigator app for map interpolation. The study area is located in Ceres, Goiás, on a medium-textured red latosol. A sample grid was established over an area of 7.11 hectares, with a spacing of 30 x 30 m to map samples at a depth of 0.00–0.20 m. Soil samples were analyzed and a descriptive analysis of the results was conducted. After interpolating the data using QGIS with the Smart-Map plugin and geostatistics, variograms and subsequent variability maps were generated with spatial information from the georeferenced data. The greatest variabilities were observed for Al, P, Mg, and Ca, in that order. The sampling grid proved to be adequate for verifying the spatial variability and dependence of soil chemical attributes. The maps produced by different positioning methods showed analogous patterns, allowing the use of a mobile application as a more economical alternative for obtaining geographic coordinates, meeting the requirements for visualizing areas with specific needs for more precise and localized recommendations.