Abstract

SOTELO RUIZ, Erasto et al. Identification of Vertisols of sedimentary origin through their spectral signature. Agric. Téc. Méx [online]. 2006, vol.32, n.3, pp.303-312. ISSN 0568-2517.

Soil classification is expensive and time consuming; therefore, it is necessary to develop alternative methods for this task. The satellite images can be used for identifying the soil class, since some properties such as: clay content, moisture, roughness, bulk density, color, and organic matter content have a characteristic reflectance. The percentage of clay and the bulk density define the Vertisols and the others properties mentioned are also related, for that reason its study in conjunction can generate a spectral pattern that contribute towards its delimitation on a satellite image. The objectives of this research were 1) To classify and determine the mineralogy in Vertisols of sedimentary origin from San Fernando, Tamaulipas, 2) To identify the spectral signature of the Vertisols present in the area of study, 3) To determine the typical properties of the Vertisol soils with respect to its reflectance on the satellite image and 4) To model the distribution of the typical Vertisols through methods of satellite image interpretation. The study was carried out in 25 000 ha in the municipality of San Fernando, Tamaulipas, Mexico. The satellite image Landsat 7 ETM+ used was taken on April 29th, 2002. The soils were classified as Vertisols and Mollisols with the same type of primary and secondary minerals, and differentiated by its content of calcite. The reflectance values of the soils were statistically different in the bands 5 and 7. However, the soils could not be differentiated by a supervised classification with the method of Maximum Likelihood of Idrisi in the satellite images, due to the fact that the content of calcite >60% and calcium carbonate >15% defined the spectral signature of both soils, Vertisols and Mollisols.

Keywords : Calcite; calcium carbonate; clay content; soils survey.

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