Routine tests to determine physical and chemical soil properties have been used for several years. However, due to economic and environmental problems, new assessment methods must be developed. In this context, diffuse reflectance spectroscopy is a promising and quick tool in the determination of these properties. The objective of this work was to study the spectral behavior of the silt, sand and clay fractions and evaluate the possibility of quantifying these properties with regression models generated for each individual element. To develop the models, individual silt, sand and clay fractions from two areas formed by different materials were used. The models were validated using the reflectance factor of soil samples in their natural state collected in the municipality of Lobato, Paraná. The results showed that it was possible to satisfactorily estimate the percentage of sand in soil samples from Lobato by individual models of the Cooperval production plant, unlike in the case of individual models adjusted for the Experimental Farm of Iguatemi. It was not possible to estimate the silt and clay fraction in the Lobato soil samples satisfactorily by the individual models. It was therefore concluded that although the results had not reached the ideal level, diffuse spectroradiometry proved to be a promising tool for the estimation of soil physical properties; in the near future this technique may support or even replace the analytical laboratory methods, reducing the time and cost spent on the analyses.
X-ray; analysis technique; spectroradiometer; soils
