Spectral analysis of soils in the lower course of the Acaraú River, Northeastern Brazil

Abstract

The objective of this research was to analyze the spectral response of alluvial soils, representative of the coastal plain in the lower course of the Acaraú River, Ceará, Brazil, and to correlate with the granulometry and soil organic matter (SOM) contents, seeking to identify the best method to predict the attributes studied. In four soil profiles (n = 23 soil samples) the sand, silt, and clay and SOM contents were determined and was carried out the mineralogical characterization. Soil samples were submitted to spectral analysis using a spectroradiometer, with spectral range from visible to shortwave to near infrared (350 - 2,500 nm). It was possible to relate the soil attributes such as color, SOM contents, variation in granulometry and even mineralogy aspects, such as types of minerals in the clay fraction, with the spectral reflectance curves. Some spectral interpretations were useful in understanding aspects associated with the genesis of these soils, especially with regard to the formation environment and mineralogy. For the SOM contents, the best estimates were obtained by simple linear regression and higher correlation for the 564 nm spectrum range. Regression methods were efficient in estimating soil attributes, but the study is limited to the small sample size.