Development of Reflectance Spectral Libraries for Characterization of Soil Properties

Abstract

Methods for rapid estimation of soil properties are needed for quantitative assessments of land management problems. We developed a scheme for development and use of soil spectral libraries for rapid nondestructive estimation of soil properties based on analysis of diffuse reflectance spectroscopy. A diverse library of over 1000 archived topsoils from eastern and southern Africa was used to test the approach. Air-dried soils were scanned using a portable spectrometer {0.35-2.5 J.lm) with an artificial light source. Soil properties were calibrated to soil reflectance using multivariate adaptive regression splines (MARS), and screening tests were developed for various soil fertility constraints using classification trees. A random sample of one-third of the soils was withheld for validation purposes. Validation

Soil spectral library and its use in soil classification

“…In many recent studies, the application of remote sensing techniques has gained much attention, mainly because these techniques have been shown to generate faster and cheaper characterizations, earning them credibility in the scientific community. The application of remote sensing techniques in soil studies began in the 1960s (Bowers & Hanks, 1965) and expanded to various applications, including quick and nondestructive quantification of soil attributes (Janik et al, 1998;Shepherd & Walsh, 2002, Dunn et al, 2002ViscarraRossel, et al, 2006a;Demattê & Nanni, 2006;Brown, et al,. 2006), soil survey and classification (Demattê et al, 2004, Ben-Dor et al, 2008, mineralogical measurements (Madeira-Netto, 1996;Viscarra-Rossel et al, 2006b;Sellito et al, 2009), digital soil mapping (Viscarra-Rossel & McBractney, 2008), precision agriculture (Thomasson et al, 2001Mouazen et al, 2007) and quantification of heavy metals (Wu Zhao et al, 2005).…”

“…Dunn et al (2002) pointed out that, in order for spectroscopy techniques to be commercially applicable, there must be a wide range of data from different soil types with variations in their organic and inorganic components. Shepherd & Walsh (2002) reported that although existing spectral libraries include geological spectral curves of soils (Clark, 1999), there are not many examples of spectral libraries that contain a high diversity of soils and their physical-chemical information. stated that there are several studies about spectral libraries covering various soils of different geographical areas, such as those of Dunn et al (2002), Shepherd & Walsh (2002) and Brown et al (2006).…”

“…Shepherd & Walsh (2002) reported that although existing spectral libraries include geological spectral curves of soils (Clark, 1999), there are not many examples of spectral libraries that contain a high diversity of soils and their physical-chemical information. stated that there are several studies about spectral libraries covering various soils of different geographical areas, such as those of Dunn et al (2002), Shepherd & Walsh (2002) and Brown et al (2006). According to these authors, there are three basic requirements for developing a spectral library of soil: (a) an SL must contain a sufficient number of samples, representing the variability of soils found in the region to which the SL refers; (b) samples must be carefully sub-sampled, handled, prepared, stored and scanned (anything that happens to the sample will affect its spectral curve); (c) the analytical reference data from the samples to be used in calibrations must be acquired through recognized and trusted analytical procedures.…”

Multiple Geotechnological Tools Applied to Digital Mapping of Tropical Soils

“…For point (punctual information) data, the variables of class, color, and texture showed better performance (good) compared to the variables of fertility and Fe (Table 4). The highest value for soil class shows that soil classification and determination of textural groups in the 1 st category level were efficient, in agreement with Shepherd and Walsh (2002) and Islam et al (2003). Color obtained a high index of success because it was obtained in the colorimetric technique (Campos and Demattê, 2004).…”

“…Studies on spectroradiometry show a strong relationship between spectral responses and soil properties, such as cation exchange capacity, organic carbon, Fe oxides, and clay (Chang et al, 2001;Shepherd and Walsh, 2002;Franceschini et al, 2013;Nanni and Demattê, 2006;Demattê et al, 2014a). In fact, this led Demattê et al (2004a) to use a spectroscopy information to aid in pedological mapping.…”