Potential of VIS-NIR spectroscopy to characterize and discriminate topsoils of different soil types in the Triffa plain (Morocco)

Abstract

This study aims to identify the influence of soil organic matter (OM) content and calcium carbonates (CaCO3) on soil reflectance and select the optimum spectral bands for discriminating between topsoils of different soil types situated in the irrigated perimeter of the Triffa plain (Morocco) using VIS-NIR reflectance spectroscopy. Soil samples were collected from the plow layer in 26 sampling sites. The spectral measurements were conducted in the field using an ASD Fieldspec portable spectroradiometer (350–2500 nm), while the soil samples were analyzed in the laboratory. The spectral data were pre-processed to remove the noise effects and then analyzed with the CovSel (selected covariance) method, validated by linear discriminant analysis in order to select the most optimal spectral variables to discriminate between topsoils of different soil types in the plain. The results of the soils reflectance curves showed that low reflectance intensity marked the soils with high OM contents throughout the VIS spectrum. The influence of the soil OM content was very apparent in the VIS range (between 580–750 nm). Regarding the CaCO3 content, it was noted that the soil samples with a high percentage of CaCO3 increase the reflectance in all spectral domains situated between 350 and 2500 nm. The spectral bands of 1999, 686, 1280, 2340 and 1951 nm were the most optimal for the soil discrimination in the Triffa plain. This study concluded that the VIS-NIR spectroscopy demonstrates an excellent ability to characterize and discriminate between topsoils in the Triffa plain.

Physicochemical and Mineralogical Characterization of the Mediterranean Soils of Triffa Plain (Northeast of Morocco) by the Physicochemical Analysis, X-ray Diffraction and Vis-NIR Spectroscopy

“…Soils in the study area are rather alkaline with an average pH of 7.32 and are characterized by sufficient content of plant available phosphorus (P). The calcium carbonates (CaCO3) content indicate that the soils of Triffa plain are slightly to moderately calcareous, our result confirmed those obtained by Lazaar et al (2019) [10]. The soil salinity (CE) corresponds to the normal values for arable lands.…”

“…Based on organic matter content, the soils are characterized by OM value varying between 2.39 to 3.34 % which indicates that the different soil types are characterized by medium to high values of organic matter. Soil texture fractions (clay, silt, and sand fractions) for the study area were generally coarse-textured, with low clay content and high silt and sand content, which indicate that soil types of the study area was dominated by a silt-loam texture, this results confirmed those obtained by Lazaar et al (2019).…”

“…The Triffa Plain is formed mainly by geological formations of Quaternary, Mesozoic and Cenozoic age, all overlying a Hercynian basement [9]. It is characterized by a diversified pedological cover represented by isohumic, brown calcareous, fersialitic, rendzina, less-developed and hydromorphic soils [10]. The isohumic soils are brown, rich in terms of organic matter and occupy almost half of the study area.…”