Spectral Characteristics of Soil Types in Northwestern Jordan Considering Iron Oxides Effects and Colors

Abstract

Remote sensing as a tool to map and monitor soil cover in Jordan is very significant for agriculture production. Nonetheless, the still poor state of information about spectral characteristics of Jordan's soils is a challenge, where the understanding of soil spectra is of essential importance. It is especially suited to demonstrate relationships between spectral reflectance data and various soil properties, which correspond to well-known relationships of color, mineral assemblages, and chemical compositions. This study explores the spectral characteristics of soil types in northern Jordan with regard to soil colors and explains the effects of iron oxides on the shape of the spectral curves. A total of 160 bulk samples were collected systematically from the soil surface at 40 locations. Based on laboratory measurements with analytical spectral devices (ASDs), a mean soil reflectance spectrum (MSRS) was calculated. Color measurements of soils were conducted with a spectrophotometer using the CIELAB color space (Commission Internationale de l'Eclairage CIE, (1978)). The results show high correlations between spectral characteristics, soil color variations, and Fe oxides. Whereas organic matter contents seem to play no detectable role. Based on these findings, we were able to distinguish six soil groups in the study area.