Spectral Reflectance Characteristics of Laboratory-Grown Salt Crusts on Silty Clay and Sandy Soils

Salinization of soils has led to the loss of cropland and represents a major threat to food production. Hyperspectral imaging may prove to be useful for characterizing the spectral behavior of salt-affected soils but the methodology needs to be better evaluated. In this study, we characterized the spectral behaviors of four types of chloride salt crusts [calcium chloride dehydrate, magnesium chloride dehydrate, potassium chloride, and sodium chloride (CaCl2 center dot 2H(2)O, KCl, and NaCl)] formed in the laboratory. We found that (1) as salt concentration increased, the reflectance intensity decreased for both soil types, and the decreases were especially pronounced for the soils leached with the CaCl2 center dot 2H(2)O and MgCl2 center dot 2H(2)O solutions; (2) soil texture had little if any effect on reflectance; and (3) reflectance intensity decreased in the order CaCl2 center dot 2H(2)O < MgCl2 center dot 2H(2)O < KCl < NaCl. By clarifying the spectral behavior of chloride salt crusts on soils, our work demonstrates hyperspectral imaging may differentiate some types of salts and determine relative salt concentrations.