Reflectance Properties of Soils

Abstract

This chapter discusses the reflectance properties of soils. In delineating differences among soils and in describing the characteristics of a soil profile, color is one of the most useful attributes for documenting these differences. Soil visible reflectance, or color, is a differentiating characteristic for many classes in all modern soil classification systems and is an essential part of the definitions for both surface and subsurface diagnostic horizons. The chapter includes instrumentation for reflectance measurements. Instruments that are used to measure the reflectance of soil are divided into two broad classes—namely, spectroradiometers and multiband radiometers. Multiband radiometers contain several optical filters to define the spectral bandpasses. These spectral bandpasses are selected to sample discrete portions of the optical spectrum, e.g., the Landsat multispectral scanner or the thematic mapper bands. The character of reflected light from a soil surface depends on the nature of the surface and the intensity and spectral quality of the radiation incident upon the surface. The soil surface may be irradiated by direct sunlight, scattered skylight, and thermal radiation from the surroundings.