Soil Particle Size Effect on Absorbance Spectra of Sandy Soils in UV-VIS-NIR Regions

Abstract. The reflectance spectra of the soil samples are influenced by soil particle size. Elimination of this effect requires a calibration model to remove the effect of soil particle size. Therefore, this study aimed to investigate the effects of soil particle size on reflectance spectra of sandy soil samples and to produce a particle size calibration model for the spectra of a sandy soil sample. Sandy soils were obtained from Edgar, Putnam County in Florida. Soil was sieved into three fractions. Leaching with de-ionized water and hydrochloric acid (0.1 molar HCl) was conducted in order to remove the current nutrient contents, which may contribute to the reflectance spectra of a soil sample. Reflectance spectra of soil samples were measured in UV, VIS and NIR regions between 200 and 2500 nm with a sampling interval of 1 nm. A particle size calibration model was developed using multiple linear regressions (MLR). The results from this calibration model enhanced the prediction accuracy terrestrial phosphorus (P) sensing in the Lake Okeechobee drainage basins.