Spectral Signatures for the Lake Okeechobee Soils Using UV-VIS-NIR Spectroscopy and Predicting Phosphorus Concentrations

Abstract. Developing a phosphorus sensing system using UV, VIS and NIR provides a non-contact, cost & time effective, less laborious measurement of phosphorus (P) concentration in a soil sample. The determination of soil spectral signatures in the Lake Okeechobee basins in Florida improves the prediction accuracy of calibration models produced for the determination of soil P concentration for Okeechobee originated soils. This study aimed to obtain spectral signatures of soil samples collected from the Lake Okeechobee basins and find the significant absorption bands for sensing P concentration in a soil sample. A total of 345 soil samples were collected from the surrounding area of the Lake Okeechobee to obtain broad range of P concentrations from very low to very high (1.1-2709 mg/kg). Thirty-eight soil samples from different fields were sub-sampled and leached in order to remove existing nutrient content. The reflectance spectra of leached and un-leached soil samples were measured using UV, VIS and NIR spectroscopy. P concentrations of the samples were correlated with the absorbance of the same sample. Leached soil signatures were subtracted from those of un-leached soil samples to obtain only nutrient spectrum. Data analysis for P concentration determination was conducted with and without soil signature corrected. For each set, two-third of data was used for calibration while one-third of data was for validation. PLS analysis (partial least squares) was applied to data set.