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Assessment of P-concentration in the Lake Okeechobee Drainage Basins with Spectroscopic Reflectance of VIS and NIR

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  031139,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13745) @2003
Authors:   Ismail Bogrekci, Won Suk Lee, Juan Herrera
Keywords:   Reflectance, Sensor, Phosphorus, Lake Okeechobee, VIS, NIR, PLS

High phosphorus level in the Lake Okeechobee basins results in life risking problems for the habitat within the Lake itself and the surrounding basins. Phosphorus (P) entering the Lake Okeechobee comes from the sources around the Lake such as agricultural operations, dairy, and beef farms and ranches. The determination of high phosphorus areas around the Lake may improve the prevention of excess phosphorus entering the drainage system and the Lake from the original resources. This study aimed to develop a realtime, non-contact measurement system using spectroscopic reflectance of VIS and NIR, since current monitoring methods are so labor intensive, costly, and time consuming. Soil samples were obtained from the beef and dairy farms in the Lake Okeechobee basins. P concentrations of the samples were analyzed and reflectance of the samples was measured between 400-2500 nm with a 1nm interval. Two-third of the samples were used for developing a calibration model while one-third of the samples were used for validation.

PLS (Partial Least Squares) and stepwise multiple linear regression analyses were applied to the data set. The results showed that the stepwise multiple regressions did not successfully predict P concentrations, although the calibration models showed very high R2 values of 0.84 and 0.91 for the wet and dry soil samples, respectively. The calibration models developed by the PLS predicted P concentrations better. R2 values of 0.78 and 0.89 were found for the wet and dry soil samples for validation, respectively.

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