Vis-NIR spectrometry, soil phosphate extraction methods and interactions of soil attributes.
2015
OLIVEIRA, J. F. de | BROSSARD, M. | CORAZZA, E. J. | MARCHAO, R. L. | VENDRAME, P. R. S. | BRITO, O. R. | GUIMARAES, M. de F. | JOSÉ FRANCIRLEI DE OLIVEIRA, UEL; MICHEL BROSSARD, UEL; EDEMAR JOAQUIM CORAZZA, SCT; ROBELIO LEANDRO MARCHAO, CPAC; PEDRO RODOLFO SIQUEIRA VENDRAME, UEL; OSMAR RODRIGUES BRITO, UEL; MARIA DE FÁTIMA GUIMARÃES, UEL.
Abstract: The objective of this study was to evaluate the relationships between the spectra in the Vis-NIR range and the soil P concentrations obtained from the P-M and P-rem extraction methods as well as the effects of these relationships on the construction of models predicting P concentration in Oxisols. Soil samples' spectra and their P-M and P-rem extraction solutions were determined for the Vis-NIR region between 400 and 2500 nm. Mineralogy and/ or organic matter content act as primary attributes allowing correlation of these soil phosphorus fractions with the spectra, mainly at wavelengths between 450-550, 900-1100 nm, near 1400 nm and between 2200-2300 nm. However, the regression models generated were not suitable for quantitative phosphate analysis. Solubilization of organic matter and reactions during the P-M extraction process hindered correlations between the spectra and these P soil fractions. For P-rem,, the presence of Ca in the extractant and preferential adsorption by gibbsite and iron oxides, particularly goethite, obscured correlations with the spectra.
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