Foliar analysis using near infrared reflectance spectroscopy

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Abstract
Near infrared reflectance spectroscopy was evaluated as a method for measuring nitrogen and lignin content in foliage of native forest and prairie species. Near infrared reflectance spectra (1590 to 2357 nm) were obtained for 163 samples of dried green leaves and leaf litter from 18 deciduous and 2 coniferous tree species. Forty additional spectra were obtained from grass species. Reflectance (R) spectra were recorded as log (1/R) and transformed to the first and second derivative of log (1/R). Multiple linear regressions, predicting wet chemistry values based on near infrared reflectance spectra, yielded correlation coefficients of 0.98 for Kjeldahl nitrogen and 0.78 for lignin, with standard errors of 0.11% for nitrogen and 2.9% for lignin. Results suggest that near infrared reflectance spectroscopy is very effective for rapid (approximately 2 min per sample) determination of foliar lignin and nitrogen and should be considered for use as a routine analytical method.