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Abstract
Lignin plus cutin (LIC) content and biological stability index (BSI) are well-recognized indexes of potentially recalcitrant carbon (C) in organic products, and C / nitrogen (N) and lignin/N ratios have been related to potentially mineralizable N (PMN). Our objective was to use Fourier-transform near-infrared (FT-NIR) spectroscopy to estimate PMN and BSI of plant residues, composts, and manures. We also evaluated FT-NIR for determining the C/N, LIC/N, and BSI/N ratios as indexes of N mineralization in selected organic products. We analyzed 148 organic products for biochemical composition and total C and N. A subset of 10 products was incubated in a sandy soil to determine PMN. The FT-NIR successfully determined lignin and cutin (LIC) and BSI from r2, the ratio of prediction to standard deviation, and the ratio error range criteria. The PMN was less closely related to the C/N ratio (r2 = 0.64) than the BSI/N (r2 = 0.84) and LIC/N (r2 = 0.87) ratios. There was some N immobilization at an early stage of incubation when C/N, LIC/N, and BSI/N ratios exceeded 14, 10, and 15, respectively. There is a need to characterize a larger number of organic compounds in the soluble and LIC fractions to improve the BSI equation.
Acknowledgments
We acknowledge the financial support of the Fonds Québécois de Recherches sur la Nature et les Technologies (FQRNT Industrial Fellowship Program and Centre SÈVE), the Conseil des recherches en pêche et en agroalimentaire du Québec (CORPAQ 603015), Agrégats Waterloo Inc., Cultures Dolbec Inc., Ferme Daniel Bolduc et Fils (1980) Inc., and the Natural Sciences and Engineering Research Council of Canada (CRDPJ 305166-03 and BPRDI 6715-2005-335759). We also thank Marie-Hélène Lamontagne and Rahima Abdelhafid for technical support.