Determination of soil organic carbon and nitrogen at the field level using near-infrared spectroscopy

This study explored the use of near-infrared spectroscopy (NIRS) for the rapid analysis of organic C (C(org)) and organic N (N(org)) in the A horizon of soil within a single field. Soil was sampled throughout a field in Manitoba, Canada to capture soil variability associated with topography. The soi...

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Bibliographic Details
Published in:Canadian journal of soil science 2002-11, Vol.82 (4), p.413-422
Main Authors: Martin, P.D, Malley, D.F, Manning, G, Fuller, L
Format: Article
Language:English
Subjects:
acid treatment
carbon sequestration
carbonates
combustion
landscapes
least squares
linear models
monitoring
near-infrared spectroscopy
nitrogen
nitrogen content
principal component analysis
rapid methods
soil heterogeneity
soil organic carbon
soil sampling
topography
variance
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Summary:This study explored the use of near-infrared spectroscopy (NIRS) for the rapid analysis of organic C (C(org)) and organic N (N(org)) in the A horizon of soil within a single field. Soil was sampled throughout a field in Manitoba, Canada to capture soil variability associated with topography. The soil samples were oven-dried and treated with acid to remove carbonates, after which C and N were determined by dry combustion. In this study, portions of the dried soil samples not treated with acid were scanned with a near-infrared scanning spectrophotometer between 1100 and 2500 nm. Correlating the spectral and the chemical analytical data using multiple linear regression or principal component analysis/partial least squares regression gave useful correlations for C(org). Over the range of 0–40 mg g-1 C(org), NIR-predicted values explained 75–78% of the variance in the chemical results. Results were improved to 80% for calibrations developed for the 0–20 mg g-1 organic C range. Useful results were not obtained for N(org) although the literature shows that total N in soil is predictable using NIRS. It is likely that the acid treatment altered the composition of the samples in an inconsistent manner such that the chemically analyzed samples and those scanned by NIRS were different from each other in N(org) concentration or composition. Extrapolation of these C(org) results to the landscape scale implies that NIRS has potential to be a suitable method for mapping C for the purposes of monitoring C sequestration.
ISSN:0008-4271
1918-1841
DOI:10.4141/S01-054