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Feature Article - Australian Journal of Soil Research, Volume 45 Number 2, 2007

The prediction of soil carbon fractions using mid-infrared-partial least square analysis
L. J. Janik A , J. O. Skjemstad A , K. D. Shepherd B and L. R. Spouncer A

A CSIRO, Land and Water, and CRC for Greenhouse Accounting, PMB No. 2, Glen Osmond, SA 5064, Australia.
B World Agroforestry Centre (ICRAF), PO Box 30677 – 00100, Nairobi, Kenya.
C Corresponding author. Email: jan.skjemstad@csiro.au
Abstract
This paper describes the application of mid-infrared (MIR) spectroscopy and partial least-squares (PLS) analysis to predict the concentration of organic carbon fractions present in soil. The PLS calibrations were derived from a standard set of soils that had been analysed for total organic carbon (TOC), particulate organic carbon (POC), and charcoal carbon (char-C) using physical and chemical means. PLS calibration models from this standard set of soils allowed the prediction of TOC, POC, and char-C fractions with a coefficient of determination (R2) of measured v. predicted data ranging between 0.97 and 0.73. For the POC fraction, the coefficient of determination could be improved (R2 = 0.94) through the use of local calibration sets. The capacity to estimate soil fractions such as char-C rapidly and inexpensively makes this approach highly attractive for studies where large numbers of analyses are required. Inclusion of a set of soils from Kenya demonstrated the robustness of the method for total organic carbon and charcoal carbon prediction.
Keywords: mid infrared, MIR, PLS, organic carbon, TOC, carbon fractions, charcoal.

Australian Journal of Soil Research 45(2) 73–81

Submitted: 6 July 2006  -  Accepted: 19 December 2006 -   Published: 28 March 2007
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