Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2024307 | Soil Biology and Biochemistry | 2016 | 8 Pages |
Abstract
Mid-infrared spectroscopy has been used with various degrees of success in quantitative and qualitative analysis of soil organic matter (SOM). This study evaluated the spectral interference caused by soil carbonates on the feasibility of using the specific peak area approach obtained by diffuse reflectance infrared Fourier transform spectroscopy in mid-range (midDRIFTS) as an indicator of SOM quality and composition. A midDRIFTS peak area corresponding to more labile SOM compounds (2930 cmâ1) was related to microbial biomass carbon and nitrogen (Cmic, Nmic) and hot water extractable carbon and nitrogen (CHWE, NHWE) across two contrasting agroecological regions (Kraichgau (K) and Swabian Alb (SA), Germany) with soils containing carbonates up to 41 g kgâ1 soil. Although, the 2930 cmâ1 peak showed its potential use as an index for representing labile soil carbon, a poor regression performance between the relative peak area at 2930 cmâ1 (rPAnt 2910 cmâ1) and labile SOM fractions (R2 = 0.31-0.45) was attributed to inorganic carbon (IC) potentially interfering with this particular peak. To avoid carbonate interference, a spectral-based coefficient was developed using a multiple linear regression model consisting of TOC and TIC as predictors of the difference between peak areas at 2930 cmâ1 of non-acid and acid treated spectra (ÎPA 2930 cmâ1) of bulk soils. Peak areas at 2930 cmâ1 of non treated spectra (PAnt 2930 cmâ1) were corrected using a coefficient of 0.21 for carbonates (PAcorr 2930 cmâ1), which greatly improved relationships with Cmic, Nmic, CHWE and NHWE (R2 = 0.68-0.75; P < 0.0001). We further developed a regression equation to correct PAnt 2930 cmâ1 for future application using the relationship between PAnt 713 cmâ1 (assigned for carbonates (mainly calcite)) and PA at 2930 cmâ1 (ÎPATIC 2930 cmâ1) (R2 = 0.98). We concluded that PA 2930 cmâ1 has a high potential to be used as an indicator of SOM composition once carbonate interference is corrected for in carbonated containing soils. The proposed approach is free of multivariate calibration and the spectral index developed (PAcorr 2930 cmâ1) is suited to predict accurately labile SOM without the need of additional laboratory measurements. For general applicability of the approach, it should be tested on additional soil types of varying TOC and TIC contents.
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Agricultural and Biological Sciences
Soil Science
Authors
R. Mirzaeitalarposhti, M.S. Demyan, F. Rasche, G. Cadisch, T. Müller,