Use of Near Infrared Reflectance Spectroscopy (NIRS) to determine the Indicator of Residual Organic C in soil (IROC) and RothC model pools of Exogenous Organic Matters

The use of Exogenous Organic Matter (EOM) in croplands can contribute to increase soil organic matter (SOM) content and improve soil fertility. Several tools can be used to evaluate the potential C incorporation in soils after EOM application: (i) IROC, indicator of residual organic C, corresponding to the proportion of residual C from EOM incorporated into SOM (ii) multi-compartment models such as RothC simulating the long term C evolution in soil. The indicator IROC is calculated from the proportion of EOM C mineralized after 3 days of incubation and from biochemical fractions determined by laboratory measurements which are rather costly, time consuming and generating polluting wastes. The C dynamic models are poorly parameterized for the use of EOM. There is a need to find more effective methods to either determine the IROC or the RothC model pools for a large variety of EOMs. Near Infrared Reflectance Spectroscopy (NIRS) has been shown to be a suitable and promising method to predict various characteristics in soils or for EOMs. The objective of the study was to assess the potential use of NIRS to determine for 441 EOMs of various origins the IROC indicator and RothC model pools. The indicator IROC was correctly predicted using NIRS, with fairly good R² and RPD (ratio of standard deviation of the reference data to standard error of cross-validation or standard error of prediction) for the both calibration and validation subsets (R²=0.87 and 0.79, RPD=2.6 and 2.1, respectively). The proportions of EOM carbon into RothC pools DPM (labile), RPM (resistant) and HUM (humified) were calculated by fitting RothC to C mineralization kinetics measured during 91-days laboratory incubations. RothC was well adjusted to incubations data (mean R²=0.98, mean RMSE=2.6, n=441). The DPM pool and IROC were highly negatively correlated (r=-0.88). The prediction of DPM pools using NIRS was promising with R²=0.85 and 0.67 and RPD=2.4 and 1.7 for the calibration and validation subsets, respectively. The results obtained show that NIRS can be used as a rapid and inexpensive method to determine the IROC indicator and to estimate the RothC DPM pools fitted to laboratory incubations data. (Texte integral)

Bibliographic Details

Main Authors:	Peltre, C., Houot, Sabine, Barthès, Bernard, Brunet, Didier, Martin, Manuel, Thuriès, Laurent
Format:	conference_item biblioteca
Language:	eng
Published:	Program and abstracts of the International symposium on"Soil Organic Matter Dynamics: Land Use
Subjects:	U30 - Méthodes de recherche, P33 - Chimie et physique du sol, Q70 - Traitement des déchets agricoles,
Online Access:	http://agritrop.cirad.fr/568688/ http://agritrop.cirad.fr/568688/1/document_568688.pdf
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