Contents lists available at ScienceDirect Geoderma journal homepage: www.elsevier.com/locate/geoderma Performance comparison between a miniaturized and a conventional near infrared reflectance (NIR) spectrometer for characterizing soil carbon and nitrogen Bernard G. Barthès a, ⁎ , Ernest Kouakoua a , Michaël Clairotte a,1 , Jordane Lallemand b , Lydie Chapuis-Lardy c,d , Michel Rabenarivo e , Sylvie Roussel b a Eco&Sols, Université de Montpellier, Cirad, Inra, IRD, Montpellier SupAgro, Montpellier, France b Ondalys, Clapiers, France c Eco&Sols, Université de Montpellier, Cirad, Inra, IRD, Montpellier SupAgro, Dakar, Senegal d LMI Iesol, IRD, Dakar, Senegal e Laboratoire des Radio-Isotopes, Université d'Antananarivo, Antananarivo, Madagascar ARTICLE INFO Handling Editor: Alex McBratney Keywords: Near infrared reflectance spectroscopy (NIRS) Soil organic carbon Soil total nitrogen Microspectrometer Madagascar ABSTRACT Miniaturized near infrared spectrometers are now available, at more affordable prices than conventional spec- trometers, but their performances have been poorly studied to date. This paper aimed at comparing the per- formances of the JDSU MicroNIR 2200 spectrophotometer (weight < 0.1 kg) with those of a conventional bench-top instrument for predicting carbon and nitrogen contents in laboratory conditions, on a range of re- presentative Malagasy soils. Though its noticeably narrower and less resolved spectra (1151–2186 nm at 8.15 nm step vs. 1100–2498 nm at 2 nm step), the microspectrometer yielded predictions in independent validation that were almost as accurate as those of the conventional instrument (standard errors of prediction were 4.6 vs. 3.4 gC kg -1 , but 3.9 vs. 3.4 gC kg -1 after bias correction, and 0.36 vs. 0.35 gN kg -1 , respectively). Due to noisy features, the MicroNIR spectra needed mathematical pretreatment (e.g. standard normal variate SNV), and bias correction for C, for providing accurate predictions, while the raw absorbance spectra from the conventional instrument did not. Furthermore, building multivariate models with MicroNIR spectra required less latent variables than with their conventional counterparts, and these models were less prone to performance degradation when applied to in- dependent validation samples. Fitting the spectra of the conventional instrument to those of the MicroNIR (1150–2182 nm at 2 or 8 nm step) showed that (moderately) less accurate MicroNIR predictions could be firstly attributed to narrower spectral range rather than to poorer resolution. Considering their performances, such microspectrometers could thus represent a cost-effective alternative to conventional spectrometers. They have now to be tested in field conditions. 1. Introduction Facing the increase in the global food demand while limiting the carbon footprint of agroecosystems requires optimizing soil manage- ment, which in turn requires characterizing soil properties more ex- tensively (Krishna, 2014; Oelbermann, 2014). This can hardly be achieved using conventional characterization approaches, especially physico-chemical analyses, which are often time-consuming and ex- pensive. Near infrared reflectance (NIR) spectroscopy (NIRS) has been reported to provide accurate determination of many soil properties time- and cost-effectively (Stenberg et al., 2010; Soriano-Disla et al., 2014). However, even though characterizing one sample by NIRS is cheap, as it does not require any laboratory supply, buying a NIR spectrometer remains rather expensive (> 40 k€ in general). Nowa- days, a new generation of spectrometers is available, much smaller in size and at more affordable prices; but the performances of these spectrometers have been poorly studied to date (O'Brien et al., 2013; Sun et al., 2016; Urraca et al., 2016), especially regarding the https://doi.org/10.1016/j.geoderma.2018.12.031 Received 27 February 2018; Received in revised form 26 November 2018; Accepted 17 December 2018 ⁎ Corresponding author. E-mail addresses: bernard.barthes@ird.fr (B.G. Barthès), michael.clairotte@ec.europa.eu (M. Clairotte), jlallemand@ondalys.fr (J. Lallemand), lydie.lardy@ird.fr (L. Chapuis-Lardy), sroussel@ondalys.fr (S. Roussel). 1 Present address: European Commission Joint Research Centre, Directorate for Energy, Transport and Climate, Sustainable Transport Unit, Ispra, Italy. Geoderma 338 (2019) 422–429 0016-7061/ © 2018 Elsevier B.V. All rights reserved. T