Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Biosystems Engineering 448-452 2008 fdi:010042712 ENG Biosystems Engineering 1537-5110 ISI:000258015600015 3 10.1016/j.biosystemseng.2008.04.008 https://www.documentation.ird.fr/hor/fdi:010042712 https://www.documentation.ird.fr/intranet/publi/2008/08/010042712.pdf 100 Horizon (IRD) Increasing attention is being paid to near-infrared reflectance (NIR) spectroscopy for the rapid and cost-effective determination of soil carbon (C) and nitrogen (N) contents. The objective of the present paper was to compare the performances of two spectrometers: one covered the visible and NIR ranges (Vis-NIR, 350-2500 nm) and included a fibre-optic probe and the other covered the NIR range only (1100-2500 nm) and included a sample transport module. The comparison was carried out on two sets of clayey (n = 97) and sandy (n = 72) soil samples from tropical Africa and America. On the whole, both technologies provided good calibrations (R-2>0.74) and predictions (R-2>0.62) of soil C and N contents. The most accurate calibrations were achieved with the NIR spectrometer (R-2>0.86), which also yielded the most accurate predictions for the sandy soils (R-2 = 0.90 and standard error of prediction < 15% of the mean). For the clayey soils, the best predictions of both spectrometers were similar (R-2 >= 0.68 and standard error of prediction <20% of the mean). Using first or second derivatives of spectra did not affect calibration but had an impact on validation. 068 UR179