meth_2.26 Soil visible-near infrared vis-NIR spectra for BASE samples

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Citation: Viscarra Rossel, R. A., T. Behrens, E. Ben-Dor, D. J. Brown, J. A. M. Demattê, K. D. Shepherd, Z. Shi, B. Stenberg, A. Stevens, V. Adamchuk, H. Aïchi, B. G. Barthès, H. M. Bartholomeus, A. D. Bayer, M. Bernoux, K. Böttcher, L. Brodský, C. W. Du, A. Chappell, Y. Fouad, V. Genot, C. Gomez, S. Grunwald, A. Gubler, C. Guerrero, C. B. Hedley, M. Knadel, H. J. M. Morrás, M. Nocita, L. Ramirez-Lopez, P. Roudier, E. M. Rufasto Campos, P. Sanborn, V. M. Sellitto, K. A. Sudduth, B. G. Rawlins, C. Walter, L. A. Winowiecki, S. Y. Hong, and W. Ji.  (2016). A global spectral library to characterize the world’s soil. Earth-Science Reviews, 155, 198-230. doi:https://doi.org/10.1016/j.earscirev.2016.01.012

AM Project ID: AM_BASE

Soil samples were sub-sampled as outlined in Bissett et al., (2016). For spectroscopic analysis, sub-samples were air-dried and crushed to a particle size of approximately 2mm. Visible-near infrared (vis-NIR) spectra was measured as described in Viscarra Rossel et al., (2016). We measured the diffuse reflectance spectra of air-dried, 2 mm sieved soil samples with a Labspec 2500 vis–NIR spectrometer (Analytical Spectral Devices, PaNalytic, Boulder, Colorado, USA) following the protocols described in Viscarra Rossel et al. (2016). The spectrometer has a spectral range from 350 to 2500 nm. The measurements were made with its high intensity contact probe (PaNalytic, Boulder, Colorado, USA), and a Spectralon^® white reference panel was used for calibration once every 10 measurements. For each soil measurement, 30 spectra were averaged to improve the signal-to-noise ratio. We collected spectra with a sampling resolution of 1 nm so that each spectrum comprised 2151 wavelengths.