Soil spectral library of the ‘Chimiometrie 2006’ challenge. The database contains absorbance spectra of dried and sieved soil samples measured between 1100 nm and 2498 nm at 2 nm interval. The soil samples come from agricultural fields collected from all over the Walloon region in Belgium. Three parameters are associated with the spectral library: Nt (Total Nitrogen in g/Kg of dry soil), CEC (Cation Exchange Capacity in meq/100 g of dry soil) and Ciso (Carbon in g/100 g of dry soil). Carbon content has been measured following the ISO14235 method.