The potential of near-infrared reflectance spectroscopy to analyse soil chemical and physical characteristics

Near-infrared reflectance spectroscopy (NIRS) was used for the analysis of soil samples for silt, sand, clay, calcium (Ca), potassium (K), sodium (Na), magnesium (Mg), copper (Cu) and iron (Fe). A total of 332 samples of different soils from Uruguay (South America) were used. The samples were scanned in a NIRS 6500 (NIRSystems, Silver Spring, MD, USA) in reflectance. Cross validation was applied to avoid overfitting of the models. The coefficient of determination in calibration (R) and the standard errors in cross validation (SECV) were 0.80 (SECV: 6.8), 0.84 (SECV: 6.0), 0.90 (SECV: 3.6) in per cent for sand, silt and clay respectively. For both macro and microelements the R and SECV were 0.80 (SECV: 0.1), 0.95 (SECV: 2.9), 0.90 (SECV 0.8), for K, Ca, Mg in g/kg respectively, and 0.86 (SECV: 0.82) and 0.92 (SECV: 25.5) for Cu and Fe in mg/kg. It was concluded that NIRS has a great potential as an analytical method for soil routine analysis due to the speed and low cost of analysis