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-cal(2)) 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-cal(2) 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.