Rapid measurement of zinc contents in soils by near-infrared diffuse reflectance spectroscopy

The quantification model of zinc rapid analysis in the soils was established by using near-infrared diffuse reflectance spectroscopy and a Partial Least Square (PLS) method, and the optimal measured wave band was also selected. All the samples were divided into calibration set and prediction set based on the prediction effect of single wavelength model, and then the spectra were pretreated by Multiplicative Scatter Correction (MSC) and Savitzky-Golay (SG) smoothing methods. The following five wave bands, the whole region 400-2500 nm, 400-1100 nm, 1100-1900 nm, 1900-2500 nm, 580-900 nm were selected, and 15 calibration models were constructed for each band selected by the original spectra, the first derivative spectra and the second derivative spectra respectively. By simultaneous adjusting the numbers of SG smoothing points and PLS factors, the PLScomputational experiments for each model were carried out and the best model was selected according to the prediction effect. The results indicate that the prediction effect of the model using the first derivative spectra in 1900-2500 nm is the best, and its prediction correlation coefficient (RP), RMSEP and RRMSEP are 0.806, 31.0 mg/kg, and 19.96% respectively. Obtained results show that 1900-2500 nm can replace the whole band to get a better calibration effect, and can provide a basis for the design of special soil near-infrared spectroscopy instruments.