Rapid Assessment of Soil Quality Indices Using Infrared Reflectance Spectroscopy

In this present study, we investigated the use of near infrared reflectance spectroscopy (NIRS) as a rapid and robust method to assess and evaluate soil quality namely soil carbon organic (SOC) and pH. Diffuse reflectance spectral data were acquired and recorded for 20 g soil samples from four different site locations in Aceh province. Spectra data, in the wavelength range of 1000-2500 nm, were corrected and enhanced using de-trending (DT). Actual SOC and pH parameters were measured using standard laboratory procedures whilst prediction models, used to predict SOC and pH of soil samples, were established using integration principal component analysis and multiple linear regression (PCA+MLR) approach. Prediction performances were evaluated and justified based on statistical indicators: coefficient correlation (r), root mean square error (RMSE) and residual predictive deviation (RPD) index. The results showed that both soil quality indices (SOC and pH) can be predicted simultaneously with coefficient maximum correlation (r) were 0.97 for SOC and 0.99 for pH, whereas residual predictive deviation (RPD) indexed were 4.84 for pH and 3.96 for SOC respectively. It may conclude that near-infrared reflectance spectroscopy can be used as a fast, robust and accurate method in assessing soil quality indices in the form of soil carbon organic (SOC) and pH simultaneously.