NIR analysis as an integrated tool for the assessment of soil quality

Abstract

Near infrared reflectance spectroscopy (NIRS) is a rapid, non-destructive, reproducible and cost-effective analytical method involving diffuse reflectance measurement in the near infrared region (NIR; 780-2500 nm). A NIR sensing device able to collect in-situ 3D spectral data through an entire soil profile, allowing a rapid and objective soil classification. A set of regression methods allows the prediction of many properties of unknown samples using calibration equations that relate spectral information to sample properties measured by conventional methods, within a calibration subset. soil quality (pH, organic C, total N, P, Ca, Mg, K, CEC, clay, silt) and developed ordinal soil condition classes (poor, average, good), which were used to identify spectral wavebands that could diagnose soil condition. They found that five wavelengths were related to their soil quality index: relative reflectance at 570, 1410, 2040 and 2390 nm were negatively correlated with soil condition class whereas relative reflectance at 1940 nm (which is almost certainly due to O–H bond of water) was positively correlated with soil condition class.