Prediction of multiple soil fertility parameters using VisNIR spectroscopy and PXRF spectrometry

Abstract

Visible and near-infrared (VisNIR) spectroscopy and portable X-ray fluorescence (PXRF) spectrometry are successful in estimating soil attributes. However, it is still necessary to investigate their performance in estimating soil fertility properties. In this study, for the soil fertility properties of soil organic C (SOC), available N, total P, available P, total K, and available K, the performance of using VisNIR and PXRF individually and combined, three data fusion methods (concatenation, model fusion and model averaging), and two modeling methods was evaluated. The results showed that combining VisNIR and PXRF did not substantially improve the prediction accuracy of SOC, total P, total K and available K. Using VisNIR alone could predict them well, achieving the best prediction in total K (R 2 = .90, ratio of performance to interquartile distance [RPIQ] = 5.08, and residual prediction deviation [RPD] = 3.13), followed by SOC (R 2 = .77, RPIQ = 2.05, and RPD = 2.10), total P (R 2 = .63, RPIQ = 2.35, and RPD = 1.64), and available K (R 2 = .53, RPIQ = 2.04, and RPD = 1.41). Both available N and available P were poorly estimated by all the methods proposed in this study. Although PXRF alone could predict total P, total K, and available K with acceptable accuracy, it did not perform well on SOC (R 2 < .32, RPIQ < 1.16, and RPD < 1.19). Hence, for the precision application of organic and NPK fertilizers, VisNIR is supposed to be the optimal way to rapidly obtain soil information.

Prediction of Heavy Metal Concentrations in Contaminated Sites from Portable X-ray Fluorescence Spectrometer Data Using Machine Learning

“…Portable X-ray fluorescence (pXRF) spectrometers can provide simple, rapid, nondestructive, and cost-effective analysis of the metal contents in soils and have been widely used to assess environmental risks, predict soil properties, and evaluate soil fertility, among other uses [5][6][7][8][9]. According to the Chinese Standard Technical Guidelines for the Investigation on Soil Contamination of Land for Construction [10], the heavy metal rapid detector is recommended for the qualitative and quantitative analysis of heavy metals in soils in situ.…”