Mobile Laser-Induced Breakdown Spectroscopy for Future Application in Precision Agriculture—A Case Study

Abstract

In precision agriculture, the estimation of soil parameters via sensors and the creation of nutrient maps are a prerequisite for farmers to take targeted measures such as spatially resolved fertilization. In this work, 68 soil samples uniformly distributed over a field near Bonn are investigated using laser-induced breakdown spectroscopy (LIBS). These investigations include the determination of the total contents of macro- and micronutrients as well as further soil parameters such as soil pH, soil organic matter (SOM) content, and soil texture. The applied LIBS instruments are a handheld and a platform spectrometer, which potentially allows for the single-point measurement and scanning of whole fields, respectively. Their results are compared with a high-resolution lab spectrometer. The prediction of soil parameters was based on multivariate methods. Different feature selection methods and regression methods like PLS, PCR, SVM, Lasso, and Gaussian processes were tested and compared. While good predictions were obtained for Ca, Mg, P, Mn, Cu, and silt content, excellent predictions were obtained for K, Fe, and clay content. The comparison of the three different spectrometers showed that although the lab spectrometer gives the best results, measurements with both field spectrometers also yield good results. This allows for a method transfer to the in-field measurements.

Advancing Soil Health: Challenges and Opportunities in Integrating Digital Imaging, Spectroscopy, and Machine Learning for Bioindicator Analysis

“…This model achieved high accuracy, indicated by an R 2 of 0.92. On the other hand, Erler et al 82 applied LIBS (wavelength 278−769 nm) for SOM measurement using pelleted soil samples. Principal component analysis (PCA) was applied for feature selection, and SVM regression was used for analysis, with 10-fold cross-validation and split data sets for validation.…”

Bayesian optimization of the conditions for highly sensitive detection of surface contamination by laser-induced breakdown spectroscopy

“…It was used only for multivariate regression analysis of soil nutrients. 19,20 This should be the first report on BO based on GPR in context with LIBS.…”