Laser-Induced Breakdown Spectroscopy (LIBS) for tropical soil fertility analysis

Author(s)

Tavares, Tiago R. ^{[1, 2]} ; Mouazen, Abdul M. ^[3] ; Nunes, Lidiane C. ^[1] ; dos Santos, Felipe R. ^[4] ; Melquiades, Fabio L. ^[4] ; da Silva, Thainara R. ^[5] ; Krug, Francisco J. ^[1] ; Molin, Jose P. ^[2]

Affiliation

^[1] Univ Sao Paulo, Ctr Nucl Energy Agr CENA, BR-13416000 Piracicaba, SP - Brazil

^[2] Univ Sao Paulo, Luiz de Queiroz Coll Agr ESALQ, Dept Biosyst Engn, Lab Precis Agr LAP, BR-13418900 Piracicaba, SP - Brazil

^[3] Univ Ghent, Fac Biosci Engn, Dept Environm, Precis Soil & Crop Engn Grp Precis SCoRing, Coupure Links 653, Blok B, 1st Floor, B-9000 Ghent - Belgium

^[4] Londrina State Univ UEL, Dept Phys, Lab Appl Nucl Phys LFNA, BR-86057970 Londrina, Parana - Brazil

^[5] Univ Sao Paulo, Fac Anim Sci & Food Engn FZEA, Dept Biosyst Engn, Lab Agr Machinery & Precis Agr LAMAP, BR-13635900 Pirassununga, SP - Brazil

• Document type: Journal article
• Source: SOIL & TILLAGE RESEARCH; v. 216, FEB 2022.
• Web of Science Citations: 0

Abstract

The Laser Induced Breakdown Spectroscopy (LIBS) is a promising technique for soil fertility analysis in a rapid and environmentally friendly way. This application requires the selection of an optimal modelling procedure capable of handling the high spectral resolution of LIBS. This work aimed at comparing different modelling methods of LIBS data for the determination of key fertility attributes in Brazilian tropical soils. A benchtop LIBS system was used for the analysis of 102 soil samples, prepared in the form of pressed pellets. Models for the prediction of clay, organic matter, pH, cation exchange capacity, base saturation, and the extractable nutrients P, K, Ca, and Mg were developed using univariate linear regression (ULR), multiple linear regression (MLR) and partial least squares regression (PLS). The following input data for PLS were used: (i) the full spectra from 200 to 540 nm (38,880 variables), and (ii) variables selected by the interval successive projections algorithm (iSPA). The multivariate models achieved satisfactory predictions {[}residual prediction deviation (RPD) > 1.40] for eight out of nine fertility attributes. However, the best performances were obtained for the PLS with the variable ranges selected by the iSPA, which achieved satisfactory predictions (RPD >= 1.44) for seven out of the nine soil attributes studied. The MLR method obtained lower prediction performance than the iSPA-PLS using only 21 variables. The iSPA-PLS approach allowed a reduction from 3 to 160-fold in the total of variables compared to the full LIBS spectra, making it efficient and accurate modelling method that uses reduced number of variables. Although LIBS technique proved to be efficient for predicting fertility attributes in tropical soils, further research is encouraged in order to reduce the amount of sample preparation conducted in this study. (AU)

• FAPESP's process: 04/15965-2 - Implementation and development of Laser Induced Breakdown Spectroscopy (LIBS)
• Grantee: Francisco José Krug
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/21969-0 - Evaluation of alternative techniques to traditional laboratory analysis for prediction of attributes in agricultural soils: approaches using VisNIR, XRF and LIBS spectroscopy
• Grantee: Tiago Rodrigues Tavares
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 20/16670-9 - Spectral data modelling for tropical soil fertility analysis: association of vis-NIR and XRF techniques for the modernization of the traditional methods of analysis
• Grantee: Tiago Rodrigues Tavares
• Support Opportunities: Scholarships in Brazil - Post-Doctoral