Portable X-ray fluorescence (pXRF) spectrometry applied to the prediction of chemical attributes in Inceptisols under different land uses

Abstract

Portable X-ray fluorescence (pXRF) spectrometry has been increasingly adopted for varying studies worldwide. This work aimed at characterizing effects of soil management on the content of chemical elements detected by pXRF in managed and unmanaged areas of Inceptisols, and evaluating the potential of using pXRF data to generate prediction models for soil fertility attributes, evaluating the effect of land uses on such models. Samples were collected in A, B, and C horizons of soils under native forest, native Cerrado, coffee crops with 1 and 5 years of implantation and eucalyptus. Soil fertility attributes were determined through laboratory analyses, whereas, elemental contents were obtained through pXRF analysis. PXRF data were used for modeling (regressions) and validation of soil fertility attributes and necessity of lime (NL) application, with or without distinction between managed and unmanaged areas. Management practices on coffee crops increased the levels of Sr, CaO, P2O5, Cu, and Zn. CaO content was efficient for prediction of exchangeable Ca2+ contents (R2 = 0.91), pH (R2 = 0.88), base saturation (R2 = 0.89) in managed areas. General models presented adequate results to predict exchangeable Ca2+ (R2 = 0.92), pH (R2 = 0.85), and base saturation (R2 = 0.90). Models for unmanaged areas were less effective. PXRF detected modifications in elemental contents caused by management practices and provided reliable predictions of soil fertility attributes.

Tropical Soil Toposequence Characterization via pXRF Spectrometry

“…This fact is also corroborated by the lack of Ca‐bearing minerals in quartzite‐derived soils (Araujo et al, 2014). Similar results were found in Inceptisols of the Brazilian Cerrado developed from phyllite (Teixeira et al, 2018; Silva et al, 2017).…”

“…This fact is also corroborated by the lack of Ca-bearing minerals in quartzite-derived soils (Araujo et al, 2014). Similar results were found in Inceptisols of the Brazilian Cerrado developed from phyllite (Teixeira et al, 2018;Silva et al, 2017). Since Y accumulates during weathering processes, a positive correlation with clay was observed in soils developed from parent materials other than quartzite (Marques et al, 2004b).…”

“…Some of those relationships were not found for soils derived from phyllite (Silva et al, 2018a). Finally, the strong correlations found herein indicate that the pXRF data can be used as basis for the development of prediction models for quantifying soil physicochemical properties, as already investigated in temperate regions (Sharma et al, 2014;Zhu et al, 2011;Rawal et al, 2019), and with initial efforts in tropical regions such as Brazil (Pelegrino et al, 2018;Teixeira et al, 2018).…”

“…The correlations between elemental contents obtained by pXRF and soil properties provide new insights of relationships (positive or negative correlation) previously less explored, mainly in quartzitederived soils, such as: Rb, Zn, K 2 O with silt content; Sr and Ti with soil fertility properties; Zn with fine sand content; and Zr and clay content. Others already reported in Brazilian soils (Silva et al, , 2018bTeixeira et al, 2018) include: CaO and exchangeable Ca 2+ , Mg 2+ , Al 3+ , pH, and other soil properties; SiO 2 and sand (positive) and clay (negative) content; and Al 2 O 3 with clay content. The relationships between the elemental contents obtained by pXRF may contribute to studies focusing on the understanding of the geochemical behavior of some elements, such as Ca with Sr, and K and Zn with Rb.…”

“…4. Cl and Zn were not detected by pXRF in the quartzite, but these elements were found in all soils, probably due to their addition in soils through anthropogenic activity (Teixeira et al, 2018). Singh et al (2017) analyzed 25 samples of quartzite from various stratigraphic regions in Cuddapah Basin, India, via wavelength dispersive x-ray fluorescence spectrometry, in which Cl was also not reported and Zn ranged from <10 to 75 mg kg -1 .…”