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Open AccessArticle

Simplifying Sample Preparation for Soil Fertility Analysis by X-ray Fluorescence Spectrometry

1
Laboratory of Precision Agriculture (LAP), Department of Biosystems Engineering, “Luiz de Queiroz” College of Agriculture (ESALQ), University of São Paulo (USP), Piracicaba, São Paulo 13418900, Brazil
2
Laboratory of Analytical Chemistry (LQA), Center for Nuclear Energy in Agriculture (CENA), University of São Paulo (USP), Piracicaba, São Paulo 13416000, Brazil
3
Laboratory of 14 Carbon (LC14), Center for Nuclear Energy in Agriculture (CENA), University of São Paulo (USP), Piracicaba, São Paulo 13416000, Brazil
4
Laboratory of Nuclear Instrumentation (LIN), Center for Nuclear Energy in Agriculture (CENA), University of São Paulo (USP), Piracicaba, São Paulo 13416000, Brazil
*
Author to whom correspondence should be addressed.
This paper is an extended version of our paper published in “Sample preparation for assessing the potential use of XRF on soil fertility analysis”. In Proceedings of the 5th World Workshop on Proximal Soil Sensing, Columbia, MO, USA, 28−31 May 2019.
Sensors 2019, 19(23), 5066; https://doi.org/10.3390/s19235066
Received: 26 August 2019 / Revised: 13 October 2019 / Accepted: 15 November 2019 / Published: 20 November 2019
(This article belongs to the Special Issue Smart Sensing Technologies for Agriculture)
Portable X-ray fluorescence (pXRF) sensors allow one to collect digital data in a practical and environmentally friendly way, as a complementary method to traditional laboratory analyses. This work aimed to assess the performance of a pXRF sensor to predict exchangeable nutrients in soil samples by using two contrasting strategies of sample preparation: pressed pellets and loose powder (<2 mm). Pellets were prepared using soil and a cellulose binder at 10% w w−1 followed by grinding for 20 min. Sample homogeneity was probed by X-ray fluorescence microanalysis. Exchangeable nutrients were assessed by pXRF furnished with a Rh X-ray tube and silicon drift detector. The calibration models were obtained using 58 soil samples and leave-one-out cross-validation. The predictive capabilities of the models were appropriate for both exchangeable K (ex-K) and Ca (ex-Ca) determinations with R2 ≥ 0.76 and RPIQ > 2.5. Although XRF analysis of pressed pellets allowed a slight gain in performance over loose powder samples for the prediction of ex-K and ex-Ca, satisfactory performances were also obtained with loose powders, which require minimal sample preparation. The prediction models with local samples showed promising results and encourage more detailed investigations for the application of pXRF in tropical soils. View Full-Text
Keywords: precision agriculture; X-ray fluorescence; spectroscopy; soil nutrients; proximal soil sensing; soil testing precision agriculture; X-ray fluorescence; spectroscopy; soil nutrients; proximal soil sensing; soil testing
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MDPI and ACS Style

Tavares, T.R.; Nunes, L.C.; Alves, E.E.N.; Almeida, E.; Maldaner, L.F.; Krug, F.J.; Carvalho, H.W.P.; Molin, J.P. Simplifying Sample Preparation for Soil Fertility Analysis by X-ray Fluorescence Spectrometry. Sensors 2019, 19, 5066.

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