Development and validation of a portable X-ray fluorescence approach for quantifying silicon in plants

Background and Aims: Portable X-ray fluorescence spectrometry (pXRF) has emerged as a robust analytical approach for elemental determination in plant tissues, enabling rapid, non-destructive, and reagent-free measurements. This study developed and validated an empirical calibration of pXRF for quantifying silicon (Si) in plants, using autoclave-induced digestion (AID) as the reference method. Methods A total of 374 samples from seven plant species (rice, maize, soybean, cowpea, sorghum, lettuce, and beet) were analyzed. Silicon concentrations obtained via AID ranged from 1.07 to 19.23 g kg ⁻ ¹ (mean = 4.48 g kg ⁻ ¹; coefficient of variation = 67%), reflecting substantial interspecific variability. Each sample was also analyzed by pXRF under optimized instrumental conditions, and a calibration model was constructed using 75% of the dataset to predict Si concentrations relative to AID values. Results The pXRF calibration exhibited a strong linear relationship with AID results (R² = 0.94; R = 0.97; p < 0.001). Validation using the remaining 25% of samples confirmed high predictive accuracy, with consistent performance across all species, particularly rice (R = 0.96) and soybean (R = 0.93). Conclusions The pXRF exhibited excellent agreement with the reference method and high predictive accuracy, while markedly reducing analytical time and eliminating the use of hazardous reagents. These results establish pXRF as a reliable, rapid, and sustainable alternative for large-scale Si monitoring in both agronomic and environmental applications.