IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 188 Poster Session / Analysis and Characterization Hall A experiments and operational research plots). These equations achieved a high degree of agreement between laboratory methods and NIRS measurements. This agreement is expressed by the coefficient of determination (R²): for SOC calibration, R² = 0.89–0.96; and for SOC validation, R² = 0.87–0.97. Furthermore, for the fractionation of humic substances (HS, HA, FA), the calibration R² ranged from 0.77 to 0.93, and the validation R² from 0.78 to 0.92. For the colour quotient (Q4/6) parameter, a very high agreement with the laboratory method was achieved (calibration R² = 0.91–0.97; validation R² = 0.87–0.94), as well as aromaticity index (iAR) and potential wettability index (PWI) parameters (calibration R² = 0.93–0.94; validation R² = 0.88–0.89). Both the number of calibration samples (a larger sample size yields better calibration parameters) and the heterogeneity of conditions (such as soil type and climatic conditions) significantly affect prediction accuracy. NIRS analysis requires only a small amount of soil sample (approximately 5–10 g). The main advantages of this method include workplace safety and environmental friendliness, as no materials are consumed and no chemical waste is generated. Overall, the measurements are fast (taking about 2–5 minutes, depending on instrument settings), highly accurate, safe, environmentally benign, and cost-effective. References 1. K. Heil and U. Schmidhalter, Sensors 2021, 21, 4, 1423. 2. W. Zhou et al., J Soils Sediments 2023, 23, 6, 2506–2517. 3. J. L. Safanelli et al., PLoS One 2025, 20, 1, e0296545. 4. S. Poudel et al., Environ Syst Res 2026, 15, 17. Acknowledgement This research was supported by the Ministry of Agriculture of the Czech Republic (NAZV, projects QK21010124 and QL26010085) and by institutional support MZE-RO0426.
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