BOOK OF ABSTRACTS 187 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Analysis and Characterization P1.6 Determination of Soil Organic Matter Quality in Agricultural Soils Using NIR Spectroscopy Ladislav Menšík1, Lubica Pospíšilová2, Pavel Nerušil3, Jana Plisková3, Michaela Smatanová4, Jiří Balík5 1 Division of Crop Management Systems, Czech Agrifood Research Centre, Drnovská 507/73, 161 00 Prague, Czech Republic; ladislav.mensik@carc.cz 2 Mendel University in Brno 3 Czech Agrifood Research Centre 4 Central Institute for Supervising and Testing in Agriculture 5 Czech University of Life Sciences Prague A modern and highly promising area of research for determining carbon content and its fractions in soil is the use of near-infrared spectroscopy [NIRS]. Based on characteristic absorption bands in the measured spectra, and following appropriate chemometric analysis (e.g., principal component regression [PCR], partial least squares regression [PLSR], modified PLSR [MPLSR], and other methods), the content of specific chemical components in a sample can be quantified. Compared with conventional laboratory methods, NIRS is inexpensive, fast, and non-destructive; it produces no chemical byproducts and requires minimal sample preparation, making it highly attractive [1–4]. The aim of this study is to present the latest methods for determining the qualitative parameters of soil organic matter [SOM] such as soil organic carbon [SOC], humic substances [HS], humic acids [HA], fulvic acids [FA], and colour quotient [Q4/6] in dried and sieved soil samples using NIRS. This is demonstrated using examples from various long-term research experiments conducted by the Czech Agrifood Research Centre and the Central Institute for Supervising and Testing in Agriculture, as well as from operational research plots at the agricultural company AGROSPOL, Knínice, under various soil (e.g., Chernozem, Luvisol, and Cambisol) and climatic conditions in the Czech Republic. The assessed parameters of soil organic matter content and quality were determined by traditional standard laboratory methods and subsequently analysed by near-infrared spectroscopy with a FOSS NIRSystems 6500 instrument (FOSS NIRSystems, Inc., Silver Spring, MD, USA). Calibration equations were developed using the multivariate calibration methods PCR, PLSR, and MPLSR. Calibration equations for measuring SOC, HS, HA, FA, Q4/6, and other parameters in soil using NIRS were developed based on samples collected from various regions of the Czech Republic (e.g., from long-term field
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