The usefulness of the Munsell colour indices for identification of drained soils with various content of organic matter

Abstract

Purpose: The aim of the study was to determine the usefulness of the Munsell colour indices for identification of drained soils with various content of organic matter, developed on the sandy substrate. Methods: The analysed soils, according to the Polish Soil Classification (PSC 2019), belong to thin murshic soils (WRB 2022: Murshic Histosols/Histic Gleysols), typical semimurshic soils (Mollic/Umbric Gleysols (Arenic, Drainic, Mulmic)) and to postmurshic soils (Umbric Gleysols (Arenic, Drainic, Nechic)). The following dry colour indices: value (V), chroma (Ch), V+Ch, V+0.5Ch, V×Ch and V/Ch, were correlated with soil variables (LOI, Corg., Ntot., C:N and FeHCl, MnHCl—elements extracted with 0.5 M HCl). Results: The strongest correlation with the SOM content was displayed by the Munsell value, which allows one to estimate the SOM, Corg., Ntot. content in the soils studied. The classification and regression trees (C&RT) revealed that the analysed soil materials could be successfully divided based on the Munsell value alone. The V/Ch quotient demonstrated significant correlations with LOI, Corg., Ntot., C:N, FeHCl and MnHCl. This quotient equalled 1–2 for murshic (≥ 12% Corg.) and semimurshic (≥ 6.0 Corg. < 12.0%), but varied greatly (1–5) for postmurshic (≥ 0.6 Corg. < 6.0% Corg.) soil materials. Conclusion: The analysed soil materials had the Munsell value differentiated enough to enable their identification. The V/Ch quotient can help to trace the origin of postmurshic soils. Its narrow value (1–2) indicates that the postmurshic soil developed through advanced transformation of murshic soil materials, whereas a broader value (2–5) indicates that the postmurshic soil originated from dewatered Gleysols.