Application of portable colorimeter for identification of mollic horizon and mollic-based soil groups

Abstract

Identifi cation of soil colours, which have crucial importance as diagnostic criteria for mollic horizon and mollic-based soil groups, is considered to be impacted by personal skill and experience of the researcher. The experiment with soil colour identifi cation in the fi eld using standard Munsell charts and the laboratory identifi cation by four groups of experts, as well as using the electronic portable colorimeter was conducted using 30 loess-and alluvium-derived soils. The manual fi eld identifi cation of mollic horizons by individual highly experienced researcher, based on colour value and chroma (using the Munsell charts), may be overestimated up to 17% compared to manual identifi cation by group of experts under laboratory conditions. The differences between groups of experts were statistically insignifi cant; however, a weak tendency to identify the lower value (dry) and higher chroma (moist) with increasing expert age or experience was observed (in the order: MSc students -PhD students -doctors -professors). No signifi cant difference in soil colour identification was observed in relation to gender of experts. An electronic measurement of soil colours by portable colorimeter confi rmed an overestimation of the manual identifi cation of mollic horizons by 17% and 7%, compared to individual (fi eld) and group (lab) recognition, respectively. The study confi rmed the suitability of standard portable colorimeter for the verifi cation of colours required for mollic horizon, in particular in soils those colour values are close to the classifi cation threshold and their manual recognition depends on individual expert's skills.