The role of chemical indicators to correlate some Estonian soils with WRB and Soil Taxonomy criteria

There has been much research and collection of data about chemistry of soils in Estonia but we face problems when correlating the national classification with an international soil taxonomy especially with regard to the lower taxa. One aim of our study was to clarify the need of soil chemical analysis to enhance soil classification in Estonia using WRB and Soil Taxonomy classifications to examples. Estonian soil classification is based on concepts of soil genesis and their morphological outcomes. Because of our limited range of environmental conditions few chemical analyses are needed to classify soils in the field at the level of soil type. In fact, all the necessary chemical and physical analyses needed to classify soils can readily be done in the field. An important criterion for recognizing soils in Estonia is the occurrence of free carbonates in soil, detected with 10% HCl and the depth of “fizz”. Soil acidity measured by universal indicator gives additional information but is not so important for soil classification. Finger testing for determining soil texture has been sufficient to recognize significant differences for management and use. Soil genetic horizons are separated by color, texture and intensity of processes measured by horizon thickness. In many cases no additional analyses are necessary for characterizing soil, however specific laboratory analyses, such as base saturation, cation exchange capacity, levels of Al, Fe and Si measured with different methods etc., are needed to correlate our national soil types with international classification. General relationships (rules of thumb) between our field laboratory data related to genetic concepts and the defined diagnostic properties of WRB and ST would facilitate correlation decisions and this study may be a start. Procedures to determine degrees of partial membership among data sets would be a useful alternative to the current “all-or-nothing” approach requiring detailed chemical data for correct placement of soils in international systems.