Cartography of the Composition of Clay Minerals in Soils and Parent materials in Moldova

Abstract

A brief review of world experience in mapping the mineralogical composition of soils is given; in particular, the results gained in Great Britain (England and Wales), Canada, the United States, Australia, Hungary, the former Soviet Union, and Russia are analyzed. In the majority of countries, the composition of clay minerals was the only object of mapping, except for the United States, for which the data on the mineral composition of coarse fractions were included. This publication is aimed at the analysis of the experience in mapping the mineralogical composition of soils in Moldova—a small country with steppe and forest-steppe landscapes—and elucidates the achievements and problems in this area. Unlike other countries, where the associations of clay mineral were the object of mapping, the specific mineralogical composition of soils and parent materials in Moldova, together with the development and application of appropriate analytical methods and databases, made it possible to compile the maps reflecting the contents of individual minerals both in the clay and coarse fractions. For the first time, digital maps of the contents of various minerals in soils of Moldova were developed on the basis of data of quantitative X-ray diffractometry and their statistical analysis. A close relationship was found between the content of certain minerals and the particle-size distribution data, which permitted us to perform mapping of the mineralogical composition of soils with due account for their textures. As an example, digital maps of the contents of clay minerals (smectite and illite) in the A horizon and in the parent material of Moldavian chernozems and forest soils on a scale of 1 : 3 M are presented. Statistical data on the contents of these minerals in the soils of different textures are discussed. The content of smectite varies within 6–43%, and the content of illite varies within 3–16%. Their distribution in the soil profiles attests to a statistically reliable difference between the contents of these minerals in the A horizon and in the parent material. The mapping procedure is described, and the areas of the practical application of such maps are specified.