Sola Incognita: Unsolved Problems of Genetic Soil Science

For the anniversary of the Faculty of Soil Science of Moscow State University, the author considers the issues remaining unresolved in the field of classical pedology over the past half century and offers a list of problems that will require solutions in the near future. It is noted that, against the background of a decreased interest in pedogenetic studies, challenges are accumulating in related fields that require a clear understanding of the soil genesis: soil classification, soil digital mapping, paleopedology, and soil assessment. There is no single conceptual apparatus describing soil-forming processes. The estimation of the rates of soil-forming processes, without which it is difficult both to reconstruct the evolution of soils in the past and to predict the behavior of soil systems in the future, is one unsolved issue. Several examples of insufficiently studied and controversial pedogenetic processes are given. In particular, the mechanisms of textural differentiation have not been deciphered in both temperate and tropical regions; in many cases, soils that are clearly differentiated by clay content are adjacent to soils with a profile homogeneous in granulometric composition. The mechanisms of deep illuviation of humus in the absence of the traits of the Al-Fe-humus process or solonetzation are unknown. There is no clear understanding of the mechanisms of formation of compacted soil horizons (fragipan) and horizons cemented by opal (duripan). It is proposed to create a database of unresolved soil-genetic issues that require the analysis and understanding.