Evolution of terminology in the sphere of organic matter of soil and humus

Abstract

Goal. To analyze the existing concepts in de­termining the organic matter of the soil and humus and to separate the modern ideas that have developed as a result of a long study of the nature of these substances. Method. Theoretical and analytical. Results. The reasoning of prominent scientists of the 20th century is given, as well as modern researchers regarding the origin, composition, and properties of soil and humus organic matter. Based on an analytical review of scientific publications, the basic terminology of soil organic matter, humus, humus substances, and humification, which has changed over time, is given, and the definition of unified formulations is discussed. The concept of loss (dehumification, dehumus), preservation, and accumulation (sequestration, deposition) of organic matter in soils are considered, and the formulation of separate terms is proposed. Conclusions. At the beginning of the XXI century scientists understand soil organic matter as a system of organic particles of various sizes and biomolecules of plant, animal, and microbiological origin, which consists of plant residues (2–10 mm), solid particles of semi-decomposed organic material (0.053–2 mm), humus (≤0.053 mm) in the form of biomolecules chemically bound to mineral particles, humic and dissolved substances (≤0.45 µm). Humus is a part of the soil organic matter, which in modern literature is called “mineral-associated organic matter”, contained in fractions of dust and clay with a size of ≤0.053 mm.