Contens: Organic matter of the soil. Modern concepts of humus formation. Composition and properties of humus. The importance of humus in soil formation.
Scientific study of the organic matter of soils - the first half of the 9th century. (Sprengel in Germany, Berzelius in Sweden, Herman in Russia, Mulder in Holland). PA Kostychev - the role of microorganisms in the synthesis of humic substances. The first quarter of the twentieth century. the study of the chemical nature of humus substances of non-specific compounds for humus.
Processes of transformation of organic residues Mineralization of organic matter to final products (СО2, Н2О and simple salts) arid regions. Humification is a complex of biochemical, physicochemical and chemical processes of transformation of organic residues into humus substances. Preservation of organic matter in the form of peat with excess moisture, low temperatures tundra, taiga areas.
Modern concepts of humus formation Condensation (polymerization) AG Trusov, MM Kononova, V. Fleiig. The process of humification begins with simple monomers - the products of the decomposition of biological macromolecules or metabolites of soil microorganisms. According to the condensation concept of humus formation, fulvic acids are precursors of humic acids.
Biological concepts of humus formation Humic substances are products of synthesis of various microorganisms. (V. P. Williams), the qualitative heterogeneity of humus substances of soils is associated with the participation in their formation of various groups of microorganisms - aerobic and anaerobic bacteria, fungi. Different groups of humic substances are exoenzymes of different groups of microorganisms.
Humus is a complex of organic compounds formed during decomposition and humification of organic residues in the soil. The composition and content of humus depends on: - on the conditions and nature of the soil-forming process (micro-organisms - bacteria, actinomycetes and fungi); - the composition of plant residues entering the soil; - on the pH of the soil solution (strongly alkaline and acidic unfavorable); - oxygen regime (aerobic or anaerobic transformation medium of plant residues); - the degree of humidity, aeration; temperature conditions; mechanical and mineral composition of the soil.
COMPOSITION OF GUMUS Humic acids С – Н – 3- 5,5 О – N – 3,5 - 5 Fulvic acids С – Н – 3,5- 5,5 О – N – The huma- melanovoi acid Humin
Fulvic acids The most soluble GB (in water); less complex in structure, with lower molecular weights as compared to HA; with high migration ability; with high acidity (capable of destroying minerals); ability to complex formation; participate in podzol formation; salts (fulvates) are soluble in water; podzolic, sod-podzolic, serozems 35-50%
Humic acids Insoluble in water, acids; dark brown color; more complex structure, with higher molecular weights, higher content of C; in chernozems, gray forest 20-40%,