Som lecture 1
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History of Soil Organic Matter Studies, Developments during early 18th and 19th centuries, Contribution by Various Scientists on SOM studies
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Som lecture 1
- 2. Dynamics of soil Organic matter Historical Development 1. Initial Period: Second half of 18th century and beginning of 19th century 2. First half of 19th century: Study of chemical nature of Humic Substances 3. Second half of 19th century: study of humic substances as natural components – Biological nature of Soil Humic Substances
- 3. 4.First two decades of 20th century: Contradictions on the nature and development of Soil Humic Substances – Chemical and Biological nature of SOM was recognized 5.Further investigations during the 20th century: Chemistry of Humus, Peat, Coal and other such constituents – synthesis of Humic Substances 6. Present developments in the study of Soil Humus
- 4. 1. Initial Period Scientist Contribution Wallerius Book on Agricultural chemistry – Humus formed (1761) by decomposition of plants – Plant food possessing properties of absorption of water and nutrients Lomonosov Book on First Principles of Metallurgy or Mining - (1763) humus originated from rotting of animal and plant residues with time Komov Book on Agriculture – role of humus on soil (1782) fertility – Apply Organic Manures – Wider Sowing of Perennial Grasses Achard Isolated Humic Substances from Peat by treating (1786) with alkali – Acidified – Dark Amorphous PPT
- 6. 1. Initial Period Continued Scientist Contribution Vanquelin, 1797 Humic substances from xylem of plants infected with fungi Thomson, 1807 Proposed the name “Ulmin” for the above substances DeSaussure, Humus contains more C and less H and O. 1804 Humus Nutrition Theory Thaer, 1809 Humus Nutrition Theory further developed – Humus sole and direct source of nutrients Braconnot, Brown alkali soluble extracts from carbohydrates 1807, 1819 and plant residues by treating with mineral acids – named them as Ulmin
- 8. II. First Half of 19th century Scientist Contribution Boullay, 1830 Glucose heated with alkali – Dark liquid – Acidified – Brown flocculent precipitate – Ulmic acid Sprengel, 1826, Humic acid has 58% C. Properties of HA and its 1837 salts – Differential Solubility – Humus Coal – Acid nature of HA – Silicic acid from Silicates – Combines with Bases – Sweet Humus – poor fertility in peats Berzelius, 1806, Identified black coloured HS soluble in alkali, 1839 Text Book Yellow coloured crenic and apocrenic Acids, and of Chemistry inert Humin equivalent to Sprengel’s Humus coal – Isolation, Composition and Properties of Salts – Humus Nutrition Theory – Organic Manure Application Sibirtzev, 1901 Role of crenic and apocrenic acids in soil forming processes – crenic acids – podzol soils
- 10. II. First Half of 19th century Contd. Scientist Contribution Malaguti, Artificial Humic Substances – identical with 1835 Natural HS – Humification is a dehydration process – C22H12O11=C12H12O6 + 5H2O Mulder, 1840, Natural and Artificial HS – Chemical 41, 61 and 62 Composition and Properties – identified three types of HS – Insoluble in alkali (Humin and Ulmin), Soluble in alkali (HA, Brown & UA, Black), Soluble in water (Crenic & Apocrenic Acids, Black) – HS chemically individual compounds - N, a contaminant – Purified and dehydrated – chemical composition determined – Ulmin, C40H32O11 – Humin, C40H30O15 – UA, C40H28O12, HA, C40H24O12 or C40H30O15 – CA, C40H24O16, AA, C24H12O12
- 11. II. First Scientist Half of 19Contribution th century Contd. German HS not chemically individual cpds – 1836, 37, 41, Humus Nutrition Theory – Cultivated 42 & 45 soils had less humus than virgin soils – Isolated 16 different HS – Mainly three groups of Berzelius and Mulder – HA & UA, Crenic & Apocrenic and humin & Ulmin, based on composition rather than structure – criticized A Manufacturer Of HS – N as constituent of humus – not contaminant Other HS Mudeous acid of Johnson, isolated Fumic acid of Thenard, Lignoic acid of Hesse, Hymatomelanic acid of Hoppe - Seyler
- 12. Summary of Investigations – Second Phase 1. Studies on Chemical Nature of HS 2. Isolation of New HS – Crenic & Apocrenic Acids 3. New Classification Schemes of HS 1.HS – Chemically individual cpds 2.Chemical nature, structure & properties not known 3.Chemical methods to reproduce humification of plant materials
- 13. Second Half of 19th century Scientist Contribution Eggerts, 1889 Crenic & Apocrenic acids natural products – criticized HA, UA & Humus Coal Van Bemmelen, complexity of chemical composition – HS 1888 amorphous and colloidal Baumann, 1909 HS complex mixture of plant & animal residues in varying stages of decomposition – cannot be separated Baumann & Gully, Acid nature of HS not due to functional 1910 groups but colloidal properties Liebig, 1840 Mineral Nutrition theory as against humus theory – Humus only C source
- 14. Second Half of 19th century Scientist Contribution Grandeau, 1872 Mineral Humus Theories combined – Organo Mineral Plant Nutrition Theory – HS dominant role in dissolving, absorbing and exchange reactions in soils Pasteur, van Post,Humus not chemical or physical but Darwin, 1882,biological with diverse activities of Kostychev, 1886, microbes, protozoa, and various other 89, Muller, 1887, organism Ramann 1888 Kostychev, 1890, Humus source of plant nutrients – Schloesing, 1902, promotes soil structure – favourable air Dehrain, 1888, and water regimes in soil Dehrain and Demoussy, 1896
- 15. Second Half of 19th century Contd. Scientist Contribution Dokuchaev, 1883 “The Russian Chernozems” Kostychev, 1886 “Soils of the Chernozem of Russia” Biological Activity – Perennial Grassy Vegetation – Chernozem Formation Sibirtzev, 1900 - 01 Role of Crenic and Apocrenic acids in podzol formation Hoppe Seyler, 1889 Biochemistry of decomposition of some organic substances Omelyansii, 1902 Biochemistry of decomposition of Cellulose Van Iterson, 1904 Anaerobic Decomposition of Cellulose Snyder, 1898 and Humification of isolated carbohydrates, Suzuki, 1906 – 08 oils and fats
- 16. Second Half of 19th century Contd. Scientist Contribution Kostychev, 1886 HS formed by synthesis between proteins Hebert, 1892 and encrusting substances Dehrain, 1902 Walksman, 1937 Lignoprotein complexes form the nucleus of humus Summary HS formed by two reciprocal processes – decomposition and synthesis Participation of two or more plant materials in the process Biological activity plays a major role in humus synthesis Resistant compounds like lignins and pectins encrust soluble cpds like proteins