Elsevier

Advances in Agronomy

Volume 68, 1999, Pages 1-30, 30A, 30B, 31-58
Advances in Agronomy

A Lifetime Perspective on the Chemistry of Soil Organic Matter

https://doi.org/10.1016/S0065-2113(08)60842-1Get rights and content

The author has researched the chemistry of soil organic matter for almost 50 years. In this chapter, he presents a personal account of how soil organic matter chemistry has evolved during the second half of this century from wet to computational chemistry. The chapter begins with a definition of soil organic matter and how it relates to humus and humic substances. Problems associated with the extraction of organic matter from soils, separation of the extract into humic substances, and purification of the resulting fractions are then discussed. New experimental approaches to the in situ analysis of organic matter in whole soils to overcome these problems are described. Investigations on the chemistry of soil organic matter are outlined in terms of (a) an analytical and (b) a structural approach. The analytical approach involves determinations of the characteristics of humic substances by chemical methods, infrared, 13C nuclear magnetic resonance, electron spin resonance spectroscopy, and electron microscopy, whereas the structural approach consists of oxidative and reductive degradations, pyrolysis-field ionization mass spectrometry, and Curie-point pyrolysis-gas chromatography/mass spectrometry. The author recounts how the results of the analytical and structural studies led to the formulation of a two-dimensional humic acid model structure and how the latter was converted with the aid of computational chemistry to a three-dimensional humic acid model structure and later to three-dimensional model structures of soil organic matter and whole soils. The next topics discussed by the author are advances in the chemistry of N-, P-, and S-containing components of soil organic matter. Especially noteworthy is progress in the chemistry of N in soil organic matter, which points to a prominent role of heterocyclic N. As far as colloid-chemical characteristics of humic substances are concerned, the three parameters that control the molecular characteristics (molecular weight, size, and shape) of humic and fulvic acids are (a) the concentration of the humic substance, (b) the pH of the system, and (c) the electrolyte concentration of the medium. In the last part of the chapter, the author discusses how humic substances interact with water, metals, minerals, pesticides, and herbicides; lists functions and uses of humic substances; and describes personal encounters with outstanding scientists who influenced his research.

References (94)

  • H. Knicker et al.

    13C and 15N-NMR spectroscopic examination of the transformation of organic nitrogen in plant biomass during thermal treatment.

    Soil Biol. Biochem.

    (1996)
  • B. Lakatos et al.

    EPR spectra of humic acids and their metal complexes.

    Geoderma

    (1977)
  • P.G. Manning et al.

    Equilibrium studies of metal ion complexes of interest to natural waters. VII

    J. Inorg. Nucl. Chem.

    (1973)
  • R.I. Patience et al.

    The functionality of organic nitrogen in some recent sediments from the Peru upswelling region.

    Org. Geochem.

    (1992)
  • M. Schnitzer

    Humic substances: Chemistry and reactions

  • N. Senesi et al.

    Binding of Fe3+ by humic materials.

    Geochim. Cosmochim. Acta

    (1977)
  • F.J. Sowden et al.

    The nitrogen distribution in soils formed under widely differing climatic conditions.

    Geochim. Cosmochim. Acta

    (1977)
  • C. Steelink et al.

    Stable free radicals in soil humic acid.

    Biochim. Biophys. Acta

    (1962)
  • G. Anderson

    Nucleic acid derivatives in soil.

    Nature (London)

    (1957)
  • G. Anderson

    Identification of derivatives of deoxyribonucleic acid in humic acid.

    Soil Sci.

    (1958)
  • G. Anderson

    Estimation of purines and pyrimidines in soil humic acid.

    Soil Sci.

    (1961)
  • F.K. Archard

    Chemische Untersuchung des Torfs.

    Crell's Chem. Ann.

    (1786)
  • M.A. Arshad et al.

    Attempts to improve solid-state 13C NMR spectra of whole mineral soils.

    Can. J. Soil Sci.

    (1988)
  • N.M. Atherton

    “Electron Spin Resonance.”

    (1973)
  • D.H.R. Barton et al.

    A new experimental approach to the humic acid problem.

    Nature (London)

    (1963)
  • C.N. Bedrock et al.

    31P NMR studies of humic acid from a blanket peat

  • L. Benzing-Purdie et al.

    Elucidation of the nitrogen forms in melanoidins and humic acid by 15N cross polarization-magic angle spinning nuclear magnetic ressonance spectroscopy.

    J. Agric. Food Chem.

    (1983)
  • L. Benzing-Purdie et al.

    Fate of N-15 glycine in peat as determined by 13C and 15N-CPMAS NMR spectroscopy.

    J. Agric. Food Chem.

    (1986)
  • S.A. Boyd et al.

    The mechanism of a copper (II)-humic acid complex and some adducts with nitrogen donors.

    Soil Sci. Soc. Am. J.

    (1981)
  • E. Breitmaier et al.

    13C NMR spectroscopy

  • J.M. Bremner

    The nitrogenous constituents of soil organic matter and their role in soil fertility.

    Pontif. Acad. Sci. Scr. Varia

    (1967)
  • L. Celi et al.

    Mechanism of acifluorfen interaction with humic acid.

    Soil Sci. Soc. Am. J.

    (1997)
  • L. Celi et al.

    Analysis of carboxyl groups in soil humic acids by a wet chemical method, Fourier-transform infrared spectrophotometry, and solution-state carbon-13 nuclear magnetic resonance. A comparative study.

    Soil Sci.

    (1997)
  • Y. Chen et al.

    Water adsorption on humic substances.

    Can. J. Soil Sci.

    (1976)
  • Y. Chen et al.

    Scanning electron microscopy of a humic acid and a fulvic acid and its metal and clay complexes.

    Soil Sci. Soc. Am. J.

    (1976)
  • Y. Chen et al.

    The surface tension of soil humic substances.

    Soil Sci.

    (1978)
  • Y. Chen et al.

    Sizes and shapes of humic substances by electron microscopy

  • Y. Chen et al.

    Use of the scanning electron microscope for structural studies on soils and soil components

  • M.V. Cheshire et al.

    Electron spin resonance spectroscopy of organic and mineral particles

  • B.T. Christensen

    Carbon in primary and secondary organo-mineral complexes

  • J. Cortez et al.

    Purines and pyrimidines in soils and humic substances.

    Soil Sci. Soc. Am. J.

    (1979)
  • K. Ghosh et al.

    Macromolecular structures of humic substances.

    Soil Sci.

    (1980)
  • D.J. Greenland

    Interaction between humic and fulvic acids and clays.

    Soil Sci.

    (1971)
  • J.S. Gregg et al.

    “Adsorption Surface Area and Porosity.”

    (1967)
  • S.M. Griffith et al.

    Oxidative degradation of soil humic substances

  • E.H. Hansen et al.

    Zinc dust distillation and fusion of a soil humic and fulvic acid.

    Soil Sci. Soc. Am. Proc.

    (1969)
  • M.B.H. Hayes et al.

    Degradations with sodium sulfide and phenol

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