Plant and Soil

, Volume 10, Issue 1, pp 9–31 | Cite as

The effect of soil drying on humus decomposition and nitrogen availability

  • H. F. Birch
Article

Summary

Respirometer experiments show that when a dry soil is moistened a characteristic pattern of decomposition occurs in which an initial period of relatively rapid decomposition (Stage 1) falls, during a few days, to a slow steady rate (Stage 2). This pattern is repetitive with successive dryings and rewettings and is common to all soils so far investigated. The magnitude of decomposition depends in the percent carbon in the soil and on the drying conditions, air-drying being less effective than oven-drying. Decomposition during Stage 1 conforms approximately to a first-order reaction and proportionate amounts of nitrogen are mineralised. A similar pattern of decomposition occurs under field conditions throughout successive wet and dry seasons.

Evidence is presented to show that decomposition involves direct microbial attack of the solid organic substrate and that the recurrent pattern of decomposition is due to the state in which the microbial population is left after drying and its subsequent behaviour on rewetting. The rapid decline in the rate of decomposition on rewetting (Stage 1) appears not to involve (1) the development of toxic conditions, (b) physical changes in the soil (since similar patterns of decomposition also occur with organic material alone or in sand) or (c) rapid decomposition of organic material made soluble by drying.

The operation and repetition of this pattern of decomposition in the field has important consequences in the rundown of soil carbon and the mineralisation of soil nitrogen particularly where well-defined wet and dry seasons occur. These consequences are discussed in relation to climate and certain agricultural practices.

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References

  1. 1.
    Allison, F. E., Sherman, M. S. and Pinck, L. A., Maintenance of soil organic matter. Soil Sci.68, 463 (1949).Google Scholar
  2. 2.
    Bail, O., Z. Immunitätsforsch.60, 1 (cited in Porter15).Google Scholar
  3. 3.
    Birch, H. F. and Friend, M. T., Humus decomposition in E. African soils. Nature178, 500 (1956).Google Scholar
  4. 4.
    Birch, H. F. and Friend, M. T., The organic matter and nitrogen status of E. African soils. J. Soil Sci.7, 156 (1956).Google Scholar
  5. 5.
    Bunt, J. S. and Rovira, A. D., Microbiological studies of some Subantarctic soils. J. Soil Sci.6, 119 (1955).Google Scholar
  6. 6.
    Chase, F. E. and Gray, P. H. H., Application of the Warburg respirometer in studying respiratory activity in soil. Can. J. Microbiol.3, 335 (1957).Google Scholar
  7. 7.
    Cornish, E. A., Yield trends in the wheat belt of South Australia during 1896–1941. Australian J. Sci. Research Ser. B2, 83 (1949).Google Scholar
  8. 8.
    Curran, H. R., and Evans, F. R., The viability of heat activatable spores in nutrient and non-nutrient substrate as influenced by prestorage or poststorage heating and other factors. J. Bacteriol.53, 103 (1947).Google Scholar
  9. 9.
    Glover, J., The relationship between total seasonal rainfall and yield of maize in the Kenya Highlands. J. Agr. Sci.49, 215 (1957).Google Scholar
  10. 10.
    Jenny, H., A study of the influence of climate upon the nitrogen and organic matter content of the soil. Missouri Agr. Expt. Sta. Research Bull.152 (1930).Google Scholar
  11. 11.
    Knaysi, G., The endospore of bacteria. Bacteriol. Rev.12, 19 (1948).Google Scholar
  12. 12.
    Lebedjantzev, A. N., Drying of soil as one of the natural factors in maintaining soil fertility. Soil Sci.18, 419 (1924).Google Scholar
  13. 13.
    Mann, H. H. and Barnes, T. W., The permanence of organic matter added to soil. J. Agr. Sci.48, 160 (1956).Google Scholar
  14. 14.
    Peat, J. E., and Brown, K. J., Empire Cotton Growing Corp. Progr. Repts. Expt. Stats. Lake Province, Tanganyika Territory. Season 1955–1956.Google Scholar
  15. 15.
    Porter, J. R., Bacterial Chemistry and Psychiology. John Wiley and Sons, Inc., New York (1950).Google Scholar
  16. 16.
    Prescott, J. A., The soils of Australia in relation to vegetation and climate. Australia C.S.I.R. Bull.52 (1931).Google Scholar
  17. 17.
    Richardson, H. L., The nitrogen cycle in grassland soils with special reference to the Rothamsted Park grass experiment. J. Agr. Sci.28, 73 (1938).Google Scholar
  18. 18.
    Winsor, G. W. and Pollard, A. G., Carbon-nitrogen relationships in soil. IV. Mineralisation of carbon and nitrogen. J. Sci. Food Agr.7, 618 (1956)).Google Scholar
  19. 19.
    Wooldridge, W. R., and Glass, V., Variability in the activity of bacterial enzymes. Biochem. J.31, 526 (1937).Google Scholar

Copyright information

© Martinus Nijhoff 1959

Authors and Affiliations

  • H. F. Birch
    • 1
  1. 1.East African Agriculture and Forestry Research OrganisationKikuyuKenya

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