Plant and Soil

, Volume 105, Issue 1, pp 41–46

Characterization of organic matter from animal manures after digestion by earthworms


  • F. Petrussi
    • Institute of Crop ProductionUniversity of Udine
  • M. De Nobili
    • Institute of Crop ProductionUniversity of Udine
  • M. Viotto
    • Institute of Crop ProductionUniversity of Udine
  • P. Sequi
    • Institute of Agricultural ChemistryUniversity of Bologna

DOI: 10.1007/BF02371141

Cite this article as:
Petrussi, F., De Nobili, M., Viotto, M. et al. Plant Soil (1988) 105: 41. doi:10.1007/BF02371141


The humification index (HI) values of three different manures and earthworm casts were calculated for three different extractant solutions (0.5M sodium hydroxide, 0.1M sodium pyrophosphate pH 7 and 0.1M sodium pyrophosphate plus 0.1M NaOH). The alkaline sodium pyrophosphate solution was found to be the most suitable because of both its extraction efficiency and the quality of the organic matter extracted which allows a good characterization of the stabilization degree attained by composting. Neutral sodium pyrophosphate extracts also show characteristic HI values for different samples but lower extraction efficiencies. The HI values for sodium hydroxide extracts show only little differences between manures and composts. The good correspondence found between HI data and isoelectric focusing (IEF) patterns confirmed on one side that humification indexes give a quantitative measure of the humification degree, on the other side that IEF is a suitable technique in order to obtain qualitative informations on organic matter stabilization in earthworm casts.

Key words

extractionnumification indexisoelectric focusingorganic matterworm cast

Copyright information

© Martinus Nijhoff Publishers 1988