World Library  
Flag as Inappropriate
Email this Article


Humus has a characteristic black or dark brown color and is organic due to an accumulation of organic carbon. Soil scientists use the capital letters O, A, B, C, and E to identify the master horizons, and lowercase letters for distinctions of these horizons. Most soils have three major horizons—the surface horizon (A), the subsoil (B), and the substratum (C). Some soils have an organic horizon (O) on the surface, but this horizon can also be buried. The master horizon, E, is used for subsurface horizons that have a significant loss of minerals (eluviation). Hard bedrock, which is not soil, uses the letter R.

In [2] Humus significantly influences the bulk density of soil and contributes to moisture and nutrient retention.


  • Jerzy Weber. "Types of humus in soils". Agricultural University of Wroclaw, Poland. Retrieved 2013-12-12. 

External links

  1. ^ "humus." Unabridged (v 1.1). Random House, Inc. 23 Sep 2008.
  2. ^
  3. ^ "humus." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2011. Web. 24 Nov 2011. .
  4. ^ Chertov, O.G., Kornarov, A.S., Crocker, G., Grace, P., Klir, J., Körschens, M., Poulton, P.R., Richter, D., 1997. Simulating trends of soil organic carbon in seven long-term experiments using the SOMM model of the humus types. Geoderma 81:121–135.doi:10.1016/S0016-7061(97)00085-2
  5. ^ Baritz, R., 2003. Humus forms in forests of the northern German lowlands. Schweizerbart, Stuttgart, Germany, 145 pp.[1]
  6. ^ Bunting, B.T., Lundberg, J., 1995. The humus profile-concept, class and reality. Geoderma 40:17–36.doi:10.1016/0016-7061(87)90011-5
  7. ^ Hargitai, L., 1993. The soil of organic matter content and humus quality in the maintenance of soil fertility and in environmental protection. Landscape and Urban Planning 27:161–167.doi:10.1016/0169-2046(93)90044-E
  8. ^ Hoitink, H.A., Fahy, P.C., 1986. Basic for the control of soilborne plant pathogens with composts. Annual Review of Phytopathology 24:93–114doi:10.1146/
  9. ^ C.Michael Hogan. 2010. . Encyclopedia of Earth. eds Emily Monosson and C. Cleveland. National Council for Science and the EnvironmentAbiotic factor. Washington DC
  10. ^ De Macedo, J.R., Do Amaral Meneguelli, N., Ottoni, T.B., Araujo de Sousa Lima, J., 2002. Estimation of field capacity and moisture retention based on regression analysis involving chemical and physical properties in Alfisols and Ultisols of the state of Rio de Janeiro. Communications in Soil Science and Plant Analysis, 33: 2037–2055.doi:10.1081/CSS-120005747
  11. ^ Hempfling, R., Schulten, H.R., Horn, R., 1990. Relevance of humus composition to the physical/mechanical stability of agricultural soils: a study by direct pyrolysis-mass spectrometry. Journal of Analytical and Applied Pyrolysis 17:275–281.doi:10.1016/0165-2370(90)85016-G
  12. ^ Soil Development: Soil Properties
  13. ^ a b Szalay, A., 1964. Cation exchange properties of humic acids and their importance in the geochemical enrichment of UO2++ and other cations. Geochimica et Cosmochimica Acta 28:1605–1614.doi:10.1016/0016-7037(64)90009-2
  14. ^ Elo, S., Maunuksela, L., Salkinoja-Salonen, M., Smolander,A., Haahtela, K., 2006. Humus bacteria of Norway spruce stands: plant growth promoting properties and birch, red fescue and alder colonizing capacity. FEMS Microbiology Ecology 31:143–152doi:10.1111/j.1574-6941.2000.tb00679.x
  15. ^ a b Vreeken-Buijs, M.J., Hassink, J., Brussaard, L., 1998. Relationships of soil microarthropod biomass with organic matter and pore size distribution in soils under different land use. Soil Biology and Biochemistry 30:97–106doi:10.1016/S0038-0717(97)00064-3
  16. ^ di Giovanni1, C., Disnar, J.R., Bichet, V., Campy, M., 1998. Sur la présence de matières organiques mésocénozoïques dans des humus actuels (bassin de Chaillexon, Doubs, France). Comptes Rendus de l'Académie des Sciences de Paris, Series IIA, Earth and Planetary Science 326:553–559doi:10.1016/S1251-8050(98)80206-1
  17. ^ Nicolas Bernier and Jean-François Ponge (1994). "Humus form dynamics during the sylvogenetic cycle in a mountain spruce forest" ( 
  18. ^ Humintech® | Definition Of Soil Organic Matter & Humic Acids Based Products
  19. ^ Berg, B., McClaugherty, C., 2007. Plant litter: decomposition, humus formation, carbon sequestration, 2nd ed. Springer, 338 pp., ISBN 3-540-74922-5
  20. ^ Levin, L., Forchiassin, F., Ramos, A.M., 2002. Copper induction of lignin-modifying enzymes in the white-rot fungus Trametes trogii. Mycologia 94:377–383 [2]
  21. ^ González-Pérez, M., Vidal Torrado, P., Colnago, L.A., Martin-Neto, L., Otero, X.L., Milori, D.M.B.P., Haenel Gomes, F., 2008. 13C NMR and FTIR spectroscopy characterization of humic acids in spodosols under tropical rain forest in southeastern Brazil. Geoderma 146:425–433doi:10.1016/j.geoderma.2008.06.018
  22. ^ Knicker, H., Almendros,G., González-Vila, F.J., Lüdemann, H.D., Martin, F., 1995. 13C and 15N NMR analysis of some fungal melanins in comparison with soil organic matter. Organic Geochemistry 23:1023–1028doi:10.1016/0146-6380(95)00094-1
  23. ^ Muscoloa, A., Bovalob, F., Gionfriddob, F., Nardi, S., 1999. Earthworm humic matter produces auxin-like effects on Daucus carota cell growth and nitrate metabolism. Soil Biology and Biochemistry 31:1303–1311doi:10.1016/S0038-0717(99)00049-8
  24. ^ Vermiculture
  25. ^ Dungait, J. A.; Hopkins, D. W.; Gregory, A. S.; Whitmore, A. P. (2012). "Soil organic matter turnover is governed by accessibility not recalcitrance". Global Change Biology 18 (6): 1781–1796.  
  26. ^ Oades, J. M. (1984). "Soil organic matter and structural stability: mechanisms and implications for management". Plant and soil 76: 319–337.  
  27. ^ Lehmann, J., Kern, D.C., Glaser, B., Woods, W.I., 2004. Amazonian Dark Earths: origin, properties, management. Springer, 523 pp. ISBN 978-1-4020-1839-8
  28. ^ Elo, S., Maunuksela, L., Salkinoja-Salonen, M., Smolander, A., Haahtela, K., 2006. Humus bacteria of Norway spruce stands: plant growth promoting properties and birch, red fescue and alder colonizing capacity. FEMS Microbiology Ecology 31:143–152doi:10.1111/j.1574-6941.2000.tb00679.x
  29. ^ Eyheraguibel, B., Silvestrea, J. Morard, P., 2008. Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize. Bioresource Technology 99:4206–4212doi:10.1016/j.biortech.2007.08.082
  30. ^ Zandonadi, D. B.; Santos, M. P.; Busato, J. G.; Peres, L. E. P.; Façanha, A. R. (2013). "Plant physiology as affected by humified organic matter". Theoretical and Experimental Plant Physiology 25: 13–25.  
  31. ^ Olness, A., Archer, D., 2005. Effect of organic carbon on available water in soil. Soil Science 170:90–101
  32. ^ Effect of Organic Carbon on Available Water in Soil : Soil Science
  33. ^ Kikuchi, R., 2004. Deacidification effect of the litter layer on forest soil during snowmelt runoff: laboratory experiment and its basic formularization for simulation modeling. Chemosphere 54:1163–1169doi:10.1016/j.chemosphere.2003.10.025
  34. ^ Caesar-Tonthat, T.C., 2002. Soil binding properties of mucilage produced by a basidiomycete fungus in a model system. Mycological Research 106:930–937doi:10.1017/S0953756202006330
  35. ^ Huang, D.L., Zeng, G.M., Feng, C.L., Hu, S., Jiang, X.Y., Tang, L., Su, F.F., Zhang, Y., Zeng, W., Liu, H.L., 2008. Degradation of lead-contaminated lignocellulosic waste by Phanerochaete chrysosporium and the reduction of lead toxicity. Environmental Science and Technology 42:4946–4951doi:10.1021/es800072c


See also

  • The process that converts raw organic matter into humus feeds the soil population of soil life.[15][28]
  • The rate at which raw organic matter is converted into humus promotes (when fast) or limits (when slow) the coexistence of microbes in soil.
  • Effective humus and stable humus are further sources of nutrients to microbes, the former provides a readily available supply, and the latter acts as a longer-term storage reservoir.
  • Decomposition of dead plant material causes complex organic compounds to be slowly oxidized (lignin-like humus) or to break down into simpler forms (humic acids), which bind to clay minerals and metal hydroxides. There has been a long debate about the ability of plants to uptake humic substances from their root systems and to metabolize them. There is now a consensus about how humus plays a hormonal role rather than simply a nutritional role in plant physiology.[29][30]
  • Humus is a colloidal substance, and increases the soil's cation exchange capacity, hence its ability to store nutrients by chelation. While these nutrient cations are accessible to plants, they are held in the soil safe from being leached by rain or irrigation.[13]
  • Humus can hold the equivalent of 80–90% of its weight in moisture, and therefore increases the soil's capacity to withstand drought conditions.[31][32]
  • The biochemical structure of humus enables it to moderate – or buffer – excessive acid or alkaline soil conditions.[33]
  • During the humification process, microbes secrete sticky gum-like ecosystem.[35]
  • The dark color of humus (usually black or dark brown) helps to warm up cold soils in the spring.

Benefits of soil organic matter and humus

Much of the humus in most soils has persisted for more than a hundred years (rather than having been decomposed to CO2), and can be regarded as stable; this is organic matter that has been protected from decomposition by microbial or enzyme action because it is hidden (occluded) inside small aggregates of soil particles or tightly attached (sorbed or complexed) to clays.[25] Most humus that is not protected in this way is decomposed within ten years and can be regarded as less stable or more labile. Thus stable humus contributes little to the pool of plant-available nutrients in the soil, but it does play a part in maintaining its physical structure.[26] A very stable form of humus is that formed from the slow oxidation of black carbon, after the incorporation of finely powdered charcoal into the topsoil. This process is thought to have been important in the formation of the fertile Amazonian dark earths or Terra preta do Indio.[27]


manure there is.[24]

[18] This suggests a fuzzy boundary between humus and organic matter. In most literature, humus is considered an integral part of [17] It has no determinate shape, structure or character. However, humified organic matter, when examined under the microscope may reveal tiny plant, animal or microbial remains that have been mechanically, but not chemically, degraded.[16] It is difficult to define humus precisely; it is a highly complex substance, which is still not fully understood. Humus should be differentiated from decomposing organic matter. The latter is rough-looking material and remains of the original plant are still visible. Fully humified organic matter, on the other hand, has a uniform dark, spongy, jelly-like appearance, and is amorphous. It may remain like this for millennia or more.

The process of "humification" can occur naturally in [14][15]

Transformation of organic matter into humus



  • Humification 1
    • Transformation of organic matter into humus 1.1
    • Stability 1.2
  • Benefits of soil organic matter and humus 2
  • See also 3
  • References 4
  • External links 5

[6] humus profile).[5] humus form,[4]

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.