Humus

In classical^[1] soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Latin word for "earth" or "ground".^[2]

In agriculture, "humus" sometimes also is used to describe mature or natural compost extracted from a woodland or other spontaneous source for use as a soil conditioner.^[3] It is also used to describe a topsoil horizon that contains organic matter (humus type,^[4] humus form,^[5] or humus profile^[6]).

Humus has many nutrients that improve the health of soil, nitrogen being the most important. The ratio of carbon to nitrogen (C:N) of humus commonly ranges between 8:1 and 15:1 with the median being about 12:1.^[7] It also significantly affects the bulk density of soil. Humus is amorphous and lacks the cellular structure characteristic of plants, microorganisms or animals.^[8]

^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, "The latest edition of The Nature and Properties of Soils, published in 2016, cites Lehmann's 2015 paper and acknowledges that "our understanding of the nature and genesis of soil humus has advanced greatly since the turn of the century, requiring that some long-accepted concepts be revised or abandoned."
^ "Humus". Retrieved 23 September 2008 – via Dictionary.com Random House Dictionary Unabridged.
^ "Humus". Encyclopaedia Britannica Online. 2011. Retrieved 24 November 2011.
^ 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 (1–2): 121–135. Bibcode:1997Geode..81..121C. doi:10.1016/S0016-7061(97)00085-2.
^ Baritz, R. (2003). Humus Forms in Forests of the Northern German Lowlands. Stuttgart: Schweizerbart.
^ Bunting, B. T.; Lundberg, J. (1995). "The humus profile-concept, class and reality". Geoderma. 40 (1–2): 17–36. Bibcode:1987Geode..40...17B. doi:10.1016/0016-7061(87)90011-5.
^ Weil, Ray R.; Brady, Nyle C. (2017). The Nature and Properties of Soils (15th ed.). Columbus, Ohio: Pearson Education (published April 2017). p. 536. ISBN 978-0-13-325448-8. LCCN 2016008568. OCLC 936004363.
^ Whitehead, D. C.; Tinsley, J. (1963). "The biochemistry of humus formation". Journal of the Science of Food and Agriculture. 14 (12): 849–857. Bibcode:1963JSFA...14..849W. doi:10.1002/jsfa.2740141201.

[1] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, "The latest edition of The Nature and Properties of Soils, published in 2016, cites Lehmann's 2015 paper and acknowledges that "our understanding of the nature and genesis of soil humus has advanced greatly since the turn of the century, requiring that some long-accepted concepts be revised or abandoned."

[2] "Humus". Retrieved 23 September 2008 – via Dictionary.com Random House Dictionary Unabridged.

[3] "Humus". Encyclopaedia Britannica Online. 2011. Retrieved 24 November 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 (1–2): 121–135. Bibcode:1997Geode..81..121C. doi:10.1016/S0016-7061(97)00085-2.

[5] Baritz, R. (2003). Humus Forms in Forests of the Northern German Lowlands. Stuttgart: Schweizerbart.

[6] Bunting, B. T.; Lundberg, J. (1995). "The humus profile-concept, class and reality". Geoderma. 40 (1–2): 17–36. Bibcode:1987Geode..40...17B. doi:10.1016/0016-7061(87)90011-5.

[7] Weil, Ray R.; Brady, Nyle C. (2017). The Nature and Properties of Soils (15th ed.). Columbus, Ohio: Pearson Education (published April 2017). p. 536. ISBN 978-0-13-325448-8. LCCN 2016008568. OCLC 936004363.

[Whitehead1963-8] Whitehead, D. C.; Tinsley, J. (1963). "The biochemistry of humus formation". Journal of the Science of Food and Agriculture. 14 (12): 849–857. Bibcode:1963JSFA...14..849W. doi:10.1002/jsfa.2740141201.

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