Organo-Mineral Complexes and their Effects on the Physico-Chemical Properties of Soils
Yona Chen, Jorge Tarchitzky, 2009. "Organo-Mineral Complexes and their Effects on the Physico-Chemical Properties of Soils", Carbon Stabilization by Clays in the Environment: Process and Characterization Methods, David A. Laird, Javiera Cervini Silva, Yona Chen, Claire Chenu, Françoise Elsass, Javier M. Gonzalez, Michael H.B. Hayes, David A. Laird, Alain Plante, Andre J. Simpson, Guixue Song, Jorge Tarcjotzly, Michael L. Thompson, I. Virto, Robert L. Wershaw
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Most arable soils contain 0.1 to 5% organic matter (OM) by weight. The lowest figures represent sandy soils of arid zones, whereas the higher values are typical of clayey temperate zones. The vast majority of these soils are physically and chemically influenced by the OM which they contain. In addition to the nutritional value of the OM, it plays a critical role in the formation and stabilization of soil structure, which in turn produces desired tilth and drainage as well as resistance to erosion.
To a remarkable degree, increased OM can counteract the diverse structure effects that may prevail in either highly sandy or clayey soils. Increasing soil organic matter (SOM) content usually results in a decrease in bulk density and increase of total porosity. Over a wide range of 10 to 60 g organic C per kg soil, a curvilinear decrease in bulk density from 1.7 to 0.8 Mg m−3 has been observed (Franzluebbers et al., 2001). A curvilinear positive dependence between the C content of soils in New Zealand and aggregate stability was also shown by Haynes (2001). Friability of soils, namely, their tendency to form clods that easily crumble into their constituent natural aggregates is most commonly related to OM content as well as aggregate stability and bulk density (Macks et al., 1996).
Soil mineral particles usually aggregate into granular structures. The stability of soil aggregates (or micro-aggregates – the small particle size fraction of the aggregates – see below) is